350 swap

[skysoldier173rd]

Been reading posts regarding swaping a 350 into one of our trucks. So much info I am overwhelmed and confused by all the different opinions on the motor mount question. Sounds like a lot of little pecularities depending on what combination you have. Mine is a 1960 GMC shortbed step side with a 305 v6 engine. Has the 4spd manual. My donor vehicle is a 1986 GMC half ton with 350 and 700r4. I understand the rear crossmember thing and that i don't need the old crossmember. I am confused on motor mounts. Will either the mounts in the 60 or 86 work for the 350 in the 1960 truck or do i need to get some of the "perch" style i see in some of the posts. If so, what kind and where can i get them. Also, will standard full length headers work with this combo. Saw someone talking about exhaust problems because of problems clearing the tortion bars which my truck has. Anyway, what's your opinion/advice on this swap. thanks in advance.

[Captainfab]

You can use the motor mounts and frame brackets from the '86. However the '86 frame is taller than the '60 frame, so a spacer on top of the frame will be necessary. The frame brackets used on the '73-'87 3/4 tons were a little shorter than the 1/2 ton brackets. There were V8 mounts used in the '60-'62 trucks, but they are quite rare. The other option would be the frame brackets used in the '67-'72 small block trucks. These frame brackets sat farther forward than the '63-'66 brackets, so they are shorter. The actual motor mounts for the small block are the same from '63-'72. Personally I prefer the '73-'87 style of motor mounts. They are a better design IMO.

[skysoldier173rd]

By using the spacers, will redrilling of holes on the frame be necessary? Also, wondering about the driveshaft. I'm replacing the 4 spd manual with a 700R4 automatic. Will i need to cut and shorten the driveshaft and also will the splines be the same? Also, wondering what is a good aftermarket shifter to use on this setup? It seems like there is also an issue with overdrive hookup on these trannys. I think they have an electric locking torque converters and that there is something similar to a tv cable that controls this and it can be hooked to a manual switch. I'm just full of questions, but getting answers here. Great site.

[steverino66]

I put a big block in my 66 truck, had to re-drill frame holes for perches moving the engine forward a bit (used the taller perches from a 71 truck for left side header clearance).
On the 700r4, the 350 yoke will work; depending on 350 tail section length, driveshaft will probably need to shorten 3" and the crossmember for rear mount goes back same amount on the frame.
You can get a converter lockup switch kit from several sources, Jegs, Summit, etc. The trickiest part of that trans install is getting the correct TV cable geometry between the trans and carb - if you have carb, manifold/bracket from a factory orig. setup, great, but if you use an aftermarket carb you may have to get a kit from bowtieoverdrives.com. Fluid pressure controls your shifts and TV setup has to be precise. I put one in my El Camino, but I've read you won't get huge mileage increase in the full size truck.

[skysoldier173rd]

i am using the same carb, transmission and motor out of the 86 truck. In fact I don't plan to even seperate them during removal and reinstall, just clean em up real good and install. So, I'm hoping I'm getting out of this part pretty easy. If fluid controlls the lockup, should be no change.

[steverino66]

Originally Posted by skysoldier173rd

i am using the same carb, transmission and motor out of the 86 truck. In fact I don't plan to even seperate them during removal and reinstall, just clean em up real good and install. So, I'm hoping I'm getting out of this part pretty easy. If fluid controlls the lockup, should be no change.

That should eliminate TV cable problems. I believe the converter lockup is electrically controlled, and your old truck has no provision for it - on mine I added the switch to the right side of tranny; see here:

http://www.jegs.com/i/TCI/890/376600/10002/-1

[62gmc910]

the lock up switch should be on the firewall of the '86 ,it just needs key power to one side after the swap. What is your plan for rad / trans cooler , the '86 rad won,t fit with out cutting the inner fenders

[markeb01]

Here's a thread on mounting options:

http://67-72chevytrucks.com/vboard/s...d.php?t=369663

And here's another thread should you choose to replace the torsion bar suspension:

http://67-72chevytrucks.com/vboard/s...d.php?t=366850

[skysoldier173rd]

im staying with the tortion bars. can't believe how good this old truck rides. I've got the big 6cyl radiator so i'm keeping it. I'm planning to put a large rv towing type cooler on to cool the trans and not using the radiator for that. will this work?

[Martin64]

Sure, you just have to find a place to mount it. Shouldn't be a problem.

[markeb01]

Just make sure you have a big enough fan, and a well fitting shroud. Not sure how hot it gets where you live, but the big trans coolers can reduce radiator efficiency same as an a/c condensor.

[Captainfab]

Running an auxilary trans cooler will work. However it is not recommended to run that type of cooler only. The reason being that in colder tempertaures, the engine coolant helps the trans to get up to operating temp sooner. With that said, I've been running my Suburban with only an auxilary cooler for probably 10 years on this trans without any issues. Of course when it does get driven in colder temps, I let the it warm up before taking off. I also cover up the cooler in the colder months. I've been meaning to plumb in a thermostatic valve (http://www.summitracing.com/parts/PRM-1070/), but never seem to get around to it.

Also on the converter lockup, you will want to wire that up and make it functional.IIRC that gives full pressure when in OD. Also make sure that the TV cable is adjusted correctly, even though you are using the OEM bracket. An improperly adjusted TV cable will butn up a 700R4 in a hurry. Do a search over in the 'Engine and Drivetrain' section and I'm sure you will find the answer. There are a couple of transmission experts that hang out over there.

Regarding your '86 engine, in light of another members ignition issues with his '86 truck, I would suggest getting rid of the '86 distributor (ESC controlled) and going with a standard HEI distributor. In converting from a 4 speed to the 700R4, you will likely need to shorten your driveshaft, and also you will need a slip yoke at the trans end.

Edit: I almost forgot, there's a thread in the FAQ's on adjusting the TV cable.

[skysoldier173rd]

my donor vehicle a 1986 GMC has a carburated engine, not TBI or Fuel Injection. Does this affect the 700r4 transmission swap thing. Also it appears to have a regular HEI dist. I'm hoping that will make it less complicated. Also, I'm assuming the trans is a 700r4. How can i tell for sure. It has PRNDD as far as the selector.

[Rich 5150 69]

Carb will make it easier for you, go here for linkage if needed, also will help you id trans.
http://700r4.com/faq/faq.shtml