MelloBoy

Hi all,
been lurking around for a while. I did a few searches and couldn't find the answer so i'll ask and hope i don't get flamed This is for an 87 Turbo II motor.

I noticed in the factory service manual that the compression should be ~85psi give or take with the differential between the 2 rotors being less than 21psi. Yet, as I'm reading around, I notice alot of people saying that 90psi is borderline OK and that compression should be around 100-120psi or so. Could someone clarify this?

Mello

13bpower

New factory compression- 120-125
Good rebuild- 110-120
still healthy- 90 and above
In trouble- below 90

those numbers are not set in stone. others might think a little differently.

MelloBoy

13bpower,
I understand ppl saying that 110-120psi is a good rebuild, but when you look at the Factory Service Manual (P.10-11 in the engine section for an 87) it says the compression should be approximately 85psi with a differential between the 2 chambers being no greater than 21psi, which is what is throwing me off.

Factory manual saying 85psi is 25-35psi lower than what people say on here with 110psi being a healthy engine which is a significant difference imho.

Mello

13bpower

Yeah, they are on crack. Mazda also tries to sell little pieces of plastic for $150.

My 120k mile original T2 engine has 100/98 compression for what it is worth. 85 is not good.

I think they mean that it should be at LEAST 85, even though they don't make it clear what they are saying.

SDrotary-FC

i think there are diff. way of testing the comp. of the motor.

MelloBoy

ok that's what i needed to know
so what do you think....

87 Turbo II
120k miles
Claimed rebuilt at 108k
slightly beat up interior
85psi front rotor, 89psi rear rotor (is that the term?)
No dents whatsoever on the body
$1200

thanks
Mello

SpeedFreak03

13Bpower is right, honestly I don't know what Mazda means by that. Also you need to take into account the differences between each rotor, like his is 100/98. Since its only 2PSi difference, his engine is in good shape (not to mention high numbers). Good luck with the test!

SpeedFreak03

So wait, it was rebuilt 12K miles ago, and its only getting 85-89? I call bullshit! Unless its a REALLY shitty rebuild, there is no ******* way its that low! Now I could see a 120K mile engine with 85/89, but not a 12K engine...But since its only $1200, if the tranny and everything else is in good shape, then drop 1K on a rebuild and you have a nice TII for $2200! $1200 is really low for a TurboII. But if you spend maybe like $1300 on the rebuild you should be able to get a street port done, and some thicker apex seals. Good luck!

13bpower

I think it should run, have very little power (slower than a stock N/A), and need a rebuild very soon. It sounds like a fair deal. TII's are more comon where you live than where I live so you might be able to work him down on the prices. Where I live that car wouldn't be FS for more than 2 days.

There are 2 ways of doing a comp check. The mazda way with thier fancy checker that gives you #s like 6.7,6.9,6.7 front 6.5, 6.3,6.7 rear ..... and there is the way all us home mechanics do it. A regular comp gauge with the check valve removed.

MelloBoy

i forgot to mention,
he says it was pinged a few times....
blown apex seals maybe? but the compression is pretty similar between both rotors. i was thinking of getting it while my 1jz swap on my supra was being done, then working on the FC as soon as my 1jz was done. (approx. 1-2 months before completion of my 1jz)

mello