911SC engine disassembly going great, until...crank's not turning

[bigred23]

I'm nearing the end of engine disassembly for an '82 SC, 207k miles, and will be ready to split the case once I remove the last two pistons (#1 and #3). Unfortunately, I can no longer get the crank to rotate enough to gain access to the wrist pins; the resistance feels similar as if there were a set of cam locks on the engine. The crank rotates maybe 10-15 degrees, at best.

All hardware is accounted for (nuts, washers, circlips). Not to say one of my kids could've "slipped" something in there! Anyways, in the little travel I do have, it doesn't appear any of the rods are getting hung up on the case. In addition, the cam chains do not appear to be bunched up, and are still engaged around the intermediate shaft sprockets...

Anybody encountered this? Any ideas?

[frankc]

Double check the cam chains. I had something similar when disassembling and it was one of the chains overlapped on the gear.

[bigred23]

yeah, I've checked and double checked the chains. They don't appear to overlapping...I've contemplated just cutting them, though...

[Alan L]

A pic would help. Have you got the chains hanging outside the case on the sprockets?
Can you move all the other 4 rods freely when it binds?
Have you been able to spin it 360 deg before this point? (I have had mine bind on the engine stand).
Alan

[VFR750]

Originally Posted by frankc

Double check the cam chains. I had something similar when disassembling and it was one of the chains overlapped on the gear.

+1

Cam chains can easily half jump a tooth and do exactly what you are feeling. You have to pull the chains outward and rock the crank back and forth to get the chain back on the sprockets.

Also: get used to it.

This will happen multiple times during assembly; When installing the pistons, cam housing and finally just before you time the cams.

[Flat6pac]

One of the rods is binding in the dropped back stroke, or the chain is binding on the gear.
Bruce

[bigel]

Agree with Bruce/others...my guess is rod(s) binding in bore.

Originally Posted by Flat6pac

One of the rods is binding in the dropped back stroke, or the chain is binding on the gear.
Bruce

[al lkosmal]

I was dis-assembling a 2.7 yesteryear and while rotating the crank to remove the pistons, i had the crank rotation stop several times.....it was a chain binding every time. When the rotation stops......pull on a chain and rotate the crank slowly in the opposite direction you were originally rotating it. If it was a chain issue you will feel it free up.

regards,
al

[Mark Henry]

On chains I built a simple fixture (X2) that holds out the chains so they can't bind. There is a Porsche fixture that I copied but I don't have time to look right now.

[bigred23]

Thanks for the input, guys! I hesitated to post this topic b/c it's like, "what the hell am I missing here?". Rods are free of obstruction, chains appear to be fully extended and riding on their sprockets, etc. Perhaps with the promise of fresh nitrile gloves, I can coax my better half out into the garage tonight for assistance while I muck around with the chain

[Alan L]

So, while it is bound, the 4 other rods are totally free to move? They can and will bind inside the bottom of the cylinder housings. But if totally free then really only chain or engine mount - depending how you mounted it. As stated above - rock the crank and pull on the chains - you may be able to peek down inside. But they are notorious for binding if you don not keep them outside the case. Again - not sure how you have it mounted - but with the sprockets providing weight in the ends of chain, outside case, usually avoids this.
You should be able to do this on your own - socket on crank pulley, lean back/forth, pull on L/R chain. Something should come free.
Alan

[bigred23]

Standard setup i.e. Porsche engine yoke, engine stand, etc. Yes, with the 1-3 cylinder bank orientated towards the ceiling (and 4-6 facing the ground), all 4 piston-less rods can be wiggled freely while rocking the crank. One nuclear option I've considered is to just cut the chains and remove (they'll be replaced anyways...). But as one previous post pointed out, this can/will happen on reassembly, so I need to just work it out

[Alan L]

Most likely the 1-3 chain.
turn the crank back 5-10 deg and yank on chain. If nothing pings free, go back another 5-10 deg etc. Try the bottom chain too - just in case it bound before you flipped the engine.
Alan

[JohnJL]

Originally Posted by bigred23

Standard setup i.e. Porsche engine yoke, engine stand, etc. Yes, with the 1-3 cylinder bank orientated towards the ceiling (and 4-6 facing the ground), all 4 piston-less rods can be wiggled freely while rocking the crank. One nuclear option I've considered is to just cut the chains and remove (they'll be replaced anyways...). But as one previous post pointed out, this can/will happen on reassembly, so I need to just work it out

Just to be clear, while the crank is rotated until you feel it "lock" the the other 4 rods wiggle freely? WHile gentle pressure is applied to rotate the crank? I have had this happen on every single motor I have disassembled, its totally common. In every one of my cases holding the rods perpendicular to the caseline made rotation easy. The old "elastic band through the rod and on the studs" usually works but sometimes you need to hold a particular rid 'just so' while rotating the crank.

[JohnJL]

You could also just skip ahead and take the chain housings apart so the chains are slack.

[bigred23]

aye..no luck tonight. Both chains appear to be fully engaged in their sprockets (no bunching), and the piston-less rods are wiggling freely. While my wife managed crank duties, I went around moving the rods, attempting to keep the piston pin bushings centered in the bore

Interesting finding, though, one of the the four interior chain ramps was only be held on with one of the bolts; the other side had cracked around the other bolt and a sizeable piece was missing. I'm thinking that plastic piece has found its way around one of the intermediate shaft gears and is wedged in such a way to prevent crank rotation. Possible?

[Alan L]

Yes, possible. (but you should be able to rotate in one direction I suspect - so it is spitting the piece out of the gears rather than trying to trap it.) Presumably you have the cam chain covers off. have you had a good peek down there with a torch.
Have you tried to move the ramps, or is this old?
is it now totally locked or do you have some movement?
Alan

[bigred23]

Thanks for the response, Alan. Yes, engine is two pistons away from splitting the case. Reason I'm not thinking chains, is that you can look through the bottom oil plate and see the 4-6 chain is engaged; likewise, you can look through the distributor hole and see the 1-3 chain appears to be engaged as well.

As my wife rocked the crank (ha, there's gotta be a better way to say that), I couldn't see any obstruction with the rods, and with the chains appearing unbunched, I'm thinking some interference with the intermediate shaft gears (maybe between the gear and case?). I should jury rig some clothing hanger to try and sweep in that narrow region....

Right now, I have about 10-15 degrees in crank rotation, and all chain ramps are removed.

[boosted79]

If you haven't tried already, try flipping the engine over, maybe the piece of ramp will dislodge if that is the culprit. If not then I would cut the chains and get them out of there just to eliminate that possibility.

[boyt911sc]

Originally Posted by bigred23

Thanks for the response, Alan. Yes, engine is two pistons away from splitting the case. Reason I'm not thinking chains, is that you can look through the bottom oil plate and see the 4-6 chain is engaged; likewise, you can look through the distributor hole and see the 1-3 chain appears to be engaged as well.

As my wife rocked the crank (ha, there's gotta be a better way to say that), I couldn't see any obstruction with the rods, and with the chains appearing unbunched, I'm thinking some interference with the intermediate shaft gears (maybe between the gear and case?). I should jury rig some clothing hanger to try and sweep in that narrow region....

Right now, I have about 10-15 degrees in crank rotation, and all chain ramps are removed.

Paul,

This happens a lot specially during engine teardown. To avoid getting into this predicament, I leave the chain sprockets hanging on the chain itself. The weight of the sprocket on each side provides some sort of tension preventing the chain from getting off the gear teeth.

Turn the engine up with one side up (example: 1-2-3) and side 4-5-6 down with the chain sprocket sitting on the chain (hanging down). Next pull up the chain loop for 1-2-3 and at the same time turn the crankshaft pulley slightly left and right until the impediment is removed. Now, try to turn the crank pulley clockwise and see what happens.

Rotate the whole engine back to horizontal position and let the left side chain hang with the sprocket in place. Keep us posted.

Tony