| |
Click on image for the lowdown. 
====
| | | Forums66 Topics128,026 Posts1,055,409 Members48,422 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | 
#12434 07/20/2004 1:54 PM | Joined: Dec 2000 Posts: 506 Shop Shark | | Shop Shark Joined: Dec 2000 Posts: 506 | Anybody know an easy formula to figgure the compression ratio if you know the cranking psi guage pressure reading? I've heard maybe incorrectly that if you have say a 160 psi guage pressure reading divided by 15 will equal compression ratio?
"Drugs are money, money is power, power is security." - Kent Heiner
Nedrow population 2212
Carbon footprint family of 2/11 tonnes of CO2/yr
| | |
#12435 07/20/2004 4:47 PM | Joined: Feb 2000 Posts: 985 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 985 | I dont think that is correct. I may be wrong but I have always thought that compression ratio is the difference between the volume of the piston at top dead center and bottom dead center. Now like I said I might be wrong but I doubt that you can make a correlation between psi and compression ration.
Brian Moore
1949 3100 5 window Deluxe
"Today is better than yesterday, but not as good as tomorrow"
| | |
#12436 07/20/2004 5:02 PM | Joined: Jul 2000 Posts: 962 Shop Shark | | Shop Shark Joined: Jul 2000 Posts: 962 | I had a rough formula going that equated cranking PSI to static compression ratio. accurate to within about .5:1 CR for a stock engine. Take PSI divided by atmospheric pressure of 14.7 times volumetric efficiency of engine.
Say 160 divided by 14.7 times 80 % gives a static compression ratio of 8.7:1.
This is a really crude formula, cuz it doesnt take true atmospheric pressure, VE or cam timing (dynamic) factors into account. But its fun seeing how off you are when comparing a stock motor to book spec. As stated, I've come pretty close with my "fuzzy math"
chip
Preaching the Hot Rod Gospel according to the 4-stroke apostles:
Suck, Squish, Fire and Fumes
| | |
#12437 07/20/2004 6:40 PM | Joined: Jun 2000 Posts: 2,773 'Bolter | | 'Bolter Joined: Jun 2000 Posts: 2,773 | Chips fuzzy math is about as close as you will get, there are a lot of variables to figure. The biggest is the actual size of the combustion chamber, which can vary a lot. Only way to really know that is to measure with a liquid. Saw 2 Guys Garage a while back check a head that was off more than 10% from the advertised.
Fred
52 3600
69 C-10
| | |
|
|
| |
