1960-62 GMC to SBC V8 motor & trans mounts

[markeb01]

The following shows one method of converting a 60-62 GMC V6 to a 350 Chevy small block engine with a tail shaft mounted transmission. This would apply to a Powerglide or Turbo 350 automatic, or manual 4 speed transmission such as the Borg Warner Super T10, or Muncie M21 or M22. The photos are of my 1960 GMC short stepside. Most of what follows also applies to Chevy trucks for 60-62. The main difference being the GMC motor mounts are welded to the frame and the Chevy mounts are bolted on.

Motor Mounts

Chevys have two styles of engine mounts. A U saddle style on stick shift trucks or multi-piece tower mounts on automatic equipped trucks. The different types of mounts can be seen at the following web link:

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

The first two pictures below show the factory GMC V6 engine mounts and manual transmission crossmember.




These must be removed by cutting the welds from the frame and grinding the frame rails smooth. The third pic shows the driver side frame after removing the crossmember and V6 engine mount.



This shot shows the 67-72 style motor mount tower/perch I used, resting loose in position.



To determine correct positioning, the towers were attached to the motor mounts, which were bolted to the engine. The transmission mount was loosely attached to the new crossmember (explained shortly), and the engine was rested in place. The frame on the 60-62 is 1 inch shorter in vertical height compared to the 63-66 frame. To position the tower correctly, I simply added a 1 inch spacer on top of the frame rail.

This photo shows a temporary 1 inch aluminum lowering block used to check the fit.



For the permanent installation, I substituted 2 stacked pieces of ½ inch solid steel, drilled to match the bolt holes in the towers. Everything was secured with grade 8 bolts. Sadly I didn’t take a picture of the finished install when everything was new and shiny. The next shot shows the steel spacers after 165,000 miles of road grime.



The original 60-62 automatic motor mount towers might work just as well, but they are extremely rare and expensive when found. Also, I’m not sure if new motor mounts are available for these towers. It is also unknown if they will interfere with a power steering pump.

Transmission Crossmember

The type of crossmember (xmbr) I used, came stock on 60-62 trucks with an automatic. There must be at least 2 versions of this xmbr. The type I found is straight across the upper mounting surface. I’ve seen pictures of a different version that has a shallow depression in the center of the span. Apparently, they also come in different lengths, depending presumably on whether the truck is a short or long bed. All 60-62 frames I’ve seen have 3 holes in a crescent pattern to the rear of the bellhousing crossmember, as shown: These holes are for attaching the factory automatic xmbr.



When I searched for this crossmember almost 20 years ago, these trucks were plentiful in wrecking yards. In spite of the volume of trucks available, after looking through roughly 150 trucks, I found only 3 with the bolt in crossmember. One was hacked up and drilled, one was bent and still had an engine and transmission sitting on it, and I bought the third one. I’ve seen 2 on Ebay over the years, so they are as rare as the early motor mount towers. It should be relatively easy to fabricate a similar xmbr from rectangular tubing and steel plate if a person can weld.

Unfortunately, the xmbr I bought must have come out of a long bed (I didn’t think to look when I was removing it), because it was too long by several inches. The following shows where I sectioned the excess out of the center. I drilled new slotted trans mount holes, fabricated reinforcements underneath and had a friend weld it back together. The 2nd shot shows the reinforcement many years after it was put together.




This shows what it looked like in position, further back compared to the original stick shift crossmember.



When I first did the swap I installed a Turbo 350 behind a 350 small block Chevy. A few years back I pulled the automatic and swapped in a Super T10 4 speed. The bellhousing to trans mount distance is the same, so no adjustments in the motor or transmission mounts were required.

Everything worked fine with the original torsion bar suspension, and later with a 1975 coil spring front crossmember. There are no doubt other ways to do this installation, but this was relatively simple using stock parts.

[el_bole]

I've been lookin all over for this info!!! Thanks to ChevyMike , he emailed me your thread and Im glad he did!!!

Where exactly did you obtain the "perches" from? Thanks for the great info!!



P.s. By the way I have a 1961 c10

[markeb01]

Mine came from a local wrecking yard. I just looked around for a 67-72 without an engine and five dollars later I was on the way. I see them on eBay now and then, or you might check the parts for sale section of this site.

[el_bole]

Quick update...

I found some perches on ebay and if all goes well I'll end up paying $26 with shipping and handling.\

You were right theses are hard to come by because the set I placed a bid on were the ONLY ones on all of Ebay....

Thanks again for the great info....Now I gotta get my hands on an engine hoist!!!

Thanks

[el_bole]

Man I wish my local junk yard was that cheap!! I pulled a crossmember for a 350 tranny and Ecology(out here in S.D) charged me $26.00. Probably would have been cheaper to build myself....67-72 trucks are hard to find, at the junk yard I go to.

Thanks Mark

[markeb01]

I guess I should have mentioned that was back in 1991 and there were literally hundreds of 60's Chevy trucks in the yards at the time. I sure wish I had the foresight to invest in a bunch of spare parts back when they were dime a dozen. For example I must have seen at least twenty five 60-63 cabs with the stainless windshield trim in excellent condition. At the time I didn't think it was worth the effort of grabbing a set!

[el_bole]

Yeah with all those parts you could have had your own online store...LOL.

I just had an interesting interaction with a gentleman who had a power glide

tranny that would fit my truck's 235 engine(i currently have a 4 speed tranny)

Im kinda of in a quandry to just buy the tranny or put in the V8 with 400 trannny...

He wants $350 for it but I told him about my plans with the V8 I have and the "perches".

His response was that the cross member wont handle the weight(of the engine). Because the weight of the engine is only being supported by the front and not the middle of engine. Have you had issues with this or did you put more reinforcement to the crossmember? What are your thoughts?

Thanks

[markeb01]

I’m not sure I understand what crossmember he is talking about. If he means the front suspension crossmember, it certainly is strong enough because with side engine mounts the engine IS being supported in the center of its mass right over the crossmember. In the original 1960-62 configuration, the engine was supported by the bellhousing crossmember and a front mount. Once side mounts were introduced with a small crossmember under the transmission, the bellhousing mount design became obsolete.

Unless you want to swap in a manual 3 or 4 speed using the original bellhousing, any modern transmission will require a new crossmember under the transmission tail housing. The original bellhousing crossmember needs to be removed for clearance. The side mount/tail housing arrangement has been in service for decades as standard equipment so it’s certainly a proven design.

I’m not a fan of Powerglide transmissions. My 67 Chevelle originally came with a “Slip-o-glide”. Low gear always ran out too soon, and high gear was too high, so when the engine bogged on a hill all you could do was slow down enough to go back into low gear. Climbing any steep hill or driving with a full capacity load became very annoying.

[el_bole]

Mark,

I found a '64 at the local junk yard and man was it a bear just getting to one of them lol!!!

In the end when I have both "perches", for motor mounts, it will only be about $25.00 for both!!! Better than ebay with eight people bidding on the same thing .

Where did you get the bolts from, I want new ones to install perches, the grade 8's?

I decided not to invest in Powerglide, thanks for the heads up. Thanks again Mark, I'll keep you posted on install of V8.

R

[markeb01]

Sounds like you’re making progress which is great. When I was looking for engine and transmission mounts, I had to pass on several candidates because I just couldn’t get them off safely – or at all. Junk yards do involve a bit of careful creativity at times.

I’ve always had good luck coming up with new grade 8 hardware. We have local hardware stores that carry this quality of bolts, and when I lived in a different state we had a specialty fastener company available.

[63 Chevy Stepside]

Can you tell me where I can get the engine side of the motor mount? I have the perches, but am not sure what or where to get the motor side of the mount. The ones I see a rubber mount on several sites, but it is difficult to tell if this is what I need or not. Yours seems to be a lot taller than the ones I see at the sites.
Thanks, Rick

[markeb01]

The motor mounts I have look like these:

http://www.oreillyauto.com/site/c/de...2327&ppt=C0019

The orientation of the mount in the o'reilly link is showing the top of the mount at the top. In the photos of my engine you're looking down onto that thick part which I believe is the molded in fail safe interlock. Not all motor mounts have this safety feature, so some may look differently.

And welcome to the forum!

[63 Chevy Stepside]

Thank you for the link, that has been what I have been looking at just wasn't sure it is what I needed. So, that mount in the link attaches directly to the engine and then the perch attaches to the mount when the engine is in the engine bay correct? I will try and put a pic on of my perch set up.
Thanks again.
Rick

[markeb01]

That is correct. Three bolts go through the metal plate into bosses on the side of the engine block, and the center bolt comes from underneath the perch into the threaded insert in the center of the rubber mount. It appears part of the old motor mount is still attached to your perch, and the plate that bolts to the engine has been removed or sheared off. On early mounts that did not have the interlock feature, it was not uncommon for the motor mount to tear apart from engine torque on the driver side. Before the mount was redesigned GM offered engine retrofit safety cables that connected the upper control arm to the exhaust manifold to prevent the engine from flinging over in case the motor mount separated under torque.

[codyshawn1974]

Originally Posted by markeb01

Mine came from a local wrecking yard. I just looked around for a 67-72 without an engine and five dollars later I was on the way. I see them on eBay now and then, or you might check the parts for sale section of this site.

i just finished my conversion similar to this. i had used the 67-72 perches on my first try, but the motor sat at an awful odd angle. back to the hunt. i found someone scrapping out a 1965 chevy with v8 and 3 speed on the tree. i got the perches and the "new" 350 dropped right in. no problems at all.

[padresag]

perhaps the first perches that you found were for a 292 I6 and they are the oddball ones that don't work with the other engines. the passenger side one is different
ron

[codyshawn1974]

Originally Posted by padresag

perhaps the first perches that you found were for a 292 I6 and they are the oddball ones that don't work with the other engines. the passenger side one is different
ron

nope, they were sitting under the 350 that i pulled to put in the 63 gmc.
i found my correct perches in a 1965 chevy with a 327 and 5 speed conversion. they were definately different than the ones from the 1972.
the donor truck was 1972 chevy lwb 350/ turbo 400 trans 12 bolt 3.08 richmond gears power steering disk power disk brakes.
so far i've already installed the rear end and the motor, but i kept my 4 speed trans. just upgraded to sm465 from the original sm420. rewired for hei and 3 wire alternator. added twin relay system for the headlights and added driving lights also.
i hope to be able to install the front suspension soon. i need better braking and the power steering won't hurt either.

[Captainfab]

The '67-'72 small block motor mount perches are shorter than the '63-'66 motor mount perches. This is due to the fact than in the '67-'72's the small block motor mount perches bolted into the forward sets of holes. The '63-'66's bolt into the rearward set of holes.

[codyshawn1974]

Originally Posted by Captainfab

The '67-'72 small block motor mount perches are shorter than the '63-'66 motor mount perches. This is due to the fact than in the '67-'72's the small block motor mount perches bolted into the forward sets of holes. The '63-'66's bolt into the rearward set of holes.

that's odd, because on mine, it seemed like the 67-72 perches were taller than the 63-66 perches. i used the 72's perches on my first stab, and with the rear of the motor supported by the bellhousing, the 72's made the front of my motor sit about an inch or so too tall. when i used the older set, they made the motor sit proper. and that was using a bellhousing from a 1970 3/4 chevy 350/sm465 2wd.

[LostMy65]

My engine seems to fit fine with just 1/2 spacers.

Posted via Mobile Device

[LostMy65]

Originally Posted by markeb01

When I first did the swap I installed a Turbo 350 behind a 350 small block Chevy. A few years back I pulled the automatic and swapped in a Super T10 4 speed. The bellhousing to trans mount distance is the same, so no adjustments in the motor or transmission mounts were required.

Everything worked fine with the original torsion bar suspension, and later with a 1975 coil spring front crossmember. There are no doubt other ways to do this installation, but this was relatively simple using stock parts.

Did you have to do anything special for the e-brake?

[markeb01]

I don’t remember making any changes to the emergency brake setup. Here’s an old photo of the layout. The spring looks new, so I may have added that for anti-rattle, or perhaps it replaces an original. I didn’t move or change anything however like the guys with the newer chassis have to deal with.

[LostMy65]

Originally Posted by markeb01

.
...clip...
In the original 1960-62 configuration, the engine was supported by the bellhousing crossmember and a front mount. Once side mounts were introduced with a small crossmember under the transmission, the bellhousing mount design became obsolete.
.
...clip...
any modern transmission will require a new crossmember under the transmission tail housing. The original bellhousing crossmember needs to be removed for clearance. The side mount/tail housing arrangement has been in service for decades as standard equipment so it’s certainly a proven design.
.

The previous owner of my 65 had cut one of the front v8 style engine mount stands, and had only one top bolt in the other.
I'm thinking how it survived was because of the strong bellhousing mounts.
I've since replaced and properly installed the two front mount stands.
I'm now planning on dumping the sm420 and installing a th350.
So this appears to emphasize even more so the need for good secure mounting of the engine mount stands - beings the auto transmission tail mount isn't really much for resisting twist.
I'm thinking I may want to upgrade to the newer 73-87 stands and mounts.

[50bomb]

Great info. I am in the process of figuring out how to convert my 61 longbed c10 4speed manual to a castiron powerglide. I have the orginal thriftmaster 235 I want to keep. I dont drive fast I just want a nice lil cruiser. Problem is I have no welding skills.

[LostMy65]

Here's a unique method that doesn't require welding skills;