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Old 07-21-2009, 05:15 AM
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help with timming

hello i have a 1984 firebird trans am it was a 350 with the edelbrock performance carb and perfermor intake i bought this engine from a guy and have no idea what year it is all i know its a 87-95 350 2 bolt main one peice mains seal the guy i bought it from said that when he got it they guy told him that he bored it 40 over and put it in his 88 camaro the engine code on the bell hosing is 14093638 and the serfix code is v0103arh.

im needing to set my timing for initial time a nd my total timing then ill beable to finde out what my igantion timeing curve is. so if anyone could help me out on this i woudl apprisiate it

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Old 07-21-2009, 07:19 AM
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Don't see an ARH code. Check your letters again then look here. > http://www.chevymania.com/partsid/su...fm?block=Small
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Old 07-21-2009, 08:10 AM
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Quote:
Originally Posted by 84trans-am
im needing to set my timing for initial time a nd my total timing then ill beable to finde out what my igantion timeing curve is.
The "rule of thumb" for a SBC is 36 degrees total mechanical and initial combined, an additional 10-15 degrees of vacuum advance, hooked to a manifold vacuum source.

Initial can be set at 8-12 degrees to start with, add to or subtract from this after you've determined that the total won't exceed 36 degrees.

If you do a search on this forum and/or google, there are thousands of posts and articles on timing.

Good luck.
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Old 07-21-2009, 12:36 PM
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thanks and on the block tab by my head it dose read v0103ARH
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Old 07-21-2009, 01:09 PM
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You have not stated which ignition system you are running. The factory distributor ignition timing is set to 0 degrees with the check timing connector dis-connected. These also do not have a vacuum advance canister. The ecm controls the spark timing, from information gathered by the PROM.

You may need to get a performance programed PROM, modified to a different timing curve from the factory settings.
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Old 07-21-2009, 01:16 PM
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i have a stock hei dis and my computer i beleive is been deleated from the car


reason i beleive it has been

AC been deleated went from the 700r4 to the th350 vac controled trans mechanical fan been replaced with a electric fan aftermarket fan relay.

if more info is needed i will post as needed not sure wha all neds to be put on here im new to engine building
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Old 07-21-2009, 01:22 PM
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When you say 'stock' HEI, is it the 'Coil in Cap' with a vacuum advance, or the 'externally' mounted Coil type? (with a coil wire)
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Old 07-21-2009, 01:23 PM
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coil incap with vacume advance
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Old 07-21-2009, 01:33 PM
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OK, now with that clarified, you can set the timing to 38 degrees "all in" around, or just above 3000 rpm.

This is set with the mechanical, and vacuum advances hooked up. The vacuum advance needs to be hooked up to a manifold vacuum source, so it can perform without detonating the pistons out of it.
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Old 07-21-2009, 01:48 PM
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now i have read that total timming shouldnt exceed 36 degrees but that was at 4000 rpm so at 3000rpms it would be 38?
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Old 07-21-2009, 02:01 PM
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Let me regress on my 'total' timing statement. This should be a combination of your base timing, and your distributors centrifugal advance, with your vacuum advance un-hooked and plugged. Set it's total to 38 degrees before 3000 RPM, and then hook your vacuum advance up to a manifold vacuum source, and test drive it listening for 'pinging'. It's safe to say there should not be any when set this way.
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Old 07-21-2009, 02:25 PM
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ok will give it a try my vacum advance is located on my dis so ill give this a try and go from there
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Old 07-21-2009, 02:45 PM
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"Before we get into the actual components, it's important to make sure the vacuum signal from the engine is correct. Most carburetors offer two different vacuum sources. The simplest is straight manifold vacuum, while the one you want for vacuum advance is called ported manifold vacuum. This source is designed so that the vacuum signal only occurs after the throttle blades are slightly open, which means there is no vacuum signal at idle. This ensures the engine idles on only initial timing and not the combination of initial and vacuum advance."

Ignition - Advance Basics
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Old 07-21-2009, 03:41 PM
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Let me add to my last post, that the manifold vacuum drops off when you get on the throttle, thus retarding the timing back. Once you steady the throttle movement, the manifold vacuum increases, and advances the timing back up. This is why under load you do not have over advanced timing, and a chance for pinging.

Also, your idle adjustment may need to be dropped.

I worked on a 1968 Ford F250, that was set to run 'ported' vacuum. It ran hot, and it came in for a tune-up/thermostat replacement.

I set it to run with a manifold vacuum source, and lowered the idle speed. It has run flawlessly for the last 3 years.
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Old 07-21-2009, 03:45 PM
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Quote:
Ignition - Advance Basics
Typical of "one size fits all" magazine stories, this article doesn't do justice to the vacuum advance portion of the equation.

While there are engines that will run fine w/the vacuum advance hooked up to ported vacuum (and the curve juggled to make it work), it IS NOT what's called for 90% of the time.

There's a lot to be said for running manifold vacuum to the vacuum advance can- it gives a better idle in most cases and helps carburetion tuning w/big cams, helps engines to run cooler and offers good off-idle response just to name a few advantages.
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