Basic Tuning: HELP!

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4mulaSvaliant

4mulaSvaliant

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Ok so I now have my Valiant running and have been driving the crap out of it for the last 3 days.
What I have noticed is that it needs to be "tuned" badly now.
So I am asking the experienced people to please give me some advice, from step one.
Where should I start?
What tools do I need?
What order should the steps happen in?
I know enough to get her running fairly well, but it is pinging, and seems under powered.
Here is where we will start.

360
-Stock Crank, Rods, Pistons.
-318 stock heads (yeah I know.... I have a set of J-heads to get rebuilt) :)
-Mild Cam. (don't have the specs anymore) Do remember it wasn't stock and its not real crazy. basically an "RV" if you want to call it that.
-Carb. 650 manual Choke Edelbrock.
-Functional Hood scoop (gets plenty of fresh air)
-Ignition, 74' stock MOPAR electronic ignition Swapped from a Dart. Cap, rotor, plugs and wires have recently been replaced. May have 200 miles on the set.
-Stock 904 Trans.
- 8-3/4 SG 3:23 gears. (doesn't really matter yet I suppose)

So please if you have good solid knowledge reply. Maybe if this ends up with good solid input it can become a "STICKY" on how to tune basics from square one.
Because a lot of us have "mis-matched" components from different years, Im sure I'm not the only novice who doesn't know which Timing setting to go with since I have several different items that will be affected.

Case in point: I have a 73' 360 with 74' ignition, and the most basic Carb set up(not like all the vaccum operated items from 73/74). So when I look in an old school Chiltons manual, I have so many options on where I should start with for a "base" timing. At this point it runs, so I have obviously managed that, and it will light the tires no problem too, but its still not running up to its potential.

Please if you have a good solid history on tuning (not back yard stuff, that's what I know already!:cheers:) then please fill me and others in. It will be very appreciated and used!


Thanks FABO! You all kick so much tail its ridiculous!
 
Got a vacuum gauge and a good tach?

Dial in initial timing as long as the engine picks up RPM. Reset idle back to your baseline and dial in some more. you'll reach a point where more timing won't add but a small amout of RPM.

Vacuum, dial in timing keeping idle constant, until max vacuum is reached, dial back timing when you get 1" below the max number.

Those are two ways to set initial. Don't waste your time with the original factory timing specs.
 
360
-Stock Crank, Rods, Pistons.
-318 stock heads (yeah I know.... I have a set of J-heads to get rebuilt)
-Mild Cam. (don't have the specs anymore) Do remember it wasn't stock and its not real crazy. basically an "RV" if you want to call it that.
-Carb. 650 manual Choke Edelbrock.
-Functional Hood scoop (gets plenty of fresh air)
-Ignition, 74' stock MOPAR electronic ignition Swapped from a Dart. Cap, rotor, plugs and wires have recently been replaced. May have 200 miles on the set.
-Stock 904 Trans.
- 8-3/4 SG 3:23 gears. (doesn't really matter yet I suppose)
Click to expand...

Well, more info the better, worst case, it gets mentally discarded.

IIRC, the cam was a mild one not requiring you to have a high stall converter needed. With that said, try this;

(I assume some of this has been done, but it will be repeated, so dont be offended)

As if from starting up from jump street after installing the cam and carb OOTB new....... After break in.....

Set carb idle as low as you can go, no lower than 750 RPM.
Set timing to approx 10* advanced.
turn carbs adjusting screws at approx. 2-1/2 turns out from seated.
re-set idle to 750 rpm

install a vaccum gauge and note reading. Twist carb idle screw (1) to find highest vacuum reading. Then the otherside.

This VERY basic set up will get you down the road until you have a jet/rod kit and IMO, I just love a 02 sensor to aid in tuning. Otherwise, your going to have to take a trip to the tail pipe with every adjustment and jet and rod change and smell the exhaust.
 
No offense taken. As I said. Lets start with the basics.

So here is where I stand and here are some questions.
Have tach in the car, as well as I have a Tach/dwell meter I can hook up under the hood so I can see it.
Also have a Vacuum gauge.
Questions:
Base Line Idle: Where should this be based on the specs I have given? Im guessing around 800 - 900 RPM's.

So adjusting the timing, and the idle speed to obtain very little gain from moving the distributor, is the first step!

On to the Vacuum!
As I read it, I am trying to achieve the max amount of vacuum. Does this typically coincide with the timing and idle being correct? Or is it a juggling act between all three?

Then once the max vacuum is reached.... back the timing off until you have gotten 1-inch pound, less of vacuum?
Please confirm whether I have this correct.

It seems, that there will be a bit of a juggling act when it comes to the Timing / Idle, and then maximizing the vacuum. I am thinking once I have the timing and Idle correct, that there is probably going to be a better vacuum to be had, then when I obtain the max vacuum, it will throw the other two out of wack again.

Im assuming this is where it is decided who is good at tuning and those who just try! LOL
 
Oh two other basic questions. Looking at the carb from the front of the car... There are the two adjusting screws. Which one does what?

Also, where do you hook up the vacuum gauge to get an accurate reading?
Are there any things that should be disconnected while checking vacuum? (vac advance?)
 
Here is a link and it is really geared for all motors if you can weed through all the info. These are some great tips tricks etc... I found it cool since I used to tune the brand x with nothing but a vac gauge... http://www.diamondbackengines.com/technical-white-papers/vacuum-gauges/
There are several tuning tips on this site just look to the left in the tech section... Hope this helps and can clarify some issues you are having. Note alot of this stuff is geared towards radical motors but it will work with your motor as well... :D
 
Wow lots of great info there. Unfortuantely, Ill have to take the lap top out while I tune! There is too much to remember there! I got through about 3/4 of it and then had a brain overload. Just too much to take in and comprehend / remember!
This is all great advice. Thanks guys. By all means, keep it coming! I plan to knock out some of this tomorrow night if I have the time.
 
Most tuning stuff is like that for me as well. i got a few that stick with me and I think its due to hands on. Great idea with the laptop!!! I'm sure you will retain whatever you do to it after turning the screws and jackin with the car. Good luck and hope you get the car running like ya want...
 
Timing FIRST, then worry about the carb.

The basics... get the thing to run, dial in initial timing then start messing with carb adjustments. You'll probably have to limit mechanical to hit your desired total timing number, but, that's another installment.
 
crackedback said:
Timing FIRST, then worry about the carb.

The basics... get the thing to run, dial in initial timing then start messing with carb adjustments. You'll probably have to limit mechanical to hit your desired total timing number, but, that's another installment.
Click to expand...

Exactly! Reason being is timing will affect carb settings but carb settings will not affect timing settings. For that reason you always get the timing dialed in first.

Once you get the timing dialed in tune the carb. The 2 bottom screws are what rumble referred too when he said to set them at 2-1/2 turns out. That's a good baseline to start from. When you finally get things tuned set the idle speed to whatever speed it idles good when in gear. With the way you described the cam as being an RV type most likely you won't need more than 750 rpm in neutral.
 
Thanks for all the great info!!! I def. have enough to get a good start on tuning here.

Question: By obtaining "max vacuum", what has that done with the internals of the engine. What has happened to get to the point where you have max vacuum?

Is it that the timing of spark is basically at its optimum, and now the engine is working in harmony? Or at least at that RPM.
 
Is it common for the Harmonic Balancer to "shift" so that the "0" is not really TDC?
I was asking a friend that I trust about this and was told to be sure that my TDC was truly TDC, and that it isnt too uncommon for it to be off slightly. I was told it may be worth while to find true TDC and check and remark if need be all the degrees up to maybe 40* both ways.
Is it worth the effort to make sure my "0" is truly TDC or is it typically OK to trust it?
 
It's not common, but not unheard of either. I wouldn't automatically suspect a slipper damper ring.

What is your timing now? With the small 318 chambers, and mild cam, I would suggest 5 degrees BTDC with the vac advance unplugged. Does it ping there? You (generally) want as much timing as possible without ping.

Don't even try to fine tune the carb until your timing is set so the engine wont ping. And when you do need to set the carb, the Edelbrock owners manual has a lot of great info. I believe you can download it from their site if you have lost the one which came with your carb.
 
OK so here is what happened tonight.
So, with the idle where it has been (about 750) I loosened up the dist.
Started advancing the timing, the idle rose to about 1000 RPM and I back the idle screw down til I was back at 750.
Did this back and forth until I got it to where I couldnt get the RPMs to rise anymore by advancing.
At this point it was idling pretty rough as if it had a miss.
I then snapped the throttle real quick and there was a decent lull before the RPM's picked up. At this point I wasnt too happy, but figure there were several other things to be put in place still, so I left it at that.
I then hooked up a Vacuum gauge and proceeded to adjust the 2 screws on the carb from a lightly "seated" position (all the way screwed in) and backed them out 2-1/2 turns.
I fired it up and it started hard as if the timing was to far advanced and it was firing ahead and fighting the starter when cranking.
It fired up and ran pretty rough. At this point I had 20" lbs of Vac.
I adjusted the screws very carefully in 1/4 turn increments and to my surprise it was doing nothing. I had to back them out to about 3-1/2 turns to even see any difference in the idle.
At this point Im guessing the screws were out about 3-1/2 turns on both, and the idle came up. It was still running very rough and the idle was erratic.
I snapped the throttle a few times and it was horrible! A big lull in throttle response, and very rough running.
This is where this session and method stopped. Not because I dont believe it works, but more that I must have not done something correctly.
Ill stop hear and leave this as one post.
Ill begin another with what I did next.
Please fill me in, on what I did wrong here. Thanks guys
 
So at this point the car is running worse than when I started. Since I plan to drive it tomorrow, I said OK Ill do it by ear and at least get it close to where it was.
So I now back the timing off, tighten it and go drive. Pre ignition pinging is there!
Back home and repeat.
Back out and its not as bad.
I did this about 3-4 times adjusting and driving.
Of course as I backed the timing off, I had to increase the idle speed. At this point the screws on the carb prove to be in an OK position.
I got it to where the pining is gone and the torque is GREAT!
Now Technically speaking..... I have no idea where it really sits based on numbers for timing. All I know, is it is running FAR better than it was.
So it tells me that I was way too far advanced.
Based on the info provided in the previous post, what is going on? Is there enough info to tell you seasoned guys what I did wrong?
Thanks guys!
Your help is very appreciated!
 
You need to get a timing light. If you don't want to spring for an adjustable one you can get a damper timing tape to tell how many degrees advanced your timing is at different rpms. Try unplugging your vacuum advance and checking what your timing is at 4k rpm. For a ballpark number it should be around 34-36 degrees. Then hook your vacuum line to the full vacuum port on your carb and take it for a drive. If it pings you might need to retard it a bit. That is probably all you need to be messing with at this point.
 
Earlier we said to adjust the initial timing for the most idle vacuum. Not the most rpm at idle. Big difference. But if it's running good where you have it now and not pinging you must have it pretty close. Like the old saying goes, "don't mess with it if it ain't broke". And don't worry about numbers (timing, etc..) if it's running good and not pinging. When you have an engine like yours that has different heads and cam you can't always go by numbers. You just adjust it to where it runs the best and it sounds like you got it pretty good.
 
As far as the Vacuum goes I was trying to accomplish getting the most vacuum durring idle after I had the timing adjusted "correctly" LOL, but I think it was a mute point considering I seem to have found out that it was way too advanced.
I do have a very nice timing light actually, but at this point, it seemed like I was instructed to adjust these items based on "RPMs". Im sure I misread / misunderstood!

While I do agree with "if it aint broke dont fix it" I am trying to learn a bit here just as much as I was trying to get it dialed in. I have to be honest at this point I will be hesitant to make too many adjustments considering its running pretty decent. BUT I can tell there is still room for improvement. So the possibility is still there. Just not this week. Ill run it to work and back tomorrow and see how she does. I have been making the standard commute to work. 18mi. trip about 2/3 of it is on the interstate and I cruise around 3000 RPMs, at around 65/70mph. (need to hook the Speedo back up)
Ill let you all know what I see after tomorrow. But again my test driving after my "by ear" adjustments proved to be much, much better! It has the torque back that I remember from back in the day.
I kind of figured when I switched from 2" exhaust to 2-1/2" that it was the cause of my torque going down.
While the 318 heads have smaller ports and valves, the combo proved to be very Torquey <---? I loved it that way, but it was an obvious swap when I had the opportunity. I have a set of J-heads that were supposedly a fresh rebuild, but then when I went to put em' on, I seen glass beads holding a valve open. I was had! They actually look good, it all looks fresh but I just didnt trust them after I seen that.
Once they are on it will help flow a lot! Since I drive it on the street, I prefer to have the good torque. Its much more fun that way!
Thx again for your time and knowledge guys.
Ill keep you posted.
 
Ok so here is what I came up with. Over all the performance seems better for sure. Biggest issue I see now, is that it got pretty hot while idling at a light. The outside temp was cooler than it has been lately, so I cant blame it on hot weather.
But I would have thought that it would get hot from being too far advanced. There is the possibility that it is still a bit too far advanced, because I hear pinging still, just a bit tougher to hear it.
The other thing I forgot to mention was that I added some octane boost and may have brought it up a few points. I did this mainly cause I had nearly a full tank of low grade fuel. I plan to run a higher grade in the future.
Any takes on whats up?
 
This would be why I think tuning by vacuum is a waste of effort. With what you have, you're closing the carb so much that the vacuum advance and accelerator pump cant help, plus there isnt enough airflow for the idle circuit to meter properly. get a timing light. Set the initial timing at 10°, set the idle speed to 650, and adjust the mixture to the highest vacuum reading. Then drive the car and see how it goes.
 
What ever you do you need to get all the pinging stopped. It is extremely detrimental to an engine. Will beat the bearing right out and possibly toast the pistons.

BTW: Most octane booster is misleading in it's labeling. It claims to raise the octane several points. But in reality it just raises it by tenth's. What I mean is lets say you have a 20 gallon tank full of 87 octane and you pour in a full can of octane booster that claims to raise the octane by 5 points in 20 gallons of gas. You believe your octane is now 92 octane but in reality it's only 87.5 octane. It does raise it 5 points but in reality the octane raise is only a .5 octane raise. Hopefully that's clearer than mud. LOL
 
You really need a timing light, a vacuum gauge AND a Tach...but you can do it by ear.

Do this....ok?

Screw BOTH screws on the carb BACK in....then unscrew them 1.5 turns...each.

leave them there.

Now go sit in the car.

Sit there.

Focus on paying attention to the way the engine kicks off...

Does it wawaw-wawahhhhhhhhh

or does it kick (startup) immediately when you hit the start position?

Answer that one :____________________

Now...while its Running...however its running, rough, gasping, whatever...
unplug your vacuum advance and plug the vacuum line with a handy dandy stick (I dont know...be creative- a Plug).

Then, loosen the distributor holddown bolt...adjust the distributor (and tighten down the hold-down after each setting so it doesn't move on crankup) to the point where the starter will kick the engine off (warm) as soon as you touch the start position of the ignition....you may have to adjust, shut down, restart a few times.

Once you do that...hook up the vacuum gauge and note WHAT "THAT" VACUUM READING is..thats what it needs to be..you maybe surprised to find it will be around 15-16 in/hg steady as long as your idle is under 1000 rpm....then trim back your "curb" idle to 750-800 with the idle adjustment on your carb linkage, and put the car in drive/reverse with your foot on the brake....it shouldn't die, or stumble....if it does RETARD it another 1* or so.

Once you get the INITAL timing all set correctly....plug the vacuum advance hose back onto the vacuum canister.

One screw is Air Needle, one is a Fuel needle....and there only for tuning IDLE mixture....someone correct me if I am wrong...I do not claim to be a Edelbrock carb guru.

If the car will barely run with my recommended 1.5 turns OUT from bottom, try 2.5....matter of fact 2.5 sounds richer...and richer is better than leaner so do that.

Believe me on the way it cranks though...that is spot on correct...and tools aren't necessary to guess till you get it right.

The reason no one can tell you an specific timing mark to set it on is: Every engine is different, and while 10* intial is great for alot of cars, some like 11*, some might like 9* depending on combo, wear, altitude, or a whole slew of other factors...Timing should always take precedence over carb tuning.

If you want to get more advanced.....you really need a timing light.

Then your can plot your "stock" distributors advance curve and SEE how much advance it is actually giving.
 
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