DTM Alternator Install?

Post by **doc** » Thu Jun 08, 2006 9:25 am

I am having trouble getting the fan belt pulley and the crank pulley lined up in my DTM install. (GE case, Q heads). The first pulley I put on was an old one I had laying around. It made the alternator pulley stick out past the crank pulley by about 1/2". Too much, I think, for the belt to stay on.

After scratching my head and taking it apart a couple of times, I decided that there must be a different alternator pulley; one that would sit farther back onto the alternator. The first one I put on had a pretty good gap (3/8") between the inside pulley plate and the alternator housing.

Sure enough, I found another alt. pulley and this one does have "offset". It sits way farther back on the alternator and looks like it will go a long way toward solving the out of line problem. BUT, this one sits too far back. When it seats on the housing, it hits on the outside part. Clearly, not designed for this alternator. I could put a shim around the alternator shaft to make it stand farther off the housing? Maybe I could shave the alt. housing down where it hits? (have to go look at that.) Neither sounds like a good idea.

Is there a correct pulley for the Bosch alternator and the DTM installation? I have 2 different pulleys. Are there more? Have others had this problem?

Thanks,

doc

500LbGorilla · Post by **500LbGorilla** » Thu Jun 08, 2006 9:47 am

Back cut the pulley itself, to make it clear, or get some shims. Lots of places make pulley alignment kits for the purpose of getting them aligned. How much do you lack? You can get away with shimming it out about an eighth inch or so.. More than that and you start having shortage of threads for the nut.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Thu Jun 08, 2006 10:21 am

It sounds like you may have a 6 volt pulley..

generally these issues are limited to only a few thousandths that can be addressed with thin shims.

If all else fails we have a really sweet Billet pulley that has the correct offset and is very heavy duty- much more so than the new stock type pulleys, even the German made ones

Post by **doc** » Thu Jun 08, 2006 10:55 am

Thanks, fellas. Let me work with it a little. I'm fighting through a number of issues at the same time. I'll report back with results.

There must be another pulley that I don't have. Jake, I suspect you're correct. The first pulley (hardly any offset) is probably off of an old 6V car. The "newer" pulley that I have to shim out is definitely not made for this alternator. Somewhere there has to be the "correct" pulley, I think. Perhaps a NOS German late model pulley? The one I have is kind of cadmium coating gold looking - an aftermarket job, I'll wager.

Gorilla, I hadn't thought of the backcut the pulley idea. Good one!

Jake, if all else fails, I'll get the billet.

doc

500LbGorilla · Post by **500LbGorilla** » Thu Jun 08, 2006 12:48 pm

Scott, I have an extra laying in the garage. Here is a pic of the back side of it.

The offset on the back side is about 0.78" from the edge of the pulley to the hub surface where it mounts to the alternator shaft.

If you want it say the word and I'll send it to you.

Steve Arndt · Post by **Steve Arndt** » Thu Jun 08, 2006 1:16 pm

The cast 71 Bus pulley is the ticket if you can find one.

Post by **doc** » Thu Jun 08, 2006 5:49 pm

I knew there had to be something to at least fit the alternator. Thanks, steve.

Gorilla, Thanks, you're the man. As it turns out, here's what I did. Using a variation on your back cut idea, I just ground down the back edge of the pulley, where it interfered with the alternator body. And, I made an .018" shim (just like a washer) to put on the alt. shaft and make the pulley stand out a little farther. The combination of the two, shimming out and grinding back edge, now has the "newer" back pulley half floating just outside the alt. body, no interference. When I hooked it up with the DTM, it still looks like it is running a little outside the crank pulley, but it is MUCH closer than before, maybe even ok. I don't think I'll really know til I can run the motor and I've still got a long way to go.

Thanks, all, for the help. Stay tuned. I'm bound to run into something else tomorrow.

doc

dstar5000 · Post by **dstar5000** » Mon Jun 12, 2006 1:13 pm

I had the opposite problem, but it turned out that it was because
I am using the 76 Motorla alt and had to cut a little less than 3/8s inch
off of Jake's beautiful stand to make the M alt work.

Don

Post by **doc** » Mon Jun 12, 2006 5:58 pm

The devil is in the details!

Like most of us, I'm a "at home" mechanic. Probably better equiped than many, but still I'm often stalled by the smallest details. I had to make the shim for this. Hard to find a washer that thin and, by the way, the bolt & screw store is 20 miles away. But, with a snips, a grinder, a file and a bunch of time, I think I got it to work. Cussed a bunch.

I've learned to take "bolt on" with a grain of salt.

doc