[Sirrotica]

Originally Posted by livetoridemyxlh

I just came upon this thread and I know it’s old, but it sounds like you fellas have a lot of knowledge about trannys and bell housings. I’ve got a 67 Tempest with the OHC 6. I’m thinking of abandoning the OHC and going with another straight six because I can’t find parts anywhere for this OHC. Would anyone know of a GM engine that would match with the BOP pattern on my ST300? I’d like to choose an engine that I can find parts for. The OHC was only made for a few years and parts are nonexistent. I’ve looked everywhere for an exhaust manifold and having headers manufactured seems cost prohibitive. I hope one of you guys has an answer.

Might I suggest you contact Jeff Hamlin, or Cammer Jeff, on this forum. The 2 Jeffs know a heck of a lot about these engines, and sometimes have parts for sale, or know of parts that are available.

My own experience with inline 6 engines is that there are no other GM versions that have a BOP bolt pattern on the rear other than the OHC 6 Pontiac. That problem though is easily solved, by the conversion adapter plate sold by many sources such as Jegs, or Summit. It can be bought to adapt a BOP engine to a chevy engine pattern, or a chevy engine to a BOP transmission pattern, usually under $100. Many people don't know that the 2 lower holes match, and the upper 4 holes are fairly easy to adapt with the plates.

When the OHC 6 was designed, Pontiac used some of the dimensions, and parts from the chevy 6 to defray costs, so there are some parts, and dimensions that the two engines share. Some parts are the same, others can be made to fit with some modifications.

[25stevem]

Anyone know if these TKO transmissions use a tapered input shaft bearing?

[george kujanski]

How about the inline 6's used in the early 2000 Envoy and trailblazers? Corporate transmissions, etc.

george

[Goatracer1]

If the F-bird has a later T350 trans they came with dual bolt patterns. Both Chevy and BOP possibly causing confusion.

[Schurkey]

Originally Posted by george kujanski

How about the inline 6's used in the early 2000 Envoy and trailblazers? Corporate transmissions, etc.

The "Atlas" six-popper. A truly world-class inline six, backed-up by a 4L60E in either RWD, or with 4WD or AWD transfer-case versions depending on the original application. Marvelous power plus wonderful durability EXCEPT for the exhaust manifold which has been troublesome (cracking). Aftermarket exhaust manifold kits are readily available and not expensive; but suffer from the same limited durability.

Downside is that you're likely stuck using the entire computer-control system and wire harness, plus in-tank fuel pump.

Fairly certain that it uses neither the BOP nor Chevy bellhousing pattern. Might use the 60-degree 2.8L, 3.1L, 3.4L bellhousing pattern. Not sure. But if you're slapping in an Atlas six, might as well upgrade the trans from the pathetic 300 at the same time.

[MatthewKlein]

Originally Posted by 25stevem

Anyone know if these TKO transmissions use a tapered input shaft bearing?

I believe so. That's the reason behind bellhousing alignment being so critical.