What engines bolt to an ST300?

[Rickesota]

My '65 Skylark is a budget build. I want to upgrade at least the engine, but I need to know how much power the ST300 can handle, and if it's worth using behind a V8. It's doubtful I'm going over 300 hp.

If anybody has a complete manual setup for cheap I'm all ears. In the meantime, I'm awaiting my visits from Santa, the Easter Bunny, and the Tooth Fairy.

[jmos4]

Hi,

ST300 came with 2 maybe 3 different bellhousings, 1 nailhead specific which came in rhe 65 & 66 Gran Sport.  The other came with a BOP bellhousing and came from the factory from 64 to 68 behind Buick V6, small V8, Oldsmobile V8, Pontiac V8.  Also believe there was a version behind a Chevy straight 6 that had both Chevy and BOP patterns but not positive.

The trans can be built to handle decent HP, not sure on the limits, I posted a few articles I found online in the trans section of this site. I did a few upgrades on a 65 Oldsmobile Cutlass with a 330 and it shifts harder, just haven't had time to tune the car yet, that will be next spring project.

Regards,

[Rickesota]

To clarify since I'm not quite a Buick-phile yet, the nailhead bolt pattern is different than the standard BOP bolt pattern? Mine is behind a 225 in my car now so I'm guessing mine is standard BOP. I see 350's and 455's for sale and I'm hoping to drop one in if it's a viable option until I can afford to get a TH350, TH400, or manual, and then deal with the associated driveline mkodifications.

Thanks!

[jmos4]

Hi again,

Yes a 225 has a standard BOP bellhousing.  Which will bolt to a 455, but most likely won't hold up. The V6 transmissions to my understanding less friction clutches than the V8 ones.

You could have yours upgraded, but would be better off spending the money on a stronger trans. A 200r4 would be nice for a automatic, lower 1st gear and overdrive. I personally like a manual transmission but a overdrive is nice to have, lots of options just depends on the pocket book and what you want to end up with.

Regards,

[Rickesota]

Believe me, I would MUCH rather have a manual, but from what I have read here and on v8 Buick, these parts are near impossible to find, and expensive when you do. I'm scouring Craigslist for parts cars with manuals but I haven't found one. I have seen running 350's for $275 and 455's for $500, and TH350's in the $300's so I guess it does make sense to ditch the ST300 if it probably won't hold up, anyway.

Thanks again for your input!

[jmos4]

Getting the parts to do a manual transmission swap isn't as bad as it might seem.

Bellhousing can be from most BOP applications or even look for one from a jeep as they used the 225 V6 as well. Just check the starter side as there is 3 types, drivers side, passenger side  and both.

Pedals any A-body set should work 64-66 I believe are the same or close enough between all 4 GM divisions

Linkage from the pedal to clutch fork might be tough to find or convert to hydraulic, also there is a few places that reproduce the linkage but have heard of issues, so do some research before buying a set.

Transmission any Muncie, T10 or even a Saginaw will work  depending on your engine(hp/tq) choice. Also I saw someone have a t5 in a Skylark with a sbb

Doing a 350 or 455 is much easier than a nailhead as that is the very expensive parts.

Best of luck with the project

Regards,

[TrunkMonkey]

Take a look at the steering column/firewall seal plate. I had a 1964 Special that was 300/ST300 and I did a swap and put in manual shift (the wntire driveline and front ends to disc brakes back in 1978, but I recall almost every detail) The plate had the cutout for the clutch pedal pusrod so it was simple.

I am in the process of doing the same thing with a 1964 Skylark and it has a plate for the automatic, so I had to get the correct plate (bought a column for a '65 floor shift with the plate attacthed).

You can get an aftermarket plate and seal.

Since I am doing a Nailhead and t10 swap in, I will be going with hydralics rather then trying to put together the '65 GS linkage, which is more complex than the typical a-body BOP linkage.

I have the old engine/trans out, so if you need detailed pics, measurements or anything, let me know.

I can provide the floor hump cutout location information as well

Still have detail work I am doing, so it may be two months before I have everything stuffed back in.

[cwmcobra]

I have a Muncie M21 available that came out of my 65 GS.  Replaced it with a T-10 to make it correct, but the Muncie worked just fine.  Just shoot me a PM or email if interested.

Chuck