Crankshaft seisure?? New rebuild!

[snowman]

I know this will get some peoples goat, how do they straighten a bent crank? MOst will not beleive how.

They use a big hammer and hit it real hard. REALLY. I am not pulling anyones leg.

[Doug Zielke]

Spring is coming.

[john walker's workshop]

there are indicators that tell you if an align bore/hone is needed. polished areas on the main bearings are one of them. if it has them, it needs the mainline trued. no need to go further and check it with anything really. the writing's on the wall. on a cast iron block, the block itself can be warped, and a straightedge will show that, because you're dealing with a basically flat surface, unlike the narrow main bearing saddles of a 911 case. a dial gauge will show if there's an out of round condition. if there is, it needs the fix. it would take more time and effort to carefully inspect all the journals, than it would take to just run the hone thru it. it's well documented that pretty much all 2.7 cases need to be align bored/honed. just for the hell of it, i called a machinist friend, and asked him if he ever used a straight edge to check the need for an align bore. they do machining on most anything that comes in the door. he said never. too hard to get a precision reading by slipping a feeler gauge under a straight edge in a mainline, whether it be a round or flat straight edge.

[kwikt 911]

I had the same symtoms as your engine had. The crank would'nt turn when cold, allthough it would spin freely when warm. I then disassembled the engine and sent it away for an align bore. Ollies checked the cases and machined them to 1st over. They also supplied the new mains. I put her back together and she runs fantastic and with no more tight crankshaft. It actually seems a bit quicker on acceleration. Good Luck!



Kevin
72 911T/E

[snowman]

Youall didn't read the article I took from the book did you?

Any machine shop that says that they don't wue a straight edge for this isn't a machine shop, its a schlock shop.

Align bore is checking for case worp age. Checking for out of round isn't. It may be that all 2.7 cases are out of round, but that isn't align bore. An align bore machining operation can be used to correct out of round bores. If one is smart one would do this like you resize a connecting rod, ie machine a small ammount off both flat surfaces and then rehone the center back to standard. It seems to me I read someone is doing this, probably CE.

If you read the article you will find that a warped crank can produce identical wear patterns to a warped case. One would also see that they covered how to check down in the long tube formed by checking for light leakage along the straight edge. I have done this myself and it only takes one or two minutes, plus the time to put the case halfs togather.

[Trevor Long]

...it would not hurt to check the thickness of the actual bearing inserts for consistency.

Believe it or not, bearing inserts can also have a "taper" to the high-load portion or crown. By checking with a thickness gauge or a ball micrometer (one that reads in tenths) you can find if the bearings are at fault.

This seldom happens, but it can. I consider this a next step check when the crank does not turn smoothly.

[biggtbiggt]

My journals were out of round and just needed a quick hone! I will post some pics of the bearings later!

And yes I did Case saver the head studs and the studs around the small shaft. They were pulled!

Thanks for all the help.

[Britwrench]

Did you remachine the cylinder deck and cylinder spigots after installing the case savers? Usualy you will find the cylinder deck is not straight so the center cylinder is low = oil leaks after about 2000 miles form rebuild.

[snowman]

One could easily say this is one for the professionals. But not so quick, This forum is a good place to bring up all the real possibilities that must be checked. That way the average joe can do a professional job. The only thing needed is patience, a whole lot of it.

It don't take a whole lot of sophisticated tools either. There are ways around almost everything if one wants to take the time. The biggest difference the sophisticated tools make is time. Just ask what you want to check and you will get the answers here.

[biggtbiggt]

do you measure this with a straight edge? Should I amchine off the other spigots or should I double base gasket the center cylinder? Also I am wondering if I will have to measure my clearence to the valves if I do any machining?
Thanks

[Britwrench]

You can measure the deck with a straight edge, and we do that machining on a mill, so with time and care anything is possible.
We do have a jig that measures everything off the crank centerline.

[snowman]

Unless you have some kind of super race engine, with an all out racing cam, you probably do not have to worry about valve clearence. If you have machined the thing so much that the valves have any chance of interfering with anything you will more likely have a problem with the tensioners not being tight anymore.

Anyway all the cylinders must be the same height, period. No need to place more spacers on one cylinder than another.

[biggtbiggt]

Here are the pictures of the wear on the bearings after 250 miles about 6hrs

[911pcars]

I wouldn't assume any clearance is okay without first checking, even a non-all-out race engine. I have mere E cams on RS (8.5:1) pistons and I still had to machine the pistons to provide add'l clearance in some areas. Just my particular circumstances.

biggtbiggt,
I assume the bearings took the brunt and the crank journals are okay?

Sherwood

[biggtbiggt]

everything else looks 100%.
We ran a line hone down the bore and they are all within spec now!

[snowman]

Looking at your photos its hard to say what happened. If the surface is just polished a bit, I would say this is normal. If the copper is showing then you had a problem. If you have the bearings checked for thickness and see less than 0.0001 to 0.0002 wear, then you did not have a bearing problem and should look elsewhere.

[snowman]

PS after looking at the bearings some more I do not think you had any problem here. The reason is that there is still some tin flash showing at the wear points. This flash is so thin it almost cannot be measured. This means that there is NO wear of any significance. I would have those injectors or carb floats checked.

[911pcars]

"...We ran a line hone down the bore and they are all within spec now!"

So you're saying this was "line bored" and all the bearing saddles are straight, round and "sized" to factory specs? If so, you're fortunate this was all you had to do. I suggest starting from scratch. Replace the main bearings with new ones (I don't like the looks of them - not sure if it's just the tin coating worn off) and check all bearing/oil clearances, rod side clearances, etc., then install the crank w/o the rods and make sure it rotates easily. If you want to install the rods, you can probably fashion some elastic/rubber band network to keep the small end of the rods centered in the spigots while you rotate the crank. Keep checking things until the last bolt goes in. Don't assume anything and the chances of long engine life get pretty good.

Sherwood

[J P Stein]

Mag case motors tend to collapse the main brg. bores parallel to the thru bolts. They can be line honed back to round if the case is not warped.....as bigg has learned. The bearing show the problem. Wear perpendicular to the case split, parallel to the bolts. I saw something similar on my motor ( rebuilt but not run, when I got it). The wear was done by just rolling it over by hand. A "drag hone" (the shop I used called it) cured it. I'm told the 2.7L is the worst for this....heat is the killer.

[john walker's workshop]

jack, how can you say there's no problem there? this is just the kind of misinformation i was talking about previously on the nit-pick thread. the crank didn't turn without considerable effort. is this a non-problem in your mind? and what's this have to do with injectors and carb floats?