Offset Bellhousing Dowel Pins

Anyone have experience using offset bellhousing dowel pins? After reading a little more on engine swaps, I figured I should check the center bore alignment on my replacement bellhousing. The pictures below show the results. After checking the runout I removed the factory dowels and snugged up the bellhousing bolts. After a lot of tapping with a dead blow hammer and rotating the engine, I was able to get the total runout down to under .002". I then sprayed some white paint into the dowel holes to get a better idea of the direction of movement I needed.

I am looking at RobbMC dowel pins. From my measurements, I think their .007 offset pins should put me in the ballpark. Has anyone used these? Am I headed in the right direction here or should I be looking for another bellhousing?

 

My only experience with this was a '73 CJ5, 258 four-speed.
Kept jumping out of gear, after all kinds of "professional" repairs, at great expen$e.

Finally, Borg-Warner advised me to check concentricity, as you are doing.

I shimmed the bell housing at the engine block with a piece of beer-can. Problem solved.

Looking at your numbers, I suspect the same idea might work.

 

Looking at the photos some more, I am curious if you have fully fastened and torqued the bell to the engine, before doing your measurements.

That could be important I suspect, given my experience as related above.

 

plus .003 + or - clearance of crank bearings . I think your over thinking . before you even get it all together

 

I am measuring the alignment of the center bore to the crankshaft. It sounds like you are talking about making sure that the flat surface (transmission mounting surface) is on the same plane as the back of the engine. That is within .001".

 

I think you missed a zero in the main bearing clearance. Should be .0003" (3 ten-thousandths). According to Novak, center bore alignment should be less than .005". Total runout on mine is .019" (add the readings at 8:00 and 2:00 in the first picture). If I install .007" offset dowels, I should be able to shift the bellhousing to the right enough to get below the .005" spec.

If you follow this link and scroll down to the bellhousing alignment section you will see what I am trying to do.
The Novak Guide to Clutches, Linkages & Bellhousings for Jeep® Conversions

 

Correct. But shimming one side of the back of my engine shifted the axial center at the trans, correcting the concentricity problem. YMMV

 

I see your point. You are not actually changing the alignment of the bore to match the crank, but rather changing the angle of the transmission input shaft to better align with the pilot bushing. How would you measure something like that?

Maybe, as Ron stated earlier, I am over thinking this. I Guess I just figured that, if I checked and adjusted all of the tolerances at this stage of the game, I wouldn't have to worry about it later. I guess I need to remember that these things were built about the same time I was - didn't require space age metals and laser alignment to work, just good old American ingenuity.

 

I measured the concentricity just as you are showing, and shimmed with beer-can until it was good.

Not saying it was the right thing to do, but it solved my problem - after paying for a needless transmission rebuild. Before the shimming it kept walking out of gear.

 

I will give it a shot. Thanks for the input.

 

I think that you are way over thinking this. I have personally mixed and matched at least 20 different engines and manual transmissions and have never measured the concentricy or had a problem with it. I would put it together and run it.

 

Thanks everyone for the feedback on this. I did decibe to spend the $30 and get a set of offset dowel pins. I figured that since it was still sitting on the bench, the cost of the dowels plus a couple hours of labor was worth the peace of mind that I wouldn't have to pull anything back out anytime soon.

I was very pleasantly surprised by how easy it was to correct the runout. In less than 30 minutes I had it dialed in to less than .002" - well within specs. As Norcal69 pointed out, I too have done a number of engine/transmission swaps in other cars and trucks over the years and never thought to check the alignment. That was long before the Internet and all of its readily available information.