Question, what is the compression ratio of 9.1 pistons with 67CC heads in a 350 engine??

 

do you mean they were 9.0:1 with a 76 cc head and you want to know what the c.r. is with a 67 cc head? if so, your looking at about 9.7:1 compression.

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85 IROC 350 11:1keith blacks,.555lift erson roller cam,1.5 crane roller rockers,edelbrock intake,holley 4150 750dbl pumper, nitrous oxide,full length heddman headers,true dual exhaust, 11"stall converter, 700R4, 3.73 locker

 

No way to answer that question from the info given.

However, you can answer it for YOURSELF if you check your email. I just emailed you a compression ratio checker spreadsheet.

.........or maybe not. You don't have an email listed. If you want it then shoot me an email and I'll replay back with the file.



[This message has been edited by Damon (edited May 11, 2001).]

 

Damon
info given was for 67cc heads,with 9.1 pistons(what is the piston top in cc's?)
The balance of the formula is standard 350.

 

You will still need to provide more information than that in order to get an accurate compression ratio number.

Here is a CR calculator link: http://www.prestage.com/carmath/calc_compression.asp Check it out.

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86 Trans Am WS6 Black with tinted windows, shaved door handles
ZZ4, Mini-ram, true duals, LT4 HotCam, AFR 195 heads.
***Too many other mods to mention***

"In the future, cities will become deserts,
roads will become battlefields, and the hope of mankind
will appear as a stranger" The Road Warrior

[This message has been edited by Steves ZZ5 (edited May 11, 2001).]

 

Pistons aren't measured in terms like "9.1". Damon and Bottled are exactly right. To answer your question, you need to know either what the heads the "9.1" goes with, or what the piston specs are (dish, flat, dome, volumes).

Just for reference, flat-top pistons with 64cc heads produce about 10¼:1 CR with typical .039" head gaskets.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Back again on the compression ratio, what is
the cc volume on flat top pistons with 67cc
heads and standard spec 350??

 

Flat-top pistons have ZERO cc's if they truely are flat-top pistons.........No valve reliefs.

So to answer your specific question, flat-top pistons with no valve reliefs have no CC volume whatsoever.

Some people will argue that there is a CC volume with every true flat top due to the gap between the cylinder wall and piston and the lands of the upper most ring, but this is negligible, and only comes into play when actually volume cc'ing an assembled short block.

Let us know if you have valve reliefs, and if they're of the standard type, or of the "gouge" type with the excess material wedged up on the back portion of the relief.......And use the CC Calculator I gave you in my last post.........

 

Thanks for the info, now if I plug in zero in the compression ratio formula I should get the
correct CR?

 

Yess....that is if you truely have flat-top pistons with NO valve reliefs. plug in zero in the "valve reliefs" area. All other areas must be filled out correctly in order to get an accurate compression ratio.

By the way......a stock, un-molested, SBC will have a deck height commonly between .020" to .030". The only accurate way to measure deck heigth is with a depth gauge with the heads off though.



[This message has been edited by Steves ZZ5 (edited May 11, 2001).]

 

Thanks for the info, no problem with sbc data.

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1987 Black Camaro IROC-Z (original owner) Replaced LB9 @ 86100 miles.
New 350 Crate engine
Balanced & blueprinted
WP 67cc Heads 9.6:1 C.R.
Cam: 450lift,216dur@50,110ls
TPI Induction(from 305)
22# Fuel Injectors
SLP Intake runners
New Computer chip
K&N filters & Air Foil ,
Hothkis STB
SLP 1 3/4 Headers
CATCO 3" Catalytic conv.
SLP 3" Cat Back Exhaust
700R4 Auto
SLP Torque Converter (2400 stall)
Limited Slip rear
245/45/ZR-17 Tires
17x8.5 ATI 5 Razze Wheels
EST. 340HP
380#/ft of Torque
NEW TOY!