7.9:1 or 8.7:1 compression for blower motor on E85? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-12-2008, 09:37 PM
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7.9:1 or 8.7:1 compression for blower motor on E85?

well I'm about to put on the heads for the motor i'm building and i've been talking to some people saying that my 7.9:1 compression I was planning on will be too low for E85. I was under the impression that when running a blower the lower compression you can get the better off you are since there is a less likely chance of detonation and the more boost you can run. I have a new set of 75cc afr 195 eliminator heads that give me the 7.9:1 compression but if I sell these and get a set with a 64cc chamber that would bump my compression up to 8.7:1...and since I want to run the motor solely on E85 I wanted to see if it was really worth the hassle of selling these heads and buying a set of the smaller cc heads. The goals for the motor are basically to put enough boost into the motor as I possibly can safely...I was hoping for somewhere in the 700+hp range. Here is the setup on the motor

350 "010" casting block .030 over
o ringed
.040 copper head gasket
steel crank
eagle H beam rods with sps bolts
trw 2441 dished pistons (d shaped cup) 21.1cc dish
afr 1036 eliminator heads, 75cc chamber 195cc runner
summit hyd flat tappet cam, 234/244 .488/510 lift 114lsa
weiand 671 blower (will probably sent to a shop to get it tightened up and teflon strips)
holley 750 cfm E85 carbs
mallory dist
msd digital 6 ignition

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Old 10-13-2008, 02:47 AM
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I'm no blower expert, but I'd keep what I had at 7.9. I suspect you could run 1:1 on the cogs, creating 12 lbs of boost (14.5:1 final compression ratio) and be fine on E85. And 12 lbs certainly ought to make 700hp.
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