The Stovebolt Site Forums The Shop Area Driveline '85 350, TH700r4, flexplate

Hello 'bolters,

I'm new to the forum though I did make an introduction. I have my first official question:

The guts of my '58 are as I mentioned, a built 350 out of an '85 K5 Blazer and a TH700r4. My question is about flex plates and starters.

I was told by the previous owner (who is a diesel mechanic that claims to know diddly about gas engines) that when he put in the '85 they went to hook everything up and the starter wouldn't mate up to the flex plate. They assumed it was the incorrect flex plate. Shortly thereafter he stopped working on it.

When I got the truck and heard this story I started looking into flex plates, but first I had to identify the transmission (he didn't know), which I was able to do. Also, everything seems to bolt up nicely underneath except for the starter. Also, from what I'm reading, for the 85/earlier --> TH700r4 there are 2 flex plates that could fit depending on the torque converter, the 153 or 168. Unfortunately I do not know which one I have. The question is could this be the correct flex plate and the incorrect starter??? Seems to me the '85 blazer was a manual, I'm assuming that would have used a different starter?

There are two different starter nose cones which space the starter drive pinion gear about 1/2" different side to side. If you get a starter for the big flywheel, it won't allow the drive teeth to engage the small one. One way to identify the different starters is to look at the position of the bolts that attach the starter to the block. On one of them, the bolts are directly across from each other, and on the other, the bolts are offset about 1 inch forward to back. I don't recall which one of the bolt arrangements is for the large-diameter flywheel/flex plate.
Jerry

153 straight
168 off set

They make some high toque expensive that fit both

Those high torque starters are actually Nissan or Toyota units with a planetary reduction gear setup that adapts them to the Chevy engine block. We used them a lot on the round track cars, mostly for weight reduction. They weigh about half what a regular GM starter does.
Jerry

Gentlemen, you guys are great. We were able to measure the flex plate and determined it was the 168, so with the info you guys have supplied we've closed the case...gotta replace the nosecone/starter. Thank you so much for your help. One step closer to an Apache Road Warrior.