[PLAY400]

I got the motor in my Canadian 55 Pontiac which is sort of a Pontiac body on a chevy frame. Was going to use a set of mounts from a 77 Pontiac and just weld a plate under them, gusset the whole 9 yards. But when I mocked it up it looked so butchered, clumsy, bulky and just plain ugly.

So I took the mount off and was figuring on making a plate with ears, bolting it to the first 2 lower engine mount holes and running a 2x2 off the frame to tie into it. Well my neighbor was over and he expressed concern about my not bring the top bolt on the engine into play. He figured the motor may break or crack under torque just using the lower 2 bolts especially that close to the pan rail. So I said how about it I used all 4 bolt holes. He figured I still might have problems and he would definitely incorporate the top hole into the mount design.

Any thoughts on this? Adding the 3rd bolt into the mount is going to be tough but if I have to do it I will. Prefer not to. Alan

[PLAY400]

I got the motor in my Canadian 55 Pontiac which is sort of a Pontiac body on a chevy frame. Was going to use a set of mounts from a 77 Pontiac and just weld a plate under them, gusset the whole 9 yards. But when I mocked it up it looked so butchered, clumsy, bulky and just plain ugly.

So I took the mount off and was figuring on making a plate with ears, bolting it to the first 2 lower engine mount holes and running a 2x2 off the frame to tie into it. Well my neighbor was over and he expressed concern about my not bring the top bolt on the engine into play. He figured the motor may break or crack under torque just using the lower 2 bolts especially that close to the pan rail. So I said how about it I used all 4 bolt holes. He figured I still might have problems and he would definitely incorporate the top hole into the mount design.

Any thoughts on this? Adding the 3rd bolt into the mount is going to be tough but if I have to do it I will. Prefer not to. Alan

[61-63]

I have never done what you are proposing so there is no experience here, but I would use all
original holes. Those engineers weren't stupid
and they got away with as little as they possibly could already to save production costs.
I haven't studied every street rod I've come across in depth but as I recall every one I have looked at in the motor mount area used all the mounting bolt holes in whatever block was being used. If you don't do it and ruin a block
you will be kicking yourself in the butt for quite some time I bet.

[Bill Eveland]

Any pics Alan?
I ran 2"square tubing 1/4"thick off of a plate thats welded on my frame and cut it at a 45 degree angle on the engine end and welded 1/4 plate big enough to bolt on a factory frame mount. I know my US built 55 and differant but same basic deal.

[PLAY400]

Bill this is what I'm thinking of but of course my plate to the engine would only have the 2 lower holes and the 2 holes on the motor I intend to use are the 2 closest to the front, 1 from the old style mount and 1 from the new style. Pretty much what I think you did. Alan

The first 1. Bushing is in the 2x2
http://www.progressiveautomotive.com/motor.htm

[Bill Eveland]

Here's one of mine

[Bill Eveland]

heres the other, Ihave a 66 389 so it only has the 2 bolt motor mount and solid frame mount.The rubber mount is on the mount on the block.

[GOATEY69]

Up until 1969 Pontiac only used 2 bolts on each side of the engine. They added the other bolt holes to fit the engines in Firebirds.Doug

[PLAY400]

Thanks guys,

I am sooo stupid at times. After I decided I didn't like the look with the newer motor mounts I dug out my old 1968 "3 bolt" Mustang mount out of my Pontiac junk pail. After eying it up and deciding it also used the top bolt the confusion set in. Actually the fog had come in real heavy before to @#$% this bad.

Did a quick mockup this morning and I like much better. Bill I noticed your frame top plate does not tie into the front x-memeber like the chebby kits. With this set up do you get any bowing out of the frame on the passenger side. Reason I ask is my kid pushed his jeep motor throught the frame on the passenger side when rock climbing. No x-memeber. Ripped the rubber mount in half. And my frame has no other cross memebers other than the tranny 1 I have to find.

[Bill Eveland]

My frame for the most part is a c-channel frame, but forward of the x frame around the engine it is boxed in from the factory. The first 1/4" plate is about 2" wide and starts at the top of the frame ,has a 90 degree bend and contacts the frame at the bottom end. I welded the first plate at the top, at the bottom where it contacts the frame , then added another 1/4 " filler plate horizontal of the frame to the plate to tie it in. I used frame mounts off of my 68 GTO which is a 3 bolt frame mount at the other end. The front crossmember is way too far forward to use my mounts. Thats where originally the front mount off of the timing cover mounts and the newer 389 is a side mount engine.I could have used a front engine plate to mount it to the front timing cover and may still install one for extra stability. Spotts performance had a decent looking one for under $100 bucks.
I was going to make a crossmember , but it was easier to make the 2 frame stubs.Ans i'll Still have to add in a rear crossmember for the trans.

[PLAY400]

Thanks Bill for the tip about the old mounts. Since I'm using a 455 I made a bracket to run on 3 of the engine bottom bosses and moved the mounts towards the front of the engine so I could tie into the front cross memeber. Good thing I did cause this !@#$%^ Canadian Pontiac frame and @!#$% firewall is sooo different than a real Pontiac. Figure I'll be about 4" from it when finished.

Someone once mentioned that since I was using the Chevy based frame I wouldn't have troubles with installing the motor mounts with the Pontiac steering box but try putting on the driver side head. Steering box in the way. Move the motor up a bit, oilpan hits steering linkage. Thought about offsetting the driveline but other problems. Looks like the smartest thing to do is to open up the firewall, push the engine back the distance of the center exhaust ports and build a box around it to close in the firewall. Need too much room to hammer it in.

And the worst part, The good running 455 I pulled about 4 years ago is now stuck. Was okay last spring when I put HEI in it. And to think chebbies bolt in.

Such Fun Alan