Help my compression is reading low

[BNASTYs13]

I have had my car running for years with a sr swap and its always pulled super hard, never smoked, never mixed oil and coolant, never over heated, etc. i put ras on it like 3 months ago and the head had zero sludge and looked great. Two days ago i gave my car a compression test and it was wayyy low but evern across the board. Yes the throttle was open. I used 2 different testers aswell. It was between 90 to 100 across the board. Could anything make this compression test wrong? It seems like my engine is spinning slowly compared to a normal car



Any advice will be much appreciated. Thanks


-brad

[BNASTYs13]

anyone? could the timing be slightllllly off causing it do that? im thinking of anything now

[240sxDavid]

Try the small questions thread. Alota traffic in there someone will be able to help you hopefully,

Sent from my T-Mobile myTouch 3G Slide using Tapatalk 2

[EsChassisLove]

What engine?

[godrifttoday]

Leak down test

[Chrischeezer]

^what he said

First... what engine
2nd... what made u do a compression test?

has this motor had a timing chain,cams or cam gear installed?

[airman]

Wait, your engine is spinning slowly compared to a normal car....o_O

I'm guessing you mean when it's cranking, it doesn't turn over very fast. That would give you low compression numbers. Kinda why I never trust compression testers that rely on a starter. If my starter turns the engine over at 95RPM while cranking, I'm going to get a MUCH lower compression reading than if it turns it over at 250RPM while cranking.

[EsChassisLove]

When I did the comp test on my built bottom end sr it came out to 170-120-170-170.

I thought I had a bad ring. Leak down test showed a 30% difference in the low cylinder.

Then another leak down test with a different shop showed 3-5% difference between them all on a cold engine with wiseco pistons. Pulled the pistons out and everything was perfect brand new looking.

Morale of the story, pick the right person to do the leak down test lmao.

[fliprayzin240sx]

Just cuz its even across the board, it could be something else. Drop a cap ful of oil in the cylinders and see if the compression bumps up noticeably. If it doesnt, then its not your rings. It could be the HG going bad or valves not closing all the way.

[cmg]

Your timing shouldnt be off if you only installed ras and installed them correctly. How does it run compared to before you installed them? Might just be a lousy tester.

[nautical miles]

stupid question but just for fun..... when testing one cylinder.... were the other three spark plugs removed?..... also, it helps if you hook the battery up to a charging source while cranking over and over.
or you can avoid all that hassle and do a leak down test as previously stated above