The Stovebolt Site Forums The Shop Area The HiPo Shop Putting a 350/350 in a '56 3600 - Underway

Tonight I did the truck shuffle, got the '56 in the garage and started into it. I'm taking the old, tired V8 347 and SM-420 out and swapping in a '73 350 and TH350 trans. I think I have everythng covered, but would like to hear from the world of experience out there. What things to I have to look out for? What should I avoid? I think I'll be pulling the old engine out tomorrow night and dropping the tranny Thursday. I'm really looking forward to the updated engine and trans in this truck. I plan on driving it for awhile and then finding a donor truck with disk brakes up front and a lower ratio rear end. I'll try to take some pix and update my webshots album. Come on, all you HiPo dudes out there, I'm waiting for your advice!

Well....based on the lack of replies, maybe I should have posted this in the Engine and Driveline Forum. Oh Well.

Update: The old 347 is out. The SM-420 is almost out. The "new" 350 is on an engine stand. While I'm waiting for the V8 crossmember to arrive, I'm going to swap in an electronic ignition. Right now I have two hurdles to get over 1.) Trying to fit the donor truck's radiator in the '56 front end. I'd like to keep it because it has the connections for heater return and the integral tranny cooler. 2.) Adapt the TH350 yoke to the larger 3/4T driveline. There is a great driveline shop in town that I'll take the works to. I'm thinking about keeping the yoke and first section the smaller 1/2T style, and then "bodging" that to the larger end piece. The carrier bearing needs replacing too. I'm going with a Lokar floor shifter...probably pop for thier 'nostelgia' style one that looks just like shifter off the 4 speed.

That's all for now. If any of ya'all have any suggestions for items #1 and 2 above, I'd love to hear from you.

Scott, I would have commented sooner; but I am a bit biased toward keeping GMC's stock, especially since you already had a "Poncho" power plant. A 389 (or a 370 would have been even cooler) would have dropped right in. These engines can take RPM's, but they are torquey enough to push lower numerical axle ratio's; so I would have just re-geared the rear axle to suit your need for highway speed.

Pontiac engines are pretty good, except they are a little heavy (though lighter than BB Chevy).
You have a pre-'62 version. A lot of improvements wee made on the '63 and up motors.

Well, since it's sounds like you are at a point of no return, there is nothing wrong with a SBC; it's just that they are so "generic". They are tough and I'm sure it will run for many years to come.

On your tranny yoke, take the one from your trans and the front drive shaft to the driveline shop. I'm sure they can get you a "conversion" U-joint that will allow you to use your drive shaft as- is; but I suspect you will have to cut it down some, as the SM-420 is a bit shorter than a TH-350

My "e" key is not working well.......... :mad: :rolleyes:

Thanks for the reply '248. Yeah, I really understand the "stocker" view point. That's how I am about my '65 GMC. I wanted to update the engine in the '56 and they threw the auto trans in the deal. Tell ya what, I'm learning a bunch.

I must have brain-farted earlier. The donor vehicle was a Chevy RV on a 1 Ton chassis, so the yoke on the tranny is the correct size to mate up to the existing driveline, but you are right, it will have to be shortened.

My daughters are pretty pi$$ed because I'm spending waaaay too much time in the garage but they did think it was pretty cool when I winched the old engine out.