I'm building a fresh 355 with AutoTech flatop pistons, 7A stock heads lightly resurfaced (5mil), (3 angle, valve guides, high end seals) and .60 Felpro gasket (uncompressed). What would be my approximate compression and would the XE262 cam be a detonation problem?

 

Ill take a stab at it. Ill guess 9:1. Need more info to tell for sure what it is. That was just my guess

Use this calculator http://www.csgnetwork.com/compcalc.html

 

I get 11.5, I screwed up somewhere...thought it would come in somewhere in the high 9's;

 

Well you got some of the numbers off. Stroke is wrong and are your heads really 73 cc? Here are some things you have and you need to fill in the blanks.

4.087 Bore
3.385 Stroke
What CC head?
.020 deck
.040 gasket (compressed)
4.250 Gasket bore



I get 9.91:1 with your numbers and a 68cc head, and 9.4 with a 73 cc head.

 

Thanks, I confused a 455 stroke;

...is .020 a stock deck? my block and rods are stock.

...i'm using 7A heads which I believe are 68cc.

 

Yu have to measure your deck. It depends on your piston pin height.


Im not sure what cc 7As are. 7a's around 68cc.

 

yeah this is a 7a ('72 350R), I checked my compression distance on the new pistons before installation and they were identical to my stock dish pistons (mid pin to top).

I'll go with the 9.91...any issues with the mild XE262 cam?

Thanks for the good response!

 

Yes, it's too small for 9.9:1. You need more off the seat time. If you want a little tone and want no problem with pump gas then an Erson TQ40 would be perfect.
Also I've done a custom Lunati as well. Don't use a VooDoo though, that'll be worse than the XE.

Jmo.

 

Thanks, for the cam feedback, unfortunately I've already installed an XE262 with matching lifters and springs...I wish I'd read some of your posts before...I value your opinion. Now that I'm stuck with the comp cam, aside from lack of optimum performance, would I have any catastrophic issues with this combo?

 

Milled down the heads will probably have a 67cc. Not too crazy to make a difference. I'm thinking 9.2, maybe upto 9.5 if your lucky but I'm thinking down in the low 9's

 

Depends on where your compression ratio really is.
I posted something earlier for someone else on the same topic, doing things backwards imo. I guess maybe I do them wrong.