Low compression 2 cylinders
 

Hey guys I have an 86.5 MKIII and did a compression check with the #4 & #5 were low. I think the #4 was 120psi and the #5 was only 90 psi. What could be the problem? Rings? HG? Any help would be great!
Thanks!

If your compression tester is like most it has an air chuck fitting on it, take the schrader out of the hose and the radiator cap off and hook an air line to it while its on the worst cyl. If the coolant starts to overflow or bubble then you have a bhg. Either way with those values I would think bhg, rings are not normally a problem on these car, or at least you will have lower values in all the cyls. Also bent valves don't normally happen so that should not be an issue either. If you want to check the rings, put a small amount of oil or trans fluid in the cyls and redo the compression test, if you get a large increase in compression it will be rings..

It's your piston rings. They don't always show low on all cylinders. 90psi. is definatly not caused from a bad heasgasket. But since it is free to test it. its worth a try. but I got 100 bucks on rings... rings wear out on any car regardless of make. Although they are not as prone to ring problems as they are bhg. They do wear out. In your situation is say rings.. especially unit has high mileage. Or has the boost cranked up above stock

Sorry I forgot to add that its a non turbo car.. has a little under 160,XXX. Ive been told from numberous people its either the rings or BHG. I was thinking about buying that "Blue Devil" sealant for the mean time, but I was trying to confirm it was a BHG. I dont really want to have to take apart the head because I want to do a 1jz swap in a month or two. But if it is the rings then Ill have to take the head off.

Also it has some white smoke when I start it up coming out of the exhaust, I normally only drive it around town once a day.

White smoke is a sign of piston rings. Blue smoke is sign of BHG. Like i said. bhg won't affect the compression by that much... jz swap is coming early..you will love it. I love my jz..

Where did you get your JZ? I was looking online.. the cheapest i can find one with motor and tranny is like $2100... like $1400 for just the motor. Know of anyplace cheaper? trying to buy from a direct source that has a warranty incase anything happens.

http://www.jrautoparts.com/clip_toyota_1jz.htm

3k shipped. No warranty but he sent me a video of it running. Trust me if u dont buy a front clip a 4 day project will turn into months trying to get all the little pieces

i was told white smoke was antifreeze, and blue smoke was oil...
doesnt make sense either that 160'000 would have bad rings...

ive had 4 supras and never experienced bad rings, my 85 2.8 was running 360'000km and still running strong

Yup, you've got it right