Best LS Conversion Motor Mount for G Body Swap (let me know which is your pick)

[L92 OLDS]

Thank you for your input. This is exactly what I am looking for (repurposing existing stock equipment combined with some aftermarket equipement).

Every supplier is going to make money....Not just Holley. The Holley cost is higher because unlike the others they spent time and money on engineering and offer a complete system that fits. From what I have seen there are no piece meal alternatives yet that fit as well as the Holley system. Anything else is a compromise (headers that require denting and do not exit properly, inclination angle, oil pans that drag below the frame, etc. etc.)

 

[81cutlass]

So here is my logic why Holley's "we put the engine where it belongs and perfected the driveline angles" logic doesn't deliver the benefit for the increased cost.

CTS-V oil pan is 1.83" deep (lets round up and say 2"), holley is 1.25".

An LS with th400 is roughly 42" from center of mount pads to trans tailshaft.

If both the spohn mounts and holley mounts are optimized (for arguments sake they are) you get .75" lower front engine (being generous) with a holley vs. CTS-V pan.

arctan(.75/42)=1°.

The holley kit gets you 1 degree.

Say stock is 1.5 degrees, now you are at 2.5 degrees. You lost maybe 10-20% U joint life.

Spicer themselves say 60-100k warrantied life on u joints.
https://www.dennysdriveshaft.com/c1...3.219_x_3.219_1.062_1.125_outside_snap_r.html

15% loss of life over 80k miles means they will "on average" loose 12k mile life of warrantied life. I doubt I will ever put 50k miles on my LS swap car, and likely build a driveshaft with 1350 u joints or replace them from progressive mods over the life of ownership so although optomizing u joint life in an OEM application makes sense where you design stuff to make reliability goals, that 1 degree matters, but in a hotrod application that 15% extra u joint life isn't worth it.

Worst case you loose 20% u joint life, best case (if I use .58" lowered like the pans are) you get a 0.8° angle improvement which is a 8-10% (depending how you look at the graph) maybe 8% u joint life improvement.

Basically, if you lift a pickup/suv 2" in the back and keep the engine stock you are increasing your driveline angle the same amount that the using a "wrong" driveline angle in the G body swap situation.

TLDR- driveline angles matter but there isn't enough improvement to make it pay (for the cost in my view) that you will ever notice less failed driveline parts. Maybe a slight vibration if you hit a resonance, but your poly bushings, loud exhaust, and big cam is going to so over power that you will never see it.

People raise and lower their car 1-3" and nobody cares about driveline angles, caring about 1 degree in the trans is worth it in OEM applications but by modding your car you submit to lowering design life of factory components for performance or looks.

https://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html

 

[L92 OLDS]

So here is my logic why Holley's "we put the engine where it belongs and perfected the driveline angles" logic doesn't deliver the benefit for the increased cost.

CTS-V oil pan is 1.83" deep (lets round up and say 2"), holley is 1.25".

You did some homework there. I like it and it definitely raises some good points regarding the drive line angle. One point that hasn't been discussed though is the fact that because the Holley mounts put the engine lower in the "correct position", it also allows the use of the truck accessory drive. Critical for those that are cost concious (i.e. people that always complain about the Holley cost). I use the Escalade FEAD with the big alternator and it barely clears the hood. I'm sure it would hit with higher mounts like those available on e bay and the dirty ***** set up. 🤔 This just addresses engine position. Then you still have denting headers, collector exit angle, X pipe, exhaust and transmission cross member fitment. It's all about having the cash to o it right. For me, I would rather spend a little money in confidence everything will fit.....no fabrication, hacking or welding required.

 

[xcookpac]

So here is my logic why Holley's "we put the engine where it belongs and perfected the driveline angles" logic doesn't deliver the benefit for the increased cost.

CTS-V oil pan is 1.83" deep (lets round up and say 2"), holley is 1.25".

An LS with th400 is roughly 42" from center of mount pads to trans tailshaft.

If both the spohn mounts and holley mounts are optimized (for arguments sake they are) you get .75" lower front engine (being generous) with a holley vs. CTS-V pan.

arctan(.75/42)=1°.

The holley kit gets you 1 degree.

Say stock is 1.5 degrees, now you are at 2.5 degrees. You lost maybe 10-20% U joint life.

Spicer themselves say 60-100k warrantied life on u joints.
https://www.dennysdriveshaft.com/c1...3.219_x_3.219_1.062_1.125_outside_snap_r.html

15% loss of life over 80k miles means they will "on average" loose 12k mile life of warrantied life. I doubt I will ever put 50k miles on my LS swap car, and likely build a driveshaft with 1350 u joints or replace them from progressive mods over the life of ownership so although optomizing u joint life in an OEM application makes sense where you design stuff to make reliability goals, that 1 degree matters, but in a hotrod application that 15% extra u joint life isn't worth it.

Worst case you loose 20% u joint life, best case (if I use .58" lowered like the pans are) you get a 0.8° angle improvement which is a 8-10% (depending how you look at the graph) maybe 8% u joint life improvement.

Basically, if you lift a pickup/suv 2" in the back and keep the engine stock you are increasing your driveline angle the same amount that the using a "wrong" driveline angle in the G body swap situation.

TLDR- driveline angles matter but there isn't enough improvement to make it pay (for the cost in my view) that you will ever notice less failed driveline parts. Maybe a slight vibration if you hit a resonance, but your poly bushings, loud exhaust, and big cam is going to so over power that you will never see it.

People raise and lower their car 1-3" and nobody cares about driveline angles, caring about 1 degree in the trans is worth it in OEM applications but by modding your car you submit to lowering design life of factory components for performance or looks.

View attachment 113449
https://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html

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Thanks for all the info. Let me digest it and get back to you.