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Author Topic:   compression??
jello
Member
posted November 14, 2004 02:01 PM
How much power would I gain if I got my
compression up from 130 per cylinder to
175 per cylinder? And is it true that
your camshaft helps determine your compression?? Sorry if that is a stupid
question, but I am just not real motor savvy-
yet


engineman
Member
posted November 15, 2004 08:59 AM
you must run a Sims

yes the camshaft affect's the cranking compression. and thats putting it mildly.

------------------
Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


jello
Member
posted November 15, 2004 02:44 PM
yes, I run a sims car. So are you gonna
clue me in?? Am I giving up a ton by having
that low of a compression reading? I could
still deck the block and mill the heads and
run the thin head gaskets and get another
cam if necessary. Just wondering if it is
all worth it.

thanks

engineman
Member
posted November 15, 2004 07:36 PM
yes it is worth it IMHO to get the compression as high as you can. I would cut everything as much as you could (leave around .030 for quench)

I would do this first, then you can move the cam timing around,but where it makes the most compression, it may not make the most power.

you can change the cam to one with a tighter LCA, to but when you do this you will loose Vac.
other things affect compression,duration,intake closing point..ect...
so call a good cam company to help you with the cam you need.

------------------
Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


jello
Member
posted November 15, 2004 08:28 PM
I just recently put a cam in my car with a
106 lobe center and the vaccuum is not so
good. I have tweaked and tweaked with
timing and valve lash to bring the vac.
up to 12. I am considering getting some
of those rhoads lifters to help the vac.
Over the last couple of years I have run
some pretty junky motors, but I have had
good success on dry tracks. I am beginning
to think my days of going fast with ****py
motors is pretty close to done. So I am
trying to become a little smarter with the
powertrain.

thanks for your help,
Billy

p.s. I built and sold a car to a guy in Greenville. Maybe you built his motor?

engineman
Member
posted November 15, 2004 08:35 PM
who was it? I build the motors for the 69 Larry Killian, and 4 car Jimmy Day, and a few others that run around here, who did you sell the car to?

------------------
Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


sleepy 1h
Member
posted November 16, 2004 06:17 AM
I agree with engineman, You want as much compression as your engine can take(there is a limit) are you on gas or alky? with gas I wouldn't go over 14 to 1,with alky up to 17 to 1. Depending on the head you use (if its a stock prodution head) you don't want to surface it to much (heat and cracking),however you can deck the block down to where the piston comes out of the hole no more than .005 and be pretty safe. sleepy