![]() |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
![]() |
Chad911sc |
![]()
Post
#1
|
Member ![]() ![]() Group: Members Posts: 80 Joined: 24-September 24 From: Florida Member No.: 28,374 Region Association: South East States ![]() |
I have my short block built and I’m ready to set my deck height. It’s 96mm bore with stock 71mm factory crank. This is a 2.0 2056 build. I have a Web 86a cam calling for approx 9:1 compression. I have 60cc heads with 3cc valve reliefs on my flat top pistons. If I plug all this into the calculator, I get 8.3:1 for my compression ratio if I set the deck height to .040 inch
After I set up the piston on the rod and bolt down the cylinder to the block, I get .053 inch from the piston to the top of the cylinder. My question is, what is the best way to proceed to get the 9:1 ratio with at least .040 inch total deck height. I am thinking that if I take off 6 total cc’s from the head, that will leave me with 54cc heads with the 3cc valve pocket = total 57cc’s. Bringing me now to the correct 9:1 compression ratio with the .040 inch deck height. If I am in the right ballpark, this means I need to have my heads fly cut….correct?? If this is correct, how do I go about calculating how many thousands of an inch do I need to have removed by the machine shop to remove 6cc from the head? I obviously will need to remove at least .013 inch total deck height get to my .040 goal, and that’s with no shims or head gaskets being used. Thanks for your time, Chad |
![]() ![]() |
Chad911sc |
![]()
Post
#2
|
Member ![]() ![]() Group: Members Posts: 80 Joined: 24-September 24 From: Florida Member No.: 28,374 Region Association: South East States ![]() |
Question….
When I get my heads fly cut, it looks like I need to cut about .025 out to get to my target of 57cc’s total. Does this seem reasonable? 60cc heads with 3cc valve reliefs=63cc. Take away 6cc from the heads looks to be about .025-.030 cut needed. When I looked at the head surface there is a raised outer circle of aluminum that will need to be milled as well so that it will mate with the head surface. Am I on the right track?? Flying up to Indianapolis in a couple days, taking the heads and the case with me to a shop up there that I know well. Spend Christmas with the family and get my machine work done at the same time! Kill two birds with one stone (IMG:style_emoticons/default/beerchug.gif) Thanks again guys for the help….super appreciated! The black line is the amount that needs removed. The other red arrow is the raised aluminum area I was speaking of needing removed to let the cylinder mate with the surface of the head. Attached thumbnail(s) ![]() |
![]() ![]() |
![]() |
Lo-Fi Version | Time is now: 9th May 2025 - 10:04 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |