Archive for November, 2008

Lets Talk About Engine and Transmission Swaps (aka Problems You Could Run Into)

Wednesday, November 12th, 2008

Lets say you have a 61 to 64 full size Pontiac and you want to install a later model Pontiac V-8 engine (anything except a 403). You should not have any problems bolting the engine to your original transmission, be it a stick or an automatic (Slim-Jim…etc). Your motor mounts will work as they are pretty much the same. Alternators may change sides, but for the most part, the swap is an easy one. You can continue to use your back-bolt starter too.

One problem waiting for you in the weeds has to do with Catalina & Grand Prix transmissions verses Bonneville and Star Chief transmissions. In both the automatic AND stick versions, the transmissions are 2+ inches longer in the Bonneville & Star Chief. The automatics will not interchange between the shorter wheelbase models. The transmission hump is shaped different also. A good reason why you cannot take an automatic console out of a Grand Prix and use it in a Bonneville. The manual transmission cars are the same way. The Catalina & Grand Prix used a regular Borg Warner T-10 transmission while the Bonneville and Star Chief used a T-10 with an extra long main & tail shaft to extend the transmission the extra distance of the longer wheelbase. Both had a cast iron case with an aluminum tail shaft.

OK, lets say you want to install a Turbo 350/400 or maybe a 700R or a L460E transmission up against your original 389 or 421 (64 or earlier). Houston, we have a problem. If you have noticed, all 64 and earlier full size Pontiac motors take a back-bolt starter. The blocks were not drilled for an up-bolt starter until 1965 for full size Pontiacs and 1964 for GTO. There is NO way to bolt a back-bolt starter to a modern transmission. 64 GTO’s were the first to use an up-bolt starter AND an aluminum bellhousing. There is a boss above the starter where a GOOD machine shop can drill your early block for an up-bolt starter, as long as they have you motor torn down, a new u-bolt starter and a correct flywheel bolted to your crank. An idea to consider if and when your early motor is torn down regardless if you were thinking about it now.

1964 GTO Block

The above is a photo of a 1964 GTO block.  Note the two starter holes in the lower left hand corner.  These holes are NOT on 64 and earlier big car 389’s or 421’s.  Thanks to for the photo!

This same problem will follow up if you attempt to install an early motor (64 on back) into a 65 on up car. You would be using the transmission (stick or automatic) original to the car, however that car HAD an up-bolt starter. Because of you putting in a 64 or earlier engine, you have no provisions for an up-bolt starter, be it a stick or automatic. And trust me when I tell you that “no matter how good you think you are, you can’t drill the block for an up-bolt starter from under the car.

One closing tip….when you have new exhaust bent for your car, MAKE SURE the guy doing it leaves enough room to slide the starter off the car without removing the exhaust. I am doing a 66 Grand Prix where the exhaust runs right under the starter so that means EVERY time you want to pull the starter, the LH exhaust pipe MUST be dropped. And of course, you’ll ALWAYS break off at least one exhaust stud! And use stainless steel studs with brass nuts. One final tip…always mount & use a factory air conditioning shroud. In the summer, you’re car will run 20 to 30 degrees cooler on those hot days.

Have any other tips to share? Please email me and if they are good ones, I will place them out here and give you the credit. Enjoy! Les

Update:  6-10-2009:

George Rutherford has passed on some excellent information on an adaptor you can buy to mount a Chevy Turbo 350 or any BOP transmission behind your early Pontiac engine (pre-1965) and use a Mopar starter to fire it up!  A company called Wilcap on the west coast sells this slick adaptor.  The part number is 389-350AT.  Visit them at and check out all the cool adaptors.  I found an adaptor to mount your late model Cummins diesel to an 87 Yugo transmission.  No, not really but they have it covered.  Thanks to george for finding this.  LK

Update:  12-16-2008:

I have further detailed information on 64 (late) big car blocks and more on the tranny issue from Bill K. Here we go….

From Bill K at rkcar_farm:

Have been through this debate a number of times, but ‘64 is the changeover year, this block has the ear at the back with holes drilled for a block mount starter and not having that ear is the biggest reason you can’t put a TH200R4/350/400 behind a 61-63 block. The holes may need to be tapped, but they are there - that’s the only reason I even bothered to keep the motor, or it would have gone to scrap with some parts pulled off it back in June when I cut the car up. Not all ‘64 blocks have the ear, and not all blocks with the ear are drilled or tapped, but all of the late production ’64s seem to have the ear and holes. — The ‘61-’64 Bonneville and Star Chief did not get a “Slim-Jim” - they used the same dual-coupling Hydra-matic as 56-60 Pontiac and Olds and 56-64 Cadillac (trans was repackaged somewhat for ‘60-up in a smaller, lighter case than ‘56-’59). The trans is physically larger to the point that to swap one into a Catalina you need to get a donor trans tunnel along with the trans itself, or otherwise find a way to make room for it.

They’re two completely different transmissions; the Dual-Coupling Hydra-matic won’t even interchange to the Catalina/Grand Prix without swapping the trans tunnel as well. It’s basically the same trans as used in all

Pontiacs from 56-60, and in Cadillac from ‘56-’64. Olds also used it ‘56-’60, not sure if any Olds had it for the ‘61-’64 cars. Bill K.