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ignition timing question


tzagi1

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To make a long story short, The car runs like crap when the timing is set where it needs to be yet when advanced into the 20's it runs 10 times better, I checked the cam timing and it seems to be on the money. the cam is not factory but somewhere around a 262 grind from the 80's. for reference, the block is a 77 l28 with a e31

is a streched chain a suspect here?

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When you say "run" do you mean idling, or cruising, or getting on it?  And, define "crap".

Carbs, EFI, engine details will help also.  Not much to go on.

If cam timing is on the money then stretched chain is not likely.  The chain determines cam timing.

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I tried to make a long story short..

The car is a 71, dual webers, header, zx dizzy.

"runs" means overall, at stock timing (12-15 ish) poor idle quality, poor drivability, poor acceletation. It runs "normal" at 25 or so. as far as I know the short block is all original, the timing marker and the balancer were not changed or mismatched

"cam timing"- At tdc the cam sprocket marks allign with the tower marks. the chain is very tight.

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I would go through the usual confirming that all of the timing marks are correct.  Is piston #1 really at TDC when the other marks are zero'ed, or are you assuming that zero on the damper pulley is correct?

If you're at 25 degrees and you add in the typical 18 for full centrifugal advance you'd be at 43 degrees advance under acceleration.  You should be getting detonation and knocking.  Something's off.  Does timing advance when you rev the engine and the light is on it?

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There is no detonation, with this cam it has a turbo like personality, all the power is above 4k, from there it pulls like a fright train.

I'll double check everything, I guess its possable for the outer ring of the ballancer to turn on the inner.

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There is no detonation, with this cam it has a turbo like personality, all the power is above 4k, from there it pulls like a fright train.
I'll double check everything, I guess its possable for the outer ring of the ballancer to turn on the inner.


And if it’s done that then it’s time for a new one! ;)

I’m with Zedhead - my initial thought too was timing marks are off.

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https://photos.google.com/search/_tra_/photo/AF1QipN9IidI9bnZtliZmPggTCwn227HvHlYxZYYblnJ

https://photos.google.com/search/_tra_/photo/AF1QipMCB8E7dYOsA1C4j6eH-Zzh4OhpBGHJ9zeDxel3

https://photos.google.com/search/_tra_/photo/AF1QipNy58sgEEN3ERs4pItuXXuQZVYbQVzH_cZeI2Cuhttps://photos.google.com/search/_tra_/photo/AF1QipOYCUelWJeSF9uOY-UeGBIyHIZ6hCBLfjVE2dHuhttps://photos.google.com/search/_tra_/photo/AF1QipOAgvGx4eV2PbxE3OP_YzII_egY65Eq0xIQeJne

The lack of detonation is exactly what bothers me, I cannot advance it enugh to cause it to detonate espacially with the garbage fuel we have today., the pics were taken at tdc and the tdc was verified, the piston starts moving down slightly past tdc. the timing marks are right on.. the cam timing marks are confusingbut maybe I'm not reading them correctly., by eye balling the cam it looks to be advanced to me but it could be an optical ilusion as well. I do have another complete long block that is all stock, tommorow I'll pull the valve cover and set it on tdc to compare the cam timing. I was thinking about retarding the cam to make the car more street friendly, right now its a total huligans car.

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Your links don't work.

What else can you say about the engine?  Pistons and head combination, for example.  I wonder if a low compression engine runs better with more advance.  Seems like it might since the pressure isn't there to drive the combustion.  Maybe you have dished pistons with a P79 head.

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Stock 77 short block with a E31 head, shaved too, (cam towers spacers included) should have higher then stock compression.

The links work for me..any idea of a hosting service? all the old sites I used in the past are gone.

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