TPC Motor Mount Bushing Upgrade

Just as I was about to install my LS motor, Kent Marr, the owner of TPC, reached out to me personally regarding my TPC motor mounts.  He noticed when reading my post that I purchased those motor mounts back in 2014 and knew immediately that I had a problem on my hands.

Turns out that back in the day, TPC used Speedway urethane suspension bushing and they have not performed well, with various reports of bushing damage.  They were too soft and too thin.

Kent’s business response was to completely overhaul the motor mount fabrication process for tighter tolerances, improved welding procedures, and to upgrade the bushings to PU 95A pieces which are polyurethane that has a Shore A hardness of 95 durometers.  That’s about as hard as rubber bushings get, and it’s super durable.  In addition, the bushing length was increased about 50% for better contact with the steel sleeve insert, and the bushing flanges got about 30% thicker.
Here's a good chart (and link) I found that explains Polyurethane bushing hardness and applications:

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The best part was Kent graciously hooked me up with the new bushings and matching steel sleeves via 2-Day Priority Mail, and I have already installed them.  Below is the process I used to change out the old bushings.  It was pretty simple.

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<New TPC PU 95A Bushings and Steel Sleeves>

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<PU 95A Bushing Close-up>

I used a 9/16” 3/8” drive socket and short extension as a drift to push the old steel sleeve through both the old bushings.  After getting started I switched the bottom socket to a 24mm ½” drive deep socket so I could drive the sleeve through the second bushing as well.

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<9/16” 3/8 drive socket drift>                                                      <24 mm ½” drive deep well base>

Once out, I noticed there was a coating of lithium grease between the bushing and the upright housing so I cleaned that up and replaced it with new grease.

To install the new bushings, I just set the flange end on the vise, carefully lined up the upright housing over the top end, threw on some cardboard layers to protect the powder coat and gave the housing a brisk hit with a small hammer.   The bushing started in easy enough and several light blows later it was fully seated.   Rinse and repeat for the remaining 3 bushings.

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<Old Bushings Out>                                                                           <New Bushing Going In>

For posterity, I recorded the dimensions of the new steel bushing sleeves and final bushing assembly and compared them to my original units. Overall the new bushing assembly has about 1 mm of play fore and aft in the mounting plate and the steel sleeves have about 1 mm of extra clearance as well.  Overall this may give some flexibility to connection of the drivetrain to the chassis as there is little room for error.

                                        Old Bushing Setup           New Bushing Setup
Overall Bushing Width:        61 mm                            60 mm
Steel Sleeve OD:                19.14 mm                        18.09 mm
Steel Sleeve ID:                 12.77 mm                        13.13 mm
Steel Sleeve Length:           60.83 mm                        59.15 mm
Thru Bolt (1/2"-13, Grade 5): 12.6 mm

To fill the space and as an added rust preventative, I coated the through bolts with a layer of Permatex Permashield. It’s non-hardening and should stay put.

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<Upgraded Passenger Side Mount>                                                            <Problem Areas>

So… I got everything all situated on both sides and torqued down all the bolts/nuts.   Unfortunately, upon further inspection, I now have some new problems areas as shown above.  

1. There is a gap between the back flange of the passenger side mounting plate and the new bushing.
2. The header tube is now touching the starter.

Problem Area 1:  This is the only location where there is a misalignment.  Most likely, this gap was not visible with the old urethane bushings because they compressed enough to hide it. There is no front flange gap, and there are no gaps in the driver’s side connection.  I’m leaning toward letting this ride unless someone knows it will be an issue down the road.

Problem Area 2: I’m not exactly sure how the 1/16" clearance I used to have disappeared, but I don’t want to modify the header tube. I would much rather purchase a smaller starter.   Anyone have a suggestion??? The starter I have is the stock 2002 Firebird starter.

I appreciate any feedback.

Nice. I was one of the guys with bushings that failed in 2014. Glad Kent noticed and saved you that.

On the clearances, I suggest you go around and slightly loosen all the engine mount bolts and then go back through to re-tighten them. You can even let the engine idle and warm-up a bit while things are loose to let the engine settle into it's happy place. I've had odd vibrations a couple of times when reinstalling the engine that takes doing this extra step to fix. And it might find your lost clearance.

Good luck.
Rich

Rich L. wrote:Nice. I was one of the guys with bushings that failed in 2014. Glad Kent noticed and saved you that.

On the clearances, I suggest you go around and slightly loosen all the engine mount bolts and then go back through to re-tighten them. You can even let the engine idle and warm-up a bit while things are loose to let the engine settle into it's happy place. I've had odd vibrations a couple of times when reinstalling the engine that takes doing this extra step to fix. And it might find your lost clearance.

Good luck.
Rich

Thanks Rich!

The motor is not in the car just yet and I have no way of running it otherwise.  However, I already did what you suggested with the motor while on the engine hoist and I'm just about to post an update on my build thread.  Sorry to hear you had the bushing failure... I trust you're all set now.  

Thanks for the advice.  Once I get the motor fired up I'll give it a try.

When was this updated? I think I bought mine in 2015....

I just went back and checked my project build receipts and my actual TPC conversion kit purchase was in June 2013.

Yikes.... that was eight years ago and I'm still at it!!

Kent from TPC will have to chime in to identify the actual dates he upgraded the motor mounts and also when he redesigned the long tube headers.

Motor mount bushings were updated a couple of years ago. Headers were updated about 5-6 years ago I believe.