Bellhousing Alignment

I'm moving along in my 4-speed conversion. I removed the TH-400 and went to test fit the bellhousing and it doesn't fit over the alignment pins. And yes, it is a BOP housing. I think the distance between the pins is slightly less than the holes in the bellhousing. So I apparently am going to have to replace the pins with offset pins. Can anyone suggest a method of removing the pins that are in the block? Also, does anyone have any experience with RobbMc pins (see link)? They have a great idea if they work as claimed.

http://www.robbmcperformance.com/15001/42201.html

 

That is weird. Do the bellhousing alignment holes appear to be altered? Or maybe were the 400's holes altered? If you have a clutch & plate on, make sure the BOP bellhousing is not one of the 10.5 clutchers. I had one of these once, and it would almost go on, but not quite. I think it was off of an 80's Pontiac TA.

 

The holes do not appear to be altered. And this bellhousing is supposed to be out of a Pontiac and fit 65-70. The transmission I took out is original to the car so I'm sure the pins are original. Unfortunately, with the engine in the car, I can't get a clear view of what is happening, but this bellhousing definitely won't go on as is. I'm wondering if every bellhousing is unique to the car it came with. If, at the time of manufacture, they had a jig that aligned the housing to the crank and then they drilled and pinned it so each one is slightly different. I don't see how else they could have done it given all the additive tolerances involved with every assembly.

Anyway, I'm still in need of advice on how to proceed. I'm not too excited about buying bellhousings until I find one that fits! And how do those pins come out if I have to change them??

 

My bellhousing has been on three different engines: a factory GS 455; a GM crate 455; a '70 Riv 455. So I'd say no. I bet the housing is out of spec. Several years ago I saw an article in HotRod or Camaro Craft on setting bellhousing alignment. In the case shown in the mag they were aligning a scattershield. If people figured out how to fix the problem then the problem must actually happen from time to time.

 

Hey, thanks Brad. Want to sell your bellhousing? Just kidding. Not a route I wanted to take, but I guess I'll have to buy a second one to see if the problem persists. I do think alignment is a common issue, though. I have not read one article about mounting a bellhousing that doesn't stress checking the alignment to the crankshaft with a dial gauge. Of course, you first have to be able to get the thing mounted. I can't see how it could be my block, though. The TH-400 mounted perfectly and slid right off when removed.

 

Update

Update.

Article in this month's Camaro Craft on the subject of dumping the auto for a stick. And yes, they go back to bellhousing alignment.

BTW, if I sell you my bellhousing it'll prolly have to go with the whole car.

 

I do have the new issue of Car Craft where they put a manual into a Chevy. It's interesting, but like all the car shows on TV, they make it look like you can do a full frame-off restoration over a weekend! Anyway. I'm going to fabricate a length of metal that will precisely fit the pins in my block and then compare that distance to the holes in my bellhousing. Can't figure out any other way to see how far off I am. Don't know why I'll bother doing that other than curiosity, which is an affliction I have. Ultimately, I guess I'll buy another one.

 

When switching to the 4 speed, do you need to add a bushing to the end of the crank to fit the input shaft?
Harvey

 

Harvey,

Yes - a bronze pilot bushing (some needle bearing bushings are also used) fits into a hole in the end of the crank. That hole is there whether the car is auto or manual. The bushing supports the input shaft which is supposed to spin independent of the crank unless the clutch is engaged.

The hole in the crank is sometimes corroded if its never had a bushing in it before. Good idea to clean it up before attempting to slip/drive in the bushing.

 

Interesting thread. One question I've always had, being as I've always had automatics, if you wanted to switch to a 4 or 5 speed, besides the requisite flywheel, clutch and other stuff, do you have to address the balance issue with the engine? Aren't Buicks externally balanced? Would you have to match the dampner and flywheel to the old balance with the auto? o No:

 

Jason- According to the chassis manual, just a light film on the bushing. The bushing is self-lubricating. Also, I think a light film of lithium grease on the spline and, as you say, wipe most of it off. The object is to ensure the flywheel and all clutch parts remain clean and grease free.

As for roller bearings, I have read that to use those, the alignment has to be really tight. They're not as forgiving as the bushing and will fail with poor alignment. Of course, poor alignment causes many problems no matter what.

I haven't read or heard any mention of balancing. I assume the engine (crank) is already balanced and the flywheel itself, I assume, is already balanced so if you put them together, they should both be balanced. Hope that's right because I'm not pulling my engine for that.

As for my bellhousing, I think the alignment holes in it aren't far enough apart. This weekend I'm going to figure out just how far off they are and see if I can't tweak the housing a little to correct it. Can't use it as it is anyway so not much to lose. Fingers crossed!

 

When I had my engine built last year, the machinist had to drill holes in the back of the flywheel to match balance it. This was with a new harmonic balancer and original resurfaced flywheel.

 

Check the part # on your bellhousing should be 9785581,it usually stamped on the drivers side ,here is a pic below,and as for the grease just coat the pilot bushing alittle and put some on the snout in the front and where the Throw out bearing is gonna ride on but DO NOT put any grease on the splines of the trans.

 

The other thing u may have to do is move the crossmember alittle forward than the automatic position was because the TH-400 is longer than a Muncie and places the crossmember alittle forward more,i noticed that on my conv`t.when i tried to bolt up the crossmember it turned out it wind up forward than the stock bolt location.

Thanks

 

Offset dowels are avail. from Moroso and Lakewood to cure alignment and runout problems. The Morosos are longer then the Lakewoods.
Ray

 

Well, I have determined the holes in my bellhousing are about .016 farther apart than the pins in my block. I tried to tweak the thing with a pipe clamp, but it would not hold. It would return to it's original shape as soon as the clamp was released. So I bought another housing and I'll see if this one fits better.

The number on it is correct, by the way.

I am aware of the offset pins (see the opening thread). What concerns me is using most of the offset just to get it to mount to the engine and then not having enough left over to align it to the crank. This is why I want one that fits the original pins or at least fits more closely than what I have now.

 

Hmmm thats wierd,well let me ask you this,turn the bellhosuing upside down and measure from center of the dowel hole to center of the dowel hole across on the bellhousing with a tape measure and tell me what measurement you get,it should be around 15 1/2" let me know.

Thanks

 

Will do. I'll do it after work today and post the results. Thanks.