Need Opinions. Have nothing to compare to.

[Frnknsteen]

2600
21" manifold
4" ported
3000
22" manifold
11"ported

 

[Revhendo]

Sorry man, been working extra shifts because of all the dang wind we've been having. I'll run back over your input here and see if I can add some help. @AJ/FormS can pop in and add some insight.

 

[Mattax]

Here's how I would approach it.

Figuring out the inside.

I'm planning to do a compression check of all the cylinders. I know that won't tell me the compression ratio, but it will tell me how even the motor is from cylinder to cylinder, and tell me how much air I'm moving and if I'm low, like 110psi or doing ok, like 150 - 160psi. .

Compression test will also indicate how radical the set up is. A more radical cam will have lower compression pressures. This is because the cam has the valves open longer to pack in more air at high rpm. But at low rpm it reduces the pressure you'll measure. A higher static compression will offset this somewhat. Bottom line, its a helpful indicator.

You make a good point on degreeing the cam. It wouldn't take me long to get down to that point and then I would at least know what the cam is. I was wondering if there would be markings on the end of the cam listing part# so I could tell what it i

Cool. How far you go just depends how much disassembly you want to get into. If the harmonic damper is stock mopar diameter, the Mopar Performance timing tapes with white lettering on black background are nice to use. That, a dial indicator - and if you really want, a solid lifter, you can measure all of the cams' characteristics. Or you can just try to get .050 intake and exhaust timing and from that look at Compcams catalog.

I believe CC cams are marked. Check with them to verify if you want to go about it that way.

The nice thing about finding out the cam specs is that it will help you ballpark timing curve.

Tuning your hot rodded engine.
Tips - Tuning a modified engine is an iterative process. Its rarely a one shot deal even when things are done in the prefered sequence. Hopefully the journey is part of the enjoyment and satisfaction.
Use a notebook, or some note taking and file system. You'll improve it as time goes on, but start one if you haven't.

It seems you've already got it running OK. I'd start with timing, then return to fueling. However remember they work hand in hand. Besides increasing time needed with increasing rpm; Leaner mix burn slower and so wants more timing.

Timing
Initial:
You collected a lot of useful info>

Timing according to my light is 13 initial (vacuum disconnected), 33 with mechanical advance only (vacuum disconnected) at 2600rpm, 50 at 2600 with vacuum attached to manifold vacuum port.

Perfect. Only suggestions are to note RPM at initial timing, and if to plug the vacuum hose with a golf tee or similar (if you haven't been).
13* at 600 or 800 rpm would be good for a stockish cam.
With a hot cam, the engine will probably like a bit more advance. With a manual transmission, its harder to test idle under load. OTH its not as important. But if its a little 'lazy' or wants to die when you gently slip the clutch, these suggest a little more initial advance would be good.
Try 15* or 16*

Engine vaccum at idle hovers between 12 and 13 (connected to manifold vacuum port).

This suggests to me that the cam is not terribly radical. Hence my suggestion for 15-16* initial. (Manifold vacuum at idle will go up with the increased advance. This is good - it makes tuning easier)

I connected to the ported vacuum and no vacuum at idle. Vacuum jumps when I blip the throttle.

Perfect. This shows the throttle blades are close to their intended position at idle.

Vacuum Advance:

Interestingly, timing at idle with manifold vacuum connected is 17, meaning it is not giving full vacuum advance at idle like I thought it would.

Agreed. This advance canister must be adding 4* at 13" of vacuum. Going to ported vacuum for the advance control as you've done is generally the easier and better approach for a hot rod. (But in some situations it turns out that it is better to use manifold source. The right way is whatever the engine wants. )

Timing at a steady 2600 with vacuum connected to ported vacuum is 37.

Need to know the vacuum as well. Then if you plot out the mechanical advance curve so you have the timing w/o vacuum at 2600, you can figure out the vacuum advance contribution.
Another way is to use a hand operated vacuum pump (eg Mityvac) while the engine is idling.

Vacuum advance has two main purposes.
1. Improve fuel milage by matching the timing to the leaner conditions of part throttle.
2. Keep the engine running cooler.

If the engine pings under part throttle acceleration, reduce the vacuum advance.
Otherwise leave tuning the vacuum advance until after initial and mechanical have been set.
Mopar Performance recommend the following:
a. Driving at a steady highway speed (with rpm between 2000 - 4000) note the max engine vacuum.
b. Back at the shop, set up the timing light and a vacuum pump attached to the vacuum advance. Bring the engine to the 2600 rpm and the vacuum pump to the vacuum found in step a. See what the timing is. For an B or RB engine, they recommend 56*. Adjust the vacuum pod as needed.

Centrifical Advance:

Do you think it may want more initial and less advance?

Yes it may.

Should I try pulling the vacuum advance and going back to straight mechanical, then give it a little more initial?

The secret here is to remove the vacuum advance (and plug it) when working with the mechanical. Just measure the timing (without vacuum) from the lowest rpm through 3000 or so. If your racing, you'll want to check it a little higher, but for now, don't worry about it.
Mopar Performance recommends 38* by 2600 to 2800 rpm for a production headed B/RB engine. (When gearheads talk about "total" this it, the initial plus mechanical. )

Since you've already been on the dyno, you're ahead of the game. If you check now, you'll know what the best "total" timing was after some experimentation. Then when you change the initial, recheck and if need be, the curve or the total can be adjusted. We're only talking about 2-3* more in the initial, so it shouldn't be more than that at 2600 rpm - depending on the springs in the distributor, it could be less.

Fueling
Its best to tune from idle, then to cruise, then to wide open throttle. Then accerator shot.
However, that's ideal. Many of us don't or can't always do this.

I did find it interesting that the book said to start at 1.5 turns out, but carb was set to 3/4 turns out. I adjusted them out approximately 1/4 turn more (1/8 turn at a time each) before vacuum started to drop off. Reset them back to max vacuum where it started to drop.

Absolutely fine. Expect that the mix screws will be further in with four corner idle on a stock or mild cam. The manifold vacuum at idle is stronger (pulls harder) than a more radical engine.

Cruisin'
This is the primary side main jets. When you're feeling bold, try smaller primary jets (1 or 2 sizes at most) and see what happens at a steady 60 or 65 or 70 mph. Somewhere in that range, the main circuits take over. If the engine starts surging and wants to die until you slow down - its too lean. Go richer on the jets.

WOT
First. Check the main throttles fully open when pedal is floored.

Next. Lets look at your runs.

Here is the Dyno screenshot in case anyone wants to see it.

View attachment 1715118408

If that's a steady full throttle pull in 3rd (or 4rth), the fueling doesn't look right to me. It should be much flatter, staying within 12.8 to 13.2 AFR on racing gasoline and probably a little richer on street fuel.

Being that its a dynojet, they should be able to give you the run files. They may or may not be able to give you the reader. If not, you can (or at least used to) be able to get it from Dynojet. Having the reader is nice as you can change what you want to focus on. Most are also set up with a printer, so at least you can get a paper copy.

Can there be gains in increasing the jets if the A/F ratio is already running in the 12-14 range? Wouldn't it go rich if jets are increased?

Yes.
If the air bleed correctors are the right size, changing the jets will move the entire curve up or down.

If the air bleeds and/or "emulsion holes" are not the right size, then what is really needed is to change them. That will flatten the curve. If you're curious whether the problem is more the primaries or the secondaries, my suggestion is disconnect the secondaries during a couple of pulls.

Dyno runs were from about 2000 rpm up to just under 5000 rpm. We didn't push it above 5000 rpm because we didn't know much about the motor yet and didn't want to push it too hard. Out of curiosity,... what is safe redline for these big blocks? I've always heard don't push it over 5500 for very long.

I can't answer this. Depends on how it was built. Most of the time dyno operators take it until rpm stops climbing. Depends on what you are doing. Your choices seem quite reasonable. Its not the max hp you're after. Its whether the changes made are improvements in rpm range you've run it. Perfect.

 

[Mattax]

Re: Speed Demon 750
Is this the new Carter Thermo-quad style carb? or an Barry Grant Holley 4150 style ?

 

[Killer6]

I don't recall off the top of my head what the actual vacuum was reading, but yes, it was pretty steady. I remember thinking it was a little low, but I don't remember if it was around 11 or 13. I want to say it was running around 11 inches because I don't think I would have thought 13 was low. Borderline maybe, but not low. At the time, I wasn't really thinking about specific numbers. I was just tweaking the four mixture screws a little at a time until max vacuum was reached, to make sure they were all set evenly (as per my handy dandy "Tuning Demon Carburetors" book!).

I will run back to the shop and check vacuum tonight. It's about 25 degrees colder today, but I'll let her warm up good and check it quick.

I did find it interesting that the book said to start at 1.5 turns out, but carb was set to 3/4 turns out. I adjusted them out approximately 1/4 turn more (1/8 turn at a time each) before vacuum started to drop off. Reset them back to max vacuum where it started to drop.

Yes,... he clearly said they rebuilt the motor, but it sounded like he had a shop do the rebuild because when he was talking about the engine he specifically said "They did some machine work and put in a bigger cam" not "I" or "We"

Well, You're going to have to do Your own detective work here.
1) As dukeboy_318 said, those are some lame-*** lo-po mills stock, and just putting a set of blue Felpro's on would likely drop the OE squeeze below 8:1. So unless that
things got better slugs or they whacked the 906's a ton, that's where the lazy lies. If they did whack the heads, look for the slightly raised portion of the intake surface to
be almost gone, assuming they cut the intake face to maintain the manifold alignment/height. Do a warm compression check, throttles wide open, see what You've got.

 

[Frnknsteen]

Thanks Mattax. Lot's of good information you provided. Carburetor is the Barry Grant pre-Holley double pumper style design, not the new "Street Demon" square style carb (Edelbrock style). I have not been able to find any numbers on it to find out exactly what it is. It looks like a Road Demon or Speed Demon. It has a choke horn, but no choke installed, and mechanical secondaries.

To answer some of your questions:

Perfect. Only suggestions are to note RPM at initial timing, and if to plug the vacuum hose with a golf tee or similar (if you haven't been).
13* at 600 or 800 rpm would be good for a stockish cam.
With a hot cam, the engine will probably like a bit more advance. With a manual transmission, its harder to test idle under load. OTH its not as important. But if its a little 'lazy' or wants to die when you gently slip the clutch, these suggest a little more initial advance would be good.
Try 15* or 16*

Yes, vacuum ports were capped off while checking initial and full mechanical advance at 2600 (33*) RPM was about 750-800 RPM idle while checking initial.

Agreed. This advance canister must be adding 4* at 13" of vacuum. Going to ported vacuum for the advance control as you've done is generally the easier and better approach for a hot rod. (But in some situations it turns out that it is better to use manifold source. The right way is whatever the engine wants. )

Actually,... the vaccum advance was connected to the ported vacuum when I bought it, but it didn't run as well this way and ran hot. I have it connected to full manifold vaccum port now. It seems to run better and it is running cooler at idle and cruise now.

Need to know the vacuum as well. Then if you plot out the mechanical advance curve so you have the timing w/o vacuum at 2600, you can figure out the vacuum advance contribution.
Another way is to use a hand operated vacuum pump (eg Mityvac) while the engine is idling.

I will have to get a vacuum T so I can check vacuum at ported vacuum port, but I know the mechanical advance is at 33* without vaccum attached, so wouldn't my ported vacuum be contributing 4* at 2600 if the total timing (when connected to ported) was 37*?

a. Driving at a steady highway speed (with rpm between 2000 - 4000) note the max engine vacuum.
b. Back at the shop, set up the timing light and a vacuum pump attached to the vacuum advance. Bring the engine to the 2600 rpm and the vacuum pump to the vacuum found in step a. See what the timing is. For an B or RB engine, they recommend 56*. Adjust the vacuum pod as needed.

I will do this and see what we get. I can get a longer vacuum line and bring it in the car to see what the vacuum is while running 2500 rpm down the highway (60 mph Cruising speed)

If that's a steady full throttle pull in 3rd (or 4rth), the fueling doesn't look right to me. It should be much flatter, staying within 12.8 to 13.2 AFR on racing gasoline and probably a little richer on street fuel.

Yes,.... That was steady full throttle pull and was done in 3rd gear. Fuel was 91 octane with NO ethanol from local private party full service station.

I will check into the rest of the things you suggested as weather permits. It has been holding right around freezing temperatures here so I don't want to mess too much with tuning right now.

 

[Frnknsteen]

Well, You're going to have to do Your own detective work here.
1) As dukeboy_318 said, those are some lame-*** lo-po mills stock, and just putting a set of blue Felpro's on would likely drop the OE squeeze below 8:1. So unless that
things got better slugs or they whacked the 906's a ton, that's where the lazy lies. If they did whack the heads, look for the slightly raised portion of the intake surface to
be almost gone, assuming they cut the intake face to maintain the manifold alignment/height. Do a warm compression check, throttles wide open, see what You've got.

Thanks Killer. I will take a look at the intake and see if there are any signs of the intake being milled.

 

[Mattax]

Yes, vacuum ports were capped off while checking initial and full mechanical advance at 2600 (33*)
RPM was about 750-800 RPM idle while checking initial.

Great. 750-800 rpm idle is decent for a motor with some cam.
As far as the total at 2600 rpm. My first reaction is Mopar Performance's recommendations are generally pretty close. This would explain the 'lazy' response. However you did some testing. Therefore at this point we can only assume there was a reason it didn't like or respond to more advance. Maybe the curve is too fast, or the fuel mix was off. We can see in the AFR curve that the mixture might be the reason.

Actually,... the vaccum advance was connected to the ported vacuum when I bought it, but it didn't run as well this way and ran hot. I have it connected to full manifold vaccum port now. It seems to run better and it is running cooler at idle and cruise now.

That makes sense. Now if you increase the initial timing to 16*, that should make the car less lazy, and you may find the engine prefers ported.

I will have to get a vacuum T so I can check vacuum at ported vacuum port,

T Vacuum at the ported is manifold vacuum. The difference is only at idle. The ported vacuum comes from a hole just above the throttle blades in closed position. As soon as the throttles crack open, that port is exposed to manifold vacuum. Since there is no choke, you can see it easily by taking the hose off and squirting some carb cleaner in the port. Just be super carefull not to get that stuff in your eyes when looking down the primaries! Goggles are a good idea.

but I know the mechanical advance is at 33* without vaccum attached, so wouldn't my ported vacuum be contributing 4* at 2600 if the total timing (when connected to ported) was 37*?

Maybe I need to read back to an earlier post. So forgive me if I'm misunderstanding.
33*BTC at 2600 rpm. w/o vacuum advance
4* advance is added with 13 " Hg. (Vacuum)
When the throttle is floored, vacuum is close to zero. ( 1-2"Hg at most except in a restricted situation.)
When driving, the vacuum will probably be 14-18"Hg.
Coasting will be higher,
Part throttle will be lower.
Your vacuum advance canister will start to add advance at something less than 13" and keep adding advance with more vacuum. I'll post a plot of what this looks like after dinner.
Bottom line is you can add the 4* only when the vacuum is exactly 13".

It looks like a Road Demon or Speed Demon. It has a choke horn, but no choke installed, and mechanical secondaries.

Take some photos looking down as well as from the sides. I won't be able to tell you the model, but more important, we can see what type of boosters and adjustibility it was made with.

There were a bunch of threads about the Demon carbs on the old Innovate forum, and while they had some good features, most need some needed excorsizing. My guess, based on the dyno curves you posted, is that too much air is being bled. A lot of the newer Holleys and others do that too.

 

[Mattax]

Regarding the 4 dyno runs shown.
At what rpm was throttle fully floored?
I ask because the red run looks like it could have been part throttle to 3700 ?
That would be a perfectly normal explanation for the AFR going so lean before rich.
But then why would the dark blue or black run be so different? Was the throttle brought on much more agrssively?

 

[Mattax]

This happens to be the vacuum advance from a mid to late 80s Mopar Performance distributor. The initial spring force is adjustable using an allen key. Plotted here are pretty close to the extremes of adjustment available. (Ignore 'Target'. That was specific to the situation.)

The second graph is a rebuilt Chrysler distributor (original application unknown).
A wrap of .031" diameter wire on this vacuum advance's arm limited the number of degrees that can be added. A slight adjustment was also made to the spring's preload.

 

[crackedback]

Are you sure it stopped advancing at whatever RPM point you stopped?

This is usually a HUGE error when tuning. Run the RPM up until it stops advancing, not some number picked from a recommendation or guess. It may have more advance in it than you are seeing.

Not enough initial timing is the first thing I see and would attack.

 

[AJ/FormS]

Define lazy......What are you used to driving? lol.
(torque x rpm)/5250 =hp
Working it backwards, I see you have available 292 ft lbs at 2250rpm. NET 292.
That's more than a 69 340 can muster at peak.
That's more than my HO360 can put out until nearing 4000, And there is NOTHING lazy about my 360.
Do the compression test, then you'll have a better idea of what's going on.

 

[Frnknsteen]

T Vacuum at the ported is manifold vacuum. The difference is only at idle. The ported vacuum comes from a hole just above the throttle blades in closed position. As soon as the throttles crack open, that port is exposed to manifold vacuum.

I was just saying I could put a T in the line so I can have the vacuum hooked up and still have it connected to the vacuum gauge. I did check the vacuum at different RPMs and the ported vacuum seems to climb very slowly as RPMs increase. As soon as I can get a chance, I will hook up the gauge and map the vacuum as RPM climbs so we can see the vacuum curve, but I want to say I am still at about 5" vacuum up towards 3000 RPM. Looking at your advance curves for the vacuum cans below, I don't see how we would get enough vacuum off the ported vacuum to give us much advance, even if we did adjust it

Regarding the 4 dyno runs shown.
At what rpm was throttle fully floored?
I ask because the red run looks like it could have been part throttle to 3700 ?
That would be a perfectly normal explanation for the AFR going so lean before rich.
But then why would the dark blue or black run be so different? Was the throttle brought on much more agrssively?

I can't say for sure, but he seemed to work it up through the gears into 3rd, pushed in the clutch and blipped the throttle to clear out the carb, then re-engaged the clutch and started his pull. It seemed like he accelerated the same on all pulls, but to be honest, I was watching the screen, not the throttle. I WAS wondering why the AFR have such a wave pattern and they don't follow each other. In fact, if you look at the green and red, they kind of oppose each other. Light Blue that dips below 12 was first run before he blew out the air ports (if that's what they are called) with cleaner.

I do find it strange that the dark blue line cuts out on the screen (for HP, Torque, and AFR) from 2700 - 4000 RPM and from 2900-3100 on the green run. Dark Blue run was the last one he ran, and ran up the highest in RPM. That was the one he ran after dialing the timing back down to 45 all-in (Mechanical and vacuum) after seeing the drop off from advancing it on the green run.

 

[Frnknsteen]

Before replying to CrackedBack and AJ,.... Let me just say I appreciate all the information you guys are providing. I am learning a ton about how all this ties together. I will admit that how the advance system works has always been a little bit of black magic to me, but it is starting to make sense.

 

[Frnknsteen]

Are you sure it stopped advancing at whatever RPM point you stopped?

This is usually a HUGE error when tuning. Run the RPM up until it stops advancing, not some number picked from a recommendation or guess. It may have more advance in it than you are seeing.

Not enough initial timing is the first thing I see and would attack.

Hi Rob. Yes, I'm quite confident it stopped advancing. I can't tell you the exact RPM it stopped advancing off the top of my head, but I did roll the throttle up from 2600 to 3000 - 3200 a few times and timing was stable and not climbing within that range. I can watch it advance as I roll up the throttle, then it goes stable and stays there. Next time I have the light on it, I will find out what RPM it stops advancing at.

 

[AJ/FormS]

I think the point is some lazy distributors are still advancing at 4000 rpm.
>As to the ported vacuum port, TEE into that line and watch what it does once you're in gear and driving. In N/P with no load on the engine you can see the relationship to vacuum vs ignition timing, but the relationship to rpm has no basis in reality until the car is in gear and driving.What it does in N/P is meaningless.
>As to power timing, It doesn't matter if the vacuum advance is hooked up or not because once the throttle goes to WOT-under-load, there is usually less manifold vacuum than can operate the can. If there isn't less vacuum than can operate the can, then there is something wrong; like a too small carb, or secondaries not opening, or a faulty Vcan,or a plugged/restricted exhaust. Even with the adjuster screw backed-off inside the Vcan, it usually requires a minimum of 4/5 inches vacuum to activate the can and get even 1 degree of timing out of it. So, then, you can see, it matters not under full-load-WOT, if or where it's hooked up to.
>Now why in the world the dyno operator would set the power timing to 45* all-in-including-the-can, is a mystery to me.Only he would know why.
Generally, power timing is set with the Vcan disconnected and the line plugged.After that the line can be re-installed,no big deal,IMO.Power timing on a low-compression BB, IDK much about, But I'm imagining it won't be much different than a SBM, so when I see 45*, I see REDFLAGS.
Ima thinking the power timing should be limited to 30/32*on the first pull, and increased in 2* steps, to a max of 36/maybe 38 tops. But 45*under load seems to me like hammer-out-the-bearings-and break-the skirts-timing.
>I'm still trying to figure out why you would state this combo with an A833, assuming it's in an A-body, is lazy,lol.
>Looking at the dyno-chart, she looks to have a nice fat midrange. If you converted that back to torque, I think it would actually look pretty healthy in that zone.You can do that using this formula, which is the same as the first but just rearranged to spit out torque.

Torque = hp x 5250 divide by rpm

>Pay attention to the previous posts; there is a wealth of information in them.

 

[Frnknsteen]

Define lazy......What are you used to driving? lol.
(torque x rpm)/5250 =hp
Working it backwards, I see you have available 292 ft lbs at 2250rpm. NET 292.
That's more than a 69 340 can muster at peak.
That's more than my HO360 can put out until nearing 4000, And there is NOTHING lazy about my 360.
Do the compression test, then you'll have a better idea of what's going on.

Thanks AJ,.... That was kind of the point of this whole thread. I don't have much to compare to, not knowing what kind of numbers others are getting. I appreciate you giving me points of reference! You always read these articles where people claim to be getting these big monster horsepower and torque numbers, and then you see what your car did and it's no where near those other numbers. The tech running the dyno for me said he calls their dyno "The Great Deflator" because people are always expecting bigger numbers than what they get. I DID overhear him telling one of the other techs that it must be a fun car to drive with the torque it is building in that light body,.... and it is!

It has been a while since I have driven these older cars though and like I said, I have nothing recent to compare to, other than what I'm feeling with my butt. The only thing I have to compare to that is reasonably close is my 2010 Challenger R/T (Sold it to buy this Cuda). I would say it feels fairly comparable to that in power (but this is more fun), but the numbers don't line out, and I never checked to see what my Challenger had for power, but if you believe the dealers, they are claiming 372Hp/ 401ft/lbs. I assume that is at the motor though, not the wheels. From what you are telling me though, I am seeing respectable numbers and I should appreciate what I have and enjoy it.

And I'm ok with that! I did just order a compression tester that arrived last night. Soon as we get a decent day, I will do a compression check to see where it is at.

Quick question,.... Compression check,.... Engine warm, all plugs removed, and carb throttle plates blocked open,.... Correct??

Other than that,.... I think I will turn my focus and money to getting the Charger lined out while I enjoy driving the '67. I may still play around with learning more about what I have in the Barracuda, but I'm not going to go out of my way to try to pull more power out of it. Not for now anyways.....

Thanks everyone!! I learned a ton, and will still look into things you suggested to tweak it in. I just may not dive into pulling it apart just to find out specifics.

Mark

 

[Frnknsteen]

Now why in the world the dyno operator would set the power timing to 45* all-in-including-the-can, is a mystery to me.Only he would know why.

If you are describing "Power Timing" as full mechanical curve, then timing is not 45*. Full mechanical advance at a steady 2600 RPM was 35* on his light (33* on my light) with vacuum disconnected and capped off. 45* on his light was at a steady RPM of ~2500RPM (with vacuum connected) using his light. When using my light I was seeing 50* at a steady RPM of 2500-2600 RPM. As you said, when the throttle opens and vacuum drops, the only advance that should remain is the 33* from mechanical advance. With the vacuum disconnected and capped off, and at a steady 2500-2600 I am getting 33* of timing.

I'm still trying to figure out why you would state this combo with an A833, assuming it's in an A-body, is lazy,lol.
>Looking at the dyno-chart, she looks to have a nice fat midrange. If you converted that back to torque, I think it would actually look pretty healthy in that zone.You can do that using this formula, which is the same as the first but just rearranged to spit out torque.

Please don't get me wrong,... I'm not saying the car doesn't have any power. "Lazy" is how the shop owner described it, presumably because he thought it seemed to take a bit to build RPMs on the Dyno. That may be because it was running in third gear with 3:23 gears. The car is actually fairly snappy on the road. If I am cruising along in second gear and stomp the throttle, it will break the back tires loose and want to go sideways. Not bad for straight acceleration and no clutch drop.

Like I said above,.... I just have nothing to compare it to, and when looking at the numbers, they seem lower than what is called out for my Challenger and what others say they are getting. You comparing it to a '69 340 and your 360 (<4000RPM) really helped because it tells me not to worry about the numbers so much and appreciate that it is respectable output with a nice wide power band. Hence my first post of:

I really have nothing to compare to determine if I should be happy with the output for this cruiser, or if there are some little things I could do to wake it up a bit.

Oh,..... And I do appreciate the information in the previous posts! I have learned a ton about all this and from what people have posted! That's why I have come to love this sight. The members here are extremely helpful and patient!

 

[Revhendo]

I posted this awhile back. It's an interesting read.

For those of you interested.......

This was written by a former GM engineer as a response to a similar question on a Camaro board:


As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative.

TIMING AND VACUUM ADVANCE 101

The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.

The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.

At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).

When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.

__________________

 

[Mattax]

I think A/J covered most of what I would have said.

Manifold vacuum strongly relates to load: Its a result of the combination of throttle opening and engine speed and efficiency in drawing air. I suppose it will be best when you see it for yourself. (However if you are familiar with modern cars with closed loop EFI, the MAP is the same thing, just viewed in terms of absolulte pressure.)

Lazy is a term sometimes used to describe throttle response. I believe what he probably meant.

Distributor curve. I agree it is best to know when it stops advancing. Also two points is not enough to know the shape. It may be a two stage advance. It didn't ping at WOT, so it was never too advanced at full load. The advance may slightly retard at higher rpm. Depends on the ignition box and distributor. Since your not turning it much past 5000 rpm at this point, I don't think its that important.
It's likely the difference in timing between the two lights is the electronics. At higher rpm, the slower one will show up. Or if you ignition is multi-spark, who knows. Doesn't matter as long as its consistant.

On the Dyno. Usually shops will only hit the record at full throttle. They do this because recording while the bringing the engine to full power is confusing - as you can see.

I honestly think the lean mountain we are seeing is the throttle being squeezed on. AFR should go leaner with more throttle (load) until 70-90% full throttle, then it needs to go richer. ( On Holley type carb, that additional fuel is supplied through by "power valve" opening.)
See if the guys will let you do the driving next time you go.

With Dynojets, the rpm comes from the inductive pickup. The software then matches it up with sensor info from the drum. IIRC torque is derived, based on its assumption of gear ratio (including tires). If you get the files, it will show speed in mph (from the drum), and the missing data may then appear.

 

[Frnknsteen]

I posted this awhile back. It's an interesting read.

Thanks Rev. I had read that somewhere when trying to look up ported vs manifold vacuum. It IS an interesting read!,... and makes me feel like I have it hooked up the way it was originally intended to work. I know it runs better with the way it is hooked up now, and it used to run hot when it was hooked up the way it was when I bought it (hooked to ported vacuum) and now it doesn't seem to anymore.

What I found interesting was when he was talking about running less timing and relying on the AIR systems to help burn the extra fuel. It made me remember the older cars from the 70's to early 80's running air pumps. I never really understood why they would put an air pump on the car, but it makes sense now.

 

[Frnknsteen]

Lazy is a term sometimes used to describe throttle response. I believe what he probably meant.

Thanks Mattax! That's kind of what I'm thinking too. With the 3:23 gears in there and running it in 3rd gear, it did take a bit for the throttle to pick up and you are probably right about that being the reason he said it seemed "Lazy"

Distributor curve. I agree it is best to know when it stops advancing. Also two points is not enough to know the shape. It may be a two stage advance. It didn't ping at WOT, so it was never too advanced at full load. The advance may slightly retard at higher rpm. Depends on the ignition box and distributor. Since your not turning it much past 5000 rpm at this point, I don't think its that important.

I agree. It would be nice to know what the advance curve looks like in the distributor. When I can get a warmer day, I will disconnect (and cap) the vacuum and put the timing light on it. I will start at idle and start raising RPM 200 points while checking the timing at each step. That will map the advance from idle through 3000-3500 RPM in 200RPM increments so I can graph the curve, but also see when it stops advancing.

It's likely the difference in timing between the two lights is the electronics. At higher rpm, the slower one will show up. Or if you ignition is multi-spark, who knows. Doesn't matter as long as its consistant.

Very possible. He was running what looked like an older SnapOn digital. I am using a brand new Innova Pro Digital so I can watch RPM on the timing light and adjust/check the timing. My ignition is a standard Mopar electronic ignition box with a Mopar Performance coil (mounted on the intake just like stock) so I doubt I have multi-spark ignition.

I honestly think the lean mountain we are seeing is the throttle being squeezed on. AFR should go leaner with more throttle (load) until 70-90% full throttle, then it needs to go richer. ( On Holley type carb, that additional fuel is supplied through by "power valve" opening.)
See if the guys will let you do the driving next time you go.

So, if they WILL let me drive it, what do you suggest? Get it up to 3rd gear cruising at 2000 RPM and have them start recording immediately followed by me mashing the throttle to WOT? Do I hold that through 5300RPM (Don't HP and Torque cross at 5250?). I am open to your suggestions of what to do on the dyno (How I should make the pull)

Thanks for the input!

 

[Mattax]

So, if they WILL let me drive it, what do you suggest? Get it up to 3rd gear cruising at 2000 RPM and have them start recording immediately followed by me mashing the throttle to WOT? Do I hold that through 5300RPM (Don't HP and Torque cross at 5250?). I am open to your suggestions of what to do on the dyno (How I should make the pull)

First, do what they tell you. Then you'll know their method. Also more likely they'll be honored rather than offended by the request.
When trying to pull from down low they will probably tell you to get it into third without drama and then squeeze the throttle quickly and smoothly to WOT. Then start recording.
If they prefer recording to begine earlier, that's fine. Then simply note rpm or mph when your foot the floor. Generally take it until the Hp stops climbing or your above what the valve train can probably handle (which in your case is an unknown).
Again its their shop, their (very expensive) tool, so got to respect that.

 

[Mattax]

Here's some examples of dyno runs.
First post here in this thread has a dyno run. (If you can't see it due to photobucket, theres an addon by "bridge troll" for firefox and chrome that will fix that issue).
Dyno'ed My 360..it's a pig..what next?
The thread goes off in a half dozen directions. This fellow later posted in a new thread that he adjusted the fuel curve and picked up a bunch of power. However he did with EFI rather than tuning the carb. He's probably still missing some, but he's satisfied.

Next are a couple of overlays that show a few of the things I was describing.
These are 3 pulls with (IIRC) no changes other than reducing advance of the entire timing curve (such as by twisting the distributor to reduce the initial).
-1, -2, -3 represent the timing taken out.
This is third gear (torqueflite). Because its an autotrans, the rpm going to WOT is a bit higher than can be done with a stick or a full manual valvebody.
Shown in the first image is speed of the roller in mph and Hp.
The power is pretty similar until 3 degrees is taken out.

Now the second image is the same 3 pulls, but this time with torque and AFR.
The AFR appears to change. But this is misleading. The carb wasn't touched. The wideband only 'reads' the oxygen in the exhaust and with some assumptions about how how the combustion normally occurs, provides a lambda or AFR conversion.

The point here is that if you're changing timing, don't mess with the carb just because the AFR appeared to change. Get the best timing and preferably get it first. Then use the afr reading as a guide to the effect of a change to the fuel; be it jetting or airbleeds. My preference is to to make sure the delivery is flat through the pull (generally airbleeds) and then when its flat, adjust the jets for best overall power through the rpm band of interest.

If you want to read about why the combustion products can fool a wideband, read Motorsports Village • View topic - How a Wideband gets tricked to read wrong AFR
Shrinker had done a bunch of testing with 4 and 5 gas exhaust analyzers which helped him come to the conclusions he's sharing there.

 

[Mattax]

Here's an example where the AFR is appears very lean in the beginning of the pulls.

This is because we captured the part throttle portion just after shifting into 3rd. No big deal as long as we know that WOT was achieved around 4000 rpm.
These two overlays show that while the primary AFR can be adjusted with jet changes, the secondary side probably needs the air bleeds reduced.

In this particular set of runs, I also had a datalogger recording rpm, WBO2, and vacuum. Notice the vacuum at partthottle vs WOT.