350 in 60 gmc

[skysoldier173rd]

My 60 GMC currently has the 305 v6. Can i just bolt in a SBC or do i need to do surgery. Also, have the 4spd w/creeper gear. How will this trans and rear end work with a SBC? Just wondering if i need to replace the entire drivetrain or can do just the engine swap.

[markeb01]

The transmission flange pattern you have where it bolts to the bellhousing is the same as the 3 speed standard, and passenger car 4 speed transmissions (and later 5 speed manuals). If you are happy with the granny box and rear end you can leave them alone and just install a Chevy V8 in front, just use the V8 bellhousing. If you want to keep the original hydraulic clutch find a bellhousing from the same series Chevy truck with the bellhousing motor mounts and hydraulic setup (not very easy to find).

For motor mounts you can use the later style shown on the 1st thread, or either of the early types shown at the 2nd link:

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

http://www.persh.org/pickup/perches.htm

The only reason the transmission crossmember will have to change is if you want to install an automatic transmission requiring a tailshaft trans mount.

[skysoldier173rd]

thanks for the info. Doesen't sound too scary.

[markeb01]

By the way, you probably have a Dana 44 rear axle. It remains very popular with Jeep and off road guys so parts and gear sets are readily available.

[skysoldier173rd]

I guess this is a lot different than the cars I've had of same years. About the 350 swap, if i wanted to keep the hydraulic clutch, could i just use a later model housing from a v-8 that has the hydraulic throwout bearing and use the existing cylinder? Hate to try and hook up a bunch of rods etc. where there was none. Seems like i could just hook the hoses up to the new bearing. I'll probably stick to the same transmission/rear for the time being but maybe change out the ratio on down the road. I'm used to tearing everything down, doing a frame off on every vehicle I do, but i don't think so on this. The metal is pretty good, it's from missouri and body is pretty good. the original wood is still usable in the bed and floors solid. Just the usual lower fender issues which i can fix quickly. allready ordered the panels. Also wanted to ask, does anyone use the old style front mounts on these such as tri five chevy cars have. They also have bellhousing mounts, but i think different than the trucks by the looks of things i saw on pictures here. Anyway, thanks again for the info, its nice to have input from people that know. I should be driving this old jewel within a couple weeks. It's the koolest thing i've seen in a long time.

[markeb01]

You can certainly use a hydraulic throwout bearing so long as it is compatible with the master cylinder bore size. Years ago I had a 1986 S10 and when the throwout bearing leaked it also wiped out the clutch costing $750 in repairs, so I wanted a different solution. I found a hydraulic slave cylinder kit from a Jeep outfit that works perfectly, using a standard Chevy bellhousing and fork. I used a Girling master cylinder, but the stock unit should also work. Here’s the slave cylinder kit I used. It's expensive but works perfectly. It’s a bit different cosmetically than the version I bought years ago:

http://www.novak-adapt.com/catalog/kit_hcrc.htm

Should you ever decide you want power brakes, here’s how I set up my clutch master cylinder:

http://sixty7ss.proboards.com/index....lay&thread=666

Since that time, Captainfab (a forum vendor) has released a much nicer looking version than what I engineered:

http://www.67-72chevytrucks.com/vboa...d.php?t=362375

My original suggestion being – if you could find a 60-62 Chevy truck bellhousing, it also came stock with the same hydraulic clutch setup as what is currently in your GMC V6. If those parts were available, you could just bolt it together exactly as it is now, but with a V8 in front of it.

I don’t think the 55-57 Chevy biscuit mounts were ever used in the 60-66 trucks. I believe the earliest V8’s came with the horse show mount shown in the earlier link, and trucks with an automatic transmission came with the multi piece towers than bolted to the crossmember, until the conventional side mount towers were developed.

[raycow]

I agree that the best install would be a 60-62 V-8 bellhousing. If you can't find one, use a 63-67 bell and an aftermarket external slave. A 68-72 bell will also work if you add an aftermarket spacer ring for the center hole. The only difference between these two bellhousings is the center hole size.

A hydraulic t/o bearing would be my last choice. These cost more than an external slave and can be problematic.

There are a couple of options on the front mounts. You can modify stock 63-72 frame brackets to work. The reason for needing the mod is that the frame rails are taller on the 63-up trucks. There are also aftermarket brackets that use the 58-72 car type rubber mounts.

I wouldn't advise looking for a stock 60-62 V-8 front engine bracket. These are very scarce and the mount assembly used with them is expensive when you can find it. You would need the whole mount assembly which consists of 3 or 4 rubber and metal pieces. This is in addition to the engine bracket.

You may want to keep your stock rear. Most 60-62 Chevy 1/2 tons came with a 3.90 which can get pretty unpleasant at highway speeds. The GMC engine was designed to put out power at lower rpm, so GMC rears had taller gearing. 60-62 GMC rears are a bolt-in swap for 60-62 Chevy trucks (63-up rears do NOT fit without mods), so there is some demand for them.

Ray

[skysoldier173rd]

So, i see my error here. I didn't realize there was such a thing as a "slave" used on the hydraulic clutches. I thought they all had the hydraulic throw out bearings. So i'm guessing there is a mechanical arm or rod that pushes the clutch fork? Does anyone have a picture of what one of these looks like?

[raycow]

Now you got me scratching my head. Doesn't your bellhousing have a fork sticking out of the passenger side, with a slave cylinder mounted near the front of the bellhousing and a short rod connecting it to the fork?

If you can't find it, follow the line from the master cylinder.

[markeb01]

Here you go, it's located on the passenger side of the bellhousing. The Chevy version is the same as what is in your GMC:

[skysoldier173rd]

That's exactly what i thought after reading the above post. The only type i have seen has been the hydraulic throwout bearing hooked directly to the cylinder. Later model gm trucks have these. I never realized the slave cylinder thing existed but it makes sense. I didn't know what it was on my truck. So on the inside of the bell is a typical throwout bearing? This clears up my mystery. Sorry to seem naive, but this my first old chevy truck in over 30 yrs. I had a 66 many years back, like 1970 or so. It was a v8 with a 3 speed. Had a ton of low end torque. I remember lining up against a road runner at the drags and not seeing him all the way through the quarter mile run. You just dont forget things like that. Thanks again for your tips and information.