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LT1 swap motor mount direction

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Old Aug 29, 2020 | 04:30 PM
  #1  
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From: Albuquerque NM
Car: 1985 IROC
Engine: 350HO
Transmission: T56
Axle/Gears: 10 bolt 3.23 limited slip
LT1 swap motor mount direction

Hello Thirdgener’s

PO had a carbed LT1 swapped into a 92 RS. I noticed that the back of the motor looks shifted towards the passenger side and the passenger side of the motor is lower (out of level). I did some research and it looks like the motor mounts are the correct part number (334971 driver side and 4039436 passengers side) but I’m wondering if the passengers side mount is installed backwards? On the drivers side the part number faces the firewall, on the passengers side the part number faces the radiator. Can anyone verify if the passenger mount needs to be turned around? Would that in turn move the back of the engine towards the drivers side and lift it up?

p.s. I verified that the radiator support is level so I know the entire vehicle is not crooked on the jack stands.

Thanks in advance for your time,
Ted










Last edited by Bustionironi; Aug 29, 2020 at 05:16 PM.
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Old Aug 30, 2020 | 09:43 AM
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Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: LT1 swap motor mount direction

I could be thinking wrong but, you can't bolt the clamshell part on upside down without it being in a completely different spot. 3 bolts in a triangle shape hold it to the block. If you turn it upside down and don't move it anywhere then none of the bolt holes go to anything. It can be bolted upside but it won't match the chassis at all since it moves the whole clamshell rearward to the flywheel.
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Old Aug 30, 2020 | 11:42 AM
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Car: 1984 Camaro Berlinetta
Engine: LT1
Transmission: T56 6-speed
Axle/Gears: 4.11 LS1 Rear End
Re: LT1 swap motor mount direction

Don't intend to scare you but; Engine Cradle problem ? Car been hit or in a "minor" front end crash ?? Any Welding repair work done in the front end ?

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Old Aug 30, 2020 | 12:43 PM
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Re: LT1 swap motor mount direction

Not to discount John's notion of possible damage (and he will possibly recall a conversation he and I had about this), but years ago I had done a Gen 1 swap into a V6 chassis. With the engine in place with correctly orientated engine mounts, the driver's side was higher. (check out the level not the tilted photo).



Wasn't sure what to make of it nor did I recall if the engine was also crooked in the previous 86 IROC that it was in.
Then I came across this spacer (literally just laying on the workbench along with a pile of other parts), with a GM part number stamped on it (not sure if I recorded that number anywhere). Obviously designed to fit between the mount and the block, it provided exactly the right amount of offset needed to level the engine perfectly.




I've no idea which car the spacer came from but it would have to have been a Camaro as those were the only vehicles that had rolled through the shop in any recent past. There were possibly as many as 5 different cars that rolled through. Years 85-87, a couple of Coupes, an IROC, an RS and maybe one other. Some V6 (both Coupes) and the rest V8s. No 5.7s.
That V6 chassis definitely had no signs of any collision damage.
Still a mystery to this day.
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Old Aug 30, 2020 | 03:19 PM
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From: Albuquerque NM
Car: 1985 IROC
Engine: 350HO
Transmission: T56
Axle/Gears: 10 bolt 3.23 limited slip
Re: LT1 swap motor mount direction

Originally Posted by aliceempire
I could be thinking wrong but, you can't bolt the clamshell part on upside down without it being in a completely different spot. 3 bolts in a triangle shape hold it to the block. If you turn it upside down and don't move it anywhere then none of the bolt holes go to anything. It can be bolted upside but it won't match the chassis at all since it moves the whole clamshell rearward to the flywheel.
That’s what I thought. I found one thread on thirdgen about having the clamshell installed backwards, but the engine in the bay was much more crooked than this one. I can definitely confirm that the clamshells are rotated 180 degrees from each other (they are not mirrored) but they both have 2 bolt holes towards the fender and one towards the engine.

Last edited by Bustionironi; Aug 30, 2020 at 07:27 PM.
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Old Aug 30, 2020 | 03:50 PM
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From: Albuquerque NM
Car: 1985 IROC
Engine: 350HO
Transmission: T56
Axle/Gears: 10 bolt 3.23 limited slip
Re: LT1 swap motor mount direction

Originally Posted by John in RI
Don't intend to scare you but; Engine Cradle problem ? Car been hit or in a "minor" front end crash ?? Any Welding repair work done in the front end ?

I looked it over very closely. Everything looks untouched.
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Old Aug 30, 2020 | 03:53 PM
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From: Albuquerque NM
Car: 1985 IROC
Engine: 350HO
Transmission: T56
Axle/Gears: 10 bolt 3.23 limited slip
Re: LT1 swap motor mount direction

Originally Posted by skinny z
Not to discount John's notion of possible damage (and he will possibly recall a conversation he and I had about this), but years ago I had done a Gen 1 swap into a V6 chassis. With the engine in place with correctly orientated engine mounts, the driver's side was higher. (check out the level not the tilted photo).



Wasn't sure what to make of it nor did I recall if the engine was also crooked in the previous 86 IROC that it was in.
Then I came across this spacer (literally just laying on the workbench along with a pile of other parts), with a GM part number stamped on it (not sure if I recorded that number anywhere). Obviously designed to fit between the mount and the block, it provided exactly the right amount of offset needed to level the engine perfectly.




I've no idea which car the spacer came from but it would have to have been a Camaro as those were the only vehicles that had rolled through the shop in any recent past. There were possibly as many as 5 different cars that rolled through. Years 85-87, a couple of Coupes, an IROC, an RS and maybe one other. Some V6 (both Coupes) and the rest V8s. No 5.7s.
That V6 chassis definitely had no signs of any collision damage.
Still a mystery to this day.
from the bottom of the car there is a visible difference in the space between the clam shell and the motor mounts underneath. The gap is about 3/4” on the drivers side and 1-1/4” on the passengers side. So either the drivers side clam shell is tilted in towards the motor or the passengers side clam shell is tilted out towards the fender. The passenger side mount look collapsed.

Last edited by Bustionironi; Aug 30, 2020 at 04:07 PM.
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Old Aug 31, 2020 | 05:10 AM
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Car: 92 Firebird, 77 Trans Am SE, 86 Z28
Engine: 5.7 HSR, T/A 6.6, empty
Transmission: T-5, TH350, T-5
Axle/Gears: 3.08 posi, 3.23 posi, 3.23
Re: LT1 swap motor mount direction

Are you sure it's not just a broken mount?
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Old Aug 31, 2020 | 10:44 AM
  #9  
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From: Albuquerque NM
Car: 1985 IROC
Engine: 350HO
Transmission: T56
Axle/Gears: 10 bolt 3.23 limited slip
Re: LT1 swap motor mount direction

Originally Posted by aliceempire
Are you sure it's not just a broken mount?
I think the passenger side mount is broken. Time for a replacement. Looks like a fun job
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Old Sep 3, 2020 | 07:28 AM
  #10  
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Car: '90 RS
Engine: 377 LSX
Transmission: Magnum T56
Re: LT1 swap motor mount direction

None of those pictures indicate the engine is severely out of level. There is more variability in the suspension, tires, and floor than likely whats in your mounts. It's more likely that you have one facing the wrong direction. I would check that our first.
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Old Sep 5, 2020 | 12:48 PM
  #11  
Bustionironi's Avatar
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From: Albuquerque NM
Car: 1985 IROC
Engine: 350HO
Transmission: T56
Axle/Gears: 10 bolt 3.23 limited slip
Re: LT1 swap motor mount direction

Originally Posted by ShiftyCapone
None of those pictures indicate the engine is severely out of level. There is more variability in the suspension, tires, and floor than likely whats in your mounts. It's more likely that you have one facing the wrong direction. I would check that our first.
The car is currently on (4) jack stands. The radiator support is level and the body between the windshield and t-top is level. In the picture of the level on the intake manifold you can see how much I’m lifting the passenger side of the level up. It’s lifted up a good quarter inch or more. That seems like a lot on a little 8” long level?

The passenger side mount looks beat up compared to the drivers side, that’s why I was thinking the passengers side mount is shot and needing replacement. I’m leaning towards pulling the motor out so I can go through it, replace the motor mounts and clean up the engine bay before re-install.
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Old Sep 7, 2020 | 11:33 PM
  #12  
Bustionironi's Avatar
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From: Albuquerque NM
Car: 1985 IROC
Engine: 350HO
Transmission: T56
Axle/Gears: 10 bolt 3.23 limited slip
Re: LT1 swap motor mount direction

Almost ready to pull motor out, just two stubborn torque converter bolts, two lower bell housing bolts And the motor mount bolts left to remove. I thinkI discovered part of the problem. When the PO had the LT1 put in they left the AC compressor in place on the lower passenger side but did not notch the k member. The motor doesn’t sit back far enough which gives it the funky angle. Maybe the motor mount is bad too, not sure yet.
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