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> Setting deck height for 9:1 compression
Chad911sc
post Dec 11 2024, 04:46 PM
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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
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zig-n-zag
post Jan 17 2025, 09:19 PM
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Type 4 rocker arms have different ratios for the intake and exhaust. Intake ratio is 1.36 and the exhaust ratio is 1.3.

A matched set of connecting rods can vary in length up to 0.010” due to the manufacturing process, but all the rods in the set will be the same length.
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Chad911sc   Setting deck height for 9:1 compression   Dec 11 2024, 04:46 PM
Chad911sc   I have my short block built and I’m ready to set...   Dec 11 2024, 04:49 PM
technicalninja   You're on the right track. Altering the cylin...   Dec 11 2024, 05:36 PM
930cabman   top of then cylinders MUST be in plane with each o...   Dec 11 2024, 06:24 PM
Shivers   You need to raise the compression, right? If so yo...   Dec 11 2024, 06:29 PM
cgnj   Was your case decked? Did you check the volume of ...   Dec 12 2024, 12:14 AM
Chad911sc   Thanks for the replies! I did cc the heads and...   Dec 12 2024, 09:38 AM
rfinegan   Yes Get your deck hight sorted first... Then set t...   Dec 12 2024, 10:31 AM
technicalninja   Thanks for the replies! I did cc the heads an...   Dec 12 2024, 11:08 AM
930cabman   Thanks for the replies! I did cc the heads a...   Dec 12 2024, 01:27 PM
Chad911sc   Very true!! I actually watched all of Ian...   Dec 12 2024, 02:05 PM
Chad911sc   Spent the day on your recommendation to resurface ...   Dec 14 2024, 02:10 PM
Jack Standz   This should work fine for a shade tree mechanic re...   Dec 14 2024, 03:13 PM
iankarr   All great advice. Glad you found the videos helpfu...   Dec 14 2024, 05:19 PM
Jack Standz   I'd assume that your decks aren't flat, no...   Dec 15 2024, 11:50 AM
Jack Standz   One more thought. Raby in this video says that g...   Dec 15 2024, 12:19 PM
technicalninja   :agree: Jack is right! Someone (maybe Jack ...   Dec 15 2024, 02:33 PM
Chad911sc   Thanks for all the replies! Wish I would have ...   Dec 16 2024, 02:39 PM
Superhawk996   They were both at .053 before the lapping and now...   Dec 17 2024, 09:21 AM
seanpaulmc   A guy local to me rebuilding his 912 built up a 22...   Dec 17 2024, 07:50 AM
Chad911sc   Awesome! Thanks Sean! I’ve heard of Rev ...   Dec 17 2024, 09:46 AM
seanpaulmc   Okay, so where is the build thread? As you may no...   Dec 17 2024, 06:52 PM
Chad911sc   So I have the case halves back apart and now just ...   Dec 18 2024, 01:17 PM
Chad911sc   I think I figured it out with my daughters help…...   Dec 18 2024, 01:32 PM
Chad911sc   This is the 74 914 that it is going into…one of ...   Dec 18 2024, 01:37 PM
Chad911sc   Question…. When I get my heads fly cut, it looks...   Dec 18 2024, 09:59 PM
technicalninja   On a bone stock 73 2.0l the depression in the head...   Dec 18 2024, 10:50 PM
Jack Standz   So I have the case halves back apart and now just...   Dec 19 2024, 07:15 AM
Chad911sc   I understand what you are saying about the deck pa...   Dec 19 2024, 08:41 AM
technicalninja   I understand what you are saying about the deck p...   Dec 19 2024, 10:37 AM
Jack Standz   I, personally, don't believe EVERYTHING Jake...   Dec 19 2024, 12:15 PM
Chad911sc   Thanks guys! Now worries, no offense taken. Li...   Dec 19 2024, 01:12 PM
rfinegan   duplicated   Dec 19 2024, 02:27 PM
rfinegan   Am I missing something... Machine the case to the ...   Dec 19 2024, 02:33 PM
technicalninja   The case line SHOULD be centered but... Where it ...   Dec 19 2024, 03:20 PM
rfinegan   great follow up. Thanks for the information   Dec 19 2024, 03:34 PM
technicalninja   The 911 is COOL! What's that white car in...   Dec 19 2024, 04:26 PM
Jack Standz   Chad, Awesome looking 911SC. You should be worki...   Dec 19 2024, 08:33 PM
Chad911sc   The 911sc is actually a Max Moritz built Porsche. ...   Dec 20 2024, 09:11 AM
technicalninja   Let's see here... 500 hp Vette Nice NICE NICE...   Dec 20 2024, 01:26 PM
Chad911sc   Trust me! That was my first thought when purch...   Dec 23 2024, 10:45 AM
Chad911sc   Talked to the machine shop today and they ended up...   Dec 24 2024, 12:47 PM
technicalninja   Will .010 give you the deck height you needed? I ...   Dec 24 2024, 01:02 PM
Jack Standz   Merry Christmas everyone! Well, you'll fi...   Dec 24 2024, 03:01 PM
technicalninja   I always check deck height of ALL of the pistons. ...   Dec 24 2024, 03:41 PM
Chad911sc   Merry Christmas Everyone!! After I had han...   Dec 25 2024, 09:35 AM
technicalninja   Will .010 give you the deck height you needed? I...   Dec 25 2024, 10:09 AM
sixnotfour   OMG...   Dec 25 2024, 03:24 PM
porschetub   OMG... :agree: ,hopefully for the same reason ...   Dec 25 2024, 08:29 PM
technicalninja   I have a disease….. Project mania…lol Love to...   Dec 26 2024, 10:19 AM
emerygt350   No kidding. I think it would be fun to try and bu...   Dec 26 2024, 03:37 PM
Chad911sc   That 2110cc type 1 engine was built by Sid Collins...   Dec 30 2024, 08:52 AM
technicalninja   I did do a deep dive into turbo T4s after seeing y...   Dec 30 2024, 09:47 AM
Chad911sc   I do remember that my boost exhaust gate was set a...   Dec 30 2024, 12:18 PM
technicalninja   Chad, I wouldn't spec a "draw through...   Dec 30 2024, 12:45 PM
Chad911sc   Ok…. Everything is back together after the deck ...   Jan 9 2025, 11:30 AM
technicalninja   On a single bank the jugs have to be level with ea...   Jan 9 2025, 11:55 AM
Chad911sc   10-4 That’s what I was hoping to hear… In my p...   Jan 9 2025, 12:41 PM
technicalninja   I wouldn't worry about flawless balance on any...   Jan 9 2025, 12:52 PM
Chad911sc   Ok…sounds good! I’ll leave it alone and mo...   Jan 9 2025, 12:57 PM
technicalninja   Important point! Verify camshaft base circle ...   Jan 9 2025, 01:03 PM
Chad911sc   It is a new Web cam that is advertised as base cir...   Jan 9 2025, 03:57 PM
technicalninja   ALL camshafts should be "base circle concentr...   Jan 9 2025, 04:29 PM
Chad911sc   I’m off this weekend and will be back at it. Can...   Jan 9 2025, 07:19 PM
technicalninja   Drop dead simple... Set up dial indicator so it r...   Jan 9 2025, 07:48 PM
technicalninja   Just had a post from Jack Standz in my base circle...   Jan 10 2025, 04:17 PM
GBX0073   Just had a post from Jack Standz in my base circl...   Jan 18 2025, 01:13 PM
Chad911sc   You can get those custom cut aluminum push rods fr...   Jan 16 2025, 04:31 PM
zig-n-zag   Type 4 rocker arms have different ratios for the i...   Jan 17 2025, 09:19 PM
rfinegan   let us know... CB has a set that look tempting ht...   Jan 18 2025, 06:19 PM
rfinegan   or this one... https://www.cbperformance.com/produ...   Jan 18 2025, 06:20 PM
GBX0073   Rob Great Find your always a great reference for ...   Jan 19 2025, 12:29 AM
Chad911sc   Stateside tuning has these available now. It only ...   Jan 23 2025, 04:17 PM
Chad911sc   Thanks Zigzag!!! I feel better now tha...   Jan 23 2025, 04:21 PM
Chad911sc   I ended up taking .002 off the top of the piston t...   Jan 23 2025, 04:36 PM


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