Motor mount dilema
 

I have the motor out of the race car and have completely gone through it and will soon be ready to stick it back in. While it's disassembled, I am seriously thinking about doing a motor mount change.

Currently, my 78 T/A has a rollbar, solid body mounts except the front, welded in subframe connectors and tubular control arms, so it's pretty stiff.

My 463 was bottom filled years ago and I've been running solid mounts for years with a poly transmission mount. As my horsepower has increased, a higher stall (4400) converter and now capable of using a bigger nitrous shot, I'm worried that I am starting to push my luck with the solid mounts.

The class I race in our heads up series, a front and mid plate would be breaking the spirit of the rules and I don't have near the power to race small tire. They already adjusted the rules for me to allow me to keep the fiberglass fenders so I don't even want to try it.

With that said and looking in the search features, it seems like running a solid left and a stock right mount is a good alternative. I was also thinking of buying these mounts from Butler (see picture) and running a turnbuckle.

I am a footbrake racer and I do use a progressive nitrous controller when running nitrous for heads up racing which does help my cause some.

THANK YOU!! -John

P.S. The car on motor will pull wheelies of occasion on a prepped track.

What I did on stock mounts we used some 1/16" plate and cut uut around where the bolt goes through and welded it to the metal "capturing" the bolt part clamshell so there is no movement. One on the left of the 78 TA and the IA Camaro. The rest are rubber.

I was worried about the same thing.
I went to a Alston .100 mid plate and elephant ears. Engine is located with Mighty Mounts which are rubber but the engine can not move.

Please forgive my ignorance but what are elephant ears?

Straps made out of steel or aluminum that go from the front bolts on the heads down to the frame rails.
I have made them with 3" flat bar 3/8" thick. Had aluminum ones on the HO head motor. This last one I used steel. Drilled them full of lightening holes.
The High Port heads omitted one of the three 3/8" holes on the front of their head. So I needed to drill and tap one for threads to hold the alternator mount.
The HO motor only had the elephant ears and Might Mounts and did not move.
The new engine with 100+ more horsepower has the mid plate added.
IMO its a good alternative to going to a full front plate-mid plate deal.
Engine mounts take care of fore-aft movement and keep the engine in its stock location.

I'm not a racer, just a street guy, but I do have those Butler mounts on my car. I'm at about 500 hp and as for engine movement, under any condition of load, the shaker doesn't move. When I put this motor in I thought I may need a torque strap or something based on what people were saying but with these mounts it's rock solid. I don't know what kind of an indication that is for anything else.

I use solid mount on the driver's side, factory on the right side and poly mount on the transmission. Never had an issue. My brother uses the same set up but added a torque strap several years ago.

Solid on the drivers side
Mity mount on the passenger side
Rubber trans mount

Over 500 passes no issues

I just use stock replacement rubber mounts, with a turn buckle.

What is your current 60 foot?

I ran solid motor mounts with poly tranz mount for years - no issues. 4,800 stall with 1.40 60 foots.
Car 1979 TA 3,600 lbs race weight.

I've been using solid mounts for well over 20-years and no problems.
640HP+ 275 shot. 1:36 60ft on the back tires. 70-firebird 3525lbs.

GT

If you are going to use the stock motor mount position you should try to use the newer late design 455 style, which Pontiac engineers redesigned in 1970. The 59-69 mount position puts all the tension on the middle #3 bulkhead. The redesigned late model 3 bolt mount not only puts tension on the #2 and #3 bulkhead, it also puts an attachment point halfway up the block, and is supplemented with cast iron stiffener ribs to further distribute the tension forces over a wider area.

In this early block with the 59-69 style mounts you can see that only the #3 main bulkhead is subjected to all of the tension load:

https://i.ibb.co/52ptmLB/early-2-bolt-mount-block.jpg

In this 70-76 block you can see the tension load is pulling on the #2 as well as the #3 main bulkhead. The #1 and #3 lug counting from the front of the block, plus the raised lug between the 2 soft plugs have extra iron added and put the stress over a much wider area.

https://i.ibb.co/pWMFwcz/Pontiac-400-Bottom-end.jpg

In the 69 GP dirt car in my signature pics, I couldn't keep brand new motor mounts together for more than 2-3 weeks. This was when the mounts were actually made from rubber that wasn't the consistency of silly putty. My GP had a 69 428 HO engine, Roughly a 450 HP engine, so it only had the early style mounts available.

I did some study of the stress points, and how I could mount the engine using the stock mount system, (rules dictated that no motor plates could be used). I decided to keep both rubber mounts, and limit the travel with 2 turnbuckles, one on either side of the engine. Because in dirt track racing you run into the turn as hard as possible, then stab the brakes you get some tension from slowing the engine down via the brakes, yeah, different than drag racing.

Looking the engine over I decided that the water crossover would transfer the stresses from either bank better than the rather flimsey aluminum intake manifold, so I used 2 head bolts with the 3/8 stud on the top in both lower front head bolt positions. the lower points on the frame were 2, 3/8 bolts welded to the frame rails.

Getting the attachment points as far away from the crankshaft centerline, also gives the attachment points more leverage over closer points to crank center. Just looking at the mounting points available this looked like the best attachement point in my esimation. Moving the attachment points to the top of the cylinder heads, much reduces the tension stresses upon the area just above the oil pan rails, an area of the block that isn't overly robust.

Anyway this was after a bunch of study on my part, as to why Pontiac engineers completely redesigned their mount system with the developement of the high torque, long stroke 455 engine. They obviously thought placing all the tension on one main bulkhead with the long arm 455 was less than desireable

After 2 years of running that car I retired it, when I pulled the engine the OEM style mounts were like brand new. I've since used the same style system to retain Pontiac engines very successfully in other street, and race cars, it's also a very cheap and simple way to retain the engine with rubber, while removing the twisting stress that is trying to split the block up through the oil galleries that are drilled in the middle of the bulkheads.

Block that used steel mounts on the area above the oil pan rail in a heavy drag car:

https://i.ibb.co/nQqRChZ/ddf0d19924b...da23286edb.jpg

:2cents:

This is my only/best ever 1/8th mile on nitrous, it was with a fat 125hp Powershot. I'll be running a 175hp not so fat shot this year for 1/8th mile no prep racing.

I like your post and that broke motor WOW looks like two 4-cly blocks.

GT

I have been making my living as a mechanic, and started racing Pontiacs in 1970. There were a lot of hard learned/expensive lessons along the way. At 71 YO I might as well share some of the knowledge I have, not going to do anyone any good if it goes out of this world with me.

I was baffled in the early 70s when Pontiac enginers completely redsigned their mount system. Since none of the Pontiac engineers has ever come out with an explanation that I'm aware of, I decided to science out the reason for the change. It took me awhile to reverse engineer it, but if you stand back and look at the blocks side by side, it can be seen why the change was made. Having a windowed valley on the factory block only exacerbates the splitting up the center of the block.

I know some people get away with solid mounts in the stock locations, but after careful study of Pontiac engineering, I wouldn't recommend it. As I already posted, the further out from the crank center, the torque retention device is connected, the better leverage point the device has.

I like using the turnbuckles attached to the lower row of headbolts with rubber mounts, as they can be adjusted for a preload, or a small clearance to allow the engine to use the stock mounts, and move as the engineers intended, all depends on what application the engine is being used in.

I'm glad the explanation made sense to people that read it.........;)