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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 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

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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