Bought an old BTF U4 buggy

So love fixing the PO dumbassery. The entire drivetrain was indeed mounted from above. He jack legged a crossmember for the trans/TC and the mount are in the way of the exhaust.

I think he used bubble gum to weld the brackets on and then let a rat gnaw off part that was in the way of the exhaust.

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Going to cut that crap off and top mount the trans/TC. BKOR sold out of their top mounts, 74 Weld & Bent Fab were closed today but I wanted this done. Took a bottom mount AA TH400 adapter and turned it into a top mount. Some CAD, CNC plasma, and milled the adapter to mount a bracket on the top.

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Dumbassery cut off and frame fixed. Cut a slight groove into the frame when cutting welds to remove the brackets. The frame is double wallad and welded together. I'm sure it would have been ok but being OCD I ground down the cuts and welded them up. Things no one would ever know but I do :dumbass:

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Joe_U4 said:
Looking closer I think the PO added a frame mounted cross member for the trans that was not part of the original design. The Atlas has a support from the top and mounts on the rear of the case. Looks like there is a provision for another top mount where the trans and atlas mate. I think the entire drivetrain was mounted from above and did not use a trans cross member. Another thing to ponder šŸ¤”
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we mount all of our trans and tcases from the top now as well. No mid motor plates, no head mounts. We have gotten away with lots of tcases mounted from below at the tailshaft, but that is very well braced in our chassis, but all of the transmissions are mounted from above and now even the atlas tailshafts are as well. Its just simple and easy to eliminate any potential failures by doing that. Especially if you cant guarantee that the lower part of the chassis is braced perfectly.
 
partiallycommittedracing said:
we mount all of our trans and tcases from the top now as well. No mid motor plates, no head mounts
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I remember Lee C car having head plates. Y'all decided to not keep installing them?
I agree with you they are probably not needed and overkill.

Him and I had a good discussion on the top mounting and its advantages before I gave him my extra 74weld adapter.
I like how both the trans and tcase are held together on his chassis.
 
Bebop said:
I remember Lee C car having head plates. Y'all decided to not keep installing them?
I agree with you they are probably not needed and overkill.

Him and I had a good discussion on the top mounting and its advantages before I gave him my extra 74weld adapter.
I like how both the trans and tcase are held together on his chassis.
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No there just isnā€™t a need with them already being mounted in 4 places. Especially when poly mounted ā€¦ maybe if everything was hard mounted Iā€™d want to have more conversations about mid plates and head mounts. But itā€™s just not necessary, and probably even detrimental in other chassis where you canā€™t guarantee they are truly rigid. Mine does not have head or mid plate and Iā€™m not in the slightest bit concerned even with 800+hp. The 1500 hp no budget build is the same way.

We exclusively use the 74weld adapters now, they are the best one on the market currently in my opinion.
 
Joe_U4 said:
Solid mounts should never be used in an off-road application, hard impacts would transfer stress to the drivetrain. IMO head mounts should not be used in any application, way too much stress on the head bolts. Torque twist combined with thermal expansion and you're asking for head gasket problems.
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The trick to hard mounting is 1) making sure the chassis is 100% rigid and 2) making sure your mounts are in plane, super solid, and you have enough of them.

We have done solid mount a few times and itā€™s not my favorite, but those chassis have been abused for years, and have had no issues

There are lots of chassis out there where the drivetrain actually becomes part of the rigidity of the chassisā€¦ I donā€™t believe in that, but folks do it.
 
Shreddinlettuce said:
You really donā€™t want to be over constrained, chassis flex etc will happen and that stress has to go somewhere
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In general, yea thatā€™s correct

But you can absolutely build a chassis that doesnā€™t flex and contains a solid mounted drivetrain and has no negative side effects other than assembly. There is definitely a real use case for hard mounting a drivetrain, especially in a race machine
 
Joe_U4 said:
Solid mounts should never be used in an off-road application, hard impacts would transfer stress to the drivetrain.
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There are cars that cannot take soft mounts.
I have knowledge of a few 1000+hp race cars that will absolutely wreck the rubber in the mounts in a matter of minutes.
Solid mounting was the only solution.

Joe_U4 said:
IMO head mounts should not be used in any application, way too much stress on the head bolts. Torque twist combined with thermal expansion and you're asking for head gasket problems.
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My car is head mounted. As are all Bent Fab cars that he set the drivetrain in.
I have beat the ever living crap out of it and somehow it survived everything with 0 issues. I know of plenty of other owners with no problems either.
Oh, I have had the heads out of the engine 2 times and have re-used the head bolts and the head gaskets... Iron block LS engines are incredibly tough.
It's unconventional, but it works.

partiallycommittedracing said:
The 1500 hp no budget build is the same way.
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Y'all added power to this thing?????
 
I've been building race engines for close to 40 years and using the heads to mount is a no no. Everyone is welcome to their opinion, I don't knock them, and some get by with questionable methods. Concerning high HP applications, that is another level and doesn't apply to 95% of off-roaders.

Been there done that and have the T-shirt

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Bebop said:
There are cars that cannot take soft mounts.
I have knowledge of a few 1000+hp race cars that will absolutely wreck the rubber in the mounts in a matter of minutes.
Solid mounting was the only solution.
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Lots of U4 cars are built like this. Especially mid-engine builds. Granted, those are a much different can of worms than we are talking about here...

Bebop said:
My car is head mounted. As are all Bent Fab cars that he set the drivetrain in.
I have beat the ever living crap out of it and somehow it survived everything with 0 issues. I know of plenty of other owners with no problems either.
Oh, I have had the heads out of the engine 2 times and have re-used the head bolts and the head gaskets... Iron block LS engines are incredibly tough.
It's unconventional, but it works.
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Head mounts were all the rage back in the late 2000s when offroad chassis design was still in that stage of "fuck it put a tube there I think?" Once people started figuring out the Triangle method of mounting things, head mounts stopped being as much of a thing. They really don't do anything unless you just don't have a way to conventionally mount your motor. I dont love them, but its mostly just personal preference...not because we have torn any shit up using them. BUT we have a very rigid chassis and still always use conventional mounts as well which basically just nullifies the head mounts, so im not sure it really matters. I wouldnt ever just hang one from the heads...I just couldnt bring myself to trust that.

Bebop said:
Y'all added power to this thing?????
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The 427ci with a fat whipple on top did 1500hp at the crank from Nelson Racing (allegedly...), but it did 702hp on the chassis dyno before it started just doing a burnout and then none of it mattered after that lol
My 440ci NA Thompson did 832hp on the engine dyno on the first tune from them and then we detuned a bit for some drivability changes and knocked it back to 787hp
 
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Hope that did not come across as dick but was bit frustrated sitting still in bumper to bumper traffic on 540. All because dumbasses can't drive šŸ¤¬

Back to the regular scheduled shit show.....Rear mount bracket for the Atlas mocked up and fits like it should. Need to clean it up and burn it in.

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If you see me do something stupid or have a better way please speak up šŸ˜‰
 
Skid plate bolted in place to check for clearance. Plenty of room for some horizontal supports across the bottom. I'll throw in the driveshafts to be sure of clearance and then make some supports. Trans and Atlas supports turned out good. Front one bolts in for ease on installation and removal of the trans. Rear support swings up and out of the way for access to the Atlas.

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The engine, trans, & TV are supported by the motor mounts and two vertical hanging mounts. Considering adding a lateral link bar between the front hanging mount and the frame to help with any fore/aft movement. Probably not necessary but won't hurt šŸ¤”


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Still have a few things to fix or modify but hopefully it won't be too long before the chassis is ready for blasting and painting.

Steel-it was my original plan but second guessing wether to powder coat the chassis.

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I see you're using 3 bolt flanges on the exhaust. Any particular reason you didn't use V-bands?
I'll be doing what you're doing next summer and starting to plan out my exhaust routing and components.
Granted, I've always done what you're doing. But I'm thing about V-bands for the new rig.
 
Jody Treadway said:
I see you're using 3 bolt flanges on the exhaust. Any particular reason you didn't use V-bands?
I'll be doing what you're doing next summer and starting to plan out my exhaust routing and components.
Granted, I've always done what you're doing. But I'm thing about V-bands for the new rig.
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The exhaust is from the original build otherwise I would have used V- band clamps. I just bead blasted the headers and exhaust pipe, repainted them, and wrapped them.
 
Jody Treadway said:
I see you're using 3 bolt flanges on the exhaust. Any particular reason you didn't use V-bands?
I'll be doing what you're doing next summer and starting to plan out my exhaust routing and components.
Granted, I've always done what you're doing. But I'm thing about V-bands for the new rig.
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Use V band or ball clamps. You won't regret that.
 
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