Setting deck height for 9:1 compression |
|
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. |
|
Setting deck height for 9:1 compression |
Chad911sc |
Dec 11 2024, 04:46 PM
Post
#1
|
Newbie Group: Members Posts: 21 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 |
Dec 17 2024, 09:46 AM
Post
#2
|
Newbie Group: Members Posts: 21 Joined: 24-September 24 From: Florida Member No.: 28,374 Region Association: South East States |
Awesome! Thanks Sean!
I’ve heard of Rev masters, but was unaware they did Type 4 work. I will def check out the VW shop in Winter park. It will go ahead and pull it apart and have it decked properly. I only want to do this once. Not sure how much metal work you need on your 914, I spent the last 10 months doing all of mine as well. I had to replace both of the longs due to rot from the engine bay eating through them. Also had to repair the Hell Hole, it was a major undertaking! I’m on the other side of it now, and just need to finish the motor and install the Tangerine racing transmission linkage. Hopefully smooth sailing after that. |
Lo-Fi Version | Time is now: 21st December 2024 - 08:07 PM |
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 ... |