Projects Wanted: Advice for 1959 gmc 150 I6 to v8 swap

I am planning on using the crossmember kit for a 1959 gmc. This will allow me to use the side mounts on the 283 sbc motor that will be going back in. I am looking for advice and hopefully I have the correct approach and tools to go at this.

It is a factory sm420 4 speed. I will be using the correct year sbc bell housing on the swap.

I am planning on using the crossmember kit as my gmc does not work with the chevy style front post mounts.

I am using ram horn style headers from early 60s sbc to clear everything.

My approch will be to bolt the engine and transmission together, attach rear driveline, lower and bolt in the rear transmission cross member to support the rear, then lower engine to level position and complete the install of the front cross member.

Anyone who has done a sbc swap that has any advice on what i may run into or if this is simply a fairly straight swap would be appreciated. Thanks in advance.

 

I'm not real clear on which bellhousing you are using, but if it is the Chevy one that bolts to the crossmember, you should be able to bolt everything together, set the motor at the angle you want, and install the crossmember. I put a bbc in my '59 Chevy this way, but I fabbed some mounts that bolt to the block so I could bolt it in, and not have to do any welding on my frame. The side motor mount/bellhousing mount deal seems strange, but Chevrolet did it that way up through 1972, I believe.

 

I'd start by getting the frame on jack stands, and level. Then put the engine and bellhousing in, bolt in the bellhousing mounts, then put a level on the carb flange on the engine, and support the engine in that position. the front of the engine will be 3 to 4 degrees higher than the rear. This is how you want it to sit. Then figure out how to install the mount crossmember under the engine. After I have the engine mounted, then I'll reinstall the transmission. That SM420 is a big old pain to mess with. Fortunately there's a removable floor center pan on those trucks.

btw I didn't know GMC had a V6 in 59, I thought that started in 1960. The 59 and older were straight 6.

 

also make sure you have the correct truck V8 bellhousing, the center hole in the 55-67 version will work with the SM420 but the hole in the 68-72 version is larger, to fit the SM465. If you have the large hole, you can get or make a spacer ring to center the transmission properly.

 

I thought the 59 GMC pickup was the last of the Inlines.

 

Not really relative to the above posts, but … apparently the 270'' engine saw use in stepvan GMCs thru '62.

 

Yeah, the straight 6 was around a little bit longer than 1959, but the V6 wasn't out yet in 1959 model year trucks.

 

also, anyone know if the wishbone mount from 1960's trucks will bolt directly in? this could be another option for me...problem is finding one!

 

I think the frame crossmember is different, if you're referring to the 60-62 Chevy truck front lower motor mount.

 

You could still use the front pedestal mount. and fab some perches from angle iron. Thats what I did when I put a 307 in my 57 dump truck. it originally had a 261. And if your 59 had a V6 someone swapped it in there. No 59 ever came from the factory with a V6. Now a lot of GMC came from the factory with a Pontiac V8.

 

also a lot of folks that are new to old cars/trucks, don't know the difference between a straight 6 and a V6. Stuff that is obvious to some of us, is something they never think about....

 

It was an inline 6 from the factory. Jim is right in saying that my generation is so used to "saying" v6 instead of an inline 6 as it just wasnt a common engine in our generation.