Electronic ignition reduce pre-detonation??

Today in the parking lot two guys in an early '60s Barracuda pulled in and said hi. I mentioned to them that my new motor was having trouble with pre-detonation and they said that a friend of theirs had trouble with it and when he upgraded to an electronic ignition it made the problem much better. I fail to understand how that would make the problem better.

Anyone have any thoughts on this? I wanted to get a Pertronix kit anyway to get rid of my points, but will it improve my problem with pinging? As it stands I've got to retard the timing so far to make the thing run without pre-detonation that I can't rev it up where it wants to be as it starts missing and even backfiring from not having enough timing.

I'm running a 302 with '65 289 heads, which makes for lots of compression. I need this thing to run on pump gas, as it's my daily driver. I've tried advancing the timing, and it really screams. It pulls hard and really likes to rev, but I immediately retarded the timing again so as not to blow up my new engine from pre-detonation. I'm right on the boarderline of what will run on pump gas, so any little thing that will help would be great.

Reply to
Cory Dunkle
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I don't know what predetonation is but I'll guess you have a problem with 'ping' ..... changing the ignition curve will likely help but at a severe cost in power. You are not doing yourself any favours with the 289 heads. Upgraded ignition is always a bonus but you are looking for a bandaid fix for base engine problems. I think your preignition may be more from combustion chamber design than compression ratio, though ratio still plays a significant role in the problem.

While compression ratio is a major factor in building power, we can rob ourselves of that and more by backing the timing up to compensate for substandard fuels. You could try running the coldest plugs you can find but you run the risk of low rpm fouling..... a condition that surfaces at the most embarassing times.

Here's the perfect opportunity to find some nice aluminum heads that will give you 9.5ish compression and help light up your life.

Reply to
Jim Warman

"Cory Dunkle" wrote

he upgraded to an electronic ignition it made the problem much better.

I'm with you. Electronic ignition should have no effect on preignition. One thing that can help is a radical cam. The high overlap at low rpm bleeds off compression.

There are many techniques for dealing with preignition, e.g. coatings and porting. Here's a really good article on these techniques:

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180 Out TS 28
Reply to
180 Out

V'ger jma(NO SPAM)@snowcrest.net

1965 Mustang Fastback 2+2 Burgundy w/ Black Std Interior 289 ci 4v V8 A Code Dual Exhaust C4 Auto 8" Trak Lok Vintage 40 wheels BF Goodrich g-Force T/A KDWS 225/50ZR-16 tires Petronix Electronic Ignition components oem am radio and am-fm-10cd changer with 7.5" dvd player 120w kick panel speakers Built in San Jose on my birthday, May 10th ; )
Reply to
V'ger

Unfortunately I can't afford a new set of heads. I had these 289 heads already. I bought them for my '67 (289 car), which I have since sold. They only have a couple thousand miles on them. I figured I may as well use them. I know people have run 289 heads on 302s on pump gas, it's just a matter of getting the combination right.

For now though I need it to run. I noticed the other day that when I filled up with Mobil 93 is ran more poorly than with the Sunoco 93 I had in it before that. Just a thought...

Cory

compression.

Reply to
Cory Dunkle

What do you know about the existing distributor that's in it? I had a

69 Firebird 400 and it was getting almost impossible to find high enough octane gas to keep it running without the kind of problems you are describing. One day I figured I'd check the distributor and found that it was binding and not feasibly letting the vacuum and centrifugal advance move it or return it, and also found that the little springs on the centrifugal weights had gotten badly stretched and the weights were not even getting pulled all the way back in even when it was not running. I fixed those issues and it ran perfectly on normal hi-octane gas after that.

-- Jim '88 LX 5.0 (now in car heaven) '89 LX 5.0 vert '99 GT 35th Anniversery Edition - Silver Mods to date - Relocated trunk release to drivers side, shortened throttle cable, PIAA Driving lights.

Reply to
AZGuy

I don't know much about it. It's from a '67 289 I believe... Not sure what car it was originally in. It's probably got lots of miles on it. Pretty much everything else on the motor is new, so I really ought to rebuild the distributor. I think I'll take your suggestion and take a close look at the advance and springs. I think a re-curving it may be in order as well. Thanks for the tip.

Cory

Reply to
Cory Dunkle

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