Offshoreonly.com

Offshoreonly.com (https://www.offshoreonly.com/forums/)
-   General Q & A (https://www.offshoreonly.com/forums/general-q-20/)
-   -   compression question (https://www.offshoreonly.com/forums/general-q/93360-compression-question.html)

88 MACH 1 12-28-2004 10:06 PM

compression question
 
I'd like to lower my compression so I can run a blower. Is it possible to add a spacer between the head and block? Where can I get such a spacer? If I install a spacer, will everything be OK? TIA

mikes280 12-28-2004 10:51 PM

Re: compression question
 
No,no,and No

GPM 12-28-2004 10:59 PM

Re: compression question
 
I had a set of Brodix heads CNCed with 135 cc chambers to do just that,
it wasn't any big deal. Dropped 1 point, not sure how far you want to go.

Reed Jensen 12-29-2004 12:28 AM

Re: compression question
 
Go with different pistons....

Raylar 12-29-2004 01:02 AM

Re: compression question
 
You need to post some info on your motor to answer your question properly. What motor do you have? Whats the existing compression? Do you know the thickness of your existing
head gaskets? What kind of a blower do you want to run? How much boost do you want or need? Whats your existing HP and what HP are you shooting for?
Dumb Questions are easier than dumb mistakes!
Ray @ Raylar

88 MACH 1 12-29-2004 05:30 PM

Re: compression question
 

Originally Posted by Raylar
You need to post some info on your motor to answer your question properly. What motor do you have? Whats the existing compression? Do you know the thickness of your existing
head gaskets? What kind of a blower do you want to run? How much boost do you want or need? Whats your existing HP and what HP are you shooting for?
Dumb Questions are easier than dumb mistakes!
Ray @ Raylar

454 BBC 10 to 1. Stock head gaskets. Looking at a 174 blower. running 527.94 hp now. Just looking for some more power. Thanks for the replies

mcollinstn 12-29-2004 08:27 PM

Re: compression question
 
174 blower sort of runs into an efficiency wall around 550hp. Can't generate much boost at those flow rates without whipping too much heat into the charge.

A 454 with 119cc chambers, .020 deck, .038 gasket, and 30cc popups will net a 10:1 static CR. To drop to 8:1 CR, you'd have to add a spacer 1/8" thick tween the heads and block. Obviously, this would cause issues (the bolt holes and ports on the intake manifold will no longer match up - custom pushrods will need to be used - studs would be necessary for the heads, as std head bolts would no longer work - and you would have NO squish area in the combustion chamber, to name a few of the more obvious barriers to doing this).

Do yourself the biggest favor imaginable:
don't use spacers on the heads
do get a set of 8:1 flattops
notch the bores for flow under the valves
and run a 250/256 blower at 5psi.

Gary Anderson 12-30-2004 09:33 AM

Re: compression question
 
I'm with mcollinstn.
If you lower compression and add a 177 blower, you'll go from a 527hp NA motor to a 550hp SC motor. You really spin those little blowers to get more than 5psi on a 454.

88 MACH 1 12-30-2004 06:07 PM

Re: compression question
 
Thanks for the input. I guess now just build a 502 BBC and sell the 454.......... :D


All times are GMT -5. The time now is 08:13 AM.


Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.