1987 Cutlass Build

[Pettrix]

View attachment 145108

Is that OK to run a solid motor mount like that?

A buddy did that and the vibrations transmitted through the frame were horrible. In addition, a solid mount like that pulls on the block and then the block webbing can distort, causing main bearing and crank failure. That's why racers now use front mounted engine plates which don't stress and pull on the block webbing like solid motor mounts do.

 

[84dragcutlass]

Is that OK to run a solid motor mount like that?

A buddy did that and the vibrations transmitted through the frame were horrible. In addition, a solid mount like that pulls on the block and then the block webbing can distort, causing main bearing and crank failure. That's why racers now use front mounted engine plates which don't stress and pull on the block webbing like solid motor mounts do.

Yeah never had an issue with them. The vibrations are over dramatized ive noticed in may applications. Ive ran them on SBC, LS, and soon this engine and the vibrations in my trans am were minimal at very best, i couldn't really tell much difference from stock and its a uni-body car. I would say like most things you would only run into issues if you were on the wild end of things, yes maybe an engine with 800hp and drag slicks running the quarter mile they would cause some stress on the engine, with this engine or most street engines and limited traction the stress will go right into wheel spin before any flex on that engine would happen. The purpose of this one for me IS to be a little on the odd side i mean come on its 6.5 diesel in a car so if it shakes more than usual and makes noise and offends little old ladys going to church then perfect thats exactly what i want.

 

[Pettrix]

Yeah never had an issue with them. I would say like most things you would only run into issues if you were on the wild end of things, yes maybe an engine with 800hp and drag slicks running the quarter mile they would cause some stress on the engine, with this engine or most street engines and limited traction the stress will go right into wheel spin before any flex on that engine would happen.

I do know with an Olds 455 and solid engine mounts. Even with a mild (under 450HP) application, guys with solid mounts would eventually cause the block to distort leading to crank and main bearing failures. Of course, the Olds 455 is not that stout of a block to begin with but now solid mounts are a big NO-NO and only front engine plates are recommended or rubber mounts with a torque limiter strap (aircraft cable) connected to the head stud bolt and frame on the drivers-side. Many 455's failed and even broke the block due to running solid mounts on a street car.

Each time the engine revs or accelerates, it torques under acceleration and it puts tremendous stress on the block where the mount is attached to. I really don't think the block was engineered/designed to have full pressure being applied in that area without a rubber mount to absorb the vibrations and torque twist of street driving.

Polyurethane mounts are a good alternative. Not as forgiving as rubber but not as brutally unforgiving as solid steel mounts. Plus they help deal with the vibrations of the motor running.

If you've run it before with solid mounts with no issues, then maybe the 350's are stronger at the mounting point than 455's are.

 

[fleming442]

Got a line on some poly Olds mounts?

 

[Pettrix]

Bill Travato, Olds expert, states in his engine book, " Olds experts agree that the most common failures occur at the number-4 man Web areas. I feel that the use of solid motor mounts, which are fastened to the block in that area, is the leading cause for failure. All of the engines torque and vehicle weight is transmitted in this motor mount area via two 7/16 inch diameter bolts".

 

[Clutch]

Bill Travato, Olds expert, states in his engine book, " Olds experts agree that the most common failures occur at the number-4 man Web areas. I feel that the use of solid motor mounts, which are fastened to the block in that area, is the leading cause for failure. All of the engines torque and vehicle weight is transmitted in this motor mount area via two 7/16 inch diameter bolts".

So I'm guessing the best way to not do damage or constantly break driver side motor mounts is a limiter strap perhaps to the Head? That is if you don't want to run a motor plate of course?

 

[olds307 and 403]

The 455's crank is much heavier than the 350 crank, gas blocks are about the same strength wise. The heavy crank and big mains with a flimsy block is why there are more failures than the 350's. Plus the 100+ ci allow it to make enough power to really cause damage

 

[Rktpwrd]

Got a line on some poly Olds mounts?

Bill Travato, Olds expert, states in his engine book, " Olds experts agree that the most common failures occur at the number-4 man Web areas. I feel that the use of solid motor mounts, which are fastened to the block in that area, is the leading cause for failure. All of the engines torque and vehicle weight is transmitted in this motor mount area via two 7/16 inch diameter bolts".

I noticed how this question conveniently didn’t get answered...

 

[84dragcutlass]

I do know with an Olds 455 and solid engine mounts. Even with a mild (under 450HP) application, guys with solid mounts would eventually cause the block to distort leading to crank and main bearing failures. Of course, the Olds 455 is not that stout of a block to begin with but now solid mounts are a big NO-NO and only front engine plates are recommended or rubber mounts with a torque limiter strap (aircraft cable) connected to the head stud bolt and frame on the drivers-side. Many 455's failed and even broke the block due to running solid mounts on a street car.

Each time the engine revs or accelerates, it torques under acceleration and it puts tremendous stress on the block where the mount is attached to. I really don't think the block was engineered/designed to have full pressure being applied in that area without a rubber mount to absorb the vibrations and torque twist of street driving.

Polyurethane mounts are a good alternative. Not as forgiving as rubber but not as brutally unforgiving as solid steel mounts. Plus they help deal with the vibrations of the motor running.

If you've run it before with solid mounts with no issues, then maybe the 350's are stronger at the mounting point than 455's are.

I have seen quite a bit on the 455 being weak and having had one i would probably be inclined to agree that with the thin webbing in those blocks and the overall light looking castings that those probably wouldn't survive all that well with solid mounts yanking on them, however, that would still in my opinion only be in a racing environment. Ive read Bill Travato's book and its intent is for building max performance olds V8's so i would still stick to my original statement that on the street it wouldn't matter either way because those stresses would go out in a cloud of tire smoke before distorting the block that much. All that being said however my engine is not an Olds, although altered off the original 350 olds diesel design my engine is a GM 6.5 turbo diesel partially disguised as a 350 Olds. This block is heavy duty, thick and strong. There is no way im going to hurt it even with it turned up that i will ever break the block. The 7.5 rear?? Oh for sure... the 700th trans??? eh maybe... but the block? not a chance on this planet.

 

[Pettrix]

I noticed how this question conveniently didn’t get answered...

No current poly for Olds engines but they do offer them for Chevy engines.

Best option are 2 rubber mounts and the use of a torque limiting strap on the drivers side.

For racing, use a front engine plate, 2 rubber mounts.

Even in low HP, stock applications, a solid mount transfers ALL chassis movements directly to the steel mount and then the engine block area. On a race only application for a 1/4 mile, OK, but not for a street car.