19 replies to this topic

[davecarama]

Leakdown showed 0% on 1 and 4.
Leakdown showed 30% on 2.
Leakdown showed 50% on 3.

And this is AFTER I took the head to the machine shop (a race machine shop that specializes in Miatas).

Yesterday when I checked the leak down, it was absolutely exhaust valves (the front most in cyl 2 & 3), You could feel the air coming out of the port and you could feel the air coming out of the valve.
but today the machine shop said that the vacuum test passed no problem (high end of green on 1 & 4 and low end of green on 2 & 3).

Machine shop reground the two suspect valves, retested and said there was a minimal improvement, that it can't get any better.

I am going back AGAIN tonight to put things together and check things out. Any tips on how I can be sure this is done, done correct, and troubleshooting if I see more issues?? Any tips on how to talk to the machine shop?

The only things I could fathom could be wrong is the springs, cams, or lifters (they don't have the lifters at the machine shop). Maybe the cams are out of spec? maybe one of my lifters is too tall? Maybe the valve is a little too tall? Maybe one of my springs is too short or too tired? Hell... maybe it is an intake spring?

Any other things I can look at or ask the shop to look at (that is if this last test doesn't pass)?

Thank you very much!!!
Dave

[chris haldeman]

My guess is either the valves are sunk too far into the head causing the lifters to not be able to compress enough to let the valve close or there is still oil holding the lifters from compressing and adjusting to there new location. Let the head sit overnight with those bad cylinders valves open. And the lifter should collapse

[chris haldeman]

To rule out bad machining do a leakdown with the cams not installed

[trimless]

I had a similar issue with a local machine shop. Installed the head on the engine and had 30 - 50% leakdown with leaking valves. Took it back and they found that dirt / grit had made it's way into the cylinder head and was causing the valves to not seal. They cleaned it up and did a vacume test to confirm all was OK. Re-installed and all was good.

Lesson learned, seal the cylinder head in plastic after rebuild until install!

[davew]

Assuming you still have the 95 that shows on your avatar. You may have lifters that are pumped up too far and the valves may be seated to far into the head. Once the lifters "deflate" the leakdown may be fixed. It is possible that the valves are seated WAY too far and even deflated the lifters are holding the valves open.

This problem is very common on 99+ but could also happen on an early car

Dave

[davecarama]

Yup, race car is still a '95 ITA Miata. I thought all of the NB cars had solid lifters and all the NA cars had hydraulic lifters?

Update:
As mentioned, the head was at the machine shop today. They told me they did a vacuum test and cyl 1 & 4 were on the top end of the green area and 3&4 were at the bottom end. They tore down those two cylinders and re-grinded and re vacuum tested. Said it was better, not as good as 1&4, but better. What great guys to take care of me so quickly!

So I drove back to the track, installed the head, and did the compression test with the cams out.

1&4 were great, 2 was 10%(ish) 4 was 15%(ish). I'll take it for now!

I put in the cams, timing belt, etc and re-tested. Now it was on the intake side that had massive leak
down.

So I am going to take your advice and think the valves are either too deep into the head (but these guys would never do that to me, they are too good for that, I am sure of it) or the lifters are too pumped up... which it CERTAINLY could be the case.

$125 from partsdinosaur.com and I should have 16 new lifters.

Do you think I should throw parts at this or should I try to make these ones work ?

THANK YOU ALL FOR YOUR ADVICE!

I am seriously getting overly bummed about not having a running car! I will sleep on this and make a decision on what to do tomorrow (most likely based on your recommendations)

Thanks again!

Dave

[davew]

I think you should diagnose the problem, rather than through time/money/parts/aggravation at the the car.

What is the compression numbers? leak down numbers and where is it leaking? Does it run? run well? What are the leakdown numbers with the cams loosened up? Why did you not send the cams and HLAs to the machine shop?

FYI, I have had problems with aftermarket lifters. I will only use genuine KIA lifters.

Dave

[davecarama]

Why did you not send the cams and HLAs to the machine shop?
When the head went to the machine shop, I sent the cams, not the lifters. They said they didn't need them.

What is the compression numbers? Does it run? run well?
The motor is still out of the car, so I didn't do a compression check, or run the motor.

What are the leak down numbers and where is it leaking? What are the leakdown numbers with the cams loosened up?

Leakdown with cams on (Sunday):
0%
30%
50%+
0%

My diagnosis was that air was coming out of:
the #2 cylinder front most exhaust valve
the #3 cylinder front most exhaust valve


Monday head went back to the machine shop, they re-ground the bad 2 valves even though vacuum test was good. Vacuum test was slightly better after second valve job.

Leak Down Test - Cams Off (Last Night):
0%
10%
15%
0%

Leak Down Test - Cams On (Last Night):

5%
Too Bad to record%
Too Bad to record%
5%

Diagnosis is now the same cylinders but intake side. My new thought is something is causing the valves not to close. My thought (from your recommendation is that the lifters may be soft due to sitting out of the car for as long as they did and they need some time to acclimate to being squished again.

Thoughts?

[Rob Burgoon]

My valves all sticked out for a while after the valve job. I'd put your car together and run it. Then do another leakdown.

[davecarama]

OK, that is what I'll do. Was going to buy new lifters to rule that out... but I am a poor bastard, and will save the money... after all, that is almost half of an entry fee... almost half the cost of one tire... almost half of half the cost to get this whole head redone...

Thanks again!

[MPR22]

pull head fully assembled, flip it over and use a wrench to turn the cams. Watch the valves as it goes around, you should be able to see which ones aren't closing. I'm guessing the machine shop cut the seats too deep. Also verify your HLA's are working, some people have been known to turn them into solid lifters which would also be causing this problem after a valve job.

[Jim Drago]

what you need to do first is rotate the cams to where the cam load is fully opening the valves in the cylinder in question. Let it sit that way for 10-15 minutes, then recheck. Some times the lifters stay pumped up. If you leakage problem is resolved, you have a lifter issue. And or check with cams loose so all valves are closed. I have had this issue with lifters before

[FTodaro]

If the motor is out of the car and you cannot run the motor then any compression testing or Leak down testing would not be accurate if you cannot get the motor warm when you do it. If you doing all this on a motor that has not been started i would alt least get it running or try to. Maybe I did not read all above carefully but did you just do a head job and the lower end was good before you started?? I still think a warm Head would give better results over cold? I would think the head could be bench tested?

[davecarama]

FTodaro, Yes, the head was the only thing touched this go-around. The older used bottom end was untouched for this build.
The vacuum test at machine shop was supposedly A-OK, all valves/ports in the green or better.
I brought them 2 heads, and they chose this head because it had a better casting... actually, I think they said MUCH better casting and to get rid of the other one that it was fine for a street car, but will never be a good head (poor other head).

Jim, I did post about rebuilding a lifter a while back and you told me not to... just for note... these are not the lifters from that head. The head/motor are from a car that was sitting for quite some time, so I have a feeling the lifters are stuck in the inflated form.
If it is a lifter issue, do they tend to fix themselves or does that mean they need to be replaced?

MPR22, I know they are NOT currently converted to solid. All have the plunger... and all are springy (which means they are bad according to the book, right).

Thanks for your input all! Huge help! What a great community!

[Jim Drago]

Dave
I think you need to know what is going on.. Before you buy and make changes..

I would do in this order... Pull cams, that will close all valves. Do a leak down. If all cylinders are in an acceptable level, than you have a lifter problem, which is what I think you have going on.

If the lifter is stuck open, it should fix itself after running, but if not sealed it will burn the valve. So my advice would be to change or rotate and hold as I said above until all lifters are operating properly.

Jim

[Keith Novak]

What about replacing the lifters with ones from the other head?

[davecarama]

Naw. The other head's lifters are shot. Worse than these ones.

OK Jim, I'll be doing that this weekend. I'll follow up with my findings!

[davecarama]

Wow...

Got to the garage this morning after thinking for a few days about what the issues could be. Could it be the Timing belt was off by a tooth or something - Nope, that wasn't it. I already knew that the leak down with the cams off was acceptable, so I did what Jim recommended above and left the lifters so the valves were at full open for about 20 min. That didn't fix the issue.

So I shrugged and just assembled the thing and put it into the car.

After hooking it all up, we started it and it sounded as you would imagine... Very good, the lifters were NOISY, which was expected, but no smoke!

After about 30 min, the lifters went silent and the motor just purred. So time for another compression and leak down!

Compression was in the 200-220 per cylinder
Leak down showed about 5% in cylinder 1 and about 3% in the other three...

This season is looking like it might be REAL fun! Now I need to talk the wife into letting me buy a megasquirt!

I didn't get to race this weekend. Wish I had, I really do like driving in the rain. Next weekend I was planning on instructing with NASA... but now I might do time trials to see what this thing can do!

Thank you all for the help and recommendations!

A very happy,
Dave

[Jim Drago]

great news!
Jim

[tony senese]

Awesome Dave, thanks for sharing your trials and tribulations!!