Engine has run on.

[CFMopar]

when doing the compression test. Do I just keep cranking it till the psi stops rising?


I decided I had 45 mins today and was taking my plugs out (those mechanic gloves i bought made that alot easier. no burns   ) and hooked the compression tester to cylinder 1. Cranked it over and got just over 120 psi sound bout right?

[firefighter3931]

when doing the compression test. Do I just keep cranking it till the psi stops rising?


I decided I had 45 mins today and was taking my plugs out (those mechanic gloves i bought made that alot easier. no burns     ) and hooked the compression tester to cylinder 1. Cranked it over and got just over 120 psi sound bout right?

Was the engine warmed up a bit ? It sounds a bit low but your cam could be bleeding off some cylinder pressure. Roll the motor over for 5-6 revolutions...that should be enough. Try a couple of the other cylinders as well. It also helps to have all the plugs out and the throttle wide open as i described above. Without doing it properly you won't get an accurate reading.

Ron

[CFMopar]

It wasnt cold drove it for a bit and it sat for maybe 45 mins. Going to do it today and the engine is going to be cold.

[CFMopar]

ok heres the numbers for the cylinders i could get the gauge in. The passenger side bank with the header is a Pain.

Cyl 1: 135
     2: 145
     3: 130
     5: 140
     7: 140

Did all the driver side first then tried passenger side but couldnt get in 4 6 and 8.
did it as per your instructions my electric fuel pump disabled carb left wide open and all plugs out.

[firefighter3931]

Those #'s look fine...maybe slightly on the low side. With that amount of cylinder pressure it should run fine on 94 octane. 165psi is usually the upper limit for pump gas. Keep tuning and reading the plugs....make sure the secondary side isn't too lean.

Ron

[CFMopar]

So what could the specs on the plugs be?

And with those number what would you guess the compression ratio be. I know you cant get it dead on but an idea.

[firefighter3931]

So what could the specs on the plugs be?

And with those number what would you guess the compression ratio be. I know you cant get it dead on but an idea.

It's possible you got some bad fuel which caused it to predetonate. The cam is bleeding off cylinder pressure so it's hard to say what the actual static compression ratio is. The only way to know for sure is the measure and calculate. What pistons are in this motor ? Was the block decked ?

Ron

[CFMopar]

TRW 10:1 forged pistons with valve relifes. The block and heads wernt really decked just had them cleaned. Dont recall if anything was taken off to get the flat. If any was it wasnt much

[firefighter3931]

With those pistons you'll have around 9.5:1 depending on the chamber volume of your heads. This is assuming you're using a 906/346/452 type casting. Those pistons will be ~.020 below the surface with a stock specced deck height.

Ron