Setting deck height for 9:1 compression Options

[Chad911sc]

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

[technicalninja]

I understand what you are saying about the deck parallel to the crank is super important, this is why I disassembled it. And I am grateful that you have taken the time to help me see that it was necessary to do so. When I place a level across the deck it only has a .003 of a sag in the middle where Raby says it’s thinner. Some 2.0s need that much, but it doesn’t necessarily mean mine will need that much material to be removed. I also know I will need a shim under each cylinder when I’m done to set it back to .040 for final height. My question was more in the line of does .025 -.030 sound about right to get the head chambers down to the desired cc’s for the ratio I want? And also is that amount of removal typical for a fly cut? I have read through hours and hours of posts and some people say you shouldn’t even fly cut a type 4 head. But how else could you make the pocket smaller to get your required result and keep your deck height at the desired .040?
I don’t want to beat a dead horse, but I am a painter by trade and each and every step matters, which make me a bit OCD.

Just saying "All will require XX amount of machine work" is short-sighted.

Saying "Most require XX amount of machine work" is perfectly fine.

I, personally, don't believe EVERYTHING Jake Raby says. I'd guess at times; he's kept some data "close to his chest" and allowed misinformation to flourish.

There's a BUNCH of stuff that I figured he'd be doing that tuns out he was.
In that engine video, at one point, he says "I'm using expensive Honda rods in everything now."
He WASN"T the first...
I believe The NASCAR guys did the "Will Honda rods work" jump well before him.

The whole Raby "proprietary cam shaft profiles" is sort of BS as well. Adding 20+ degrees to both intake and exhaust and THEN spreading the LSA to 112-114 degrees was a GM trick first. This ALONE got rid of the EGR valve in the second gen small block (LS1) in the late 90s...

I'd ALSO bet he's using asymmetric lobe profiles as well.
I haven't seen "asymmetric lobes" mentioned in ANY camshaft discussions regarding the T4.

Ninja rule (IMG:style_emoticons/default/ninja.gif)
Rules are for fools; wise men use good judgement.
Don't EVER believe everything you read, especially on the Internet.

By the time I had it as individual cases I'd KNOW how much I needed machined.

If you can get away with .015 you SHOULD as this solves the deck height issue.
I believe that you should have a gasket/shim between the cylinders and the case if nothing more than a carrier for sealant. I'd measure how thick the thinnest paper gasket is and have the machining slightly increased to allow for it.

To your question is .025-.030 enough to remove 6ccs.
I'm NOT sure. I have access (through my son, Bryan) to high end 3D scanning and CAD engineering software. A simple scan and CAD computation is the way I'd go now but I did find YOUR suggestion of fill the chamber up with XX amount of fluid and just LOOK at where the level is as an EXCELENT suggestion.

For this I'd want a fluid that had ZERO surface tension and Jack's suggestion of alcohol might be the very best fluid to measure this.

I'd worry about TWO things doing the measurement this way.
Is the head LEVEL and does the measuring fluid create a meniscus.
I'd guess alcohol will have a tiny one.
I'd also expect the alcohol to be an escape artist due to this feature.
I'd wipe a tiny amount of simple candle wax on the valve seats before assembly.

The way you will be going is the OLD SCHOOL way. Machine and then test, re-machine if required. This works FINE if you're the machine shop.

And it's not a requirement to be dead ass on at 9.0-1.
A CC difference will not alter the compression ratio that much.
Now, when you get above 10.5-1 it starts to get critical and anything above 13.0-1 requires accuracy at the less than 0.5 cc range.
Tenths of a CC has been HARD to hit for me.
Just making multiple volume checks on a single cylinder is hard to re-create with fine accuracy.

All important measurements I make at least three times and look at averages.
It's easy to be a tiny little bit off.

Hope this helps!

EDIT: In your case I'd talk with the machine shop. I'd say "I think I'm pretty close to flat, I want you to deck the registers TO THE MAIN BEARNG BORE and take off at least .XXX. If that doesn't clean it up, go further until it does and measure how much you had to remove in total."

That is the best way to skin that cat IMO.