Thread: How much octane additive w/ a blower & 10:1 compression???

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......Hello Everyone, I hope all of you folks had a Happy Turkey Day!!! I've got an idea but wanted to run it by everyone before acting on it. I have a 413 small block Chev in my '32 Ford. 10:1 compression, AFR 195 heads, cam is 230/236 @ .050" w/ .518 lift on a 110 LSA. If I put an 8:71 GMC on it, is it feasible to just use octane boost instead of race gas to keep it from pinging, etc? And if so, how much would I need? The local gas is 91 octane. Also, from my understanding a large cam bleeds off compression so why not just put in a huge cam to lower the compression??? Thanks Bill

Originally Posted by billlsbird

......Hello Everyone, I hope all of you folks had a Happy Turkey Day!!! I've got an idea but wanted to run it by everyone before acting on it. I have a 413 small block Chev in my '32 Ford. 10:1 compression, AFR 195 heads, cam is 230/236 @ .050" w/ .518 lift on a 110 LSA. If I put an 8:71 GMC on it, is it feasible to just use octane boost instead of race gas to keep it from pinging, etc? And if so, how much would I need? The local gas is 91 octane. Also, from my understanding a large cam bleeds off compression so why not just put in a huge cam to lower the compression??? Thanks Bill

Bill,what pistons are you running?
Is this engine 4.155 bore x 3.80 stroke?

To get started check out

http://www.blowerdriveservice.com/techcharts.php

That's a lot of huffer for a 413. Wouldn't a 6-71 be a better fit? Running around on race fuel sucks, been there and done that. Realistically you probably won't be able to run more than 4-6 psi boost.

Kitz

Hi Eric, no it's a 4.185 bore & a 3.75 stroke with forged aluminum pistons. Thanks, Bill

Don't do it. You will not be happy with the results. A blower engine needs to be designed from the bottom up if it is going to run efficiently. Octane boost will not raise your octane enough to compensate.

Originally Posted by billlsbird

Hi Eric, no it's a 4.185 bore & a 3.75 stroke with forged aluminum pistons. Thanks, Bill

With that over-bore it will be very hard to keep head gaskets in it.
My advice would be put in a larger hyd. roller cam or a smaller mech. roller cam.
With the right cam and those heads you will be over the 500 hp area.

.....Thanks, I was afraid this is what I'd hear... BUT, better to hear it & not do it than to do it & be sorry! .... My HP is 460 now & TQ 499, so I guess with a bigger cam I'd pick up 40 + HP? And my Torque converter has a true stall of 3000 so it'd handle a bigger cam.... I now have a Edelbrock Performer RPM Air Gap manifold w/ a 750 double pumper. Would you recommend a Victor Jr.??? THANKS, Bill

Originally Posted by billlsbird

.....Thanks, I was afraid this is what I'd hear... BUT, better to hear it & not do it than to do it & be sorry! .... My HP is 460 now & TQ 499, so I guess with a bigger cam I'd pick up 40 + HP? And my Torque converter has a true stall of 3000 so it'd handle a bigger cam.... I now have a Edelbrock Performer RPM Air Gap manifold w/ a 750 double pumper. Would you recommend a Victor Jr.??? THANKS, Bill

Yes,a Victor will help in the upper rpms.

....Thanks