Low compression after head install

[GooeyGus]

Hey guys,
I just spent the weekend replacing the head gasket on my talon after it developed a tiny leak.

The day we tore the car down, it compression tested at 150 across the board, no more than ~2 psi difference between the cylinders.

The top end was torn down, and re-assembled with all oem components. Timing components, all gaskets, cam seals, head gasket, valve cover gasket, ARP head studs, etc etc

The head we used was rebuilt by a machinist that knows his DSMs, and posts frequently on this forum. I am pretty confident that the head is good to go. All the head needed was HLA's, cams, and rockers, which I pulled off of the head that was in the car.

Before I installed the lifters in the new head, I bled them all down. I didn't soak them or run fresh oil through them or anything like that, just put a pin in the top until a couple squirts of oil came out and they were easily "squishable" by hand. I believe these are the original 1990 lifters with 200k miles on them.

After we got her all put back together, she started right up on the first try. We ran it for about 5 minutes and called it a night.

After work the following day I decided to check the compression. At this point the new head has *maybe* 20 minutes of run time.

I was a bit disappointed when the numbers came back. Low 100's all the way across.

I am confident that the gasket is sealed well, and I know the bottom end is healthy because the previous numbers were in the 150's.

I am 100% sure that the timing is dead on. I checked it, double checked it, and triple checked it before I even dared turning the key. All the marks line up correctly, the hydraulic tensioner has about .150" of space between the body and the arm, everything was perfectly in spec, done by the book with the correct tools.

So, what's the deal? Can this be a side effect of the lifters needing to "pump back up"? I've heard they can take a while to completely come back to normal.

What do you guys think?

 

[Benshooter]

Was the engine warm when you checked comp?

 

[FactoryChrome]

Yeah... installing squishy lifters in a head is a no-no. I dunno who told you to do that but you might question what kind of advice you take from them in the future.

What I do, is pump all the lifters back full of oil BY HAND by submerging them in oil and squishing them a few times until they won't squish anymore. After that... install them in the head and install all timing components. Do NOT start the car. Leave the lifters in the position they are in for about 30 minutes. The pressure the cam lobes are putting on the lifters will bleed some out of the ones that are having the pressure put on them. Turn the motor by hand over to the next set of cam lobes and wait a while longer for those to bleed out some pressure. Repeat this a few times until all lifters have been on the cam lobe for about 20 minutes.

Of course someone is going to say, just slap those in there and run it... "I've never had any problem doing it that way."

 

[TalonJohn94]

Did you resolve this problem?

I have the EXACT same problem except it didn't start up right away, and won't start without flooring/flooding the engine. The only thing I didn't do is flush/drain the new Topline lifters I installed with the new cylinder head.

So now I'm reading about the effects of non-working lifters on cylinder compression numbers. Because I have around 70psi compression on all four cylinders, I know it has to be something universal across the board.

Anyway, from what I've read shouldn't the lifters not be able to compress at all because the only compress via an internal valve?

So wouldn't worn lifters cause bad compression?

 

[JacksonAuto]

Did you do a leakdown test? That will tell you where the compression is going. If all four holes have the same compression, I would assume that it's likely a timing issue.

The Lifter's should have been rock hard before you put them back in. Are they tapping? When the lifter is pumped up you CANNOT squeeze it with your hand.

NO. You do not want to install lifters that are pumped up. If you do, they will hold the valves open. They need to be bled down before installation so that when they "pump up" they take up the lash. Hence "lash adjuster".

 

[TalonJohn94]

I DID NOT install the lifters with oil in them. They were new (3G) lifters, but I bled the little bit of oil that was in there by depressing the internal valve. After it was all said and done, after everything was installed - the cylinders were all low in compression across the board.

What was strange is when I originally put everything together all the cylinders had about 70psi, WITHOUT the internal valve depressed on the new lifters (unable to compress by hand). After I took the lifters back out and pushed the valve in and purged the little bit of oil out I reinstalled. Then, I did a compression test on cylinder 1 - which gave me 100psi. Then I did cylinder 2 - which gave me 80psi. Then I did cylinder number 3 and 4 which both gave me 70psi again.

So it seems that when I did the compression test right after purging the lifters it produced a higher psi in the first cylinder I tested, and diminished in each cylinder after. Does anyone think this could be lifter related?

Does anyone have a leakdown tester I could borrow, in which I would just pay shipping both ways?

 

[TalonJohn94]

Update on my situation. Basically, had the head went through again by the same machinist. Put everything back together.

The car runs and cruises well, but idles terribly.

Did a compression test and got 92-92-92-86. (Although I did it with the engine cold and didn't open throttle body during cranking)

I know the timing is dead on, and the machinist insists he vacuum tested everything after assembly.

Any ideas?

 

[donniekak]

Update on my situation. Basically, had the head went through again by the same machinist. Put everything back together.

The car runs and cruises well, but idles terribly.

Did a compression test and got 92-92-92-86. (Although I did it with the engine cold and didn't open throttle body during cranking)

I know the timing is dead on, and the machinist insists he vacuum tested everything after assembly.

Any ideas?

Do another test, warm, and wot.

 

[Anubis_4_99]

So your saying you did a compression test while the motor was cold, with the throttle body closed, and you don't know why your numbers are low? Do a compression test properly and then post your numbers. Until then no one can tell you what's wrong because we don't know what your real compression numbers are.

 

[TalonJohn94]

OK, will do. I'll report back tomorrow

 

[drewboi]

let the engine warm up and cool a few times and re torqe it, give the gasket a chance to set in then check it... results might be better.. just my opinion

 

[TalonJohn94]

Compression test while warm, with WOT:

92, 92, 92, 90

Also adjusted BISS somewhat but of course didn't help idle quality, only purposely advancing base idle would get the car idle worth a damn. (which I didn't do, base idle is correctly at 5*)

Any advice?

Does the "across the board" aspect tell me it must either still be timing or some major problem with the lifter manufacture?

 

[TalonJohn94]

Also, if all the timing marks still line up, how can I either measure belt deflection or see if timing belt tensioner is functioning properly?

 

[crazycooter]

Very interesting I also have a supposed recently rebuilt engine with low compression across all 4 cylinders... The compression is 120 across the board.... Car sounds like its cammed too... Very interested to see what your problem is because I don't know the compression of my engine before it was "rebuilt".. Car drives decent but I recently noticed oil all around the engine bay!! I think my head might had been over torqued.... I drove it around for over 200 miles with no oil in engine bay.. I know this because I did tons of work to the car after 200 miles of driving and then just recently noticed oil all around engine bay!!

 

[Palmetto_TSi]

when you built your engine, did you make sure the rings were staggered? Also, did you check the ring gap? you really do need a leak down test. Right now, you are just chasing your tail, and spending money to get no where.

 

[3kgt2nv]

Did you reuse the stock head bolts or put in studs?

 

[TalonJohn94]

I bought and used ARP studs torqued in sequence to 85 ft/lbs and used a Felpro head gasket.

Very interesting I also have a supposed recently rebuilt engine with low compression across all 4 cylinders... The compression is 120 across the board.... Car sounds like its cammed too... Very interested to see what your problem is because I don't know the compression of my engine before it was "rebuilt".. Car drives decent but I recently noticed oil all around the engine bay!! I think my head might had been over torqued.... I drove it around for over 200 miles with no oil in engine bay.. I know this because I did tons of work to the car after 200 miles of driving and then just recently noticed oil all around engine bay!!

Yeah, see thats part of the mystery for my situation, because I had 145 before cylinder head was rebuilt and re-installed, so I lost about 50psi.

As far as oil leak goes its probably unrelated to low compression. It could be that you cracked your valve cover when re-installing. That usually starts as a small crack, but they tend to spread until your losing oil and its sloshing around in the spark plug well.

 

[TalonJohn94]

So I took everything apart back to valve timing. I took some pictures to see if you guys can identify where I'm "off". What do you guys thing?

and...

 

[romeen]

You need to rotate the motor so that the dowel pins for the cam gears are in the 12 o'clock position. In the last pic they are at 6 o'clock, 180* off from where they should be.

This explains much!

 

[TalonJohn94]

Yeah, this was pointed out to me right away from a PM. So I'll have to go back out there and rotate it until the dowel pins are facing up. However, I do think the marks will still all line up.

Ill post new pics tomorrow night.

 

[luv2rallye]

Yeah, this was pointed out to me right away from a PM. So I'll have to go back out there and rotate it until the dowel pins are facing up. However, I do think the marks will still all line up.

Look at the blowup of the cam teeth in figure 11 here and notice they are just opposite of what yours are: Timing Belt VFAQ (Timing Belt TSB - ENHANCED). Hopefully when you get the dowel pins up they will be like this.

Also look at figure 12 for crank sprocket timing marks lining up. All timing marks (cam, crank, oil pump) only line up at all their proper positions only once per 6 crank revolutions due to their different speeds.

 

[TalonJohn94]

Hope this picture helps

THIS IS AN AUTO-MERGE

So I paint marked it and tried to just move it one tooth. This resulted in lower compression in cylinder #1 ~~ 65psi

And then, for some reason the crank must have spun a couple teeth unexpectedly and now everything's out of phase.

So I guess I'm just going to re-time it tomorrow. What is the trick for the oil pump/rear balance shaft gear to just let it "fall in place"?

I really don't wanna have to drop the exhaust again to insert a screwdriver in the oil pump sight hole.

 

[TalonJohn94]

Ok, redid the timing from scratch. This got me exactly 100psi across the board.

Check it out:

Does crank timing mark look right? Should I tried loosening and moving that counter-clockwise one "tooth"?

 

[TalonJohn94]

Has anyone heard of (aftermarket) lifters causing this condition?

 

[fourgsixthree33]

Man, this doesn't make any sense at all. Have you done a leak down test yet?