Help me diagnose this 3.0SC problem

[RazorRacer]

We replaced p/c/h #4 1,000 miles ago. During the replacement (my first engine drop, etc.) we removed all but one cylinder (#3). Don't ask. Let's just say that I am having fun learning.

Here's the problem:

Tapping sound around cylinder #2 & #3 top & bottom. It sounds like a very loose valve. I have checked and double checked the valves. I will check them again later this week. However, I think it might be something more serious. I have also checked that the rocker arm shafts are not loose. They may be slightly out of place.

Hot compression test with Castrol GTX 20/50.

#1: 130 psig
#2: 100 psig <-- too low + tapping sound? + exhaust leak?
#3: 142 psig
#4: 125 psig
#5: 150 psig
#6: 125 psig

There is also a sound under strong acceleration that sounds like a deep muffled exhaust leak coming from the left side.

Any ideas?

[dtw]

Check for broken studs?
Done a leakdown?

[RazorRacer]

dtw, good idea.

We replaced one broken exhaust stud. Perhaps the renewed torque on the old exhaust stud(s) caused another one (others) to break?

This would explain the low compression and the exhaust leak, but what about the tapping sound?

[goose2]

I believe Dave is referring to a head stud, not exhaust....common 3.0 problem. Makes funny noises and causes low compression, among other things. Broken exhaust studs would not affect compression readings.

[RazorRacer]

Goose2, thank you for that clarification. I should have said we replaced a head stud on the exhaust side. A friend of mine suggested replacing all of the head studs on the exhaust side, too. He might have been more correct than I thought at the time.

Is a tapping sound similar to a loose valve one of the funny noises?

[RazorRacer]

dtw, I'm sure that I could fine this answer around here, but perhaps you already know. What is the procedure for a leakdown test?

[euro911sc]

RR-

See this link for leak down instructions:

http://www.longacreracing.com/instructions/inst.asp?instid=25

My SC is down to the long block... leak down on #3=0!


Enjoy!

-eSC

[goose2]

like my signature says...I'm NOT an expert...but I do believe broken head studs and a possible compression leak caused by them could make the kind of noise you're describing. I'd pull the valve covers and check for broken studs...and do a leakdown test.

[Groesbeck Hurricane]

Craig,

I broke two exhaust studs when I first re-tightented everything down. Check them again. I would suggest replacing all the dilaver head studs, thought you had... I replaced the steel ones also as one of them broke.

[RazorRacer]

I am hoping the nuts on the cylinder #2 studs have backed off and all that I have to do is re-tighten them. I've just gotten the replacement gaskets and hope to check this out on Friday night.

Anyone up for some beer and fun tomorrow night?

[RazorRacer]

One of the exhaust head studs on the #2 cylinder was totally loose and the other was very loose. In fact, all of the exhaust head studs on the #1, #2, #3 cyclinders were loose.

I am starting to wonder if I didn't just do the first torque down of the cylinder studs on both sides of the engine.

I have access to all of the exhuast head studs, but I am wondering if I can access all of the intake head studs.

Is it common for the head studs to loosen after 1000 miles or so???

[RazorRacer]

Good news. The engine sounds right again. Thank you dtw and goose2 for pointing me in the right direction.

Hey David, will you be at the DE next week?

David, how tight did you torque the exhaust studs. The book says 23.5 or so ft. lbs. That seems awefully soft. It also seems too soft to break an exhaust head stud.

[Wayne 962]

Originally posted by RazorRacer
Is it common for the head studs to loosen after 1000 miles or so???

On the magnesium cases, it's common to see them "settle." On the aluminum cases (which yours is one of), it's very uncommon...

-Wayne

[RazorRacer]

Well, I must not have done the second round of torque to 23.5 Ft-lb. because all of the barrel nuts needed to be torqued!!!

Before re-torque (same as above)
#1: 130 psig
#2: 100 psig
#3: 142 psig
#4: 125 psig
#5: 150 psig
#6: 125 psig

After re-torque
#1: 132.5 psig
#2: 122.5 psig
#3: 142.5 psig
#4: 135 psig
#5: 150 psig
#6: 132.5 psig

Not much of an improvement except for #2 which had nuts that were totally backed off on the exhaust side.

There is still a loud tapping sound like a loose valve. When the #2 exhaust valve is tightened (over tightened) the sound softens, but is still there. The #2 cyclinder also has the lowest compression. Any ideas on what the problem might be?

[Groesbeck Hurricane]

Craig,

Sorry, missed this one again...

IIRC, 24 ft pounds on the nuts. My headstuds loosened up at about 10,000 miles after the re-build, but I've not heard of anyone else's doing this so I expect it is operator error.

I'd LOVE to be at the DE, but I've got to work at a gun show this weekend. The things we do...

[RazorRacer]

Hey David, I'm pretty sure now that I didn't torque the nuts all of the way. It's amazing that the engine held together. I also think the tapping sound is from a loose valve that appears to be tight, but isn't.

Well hopefully the car will hold together this weekend. Have you had your car to a DE yet?

[Groesbeck Hurricane]

Not to a DE yet. I've had so many things dragging me away from her. I've been addressing some electrical concerns and double checking torques on her this summer as I've had time. I'm now ready to wire up the starter and turn her over again, but just have not had the time. Maybe next week?

I need fewer jobs or one that pays better....

[2.7RACER]

The compression numbers are all over the place. When you disassembled the engine did you mark the cylinders and heads? And did those marked cylinders all go back into their original positions? Was the replacement cylinder the same size group as the other five? Were the heads worked on at all? What condition were the valves in? Did you replace the head sealing rings (gaskets)? Did you replace piston rings? Did you do any work on the cylinders? Hone? Polish? Clean? What do the spigots look like? Did you use a straight edge to check the cylinder heights? Did you check the heads with a straight edge after assembly? If so was there any difference? How much difference? Did you use new copper cylinder base gaskets? Why didn't number 3 cylinder come off?
Any one of the above could be the cause of your difficulties. I'm sure a bit more digging into this will reveal what the real problem is.
Good luck, and I hope the hurricanes stay away.

[RazorRacer]

David,

Get your 911 running, dude!

Racer2.7 you have asked a lot of questions. Thank you for your interest. Here are my answers.

When you disassembled the engine did you mark the cylinders and heads? Yes.

And did those marked cylinders all go back into their original positions? Yes.

Was the replacement cylinder the same size group as the other five? Yes.

Were the heads worked on at all? No, but #4 was replaced along with the piston and cylinder.

What condition were the valves in? I don't know.

Did you replace the head sealing rings (gaskets)? Yes.

Did you replace piston rings? No.

Did you do any work on the cylinders? Hone? Polish? Clean? No.

What do the spigots look like? What is a spigot?

Did you use a straight edge to check the cylinder heights? No.

Did you check the heads with a straight edge after assembly? Yes.

If so was there any difference? a little

How much difference? It didn't seem like enough to worry about at the time.

Did you use new copper cylinder base gaskets? Yes.

Why didn't number 3 cylinder come off? Now I know that I could have taken #4 off and left the other five alone, but at the time I took #2 off to take #3 off and #1 came off to take #2 off. Then #1 and #2 fell off (slightly) when the engine was pointing down in that direction. #3 stayed on so I didn't mess with it.

Hey, I'm just learning to be an amature. I hope I'm not upsetting to many Pelicanheads as I learn about this car. BUT, the engine is now performing and the tapping sound has gone away. I have a DE this weekend and the weather is cool and the car is hot.

Next time, I will replace the p&c's and redo the heads.

[2.7RACER]

RazorRacer,
Not to worry. You got it back together and running.
My first rebuild was a learning experience and I didn't consider half the things I asked you about.
After playing on this site for awhile and reading all the books I can get my hands on I've learned.
I didn't know what a spigot was until I read it in a book or this site. It is the hole in the case that the cylinder fits into. The surface of the spigot can get banged up with broken head studs. It is good to check across the three spigots with a straight edge just to have a good starting point. I think 0.004" (0.10mm) is the tolerance. Same with cylinders. Once the heads are on you want those surfaces close too. If they are off it's tough to get the cam tower to fit right and seal the heads to the cylinders correctly.
I learned all that from this site, so I'm just passing it on.
Kind of like Doctors, see one, do one, teach one.
Good Luck at the DE this weekend,