28* initial timing for a 318? How can that be?

[StreetSleeper]

I think I have that book, tomorrow I setup for my daughters birthday, have to clean up the house afterwards to dump off an old pair of couches and bring some new ones in after church on Sunday, it might be Monday before I get back to you. Am a single dad. I do have about 3-4 dozen performance books if anybody needs a copy of something. Usually the $20-$50 bookstore junk. Rusty used to complain/preach that we should look it up in the book instead of asking here., and I was Dan the man before he was so I started buying and reading books on deployments. Have been slacking on the auto hobby lately, but I’ll share anything I have.

 

[RustyRatRod]

I want to come back to this and give some more accurate numbers in Vixens timing. I knew I was close but I wasn't right on it. This morning I got 24 initial with vacuum can disconnected and hose pinched off. Then I got 34 total around 3000 RPM, so that's 10 in the distributor just like I welded and filed for. With the vacuum can I get 40 at idle so we're pulling in 16 with the vacuum can. Idle is "around" 850-900 with the can attached or not, although you can hear a difference when the can has vacuum on it. The cam is pretty big so it doesn't idle very smoothly. lol

 

[KevinCar]

I am new to tuning my 340( ld340 intake, headers), unsure of what cam is in motor (more lope than stocker), unsure of actual comp ratio but its a 69 340 with 894 heads, electronic dist, vac advance not connected. Bought it like this. Doesnt hestitate but seems sluggish till about 3k, heard it ping on 93 octane uphill under full throttle at top of 2nd gear on hot summer day, retarded 2 degrees(32 ALL IN) doesnt do that anymore. Edelbrock 600cfm, idles @ 650-700 in d and 750-800 in P or N.
from what i gather i need to remove carb and ensure t slots are correct gap(35-45 thou) with idle speed screw, reinstal, turn dist advancing until i reach the point where idle stops increasing? so what happens if its too fast OF IDLE THEN? if i cannot reduce idle with idle screw as that will change t slot gap? or do i just adjust dist until i have 800 rpm or so and thats my initial? I finally found a shop in my area that has a dist machine, i want to recurve based on MP performance curve, i want to regain vacuum advance for efficiency. i think the edelbrock carb is perculating fuel as it has a very thin gasket and gets very hot to the touch, uncoated headers dont help underhood temps. so many variables but i have always been inclined to adjust timing first, then carb when tuning. plugs look ok, a little rich if anything but they were accell 494 plugs and i changed them out to NGK BKR6E. Vacuum at idle is 13-14", max vacuum is 19-20" driving.
Read this entire thread, more confused as ever as i dont know cam/build etc.
Just gonna follow these links i found in other threads and learn this motor is my guess. There is no right answer, just looking for correct sequence to find best tune without getting pulled over during repeat testing while not paying gobs of $ at a far away dyno.

Distributor starting point for a curve

I get a lot of questions where my distributor curve should start this is a great guideline of different engine combinations and a good area of where the mechanical portion of the curve should be. I have been looking for something like this for a...

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Holley idle mixture screws

Holley spreadbore 650 on a stock 318 and has the stock #56 jets in carb and 9.5 PV, it idles best when the mixture screws are all the way in. Could it have too small of jets in the carb? Should I bump them up a few jet sizes?

www.forabodiesonly.com

Performance timing

AJ/FormS I have a push on chrome breather on the passenger side valve cover and a pcv valve on the drivers side. Do i need to get rid of the pcv and put on another push on breather? Also my 727 has a stock torque converter . My truck has power brakes. Do you think ill have to drill those holes...

www.forabodiesonly.com

 

[Mattax]

from what i gather i need to remove carb and ensure t slots are correct gap(35-45 thou) with idle speed screw,

That will be helpful, but there is no 'correct'. As that's my post you reference, the goal is to have the t-slot exposure in the operating range. On a Holley 4150/60 and similar that is usually .0.20 to .040" exposed.
With the carb off, observing the amount exposed for each 1/4 turn of the adjustment screw provides a future reference in your notebook.

However, it sounds like you have an Edlebrock based on Carter's AFB or AVS. The principle is similar but I don't have a numerical range to offer. Additionally, Carter used a slightly different idle circuit design. One could say its a little more sophisticated.

reinstal, turn dist advancing until i reach the point where idle stops increasing?

No. In part for the reason you ask next and because there is nothing gained by increasing idle speed (unless that's what's needed to keep it running).

so what happens if its too fast OF IDLE THEN? if i cannot reduce idle with idle screw as that will change t slot gap? or do i just adjust dist until i have 800 rpm or so and thats my initial?

If anything, your goal is the strongest idle at the lowest rpm.
Getting it running and warmed up. Then see if you can set the timing close to the initial you think is appropriate for the engine. Check the rpm. Then you have a decision to make depending on the rpm. If the rpm is too high or too low. Either adjust the throttle position slightly, or adjust the initial timing.

Since the engine is idling OK at a 750-800 its in the ballpark. Now you could try adjusting the idle mix screws. If turning them in doesn't cause the engine to stumble, then there is too much transfer slot exposed. Based on what you wrote, I suspect thats not going to be a problem.

If turning them in does cause the engine to start to die, turn them back 1/8 turn at a time until the engine cleans up, then another 1/8 turn richer. Now go check rpm and timing again. Next is decision time. Are you satisfied? I wouldn't be, but everyone is different. If it was me I'd try either a small change in throttle or a small change in initial timing. Then readjust the mix screws and recheck the rpm and timing.

The 100 rpm difference between Park and Drive is OK for modified engine, but you may be able to get it a little better. Try a little more timing and then a little less timing, and a little richer.

With most any distributor expect to find timing changing with any time the engine is over 750 rpm.
In another words, if the timing at 18* and the rpm is 800, then 18* is may not really be initial timing. When the engine is slowed to 650 rpm, then the timing may be 14*. If at 650 and 700 rpm the timing is the same, then that's the real initial, or darn close to it. Keep track of all the timing and rpms, along with any changes you make.

Vacuum at idle is 13-14", max vacuum is 19-20" driving.

It seems to suggest a 'moderate' cam. My guess is maybe something with duration around 220 at .050.

Read this entire thread, more confused as ever as i dont know cam/build etc.

LOL
This is NOT the thread to reference for working out your engine's need. At best its a discussion about factors that impact spark lead.

My advice is start a new thread. Jumping in here is liking jumping into a cow paddy throwing contest.

 

[Mattax]

Doesnt hestitate but seems sluggish till about 3k, heard it ping on 93 octane uphill under full throttle at top of 2nd gear on hot summer day, retarded 2 degrees(32 ALL IN) doesnt do that anymore. Edelbrock 600cfm, idles @ 650-700 in d and 750-800 in P or N.

This already reveals alot. Measure the rpm which you saw it was 32* BTDC.
Pinging in 2nd gear is too much advance.

just looking for correct sequence to find best tune without getting pulled over during repeat testing while not paying gobs of $ at a far away dyno.

Measure and plot out the timing curve. Once you do that, then what to do is pretty straightforward.
The sluggish accel to 3000 could be timing related too.
Dynos are great but they won't be a big help on the launch. Get it into the safe zone, which its not right now. No point in repeating a high rpm, high load test at this point.

think the edelbrock carb is perculating fuel as it has a very thin gasket and gets very hot to the touch,

Winter fuel. It has lower Reid Vapor Pressure (RVP) and sucks when we get warm days early in the year.
You can try to reduce the problem but especially idling at low or no speed not much fuel moving through the lines or the bowls so it picks up heat. There are thin insulating spacer gaskets, and phenonlic as well as wood spacers starting around 1/2" thick. Just have to watch hood clearance when adding spacers with a dual plane.

Other things to do that may help is use factory fuel filter location and steel or stainless lines as much as possible. I've insulated some of mine. Also on my current engine there is a valley pan to reduce hot oil splashing on the bottom of the intake - at least thats the concept.

 

[KevinCar]

This already reveals alot. Measure the rpm which you saw it was 32* BTDC.
Pinging in 2nd gear is too much advance.


Measure and plot out the timing curve. Once you do that, then what to do is pretty straightforward.
The sluggish accel to 3000 could be timing related too.
Dynos are great but they won't be a big help on the launch. Get it into the safe zone, which its not right now. No point in repeating a high rpm, high load test at this point.



Winter fuel. It has lower Reid Vapor Pressure (RVP) and sucks when we get warm days early in the year.
You can try to reduce the problem but especially idling at low or no speed not much fuel moving through the lines or the bowls so it picks up heat. There are thin insulating spacer gaskets, and phenonlic as well as wood spacers starting around 1/2" thick. Just have to watch hood clearance when adding spacers with a dual plane.

Other things to do that may help is use factory fuel filter location and steel or stainless lines as much as possible. I've insulated some of mine. Also on my current engine there is a valley pan to reduce hot oil splashing on the bottom of the intake - at least thats the concept.

Thanks Mattax
I have an isolator its thickness is 0.320, edelbrock 9266. I also bought some insulating and reflective sleeve for my fuel line from pump. i am also looking into some coated Dougs headers to replace the old low hanging hedmans that radiate super heat. Just havnt installed until i sort out wiring and timing, first.
i will map my curve as it is current and perhaps go from there by hiring a recurve by shop with dist machine.
i was looking at an FBO plate and spring kit, then their ecu, and curving myself via mapping, as they report the oem black box ecu i have (plus ole school oem spare) will retard timing over 3500k.
But do i really care?, its not a drag car and already doesnt get traction under hard acceleration.
your advice on using the idle air to control idle speed somewhat along with idle screw, timing and maintaining t slot makes sense vs just timing and idle speed screw, combo to best power/vacuum at idle.
I really just want efficiency via use of vacuum advance without detonation or long term damage to my engine.
So after initial and curve and full mech advance, i will have to sort the vac canister out for my motors vacuum.
Again a bit confusing as some people state manifold vac and others ported vac. i really need to look at just how quickly ported starts and ends in rpm to see where it is pulling more timing, but manifold vac may raise timing enough to keep motor cooler, especially at idle or slow in traffic, which is an issue also when hot out. might "wake" it up quicker under acceleration if it has more vacuum timing in the curve also.
Appreciate your helpful information.

 

[Mattax]

Thanks Mattax
I have an isolator its thickness is 0.320, edelbrock 9266. I also bought some insulating and reflective sleeve for my fuel line from pump. i am also looking into some coated Dougs headers to replace the old low hanging hedmans that radiate super heat. Just havnt installed until i sort out wiring and timing, first.
i will map my curve as it is current and perhaps go from there by hiring a recurve by shop with dist machine.
i was looking at an FBO plate and spring kit, then their ecu, and curving myself via mapping, as they report the oem black box ecu i have (plus ole school oem spare) will retard timing over 3500k.
But do i really care?, its not a drag car and already doesnt get traction under hard acceleration.
your advice on using the idle air to control idle speed somewhat along with idle screw, timing and maintaining t slot makes sense vs just timing and idle speed screw, combo to best power/vacuum at idle.
I really just want efficiency via use of vacuum advance without detonation or long term damage to my engine.
So after initial and curve and full mech advance, i will have to sort the vac canister out for my motors vacuum.
Again a bit confusing as some people state manifold vac and others ported vac. i really need to look at just how quickly ported starts and ends in rpm to see where it is pulling more timing, but manifold vac may raise timing enough to keep motor cooler, especially at idle or slow in traffic, which is an issue also when hot out. might "wake" it up quicker under acceleration if it has more vacuum timing in the curve also.
Appreciate your helpful information.

If the distributor was setup for the cleaner air package (CAP) then it was meant to be used with a retarded initial timing.1 In those situations, sometimes a manifold source is a quick and easy way to get initial back up where it would have been pre-emissions controls. I've posted graphs showing that - you've probably seen them.2

FBO kit: Although he has changed his kit and recommendations over time, he's still only partially correct. It's impossible to have a discussion with him. He's come on here several times with his diatribe and then disappears when a real discussion starts. His plate design is the reason a factory ECU seems to retard. Its also the reason for many years he said it couldn't be used with vacuum advance.3

1. See the Master Technicians Service Conference. Hard to beat the factory info when looking for good information. If you can recall pre-internet how difficult it was to find technical service bulletins and factory tech info, its easy to understand why a lot of speculation and assumptions were made by hobbyists. See for example 1967 Combustion in Today's Engines and Introduction to the CAP Story. Timing is also discussed in 1959 Introduction to the new distributor, and 1970 Lets Keep it Clean.
Available at the Online Imperial Club linked above, and mymopar.com
2. 1967 Service Manuals have timing specs for both CAP and non CAP versions of most engines offered that year. Graphs comparing the 440 Hi-Po timing
3. Videos showing what happens to timing with an electronic box when the distributor's advance is stopped early Lets Revisit Timing

 

[KevinCar]

If the distributor was setup for the cleaner air package (CAP) then it was meant to be used with a retarded initial timing.1 In those situations, sometimes a manifold source is a quick and easy way to get initial back up where it would have been pre-emissions controls. I've posted graphs showing that - you've probably seen them.2

FBO kit: Although he has changed his kit and recommendations over time, he's still only partially correct. It's impossible to have a discussion with him. He's come on here several times with his diatribe and then disappears when a real discussion starts. His plate design is the reason a factory ECU seems to retard. Its also the reason for many years he said it couldn't be used with vacuum advance.3

1. See the Master Technicians Service Conference. Hard to beat the factory info when looking for good information. If you can recall pre-internet how difficult it was to find technical service bulletins and factory tech info, its easy to understand why a lot of speculation and assumptions were made by hobbyists. See for example 1967 Combustion in Today's Engines and Introduction to the CAP Story. Timing is also discussed in 1959 Introduction to the new distributor, and 1970 Lets Keep it Clean.
Available at the Online Imperial Club linked above, and mymopar.com
2. 1967 Service Manuals have timing specs for both CAP and non CAP versions of most engines offered that year. Graphs comparing the 440 Hi-Po timing
3. Videos showing what happens to timing with an electronic box when the distributor's advance is stopped early Lets Revisit Timing

Thats it, i feel the curve in my car is too quick, the reason i had to knock it down from 34 to 32 all in. That mechanical curve is why i am afraid of the vacuum can being attached, it came unhooked, i believe the previous dist tuning was for lighter springs and "all in by" a lower rpm than what actual maximum power could be. I would like to try a more graduated curve and all in by 3500-5k where its making max hp, leaving a lower advance # as it passes max torque. The part that confuses me is when Vac advance is added it should make up for the higher initial just off of idle, so my thought is a lessor initial shouldnt matter if using vacuum advance except for a good smooth idle as even on ported vacuum the advance will jump up as soon as rpm is raised past 1000 rpm or so. so a heavier spring set may actually help power over a longer curve when using vacuum advance. But everyone suggests a higher initial, do they use heavy springs? or just leave power on the table? with total timing max before hp/rpm? Max torque on a 340 would likely be around 3000 and max hp would be around 5000, I would guess somewhere around 28-30 degrees at 3k and 34-36 degrees at 5k. Why does everyone suggest "all in by 2500" ? especially if running vacuum advance and "easing into" full throttle to maintain traction.

 

[TT5.9mag]

I ran my math for this engine. The numbers are startling in several ways.

I used the exact same specs for both combinations where it mattered. Peak torque at 5700 and power at 7300. And an effective compression ratio of 11.5 with a SCR of 12.4

The numbers they gave on the show for the cam the picked is 284/296 on a 112. We have no idea where it’s timed at because Dave didn’t say.

My numbers for the long rod engine:
271/282 107/105

I quickly picked some bullet lobes. This is probably what I would have used. If I looked harder at Comp and Howard’s I may pick different lobes but this is close enough.

Long rod engine:

R303/4665 303-271-193-.4665 (.782)
R314/4620 314-282-200-.4620 (.785)

IVO 46.5 BTDC
IVC 76.5 ABDC
EVO 86.0 BBDC
EVC 48.0 ATDC
94.5 overlap

Short rod engine:

R303/4665 303-271-193-.4665 (.782)
R320/4414 320-285-205-.4445 (.756)

IVO 43.5 BTDC
IVC 79.5 BBDC
EVO 92.0 BBDC
EVC 48.0 ATDC
91.5 overlap

The long rod opens the intake valve 3 degrees later than the short rod.

The long rod closes the intake valve 3 degrees sooner than the short rod.

The long rod opens the exhaust valve later than the short rod.

The long rod and the short rod engine close the exhaust valve at the time.

The long rod engine has 3 more degrees of overlap.

It would be interesting (and costly) to repeat the test and change cams for r/s ratio.

I’m not sure why the torque peak was at as low rpm as it was with 13 more degrees of intake duration on the cam they used in the test.

Man I would absolutely love to see more testing on those two engines with your cams in them.

 

[Mattax]

"All in" is practically meaningless without an rpm. It's right up there with 3/4 race cam.
If that's at 2500 rpm, that's way too quick to use with vacuum advance.
The fast advance curve and no vacuum advance is from the days of points ignition and drag racing. Vacuum advance was just one more thing not needed for drag racing and eliminating it simplified things and could be used to lock the rotor phasing.

Higher or lower initial timing is also not helpful. Plot a specific timing curve and then we can talk. Will be here for hours discussing all the possibilities and then how to tune them. Sometimes things don't act like you think they will. Then you got to figure out why. Like the example Shrinker gave of making the air fuel ratio richer and getting a cleaner burn.

As far as your guesses on torque and hp peaks, they are a bit low. There's some dyno pulls posted for stock and modified 340s. You can search them out. Some from Hot Rod magazine 1969 in this thread

lets revisit timing

A good curve for a 10:1 340 usually falls around 10 initial with another 24 mechanical for a total of about 34 at around 3000 rpm without vacuum advance which may add another 16 or so for a cruising total around 50. how might the engine performance differ with totals of 30 - 36 at wot ( no vac...

www.forabodiesonly.com

 

[Mattax]

A hot rodded engine usually needs more initial timing than a factory engine because the longer time when both the exhaust valve and intake valves are open. This often results in lower compression at idle, less well prepared and distributed fuel at idle (due to lower vacuum), and more exhaust dilution. More lead time is needed because the combustion takes longer.

Additionally, many of our cars here on FABO were made during the years (1968-74+) when retarded initial timing was used to reduce HC & CO while idling and coasting.

 

[Mattax]

Like the example Shrinker gave of making the air fuel ratio richer and getting a cleaner burn.

Bruce "Shrinker" Robertson" Regarding initial timing:
"If you enrich the mixture at idle it will require less timing and the volume of gas expelled from the chamber will be greater (because there is more fuel in the cylinder ). The greater volume exhausting resists reversion backwards up the exhaust port therefor it actually runs with a cleaner chamber. Funny stuff isn't it"

"BUT what you have to do is enrich it correctly with the right processes in the carburetor, sometimes it's not just a matter of winding out the idle screw or changing the IFR. Every engine has a design to it and Chrysler's are a bit different to the other US products, they are not chevs or fords, they are better. They have better combustion and its not necessary to follow the rules of the hotrod industry, as the industry is very Chev orientated. Now what i just said should get plenty of people jumping up and down (hopefully in fun)."
from Motorsports Village • View topic - Initial timing [link broken, sorry]

Shrinker describing his approach:
"Tuning is the process of visualizing the progression of combustion and its conversion to mechanical energy."

^^^This^^^ is not easy, but worth striving for.

 

[mopar head]

Good on you for all that help Mattax

 

[92b]

Max torque on a 340 would likely be around 3000 and max hp would be around 5000, I would guess somewhere around 28-30 degrees at 3k and 34-36 degrees at 5k.

Not saying this will be the case every time but typically what I see is less than 2000 and and over 1000 rpm between peak torque and peak hp.

Most engines will have a window of timing degrees that doesn't change power at each rpm Increment. Some engines being more fussy than others.

Usually what an engine wants at peak torque is within the window of what it will want at peak horsepower. If not it will be very close.

Where I see the difference in the window that an engine wants for timing at a particular rpm is usually below peak torque and above peak horsepower at the ends of the rpm range.

These observations are at wide open throttle and full load.

Most ignition systems will retard some amount with 1000 rpm increase. Some worse than others. Most are not so bad that they affect the engine significantly unless you are at the ends of the curve not so much at peak torque and peak horsepower.

A combination of an ignition that has a lot of retard per 1000 rpm., a fussy engine with a narrow window of acceptable timing per rpm increment, a very long usable wide open throttle rpm range and a timing curve that stops advancing very early could get you close to having different timing requirements for peak torque and peak horsepower.

This is just my opinion. You should sort out your wide open throttle fully loaded engine timing requirements for the rpm range that the engine will be operated in first. This will be your base timing measured at a specific rpm and your mechanical curve if you are using one. This is tuned for max power if that is your goal or enough power if that is you goal. More importantly it should be safe for the engine. How far you are willing to push the safety factor to be determined by you.

Next is part throttle. Use the vac advance to add timing in a tolerated amount where the engine will increase in performance and or efficiency at different part throttle loads. Most likely compromises will have to be made here. How far you push the safety factor is determined by you. I think of this tuning as icing on the cake.

Last is the idle timing. If your motor wants or needs manifold vac along with the initial timing nows the time to figure it out. Keep in mind that altering your base timing at idle should not affect the numbers you have already established for the wide open throttle fully loaded rpm timing curve. You can go less and sacrifice power but not more and sacrifice safety. And if this affects your already determined part throttle curve (lower in rpm than the wot curve) then you will have to compromise somewhere again.

Same with the vac advance can at idle. If you need it and it is too little or too much and you change it. You will now have to compromise the part throttle vac curve.

When you look at how all the methods there are to manipulate the timing curve and how they affect each other it can seem overwhelming. It does to me anyway. Does every motor need to be tuned to the max using all methods available? Probably not. Work at it until your happy that it's doing the job it needs to do. If that means locking the distributor so be it. If that means going all out using everything at your disposal then knock yourself out.

 

[RustyRatRod]

I think I have that book, tomorrow I setup for my daughters birthday, have to clean up the house afterwards to dump off an old pair of couches and bring some new ones in after church on Sunday, it might be Monday before I get back to you. Am a single dad. I do have about 3-4 dozen performance books if anybody needs a copy of something. Usually the $20-$50 bookstore junk. Rusty used to complain/preach that we should look it up in the book instead of asking here., and I was Dan the man before he was so I started buying and reading books on deployments. Have been slacking on the auto hobby lately, but I’ll share anything I have.

No, I've never told anyone not to ask here. Although I have preached heavy about getting service manuals and the MP books. That's not about trying to get people to stop asking. It's about trying to help people LEARN. If someone hands you the answer, you learn nothing. If you read it for yourself and apply it, it's a whole different game.

 

[Newbomb Turk]

No, I've never told anyone not to ask here. Although I have preached heavy about getting service manuals and the MP books. That's not about trying to get people to stop asking. It's about trying to help people LEARN. If someone hands you the answer, you learn nothing. If you read it for yourself and apply it, it's a whole different game.

EXACTLY.

Read it and then go do it and test it.

 

[hollywood hig]