thafaz

Gents,

I finally got my car together.....details in my signature.

Runs great....scares me enough that I only matted it once. First tank through was 28 mpg...took a month and a half of weekend and evening driving to get though it.

It was hot last week and I took it out; filled it up and was coming back. I decided to lean on it in 4th gear....started to ping!!! Not good!!! I dropped a gear, hit it, no problems.

I asked my mechanic buddy about this....he looked into it and says my compression is too high..14102187 58cc heads w/ flat tops works out to 10.5 - 11 compression. That, combined with premium from Mr. Gas (probably not the 94 octane I first filled with) and the weather (38C) resulted in the pinging.

Are there any long term affects on the short block due to high compression? I like the way it runs, but don't want to grenade it.

Faz

InfernalVortex

iTrader: (4)

You'll blow apart pistons, especially hypereutectics like the KBs, and the engine may still run but you'll lose huge amounts of compression on each piston that crumbles. There will come a point, sooner or later, where the damage is bad enough it wont run at all.

http://www.google.com/search?client=...N&hl=en&tab=wi

Why did you stay with the swirl ports?

thafaz

Got the heads from ebay a while ago, they came with 1.9/1.6 valves installed....chose the cam (260h) to match and to limit the power to keep the 5 speed alive. When I started building the engine, I realized the rings were loose...sent it in for a rebuild. They installed flattops......oops!!!!! If I had to so it again (and it looks like I will), I would have bought an Edelbrock power pack and been done with it.....

Sonix

iTrader: (1)

Did they deck the shortblock? know what the quench is?
With 58cc heads, and flat tops --- and your short cam - that is a lot of compression.

You can pull some timing for now, don't ever lug it around, etc. Keep it full of high octane fuel (94 if you can find it).

The ideal situation is to simply swap heads. Vortecs with a vortec carb intake would work well, or aftermarket 64cc heads would also work.

thafaz

I think 64 cc heads will be the way to go.....they've come down in price substantially since I bought the last set.

Much thanx for the input.

Faz

InfernalVortex

iTrader: (4)

Theres a lot more to head choice than chamber size and valve size.

Get a decent casting. If you want stock heads, get 906, 062, 113, or 083. There may be others but the ones I listed are fairly common. 906/062 are Vortec. Any other number IS NOT VORTEC. You'll need a new intake to fit them.

five7kid

iTrader: (14)

A mild cam and high compression is a recipe for detonation.

Those really are rotten heads. Sorry to hear you paid real money for them.

As stated, larger chamber heads that flow better are in order. This head/manifold kit would wake up your engine and eliminate the detonation problem:
http://sdparts.com/details/scoggin-d...ter/sd8060akit

thafaz

Hi 5/7,

Could you recommend a set of aluminum heads that would bolt on without replacing the intake?

Faz

Sonix

iTrader: (1)

Summit makes an inexpensive set of aluminum heads. 64cc chambers, ~200cc intake ports IIRC. I think they are ~$800 assembled for the pair. I remember thinking they were a screaming deal.
I would point to those as the best bang for the buck, personally.

thafaz

Hey Sonix,

They've gone up....

http://www.summitracing.com/parts/SUM-162111/

The bummer with Vortecs is the expensive intake replacement.....for $1200, I'm only getting $700 in performance increase....I figured $800 would get me aluminum that would at least be lighter. Then again, might end up right back where I am now....mismatched combo.

What about these?

http://www.jegs.com/i/Patriot-Perfor...ductId=1250658

Faz

Sonix

iTrader: (1)

Or of course you can look on this forum for people selling used aluminum heads, factory or aftermarket, your local classifieds, or racingjunk.com or other sites like that.
ie;
https://www.thirdgen.org/forums/engi...der-heads.html

Those patriots look like they'd do the trick too.