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post #1 of 49 (permalink) Old Aug 14th, 08, 06:17 PM Thread Starter
Ernie
 
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Question Engine timing

i have a 67 camaro with a 383 stroker motor that was built for me! i am a shade tree mechanic with a lot of drive. my question is how do i find the correct ignition timing for my engine! it seems like it pings a lot on premium fuel, and there is a hesitation when i first step on the gas. some say it maybe my ignition timing!! i also just replaced my edelbrock carb with a holley carb that i had built at the carb shop in ontario. any thoughts.

Last edited by eatrican; Aug 14th, 08 at 07:37 PM.
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post #2 of 49 (permalink) Old Aug 14th, 08, 06:32 PM
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Re: Engine timing

Well to begin with, what compression are you running? What are the specs of your cam? What is the idle RPM your running at? What thermostat rating is in the car?

These factors will help to decipher your timing.

Likely though she'll want to be set in the 14-18 BTDC range. More than likely closer to the 16* area. Then it's all a matter of tweaking the carb and getting the best vacuum you can at a decent idle. A lot of miss and some hit to get it dialed in right.

Brandon J. licence 1NASTY67

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post #3 of 49 (permalink) Old Aug 14th, 08, 07:29 PM Thread Starter
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Re: Engine timing

thank you for quick info!! i am running 10.6:1 compression, idle rpm i have it set at is 750 rpm, thermostat is i think 210, and cam is comp hyd roller cam 288 dur, intake 230, exh 236. i also am not running a line for my vacuum advance, is this common? the mechanic said i didnt have to because of the way the engine was built!
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post #4 of 49 (permalink) Old Aug 14th, 08, 07:49 PM
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Re: Engine timing

Motor shouldnt be pinging on that. shoot for 17* initial and around 34* total. You need to have your vaccum advance hooked up. that could be your bog problem. If your not gonna hook up your vaccum advance, You can run enough timing if your ALL OUT racing the car, but your advance needs to be locked out at optimal timing for that particular build. A driver/street car needs vaccum advance.
drop a 195 thermo in it. Does it have a 4 core radiator or?

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Last edited by wiskeesour; Aug 14th, 08 at 07:59 PM.
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post #5 of 49 (permalink) Old Aug 14th, 08, 07:55 PM
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Re: Engine timing

If it pings on premium then the timing is advanced too far!....Back off the timing slightly by rotating the distributor clockwise (retarded) ever so slightly, test drive and repeat procedure until it pings no more.....It's best to invest in a timing light!
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post #6 of 49 (permalink) Old Aug 14th, 08, 08:01 PM
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Re: Engine timing

Hook up your vacuum advance to full manifold vacuum, not ported vacuum.
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post #7 of 49 (permalink) Old Aug 14th, 08, 08:30 PM Thread Starter
Ernie
 
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Re: Engine timing

yes i have a 4 row radiator, so you think i need to hook up my advance!! what do you mean by total timing of 34????
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post #8 of 49 (permalink) Old Aug 14th, 08, 08:36 PM
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Re: Engine timing

Ernie - The "magic" number for a stroker 383 is 34 total. LOL... By that I mean it's a good starting point. Since you haven't given a clue to what your timing curve looks like and too much total can be had if you just set your initial without knowing the curve and what's built into the dist.

So set your total to 34 degs btdc (rev it to about 3500 rpm when setting it.) Now check your initial at idle and subtract that from the total to learn how much is built into the dist. Test drive from here and if you are not pinging any more add the vacuum advance back in. With it idling hook the vacuum advance to a manifold source and check your timing (it should go up and the idle should go up too), note the difference. Also adjust your idle back down to where it should be. Next rev the engine to about 3500 again and check your timing to see how much the vacuum advance is adding. Subtract 34 from the new number.

Now go test drive the car again, with it set as described come back, let us know how it runs and the following numbers.

Total (should be 34 +-1 maybe):
RPM total advance is reached at:
Initial (vacuum adv disconnected and source plugged):
Idle rpm:
Total advance + Vacuum Adv:
Idle advance + Vacuum Adv:

With these numbers we can help you further and tell you if your curve is off or you have too much or not enough vacuum advance, as well if the curve is too fast or too slow.

...Dennis

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post #9 of 49 (permalink) Old Aug 14th, 08, 08:37 PM
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Re: Engine timing

Quote:
Originally Posted by eatrican View Post
yes i have a 4 row radiator, so you think i need to hook up my advance!! what do you mean by total timing of 34????
accum advance and plug the vaccum port on the carb. at idle 600 750 rpm, timing should be 17*. hook up vaccum advance and rev motor to 2200 then 2800 at 2800rpm timing should be 34* total. idle timing is initial. 17* vaccum advance should pull in 17* more or so. 17+17=34 when you finished, play with distributor and retard and advance it and see where the car runs better.
Hook up a timing light to the number 1 plug wire. Unhook vaccum advance from carb and plug it. at idle timing should be initial 17*. hook vaccum back up and rev engine to 2800 and total timing should be 34*.
17* idle and stock HEI vaccum advance should pull in 17* more for a total timing of 34*

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post #10 of 49 (permalink) Old Aug 14th, 08, 08:42 PM
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Re: Engine timing

Harley - not picking on you but how do you know what his dist curve is? and when it's all in at? Maybe you have some inside info or I missed something. Just curious...

...Dennis

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post #11 of 49 (permalink) Old Aug 14th, 08, 08:44 PM
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Re: Engine timing

Quote:
Originally Posted by DjD View Post
Harley - not picking on you but how do you know what his dist curve is? and when it's all in at? Maybe you have some inside info or I missed something. Just curious...
Your right Dennis. as usual. Im just using stock Hall Effect Ignition vaccum advance curve. Stock HEI.
Well see what he says. Explanation with numbers usually helps people. I get good feedback on it.
Numbers could be plus or minus, most poeple get the idea.

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post #12 of 49 (permalink) Old Aug 14th, 08, 10:04 PM Thread Starter
Ernie
 
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Re: Engine timing

hey djd so i am trying to check my timing. i have my timing light hooked up and now do i set the degree wheel on the light to 34 and then check at 3500 rpm?? sorry i am not good with the timing, carb stuff, but i do have the equiptment and am willing to learn!!!
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post #13 of 49 (permalink) Old Aug 14th, 08, 10:05 PM Thread Starter
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Re: Engine timing

and should i check at 3500 rpm and see what number comesup and then subtract it from the 34 degrees and see what the number is????
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post #14 of 49 (permalink) Old Aug 14th, 08, 10:44 PM
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Re: Engine timing

put the light on 34 and when it flashes it should flash on the 0 mark on the timing tab. CONGRATS!! Your doin pretty good!!!

AE2(AW) Harley Moody, USNavy
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post #15 of 49 (permalink) Old Aug 14th, 08, 10:46 PM
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Re: Engine timing

Quote:
Originally Posted by eatrican View Post
and should i check at 3500 rpm and see what number comesup and then subtract it from the 34 degrees and see what the number is????
Hey Ernie I think Dennis is telling you to hook up you timing light rev up the engine to 3500 rpm, now check your timing with with your timing light, move your dist. so it reads 34 degrees, tighten down your dist. let the rpms drop to idle and recheck your timing and see what it reads. Then subtract those two numbers to see what is your built-in dist. curve is. Dennis correct me if I am wrong.
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