EDIT: see Post # 8 for a two-fer of LIVE spreadsheets for both the STATIC compression ratio, and on a separate sheet the DYNAMIC compression ratio spreadsheets. Thanx, Joe_G !
________________________________________ _________

Since there has been some interest in my post of a DYNAMIC compression ratio chart (http://forums.corvetteforum.com/show....php?t=2167025), including "What if I get these heads with those gaskets?" questions, I'm posting a STATIC compression ratio chart.

LIMITATIONS: This is ONLY for stock LS2 engines with stock pistons protruding an assumed 0.006" above the block deck. This also assumes that the stock compressed GM head gasket is 0.052" thick, and that GM's published static compression ratio of 10.9 to 1 is correct. Another limitation is that the best information I have on the combustion chamber volume in the head is from Paul (Talon90) and that it is 64.5 cc.

Row 12 for Total C.C. Volume thus includes the volume of the clearance between the crown of the piston and the cylinder down to the top ring, and the volume of the space in the ring groove above and behind the actual ring. Row 13 for Net C.C. Volume corresponds to the published combustion chamber volumes by the head vendors, or as measured with a plexiglass plate and a burette.

The variables are the combustion chamber size in the HEAD, and the compressed gasket thickness. I am primarily interested in Cometic normally available thicknesses, so those are highlighted in yellow.

What surprised me (I should have believed all those posts!) is the significant effect that head gasket thickness has on STATIC compression ratio. I am a fan of tight (as in small) SQUISH (or QUENCH) dimensions, and Cometic 0.036" gaskets can provide this with a stock LS2 short block.

Used in conjunction with my DYNAMIC compression ratio chart, this can help you select a head and cam combination that will suit your particular needs. Perhaps Gannet will volunteer to host the live version of this chart along with his generous hosting of the Dynamic C.R. chart.

 

More GREAT info from Clevite Kid!!

Hmm. what's next, advice on bearings?

Thanks for all the help. I vote to have the SCR and DCR threads a sticky to help future generations.

 

. . . or at least listed in the C6 FAQ thread . . . .


Actually, the next spreadsheet, if anyone wants to see it, will be one to show the exhaust open and close points and intake open and close points if you know the duration, LSA and advance of any camshaft. I think I will also put in defaults for "lazy" lobes and "Jumpy" lobes (COMP XE-R) and estimate intake valve closing point at advertised duration, for doing DCR estimates.

 

I just realized I as a Supporting Member of the forum I can post up spreadsheets - so if you email it to me I'll post it up!

EDIT - hey, you're more supporting than me! You can post it up under attachments.

And I'm eager to get the next spreadsheet as well. This is very interesting information. If you could work some magic trig math and essentially advise people when they are flirting with PTV issues....well...folks might donate to your paypal for that info!

 

Truth is...these would be well appreciated and no doubt sticky'd on the other forum we're both on.

 

Let's give it a try:

Attached is a LIVE version of the STATIC Compression Ratio Spreadsheet. So you can CHANGE any of the assumptions, like if you have 10cc "ditches" in your pistons to clear the valves . . . .

Joe: you asked for it, you got it.

 

Worked like a charm!

I love this stuff...I'm just mathematically challenged. Ask my wife. Or my boss for that matter.

Thanks again!

 

Math I don't know so well...but I've got a few years of spreadsheets under my belt.

I took the liberty of adding the SCR and DCR as separate tabs on the same spreadsheet for people's convenience, with your implied permission.

You might want to post this up to the first post of your SCR thread for convenience!

 

I always use engine calculation software, but this is a nice effort.

rj

 

and it's free.

 

. . . and it is FREE

 

:eek that's kind of scary...

 

At least our C6 verts are different colors . . . .

 

Thanks - I downloaded it and it's an interesting spreadsheet.

 

Great thread. Some observations: Stock gaskets are .054" on the LS2 and I've never seen a stock piston not come .008" out of the hole.