1972 Starter Motor Question

[tchp]

I have a 1972 K5 4x4 with a 307 and 3-Speed manual column shift. I replaced my starter today, and noticed that in addition to the mounting holes for the 3-bolt mount flange that my current starter uses, there also appear to be two additional, unused holes tapped into the block up above, which might correspond to the bolt pattern for the other type of starter Chevy trucks use that has two vertically oriented mount bolts. Does anyone know if you can use either of the two starter types on my engine? I only ask because about 10 years ago a mechanic broke one of the tapped holes in my engine block that my current starter uses, so I am down to using only 2 of the 3 bolts for the mounting flange (which at least has worked ok for the past decade, but if I could use the other type of starter mount that would be a good thing). TIA

 

[toomany]

To my knowledge GM small block (and big block) starter mounting styles have stayed the same since the engines were first produced. There are two differnt styles...inline bolt holes and offset holes. The inline ones are for small flywheels (153 teeth) and the offset ones are for bigger flywheels (168 teeth). I could be wrong though...since I don't recall ever working on a block that old.

 

[tchp]

The starter I am using has mount bolts that are situated in a horizontal position, and attach the starter via a typical "flange", which surrounds the pinion opening of the starter. I believe subsequent engines have starters that use two bolts (situated vertically) and an additional mounting brace/arm to secure the forward part of the starter motor to the engine block. At the Napa store, the guy initially brought out the latter type of starter, and then seemed to say that the reason he had brought out the wrong type was because it was for a 307 with an automatic tranny, rather than my 3 speed manual shift. My engine does appear to have the holes tapped for the type of starter that uses two vertical bolts to mount, but that is not to say it would work to mount that type of starter. I was just wondering if anyone ever had successfully done so.

 

[bp71k5]

My 67 327 and 69-72 350 both used the same starter with a 168 tooth flywheel. The starter bolts up underneath the block using two vertical bolts. No shims, brackets or anything else. Not sure what similarities the 307 has, but I can't imagine it's that different. I would expect 4x4High to know what the differences are though. Try PM'ing him if he doesn't chime in.

 

[bigblock72]

Most of the manual trans trucks with cast iron bellhousings up to the mid 70s (possibly later) used a starter that bolted up to the bellhousing with three horizontal bolts instead of the block with 2vertical bolts. You can bolt up a offet bolt starter and have it work ok just the dust shields won't work right.

 

[4X4HIGH]

bigblock72 nailed it although i don't think you can use the block mounted starter with a manual trans. Like he said, your starter doesn't bolt to the block, it bolts to the transmission bellhousing using 3 bolts (or 2 in your case since a flange is broken).

 

[tchp]

Thanks all. I guess I will cross my fingers and hope the surviving two bolts continue to work. They do seem to cinch down the starter pretty well. It is the lowermost bolt closest to the driver's side that has its tapped hole broken, so I at least have the upper bolt and one of the lower bolts, so it is held in pretty good. Would have been nice to use the other type of starter mount though.

 

[dremu]

One solution could be to drill and helicoil the bellhousing. You (or your machinist ) drill the hole out to a slightly larger size, tap it, then put in an insert which is threaded inside and out; the outer threads matches the new hole, and the inside threads match the bolt for it.

This however means dropping the tranny. If you were gonna drop it anyway at some point -- changing t-cases or something -- that's a good time to fix it right.

-- A

 

[tchp]

To put in a helicoil I would need to build the area back up with a welder first, as it is a section of metal that is broken off, so only half of the original tapped hole remains in the bellhousing. So, it would need to be built up, then drilled for a helicoil. Hopefully it will not come to that, and the two bolts will continue to secure it OK.

 

[dremu]

To put in a helicoil I would need to build the area back up with a welder first, as it is a section of metal that is broken off, so only half of the original tapped hole remains in the bellhousing. So, it would need to be built up, then drilled for a helicoil. Hopefully it will not come to that, and the two bolts will continue to secure it OK.

missed that part. Nemmind...

Is the bellhousing removable from the tranny, or is it one piece?

-- A

 

[imiceman44]

To put in a helicoil I would need to build the area back up with a welder first, as it is a section of metal that is broken off, so only half of the original tapped hole remains in the bellhousing. So, it would need to be built up, then drilled for a helicoil. Hopefully it will not come to that, and the two bolts will continue to secure it OK.

Well then I am guessing you have the cast bellhousing.
I have one if you decide to change it, I want $35 plus shipping which shouldn't be too bad, you are a few hundred miles from me in OR.
The repair you could do to yours would cost you more.

 

[tchp]

I tried looking at the bellhousing while I was under the truck, but stuff was so seriously greasy under there that I really could not tell much about whether the bellhousing was replaceable as a separate part or not. If it was, then yeah, I would definitely just try to get a new bellhousing if I dropped the tranny. I will probably just let the situation stand as it is, and opt to fix it only if the current starter mount fails at some point.

 

[imiceman44]

I tried looking at the bellhousing while I was under the truck, but stuff was so seriously greasy under there that I really could not tell much about whether the bellhousing was replaceable as a separate part or not. If it was, then yeah, I would definitely just try to get a new bellhousing if I dropped the tranny. I will probably just let the situation stand as it is, and opt to fix it only if the current starter mount fails at some point.

All GM belhousings for manual trannies untill the 2000 I think, were removable, I know yours for sure is, I even have your same transmission sitting on a bench.
I am not trying to sell it at this point, I just am waiting for someone that needs it.
So if you end up needing it, let me know.
I know some toyota guys would buy yours because what they do when they slap an SM465 on their toy is that they gring off the section that has the starter mount and bolt their starter to the engine.
You could also do that to yours since you have the mounts on the block.

 

[Burt4x4]

My 72K5 350 w/sm465 came with 3bolt starter mounted to the bell housing.
When I swaped in my 454 I used a gear reduction 2bolt starter that mounts to the block. Althogh my shields do not work as well as they do with the bell mount style the block mounted starter still works fine