yellowline

In a nutshell- resealed the upper balance shaft to factory manual and Clark's Garage instructions. Used Loctite 574, new mylar washer, the correct front seal for the upper shaft, torqued the cover bolts in sequence with a N-m torque wrench, everything by the book. Now the shaft doesn't want to spin.

I'm not moving on to the next one until I figure this one out. Any ideas?

xsboost90

do you have the pulley on it yet? When you put the pulley on it centers the shaft in the housing and usually frees it up. If you do, did you put the bearing cap on the same way it came off? they are bored specially after the cap is installed and torqued so its like a rod cap- backwards would make it off center.

yellowline

Pulley is off, waiting to do the other seals and WP before putting belt covers and pulleys back on.

For the bearing cap, do you mean the one on later cars that installs between the counterweights towards the back of the block? Early cars apparently don't have them...the balance shaft was free after I initially removed the cover.

Thanks all.

944 guy

My balance shafts were rather tight too, I couldn't move one of them by hand after reinstalling. But after I put the drivepulley back on I had some leverage and it freed up just nicely and went a lot smoother after the initial movement.
Just slide a pulley on (without bolting) and see what happens. If that doesn't work crank it down (as said to line up the shaft in axial direction) and give it another swing (put the rear beltcover on, it's not much work removing it again if you have to).
Don't forget the new bearings are a hell of a lot tighter than old worn ones!
My old journal bearings (between the weights) were pretty shot: the 'bottom' of the bearing as it is in the car was completely polished into the backing material for about 1/4 of the circumference, I guess from all the starting. As far as I could see the full round journals up front were in better condition, I guess overall they aren't loaded as much as the rears.

potent951turbo

I would also try sliding the gear on temporarily and seeing what happens. Sometimes just giving them a tug forward will free them up, they can get tight/stuck from being pushed in too far etc.

xsboost90

put the gear on and just hand tighten it- they are real picky as far as alignment so it will pull it straight and should spin free.

yellowline

I put the gear back on and gave it about 10 revolutions or so. It turns now and the effort isn't that high, but it still has a good bit of drag- it won't spin freely. Maybe the assembly lube is doing that?

By doing that, I haven't ruined the (old) bearings, have I? They checked out, so I didn't replace them.

944 guy

I have no idea about your assembly lube, but if it's thicker than oil it will obviously create more drag. Besides: they will never spin freely, journal bearings do that. Don't forget that people say the balance shafts take about 5hp to run, so they will always have drag.
Don't sweat it, it sounds good to me. I fired up my rebuilt engine today and it sounds great!

FRporscheman

Did this problem get resolved? Dan was referring to the front cover piece, shaped like a cylinder. The piece you press the seal into. It has 3 bolts going through it. If it is installed in the wrong orientation it can bind the shaft.

924RACR

VERY VERY interesting... we just stumbled up against this problem on an S2 motor... was the 2nd shaft we were doing... first shaft was easily done without issues first time...

Arash - can you (or anyone else) verify for us the correct orientation of the front cover???

Zero10

When bolting in the lower balance shaft, if the power steering mount is overtorqued it can bind the balance shaft, I suppose the same would go for the upper balance shaft. Once the loctite has sealed I'd be tempted to loosen those bolts a turn or two to see if it changes the effort required to turn the shaft. The sealant has a very high holding strength so just turning the shaft shouldn't break the seal, but go easy anyways.

On my 951 this was the issue, apparently I cranked down the power steering mount a bit too tight and it caused the lower balance shaft to intermittently seize up.

V2Rocket

before the pulley is installed isnt there a little bit of sliding room back to front on the balance shaft? for some reason i think there is but i havent seen mine in over 2 years so im not sure.

FRporscheman

I'm at school right now and I don't remember off-hand. But just use a marker to mark the bottom of the piece so it goes on the same way as it came off. If you suspect the piece is currently installed the wrong way, then I guess you can compare to someone else's car. I'll take a picture tonight and post it up.

For now all I can offer is this excellent illustration from the parts katalog:

yellowline

The upper cover (what was in question for me) only orients one way. I had slight axial play (front to back). I used a fairly accurate 3/8" newton-meter torque wrench and the FSM, so I'm fairly confident about that.

I chalked it up to extra drag from assembly lube and a lack of real oil. I consider myself moderately experienced when it comes to timing belt services...installed the pulleys and belts, turned it around, and it seemed normal. I've put 6000 miles on it since June, and the engine is perfectly smooth. I last checked tension about a month ago and the belt looked fine.

eohrnberger

Well, I'm at my wits end here.

Started to re-assemble the engine with Vaughan (924 RACR), got the bottom end (crank, bearings, pistons, rods and bearings) all back together, and that went just fine. Turning the crank barely requires a wrench. Sweet.

Then it was time for putting the balance shafts onto the block. The left cover went on just fine, new bearings seals and all, turns very easily, don't even need a wrench to turn it. Nice.

Then is was time for putting the right balance shaft together. Cover, seals, bearings. The front nose piece, all finger tightened down and then torque it down, to spec, and it won't turn. Oh oh! It's locked solid!

OK, so we took it all apart checked everything for cleanliness, scrubbed a bit with mineral spirits, re-lubed and re-assembled. We did the first the torque spec on blots 1 & 2, and already the balance shaft wouldn't turn anymore. With or without the nose piece on. (See picture #1)

Took it apart again. Checked the nose piece's bearing, seals, and all that. Looks good there. The shaft spins within the nose and the bearing just fine.

Then we looked at the bearing that goes into the cover's bearing journal. It looks good. Lines up nice and even with the edges of the bearing journal. Can't be that.

Checked the balance shaft with an index gauge while rotating it as it was laying in a couple of V-blocks. The shaft is as straight and true as you could possibly want.

Checked the cover to make sure that it is not warped or damaged. It's not. Laid the cover on a flat glass plane, and there is barely the slightest of rocking there kitty corner to kitty corner. Like a hair's width. Something that the oil resistant sealer would take up and seal. So it can't be that.

Looked at the balance shaft journal on the block. Clean as a whistle, cleaned it anyway with mineral spirits. Tapped the bearing into the bearing journal with the handle of a small pick. Hmm. One side is even with the block's bearing journal edge, and then the other side pushes just a bit beyond the edge of the bearing journal edge. It's like the bearing is too long for the bearing journal. Weird. (See Picture #2)

So when the proper torque is applied, the one side of the bearing is pushed by the bearing journal, deforms such that the shaft is squeezed on, and the shaft locks hard and won't turn.

OK, maybe the balance shaft bearings are bad or manufactured wrong. Ordered another set of bearings. Wait until they arrive. They did.

Played the same push one side, push the other side, screw the assembler game with the block's bearing journal and the new bearing. So it wasn't the bearings after all. It's not the cover, and it's not the shaft. It's like the block's bearing journal shrank! (Yeah, right!).

How can it be that the block distorted itself in such a manner that would cause the one balance shaft bearing journal to shrink? Can aluminum do that?

OK. So now what? Is the block trash now? I'm out of my depth both in knowledge, skills and experience. This is really my first engine rebuild.

Since I've not got 4 bearings and only need 2, I was thinking that I could carefully grind off a little bit off the end of the one bearings such that it would not extend beyond the edge of the block's bearing journal. Yea it'd be a hassle but it could be doable. Grind ever so little off. Assemble to torque. Check to for easy spin. Disassemble, grind a little bit more off. Reassemble to torque. Check it again. It could be doable.

But I have no idea what that is going to do to the engine when it finally gets running again. Remember, I want to run this car hard at the track during DE events. It's why I even got the car to begin with.

Can anyone please render some advice? Please!