Head Gasket Thickness = ?
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From: Newton (Wichita Area) Kansas
Re: Head Gasket Thickness = ? (TrueBlue ChevyDude)
That's what I was afraid of.
I have Dart Iron Eagle heads with 64cc chambers. The pistons are hypereutectic flat tops that probably have valve reliefs (cc=?). Assuming that the top of the pistons are flush with the deck at TDC and the .039 gasket thickness my static compression ratio is 11.8:1! Yikes!
I'm hearing some detonation at WOT in 3rd gear with 93 octane. Now I know why. Base timing is 7 degrees.
Bought this longblock from Speed-O-Motive. They said the comp ratio was 10.5:1. Guess I shoulda checked their math.
Anybody got some aluminum 72cc chamber heads they wanna sell?
I have Dart Iron Eagle heads with 64cc chambers. The pistons are hypereutectic flat tops that probably have valve reliefs (cc=?). Assuming that the top of the pistons are flush with the deck at TDC and the .039 gasket thickness my static compression ratio is 11.8:1! Yikes!
I'm hearing some detonation at WOT in 3rd gear with 93 octane. Now I know why. Base timing is 7 degrees.
Bought this longblock from Speed-O-Motive. They said the comp ratio was 10.5:1. Guess I shoulda checked their math.
Anybody got some aluminum 72cc chamber heads they wanna sell?
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Re: Head Gasket Thickness = ? (jmr302)
ouch! Slap my 58cc L98 head on there and see what you get!!!
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Update
Dug up the invoice for my long block and made some calls. First of all my pistons are .060" over so the engine is technically a 388. The valve reliefs in these pistons, Silv-O-Lite H3426-060 hypereutectics, add 5cc of volume to the chamber. I also found that my head gaskets are in fact .039" thick and the gasket bores are actually 4.166".
Taking all that into account gives 11.2:1 compression which is still too high to run pump gas with iron heads. All the "experts" I've talked say that if these were aluminum heads I'd be okay. I think I'll still swap to 72cc chambers anyway if I get some new heads. That knocks it down to 10.3:1. I'm not willing to bump up the camshaft duration either. If anything I'd like to go with less duration (220/220 vs 224/230) and widen the LSA to 112 from 110.
I put 5 gallons of 110 leaded race gas in over lunch. There was probably 3 gallons of 93 unleaded in there. I hope that's not bad (no cats here). The car actually idles and runs a little smoother than before. SOTP meter says power feels the same.
We'll see what she runs at the strip tomorrow!
Taking all that into account gives 11.2:1 compression which is still too high to run pump gas with iron heads. All the "experts" I've talked say that if these were aluminum heads I'd be okay. I think I'll still swap to 72cc chambers anyway if I get some new heads. That knocks it down to 10.3:1. I'm not willing to bump up the camshaft duration either. If anything I'd like to go with less duration (220/220 vs 224/230) and widen the LSA to 112 from 110.
I put 5 gallons of 110 leaded race gas in over lunch. There was probably 3 gallons of 93 unleaded in there. I hope that's not bad (no cats here). The car actually idles and runs a little smoother than before. SOTP meter says power feels the same.
We'll see what she runs at the strip tomorrow!
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Re: Update (jmr302)
The lead will mess up your O2 sensor... run that tank out and change the O2's and you should be fine.
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Re: Update (jmr302)
:lol: :lol: :lol:
yeah, it's not too bad with the cheap O2!!!!
So with that gas you get no pinging now?
yeah, it's not too bad with the cheap O2!!!!
So with that gas you get no pinging now?
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Re: Update (Marcho Polo)
So with that gas you get no pinging now?
My Formato prom's total advance at WOT is only 33*. That's probably the only reason I've made it this far on 93 octane.
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Re: Update (DarkRose94)
by the time I get my spare LT-1 built, she'll have 11.8 to 1!! But the car is going to turn into a saturday night special.
Unfortunately my car has gotta be pump gas friendly. That means 91 octane around here.
You also have reverse cooling to help thwart detonation. You lucky dog.
[Modified by jmr302, 4:22 PM 11/8/2002]
