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Old 08-08-2010, 05:01 PM
Argess Argess is offline
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Sounds of detonation when exhaust is too loud

I've had some ignition troubles since last year (with my 428 Ford), due to a barely adequate ignition system that wouldn't do the job after I did a rebuild and the compression got bumped up a bit. Finally got that sorted out and now that I have no misfires, I have a question on timing....specifially timing advance.

When I was playing with it last year, I found the engine fighting me at 28 intial and 38 max, and wound up with 20/38 which seemed good. I seem to remember 24/38 was also OK, but kept it down to 20/38 for safety in the low end. Took away all of my idle and low rpm acceleration problems.

After my igntion changes to obtain a stronger spark, I'm not so sure I can live with 20/38. At 20/38 I have a very snotty sounding engine that really barks...almost a crackle when you give it a bit of throttle ( I like it!). And this is coming out of the exhaust. The engine sounds fine otherwise. I don't think I can ever hear a "ping" or a "knock" from the engine with sidepipes.

So I tried bumping the ignition back. Didn't fiddle with the max this time, but just set it back from 20/38 to 16/ 34. Power feels the same...er....I think, but no crackle or bark. Idle is OK, but there's a small bog sometimes when I accelerate. No doubt 18/36 would be a compromise.

I'm trying to figure out if the snotty, crackle/bark is a good thing or a bad thing....i.e. might be light detonation. If you watch this you-tube video, you can hear some of the cars have this crackle, and some don't.....hard to listen and ignore the tire squealing though....LOL

http://www.youtube.com/watch?v=qqkxu8TsJfw

Next step is to try to capture an audio for both settings and post it...wait....before that, I need to try lugging it in 4th or 5th at around 1500 rpm and listen for ping/knock.

I`m really paranoid about detonation as I broke a piston before due to my balancer outer ring slipping and inadvertently setting the timing wrong. New balancer now and I double checked it for accuracy.

Info: Cam is a Crane Fireball 294 and CR is suposed ot be 9.5:1, but after the block deck and cyl head re-surfacing, it may be a bit over 10:1. I know cranking pressure went up about 7%. High test around here is 91 octane.
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