Compression Woes

[satx88supra]

New to the Toyota Supra's, nice cars however a big headache. Car is a 1988 Turbo when I got it the motor was in bad shape, leaked oil everywhere. I got a motor from my brother in law (1990 7mgte). That engine had a blown head gasket. So I brought a Felpro stock head gasket and installed in on car. The car smoked and engine shuttered badly. Did all the checks before hand, tdc, cps etc. Checked compression and from 1-6 they were 40, 25, 0, 125, 128, & 128. Took head off sent it to shop to get checked, vaccum and pressure check and it checked out ok. It had a little warpage and they resurfaced head. We installed head, did compression test and the reads are 30, 60, 90, 120, 120, & 120 got arp studs on it. Felpro gasket torqued to 80 pounds. I need to know what the next step is.

 

[hvyman]

did you check the block and the rear timing cover?

 

[ma70t]

sounds like some bad rings with those reading do a wet compression test to see i had the same problem on my 90 1 and 2 read 60 80 and the rest was at 160 that was dry reading but wet was 108 and 120 and the rest was like at the 200 plus just to make sure that i had bad ring

 

[satx88supra]

Ok i checked the timing cover yesterday before bed and it does seem the the cover is in a little bind. I positioned the cams to get to the bolts to loosen them and it moved....a little. I re-checked the torque and everything is still @ 80lbs. rechecked compression and still basically same reads. Poured a little oil in #1 cylinder and copression really didn't change. Also to note that i dont have the whole engine together. Just the intake side is all in, the exhaust side is prep (manifold and turbo) but not tighted down, CPS is not in (i think that might be a mistake), and intake water housing to block is not on. I basically was just trying to get DC to the starter to check compression. No spark no fuel just engine turning over. Was this a bad plan? Do I need to maybe un-do everything and start over and install everything then check compression?

 

[TurboStreetCar]

Are you sure you have the cam timing correct? If you put in oil and it didnt change it would be time to rebuild the entire engine. No compression is a rings and/or piston problem assuming cam timing is correct. The block would have to be REALLY warped to lose that much compression.

Just to make sure, the throttle body needs to be open 100% During a compression test. You were holding it open right?

 

[thorpedo]

Are you sure you have the cam timing correct? If you put in oil and it didnt change it would be time to rebuild the entire engine. No compression is a rings and/or piston problem assuming cam timing is correct. The block would have to be REALLY warped to lose that much compression.

Just to make sure, the throttle body needs to be open 100% During a compression test. You were holding it open right?

If the oil didn't change the compression that doesn't mean it is necessarily time to rebuild the entire engine. That would indicate the compression loss is less likely to be the rings and more likely to be head gasket and/or poorly sealing valves. The block wouldn't necessarily need to be all that bad, a tiny leak can affect compression in a major way. Take the head off, verify there is NOTHING preventing the HG from sealing. Check your valve lash as well, it is possible the shims got messed up and some of the valves are being held open. Cam timing is another potential issue.

 

[hvyman]

Are you sure you have the cam timing correct? If you put in oil and it didnt change it would be time to rebuild the entire engine. No compression is a rings and/or piston problem assuming cam timing is correct. The block would have to be REALLY warped to lose that much compression.

Just to make sure, the throttle body needs to be open 100% During a compression test. You were holding it open right?

or the rear timing plate stick up past the block. cam timing would not give you that low of compression in the first 3 and not the last 3.

 

[satx88supra]

Well i'm almost to the point of just going for a rebuild but i'm the type who wants to know whats going on and not just pay someone else to fix it. I think i'm going to take the head off again and have a local shop thats done a few 7mgte's in my area rebuild it. Also how can i check my block for warpage or is that for a shop to do? I want this car running bad cuz these stupid fart can Honda's are driving me crazy. I'll have an update Friday on what i found. :icon_mad:

 

[TurboStreetCar]

If the oil didn't change the compression that doesn't mean it is necessarily time to rebuild the entire engine. That would indicate the compression loss is less likely to be the rings and more likely to be head gasket and/or poorly sealing valves. The block wouldn't necessarily need to be all that bad, a tiny leak can affect compression in a major way. Take the head off, verify there is NOTHING preventing the HG from sealing. Check your valve lash as well, it is possible the shims got messed up and some of the valves are being held open. Cam timing is another potential issue.

If it were my motor, i would pull it and do a full rebuild rather then playing with unknowns and someone elses mistakes. This is what i did with my engine.

The block would have to be VERY warped to cause such a leak with a stock gasket. Ive seen composite gaskets seal some nasty looking surfaces.

or the rear timing plate stick up past the block. cam timing would not give you that low of compression in the first 3 and not the last 3.

He claimed only the head was milled so im assuming the block and timing cover are unmodified and at the same level.

OP: you need a straight edge to check the block and head surfaces for warpage.

 

[whitemike]

If it were my motor, i would pull it and do a full rebuild rather then playing with unknowns and someone elses mistakes. This is what i did with my engine.

The block would have to be VERY warped to cause such a leak with a stock gasket. Ive seen composite gaskets seal some nasty looking surfaces.



He claimed only the head was milled so im assuming the block and timing cover are unmodified and at the same level.

OP: you need a straight edge to check the block and head surfaces for warpage.

Either way, It's unlikely that the rings or valve seals are bad progressively starting with 1, 2, 3 and better with 4, 5, 6.. It's too unlikely of an issue. I'm with the guy above me, I think It's the timing cover. Maybe he forgot to mention the block was decked as well.

-Mike

 

[hvyman]

ya he also said the block had a bhg before so who knows what was done to it.

 

[S.A. supra]

ya he also said the block had a bhg before so who knows what was done to it.

It was my engine before. bhg but it was not bad. #6 had a small leak that would pressurize the cooling system and would boil out the reservoir. other than that it idled perfect and ran good make 10 psi the day i parked it. no oil in the coolant or coolant in the oil. It has to be something up front that won't let that head seal.

 

[satx88supra]

Block was not decked. I did take another look again and the cam cover is in a bind. I think i have now put the head i bind. with the bolts torque to 80lbs (unevenly) i'm guessing it would take move force to get the front to lay flat. I guess just loosening back and starting over might help. But i still have the issue of the cam cover. I can see an edge of it and it doesnt seemed machined at all. I'll verify that Friday when I'm off. Oh well...my brother in law said these cars will make you learn something. :runaway:

 

[TurboStreetCar]

Either way, It's unlikely that the rings or valve seals are bad progressively starting with 1, 2, 3 and better with 4, 5, 6.. It's too unlikely of an issue. I'm with the guy above me, I think It's the timing cover. Maybe he forgot to mention the block was decked as well.

-Mike

ya he also said the block had a bhg before so who knows what was done to it.

Well all we have to go on is what is said. Not a mind reader, Though it would make life much easier. :biglaugh:

Block was not decked. I did take another look again and the cam cover is in a bind. I think i have now put the head i bind. with the bolts torque to 80lbs (unevenly) i'm guessing it would take move force to get the front to lay flat. I guess just loosening back and starting over might help. But i still have the issue of the cam cover. I can see an edge of it and it doesnt seemed machined at all. I'll verify that Friday when I'm off. Oh well...my brother in law said these cars will make you learn something. :runaway:

If in a bind means that its sticking up past the deck of the block then it sounds like it is the timing cover that is the issue., i wouldn't try to tighten it down again, it will have to be machined to the same level as the block. Any difference and it will cause the compression problem you already have or an oil leak if its too low.