Camshaft binding in head

[alchole]

Doing a top end rebuild on an '88 3.2.

After building the right side of the engine I installed the cam as per Wayne's book and notice that the cam drags a bit a certain point in the rotation. I try a few different torque patterns but still the slight dragging persists.

Bummed, I move on to the left side of the engine, but on this side the cam spins smoothly. Out of curiousity I put the left side cam in the right (dragging side) and it spins freely!

Do I have a bent cam, or something different? I had them done by camginder recently(964 grind), could something have happened in the reginding process?

Thanks for any suggestions/help.

[JeremyD]

You need to change the torque sequence. The bad news is you really should remove the cam tower and start over. As in remove the loctite, and reinstall. I did not do this - and now I have a little oil leak on the cam tower that I retorqued 12 hours later... bummer.

Mine was exactly the same - one cam tower, cam spun like a champ. the other cam tower and it bound up...

[hobieboy]

yeah - i did the same thing. Disassembled the whole thing and restarted it "nonstop" until it spins freely.

[alchole]

Thanks for the replies guys....

Don't you think it's strange that the cam from the "good" left side of the engine spun freely in the right "bad" side cam carrier?

I'm doubting myself now, but I'm pretty sure it spun freely. I guess if I try the "bad" right side cam in the left side and it still binds then I would be inclined to think it was the cam.

Am I off base on this?

BTW, did you guys use loctite 574 on the copper cylinder seals?

Thanks again....

[JeremyD]

Originally posted by alchole
Thanks for the replies guys....

Don't you think it's strange that the cam from the "good" left side of the engine spun freely in the right "bad" side cam carrier?

I'm doubting myself now, but I'm pretty sure it spun freely. I guess if I try the "bad" right side cam in the left side and it still binds then I would be inclined to think it was the cam.

Am I off base on this?

BTW, did you guys use loctite 574 on the copper cylinder seals?

Thanks again....

Mine did the same, spun on one side - would not on the other. I did not use 574 on the copper cylinder seals - and wish I did now.

[camgrinder]

Put both cams on your bench next to each other. You will notice the 2 center bearings do not line up with each other. So, by installing the left cam in the right housing, the two center journals are not riding in the housing.
I straighten the camshafts to less than .0005" total indicated run out before I grind them. Unless they were damaged in shipping they will still be straight.

I would completely back off the housing and then insert the cam and check for binding. Should be fine.

[racing97]

Somtimes it is not the cam or the cam carrier's fault .
If you do any modifications in regard to the barrels or the head surfaces, to check assemble the heads on the barrels and install the cam carrier with a few of the 8 X 1.5 nuts, then torque the heads, afterwards remove the cam carrier and use a straight edge accross the heads.
If all is well apply your sealer and complete the fastening of the cam carrier, if not you can isolate the culprit.

regards

[alchole]

Quick question.

Obviously the loctite 574 has now cured. Can I safely loosen the cam carrier and try a re-torque without having the the assembly leak (assuming that I can get it to the point where the cam doesn't bind)?

Or at this point should I bite the bullet and tear the top end down, remove all the dried loctite, measure everything dry and refit?

Thanks again for all your help (camgrinder, racing97, etc...)

BTW, camgrinder, is there any quick and dirty check a can do with my cams to make sure they didn't get damaged in shipping?

[ChrisBennet]

That sucks.
You're right, now that the Loctite has dried you won't be able to get away with just retorquing.

Remove the cam carrier and clean the Loctite off both surfaces.
See if the heads are even using a machinist's straight edge or piece of ground stock. If can't do that, you can bolt the cam carrier on dry and see if your cam spins then.

Check the locating pin holes in the bottom of the cam carrier - make sure they haven't been "boogered" or plugged with sealant. Make sure there isn't any hardened Loctite "crumbs" anywhere between the sealing surfaces.

Whatever sealant you use (I use Threebond 1104 a.k.a. "yamabond") put it on thin.

This episode will be nothing compared to the pride you'll feel when you can say "Mine doesn't." the next time someone says "They all leak." (refering to 911's) .
-Chris

[camgrinder]

Heres a pic of the cam bearing journal locations. Other than removing the right side housing, you can put the right cam in the left housing backwards and the journals will all line up. That is if the soft plug at the end of the housing has not yet been installed.



If you have access to a lathe and a dial indicator you can check the cam for bearing journal run out. Chuck up a dead center on one end and use the tail stock center on the back end. Set a magnetic base dial indicator on the toolholder and spin the cam by hand.

[911pcars]

"If you have access to a lathe and a dial indicator you can check the cam for bearing journal run out. Chuck up a dead center on one end and use the tail stock center on the back end. Set a magnetic base dial indicator on the toolholder and spin the cam by hand."

Or support the cam on each bearing end with V-blocks, then measure with the dial indicator.

As racing97 pointed out, it could also be the component stack is not even between the 3 cylinders on the bank. The combined height of each crankcase spigot surface, cylinder base gasket, cylinder and cylinder head must be equal, otherwise the cam housing will tweek (or bend) slightly when the component stack is sandwiched.

Sherwood

[alchole]

Thanks everyone!

Seeing as how I put loctite 574 on the copper cylinder base gaskets, can I leave the cylinder heads torqued down and just remove the cam carrier, clean up the surfaces and try to re-fit?

[ChrisBennet]

Originally posted by alchole
Thanks everyone!

Seeing as how I put loctite 574 on the copper cylinder base gaskets, can I leave the cylinder heads torqued down and just remove the cam carrier, clean up the surfaces and try to re-fit?

Yes. Permatex Gasker Remover spray works well on removing old 574. I don't know if it's necessary but I'd mask off the springs in the head with some aluminum foil before spraying the remover.
-Chris

[davidppp]

Hello there.

I do not think 574 should be used at the cylinder base..it hardens, and if the whole assembly is not torqued very quickly, it will form an incompressible wedge.

Furthermore, there is a lot of movement here with heating cooling cycles...

I use blue Hylomar with no problems..its soft and stays that way.. you can replace stuff without cleaning it all off in a pinch..use it all the time on gearboxes etc which have to come apart in the field..(literally).

Kind regards
David

[dtw]

Originally posted by alchole
Thanks everyone!

Seeing as how I put loctite 574 on the copper cylinder base gaskets, can I leave the cylinder heads torqued down and just remove the cam carrier, clean up the surfaces and try to re-fit?

It's distinctly possible that you've just identified your problem.

See this thread

[alchole]

Well, removed the cam carrier. Cleaned off all the loctite 574 (thanks Chris for the recomendation of the Permatex, worked like a charm!). Cleaned off the heads as well and took Chris's recommendation of covering the valves springs with aluminum foil. It wasn't very fun....

Now I put the carrier on dry, bolted it down and.... still no luck. The cam continues to drag at a certain point in the rotation.

Now what the hell do I do? Where whould you get a machinists straight edge? Will that tell me anything I don't already know? Should I remove the heads, pull off the pistons and cylinders, clean the loctite from the copper gaskets, and then reassemble dry. Is there a way to deffinitively measure what's wrong? Is it possible to send the parts off to someone to measure and correct, since I don't trust myself to measure it with any precision.

Btw, I had the heads decked by Walt at Competition. I know he does great work, but could it be possible that something didn't go right?

Any suggestions?

Thanks....

[jimbauman]

Just a thought - have you tried the cam in the carrier with the carrier on the bench?
JB

[camgrinder]

I 2nd Jims Idea. back off the bolts and see if the cam spins. There could be a nick somewhere in the carrier or on the cam causing the problem.

[Eagledriver]

As others have said you should remove the 574 from the base gaskets. If it hardened before you finished torquing the heads it will be different thicknesses under the cylinders. Also with the shifting around and pounding this area takes it may crack and start to leak. A non hardening sealant is what to use here.

As far as the drag goes, my opinion is that if it's a minor drag that you can easily turn through by hand then it won't be a problem. Think about how much the cam is pushed sideways by the valve springs when the engine is running. The slight drag you are feeling will be much less force on the bearing surfaces. These surfaces are pressure lubed and can take lots of pressure. I know this goes against conventional wisdom but sometimes conventional wisdom is wrong.

-Andy

[Wayne 962]

I've been watching this thread, thinking that it was something obvious that would have been figured out by now.

Okay, if you still have the problem after doing all that, you need to start at the source:

- Measure the cylinder mounting surfaces with respect to each other. The 3.2 aluminum cases usually don't warp in this area (the 2.7s do), but you never know

- Measure the shims under the cylinders. Don't truse the manufacturers - measure everything.

- Measure the head surfaces and distances between them.

- Measure the cylinder heights.

- Swap the left and right cam towers and see what happens. If the camshaft still gets stuck, then you know the problem is with the left cam tower...

-Wayne