Compression Ratio

Advokat · Post by **Advokat** » Wed Jun 26, 2002 4:39 pm

I have seen lots and lots of posts about this subject, but there does not seem to be a clear answer.

I am building a 1904 (74 x 90.5) Heads will be dual spring 40 x 32 w/p&p. Carbs. are Dellorto 36's. The cam is a Web 119, stock rockers-1.1:1. Kymco flanged super-header w/a single quietpack.

This is to be a street car that is not going to the drag strip. I wanted some more torque and power, but wanted it to remain very driveable.

The guy doing the heads suggested c/r in the 7.8-8.2 range. (I believe some of this suggestion had something to do with the fact that I am using heater boxes) With all of that said, what do you all think a good number would be with this combo.?

Thanks

[This message has been edited by Advokat (edited 06-26-2002).]

Searoy · Post by **Searoy** » Wed Jun 26, 2002 6:40 pm

I have seen lots and lots of posts about this subject, but there does not seem to be a clear answer.

How true.

Have fun. Sounds fine to me. A little odd doing all that work and spending all that money on 90.5x74 when a 94x78 costs practically the same.

------------------
*** Teach a Man to Fish ***
Darth Searoy

"I tend to lean toward a tighter gap and a
looser skirt....a little slap never hurt." -- Joe of the West

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Wed Jun 26, 2002 6:53 pm

The reason that there are so many different opinions is because of testing and opinions from the early days...there must be a happy medium of cam/valves/CR and port work to make it all work out......

I'm not gonna post a recommendation here, email me if you want my views, as all it does here is start a war, especially since it defys most people rules.

Gib · Post by **Gib** » Wed Jun 26, 2002 9:45 pm

Advokat,
Curious. Did you mean 40 x 35.5 valves in the heads or are you going with 40 x 32's? I've heard that they are not to good in any application other than stock because the smaller exhaust valve restricts flow causing tuning and heat problems.
Gib

Advokat · Post by **Advokat** » Thu Jun 27, 2002 3:27 pm

Gib, you read right, 40 x 32. I got these from AJ Simms and he understood my setup and what I wanted. Apparently, this is a very popular configuration for those of us that still need to use heater boxes.

I thought what you did, but AJ advised that there should be no problems.

Gib · Post by **Gib** » Thu Jun 27, 2002 4:12 pm

Advokat,
Cool, just checking.
Gib

teacherguy · Post by **teacherguy** » Sun Jul 21, 2002 1:56 pm

Advocat-

I'm building a similar engine with 34ICT's instead and was wondering about the heads and all. Where can you get them and what are thos heads based off of: 040, 041, etc? Thanks for the info.

[email protected]

Advokat · Post by **Advokat** » Sun Jul 21, 2002 5:08 pm

Teacherguy,

They are AJ Simms heads using an 043 casting. There is a website at www.lowbugget.com

Good luck

bedlamite · Post by **bedlamite** » Mon Jul 22, 2002 3:36 pm

One other question, why dual springs? Do you really plan on reving over 6000RPM with stock rocker arms? Get a good quality set of single springs and your valve train will last much longer.

To answer your original question, I would keep it under 8.5:1 for a street car running pump gas.

Advokat · Post by **Advokat** » Mon Jul 22, 2002 3:52 pm

Well, two things. I am going to use stock rocker arms, but go with solid rocker shafts.

I originally was going to go with the single springs, but AJ threw in the duals for no extra cost. So, I took them.

Thanks.