odd compression test q&a

[survyor2]

I just installed a rebuilt head with headwork on my 7mgte and I'm getting some odd compression test numbers on a cold engine:

1. 95
2. 110
3. 118
4. 65
5. 90
6. 122

Now I know your thinking bhg but...

1. HKS stopper headgasket never even fired up, reused, inspected, viton throughly removed, copper sprayed all layers
2. new ARP head studs at 90 ft-lb
3. new revv oversized valves
4. cam marks line up at 0 degrees
5. all valve shims within spec
6. resurfaced head 0 miles
7. resurfaced block 500 miles ago
8. just before I removed the old head i did a warm engine compression test: 1. 155 2. 118 3. 142 4. 140 5. 134 6. 144. I contribute the old poor numbers to a warped surface which was eliminated since I got a new head. BUT this should eliminate piston rings as an issue since they were better before.

What am i missing here? Its gotta be a huge leak somewere.

Thanks,
Dennis

<Edit IJ> For those among us that either can't see or can't read.... :nono:

 

[HommerSimpson]

I just installed a rebuilt head with headwork on my 7mgte and I'm getting some odd compression test numbers on a cold engine:

1. 95
2. 110
3. 118
4. 65
5. 90
6. 122

Now I know your thinking bhg but...

1. HKS stopper headgasket never even fired up, reused, inspected, viton throughly removed, copper sprayed all layers
2. new ARP head studs at 90 ft-lb
3. new revv oversized valves
4. cam marks line up at 0 degrees
5. all valve shims within spec
6. resurfaced head 0 miles
7. resurfaced block 500 miles ago
8. just before I removed the old head i did a warm engine compression test: 1. 155 2. 118 3. 142 4. 140 5. 134 6. 144. I contribute the old poor numbers to a warped surface which was eliminated since I got a new head. BUT this should eliminate piston rings as an issue since they were better before.

What am i missing here? Its gotta be a huge leak somewere.

Thanks,
Dennis

poor a little oil in each cly and see if they come up... might be stuck rings...

 

[87M-GTE]

Valve seals?
Check what you torqued that area of the head again, maybe you didnt get astud or two as tight as they should be...

 

[Rennat]

your suppose to do the compression test with the car at operating temps. not cold.

and you never read the thread about copper spray and new MHG...

 

[survyor2]

your suppose to do the compression test with the car at operating temps. not cold.

and you never read the thread about copper spray and new MHG...

of course about the operating temperature for optimal compression numbers because of the ring gap but it is a small difference from a cold engine.

What thread about the copper spray are you referring to? I didn't do anything different than IJ did his.

Valve seals?
Check what you torqued that area of the head again, maybe you didnt get astud or two as tight as they should be...

The valve seals are outside of the combustion camber so they are irrelavant.

poor a little oil in each cly and see if they come up... might be stuck rings...

I didn't know rings could get stuck. I can't picture that but I'll give it a try.


I have an idea to try though, I'll report back.

 

[IJ.]

Dennis: Try Hommer's suggestion with the Oil and let us know if it changes.

What is the valve lash like now?

Rennat: Reading comprehension not your strong point?

Didn't I warn you to keep your nose out of Tech?

 

[survyor2]

OK. I poured 2 cap fulls of oil into No.6. It went from 122 to 185!. Can I account for anything over 160 due to the oil displacing the air? So what does this mean that I am getting good compression now? Did my rings go bad sitting for 3 months? Or are they "unstuck" now?

Thanks,
Dennis

 

[IJ.]

Ummm they were never "stuck" using Oil helps seal the ring to the bore and in this test lets us know that it's NOT a valve sealing issue.

Put Oil in comp comes up usually = bad rings

Put Oil in comp stays low usually = bad valves
(This is of course assuming no other mechanical damage or a leaking HG)

 

[survyor2]

Ummm they were never "stuck" using Oil helps seal the ring to the bore and in this test lets us know that it's NOT a valve sealing issue.

Put Oil in comp comes up usually = bad rings

Put Oil in comp stays low usually = bad valves
(This is of course assuming no other mechanical damage or a leaking HG)

wow. I guess my rings did go bad sitting. They only have 500 miles on them. JE pistons and JE moly rings, just bored over. They should have sealed by now. Any recommendations?

 

[IJ.]

I wouldn't panic just yet Dennis!

7M blocks are VERY hard iron and the JE rings are hard as well so unless it has a really agressive/deep/coarse Hone job done it'll take quite awhile to seal up! (same combination here and much the same horrible results after 4>500 miles)

Last time I checked mine it had evened out and I was happy!

Bedtime here (11:30pm) hope this eases your mind a bit.

 

[jdub]

.and you never read the thread about copper spray and new MHG...

IJ nailed it...read, don't skim...the OP removed the Viton from the MHG. The reaction between copper spray and Viton is the problem...there is no problem if the Viton is removed (on a new or used MHG).

 

[CajunKenny]

Man I learned a lot from this thread.

Thanks guys! :icon_bigg

 

[survyor2]

Yeah the more i think about it, the more I think IJ is right. Rings just haven't sealed. I haven't had oil on the rings in 3 months. The last compression test was probably better because I had just come back from a drive were the oil squitters were coating the cylinder walls. Now the walls are dry. I'm going to proceed with the reassemble. I hope they seal up soon.

 

[survyor2]

Okay...now I've got a new problem. I have coolant dripping out of my oil pan!

I had this problem before...so I found the head was a little warped (but I now I don't think it was enough to cause this problem). At the time I assumed this was the cause of coolant getting in my oil. So I went with a rebuilt head, HKS stopper headgasket. The surface on the head was machined and the block surface was machined 500 miles agp. I'm using copper spray on the headgasket. The engine hasn't even been fired up.

I pressurized the coolant system with a few psi and coolant POURS out of the oil pan. So there is no way its leaking into the cylinders. If it was leaking into the cylinders it would fill them up and drip past the rings.

I just can't believe that a resurfaced head, resurfaced block, ARP studs and a HKS stopper head gasket I have a bhg (twice) without even firing it up (once), it HAS to be something else.

 

[Zumtizzle]

I hope it's something simple bud. But if it's going into the crankcase you eighter have a cracked coolant passage somewhere or something along those lines.

But where did you get those revv valves from?

 

[flubyux2]

you know... the pistons have a -16cc volume... so two capfuls of oil probaby turned your dished pistons into flat-tops.

also, that coolant leak is most likely coming from your head gasket. since your head just came from the machine shop, its certainly had a pressure test done after the new valves were installed and they wouldnt have given it back to you w/o trying to sell you a whole new head casting... so its more likely than not a structural deficiency on the part of the head or block....

also, on the spray sealer on MLS gasket storm front; i have pulled apart a motor that had a fresh cometic with spray sealer installed. the viton coating just flaked off when it was rubbed. it was lifting in many areas as well. i had to strip it all off and apply a layer of sealant (was converting a 4G63 to a 2.3L stroker).

 

[jdub]

survyor - when you say "pours out of the oil pan", where exactly is it coming from...be as specific as you can.

flu - thanks for that info on the spray sealer on a MHG...I've seen the same thing. Been preaching for a long time not to use the spray on a new MHG because it attacks the Viton coating. Someone besides me noticed why

 

[survyor2]

survyor - when you say "pours out of the oil pan", where exactly is it coming from...be as specific as you can.

flu - thanks for that info on the spray sealer on a MHG...I've seen the same thing. Been preaching for a long time not to use the spray on a new MHG because it attacks the Viton coating. Someone besides me noticed why

it pours out of the oil pan drain plug. when i say pours I mean its a continuous stream when I put a few psi on the coolant system. Otherwise it drips with no pressure applied to the coolant system. I wish i could easily remove the oil pan and see exactly were it is coming from. Yeah, i wouldn't use copper spray on a new mhg. Viton was removed in my case. And remember it did this on the original HKS stopper viton setup.

My machinist ordered the revv valves from their shop in ft.lauderdale.

I don't believe the problem is the head since i have the same problem on this new head and the same problem on the last head.

I'm just having a hard time believing that any hg fails with a flat head and flat block without even starting it up. No stress has been applied at all. No even any coolant pressure before it started leaking. A piece of paper should have sealed it enough for what i was doing (anyways you see what i'm trying to say).

 

[Zumtizzle]

Got a link or contact info? How much were they?

I see what you're trying to say but that would be an "eazy" fix. If it is the HG.

 

[IJ.]

Only thing I can think of is a cracked block