LIZ28SS

Does anyone know a way to figure out your compression ratio using the static compression psi number? I am ranging from 240 - 249 psi which seems very high. I have searched Google and can't find a way to do it. Thanks.

GrannySShifting

iTrader: (10)

thast extrememly high

LIZ28SS

I know... it suprised me becuase all along I thought my compression ratio was 10.6:1 which is what Lunati says it will be with their 382 stroker kit. No wonder I have been haivng pinging issues. Pump gas may not cut it

GrannySShifting

iTrader: (10)

Do you have a pretty small cam, and were they flat top pistons?

You could also try a larger cam if its not already on the edge of your taste for driveability, although if it pings all the time its not very driveable. Can bleed off a bit of that cylinder pressure. Any possible valvetrain issue that might cause the valves not to fully open

LS1derfull

I dont think thats ever going to work on pump gas, when my 14 to 1 SBC was pressure tested i only had 225psi! Granted my cam timing and gear reduction starter influenced my readings, but i ran that setup on C14(VP gas). It sounds like you need to play with cam timing and or Intake centerline placement, plus maybe a intake charge intercooler?

LIZ28SS

Something doesn't sound right. I guess I will have to pull a head to verify the pistons becuase Lunati spec says -1cc flat tops NOT dome style which I would imagine would need to be in place to make compression numbers like that. How does intake centerline placement effect compression? Wouldn't the compression be unequal then from one side to the other? Probably a stupid question but a question non the less. Please advise. Thanks!

LS1derfull

Compression would be the same side to side,no i dont believe you are any where near as high as 14 to 1 but you are at a pinging pressure. You could retard cam 4* and see 10 to 15 psi drop in cranking pressure, but remember you havent really lost that pressure just moved it upward in rpm range.
I would consider fatter mixtures, maybe water or alcohol injection? I think 12 to 1 comp. is highest ive seen any one claim with good tuning to run on pump gas, anyone here have more info?

smokemup

iTrader: (6)

The only way to determine your compression ratio is to measure all the volumes and calculate it.