1st HIT doing a compression test

[Pc3]

MONTY/Chris you left me hanging@ 2nd gen
so i'll try here after i completed the gasket installation I went back and read the #'s for "1st hit"
they where 125-130 arcross the board so my question still stands is that good or bad?

[Monty Mikho]

Seems to be great for your combo!! Make sure you either write that number on the valve cover or somewhere you wont lose it. :D Check it often and make sure the numbers stay there.. Dropping 5#'s is not going to kill you.. But if you start dropping 10#'s there is something wrong.. My experience has been either the rings or the pistons pinching the ring..

[Chris Uratchko]

I agree that's not bad. Keep records and monitor cylinder to cylinder in terms of a percentage, and in terms of what your original recordings are.

Again, if there is a low initial hit, and a decent final hit then it's probably a sign of a ring problem. If the numbers do not get better by the 3rd hit or so, then its a probably a valve seat problem, and or blown gasket.

I was doing a compression test on an engine the other day.

245
260
275 :shock:

Oops.

[Pc3]

thanks GUYS "not bad" thats not good enough for me I want GOOD!!
let me give you guys a little heads up on my combo
because i have 68 cc heads and didnt want to cut them at time of biuld I looked for the thinist head gasket I could find and that was .015 MR Gasket that yielded me a 12.44 comp..Marv suggested i use the felbro 1010 wich would give me a 11.7 something.anyways I am thick headed and went back again to the .015 the second time around
. I did a third compression check 2 days ago after the intial 130 I found across the board and NOW I am getting 125-130, my guess Its going in the wrong direction.. I also found a few specks of the gasket coating in the radiator.
NOW as far as the rings when I biult this motor I file fit the rings .. je recommend a .026 for nitrous and a .022 for NA because I didnt kno9w exactly what direction I wanted to go I went .023-024. DO you think that has anything to do with it ?
OR do I just have a to thin of a head gasket for the motor?
you know that old saying penny wise dollar foolish thats me I guess!
the cylinder walls LOOKed BEAUTIFULL when I popped the heads off "shrugs"
LOL just went back and reread your reponses GREAT & NOT BAD lol CAN WE AGREE its OK for now???? :roll:
Chris I also recal a year or two back of a pic you posted where you had the heads plumbed thru the intake front to back on both sides ,would that help prolongi the life of the head gasket for me.
yea. Monty I am penny wise and dollar foolish go head say IT? LOL

[RPM]

Pc3,

Your ring end gap is not hurting you compression numbers. If you look at the gap in a big picture there isnt much of the .024" exposed, the rest is covered by the piston. What ring stack are you running? You say JE rings, what style? I get slamed when I say this but leakdown testers and compression testers leave some area of error from test to test. Here at work we check ring seal with a blowby meter. I do use a compression tester at the track as well but I do know there are variables and I have to take that into account for my readings.

Regards,
RPM.......

[ROB]

125-130 is pretty weak.

Agree the blowby meter is the best way to get an indication of cylinder seal integrity, but will also say if you're getting low leak down rates you might want to consider putting the right cam in that engine because what you've got is too big.

Are you checking compression with the throttle open? If not you should be.

[Pc3]

125-130 is pretty weak.



Are you checking compression with the throttle open? If not you should be.
Rob 125-130 for 1st HIT is weak? I dont know I'm asking if so IYO what would you like to see?
doing a compression test ..meaning max ing out the compression after three full hits yields me 180 give or take a lb or twoacross the board
and no I didnt check it with throttle open

[ROB]

Check it with the throttle open and see if it changes......