Chamber Size???
Thread Starter
Racer
Joined: Feb 2008
Posts: 435
Likes: 0
From: Bulverde TX
Chamber Size???
Ok so im lookin to get some new heads on my 85 soon and i was just tryin to figure out if 58cc chambers would cause too much compresion for the bottom end and if 76cc chambers wouldnt have enough compresion. I would appreciate some help with this little hitch in my plans. Thanks ahead of time! 
Pro
Joined: Oct 1999
Posts: 515
Likes: 0
From: Nashua NH
I had that exact prob...put a set of 113's that were decked .010, and the starter wouldn't even crank it over! It was a $30 Autozone special, but the compression would be too high to run on pump gas anyway. I ended up going with AFR 0919's...65cc chambers, 180cc runners.
Team Owner
Joined: Sep 2001
Posts: 62,016
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Stock heads are 76cc on 85-86E, so that would keep you at the same CR. Going to 58cc would probably bump it to around 11:1 with a stock gasket, so you will be using premium.
85s bottom end wouldnt have a problem with it. With a colder plug you should be ok.
I would recommend going to a bit thicker gasket though, just to bring it into a safer zone.
85s bottom end wouldnt have a problem with it. With a colder plug you should be ok.
I would recommend going to a bit thicker gasket though, just to bring it into a safer zone.
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Now there is a plan.. keep on cruising.... sounds like $1200 would buy a dinner for two times ten or twelve at least so for the object of your affection + fuel for the hot hot and fun riding with the top off on a warm summer nights for a couple of months.. seems like a no brainer..LOL but that is from a mid fifties old fart not a drag racer young guy..LOL.. after 350 hp and 400 ft lbs just how much you going to put through street times on a public road without attracting the attention of every cop for 20 square miles???
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
I don't know what caused the problem reported by Mark85Vett, but it wasn't caused by the combustion chamber size.
RACE ON!!!
