V8 Swap Question: Getting Full driveline weight on Frame w/o Mounts (1 Viewer)

[RWBeringer4x4]

Hey all,

I'm getting ready to mock-up reassemble my 283, H42, and 4-speed case w/ new transmission cover and Downey bellhousing to go back in the truck for alignment and test fitting of the new motor mounts I'll be welding in. The location of the front mounts is pretty well established here on MUD, so when the time comes, the biggest concern I have is getting the rear axle pinion lined up (Parallel) with the output shaft on my transfer-case to avoid U-joint binding/vibration issues.

This is my conundrum:

In order to truly align the pinions, I've read that the full weight of the driveline has to be on the vehicle, so the springs, etc. all flex properly and everything is at their "true" height and angles. However, there are currently no motor mounts on the frame of my truck, because that is the exact thing I'm trying to position properly.

My question to the collective V8 guys is: How did you go about this?

1. Did you just install the motor at the recommended 3-5 degree rearward tilt, and hope for the best, or then shim the rear axle accordingly if it was off?

2. Can you "sand-bag" the truck - ie: add about 700lbs of weight to the front floorboards of the tub (and maybe some off the frame horns) and deem this "close enough?"

3. Did you fab up some sort of rig of wood or metal to allow the engine to "rest" in the truck, but still be adjustable enough to get the fitment right? If so, what does this look like?

4. I was thinking you might be able to line up, and weld in (level with the ground), the front engine mounts, mount the engine to these, then support the transmission and transfercase with a jack and slowly lower it to get the desired rearward tilt (assuming the front cushions have enough flex to allow this) and determine the height and location of the transfercase mounts. Of course, then the jack is still taking some of the driveline weight...

The truck is currently on a standard spring setup (SUA) with stock leaf springs. In the future I may go to a 2.5" lift but I suspect this won't change the pinion angle much, and, if it does, I'll shim the rear axle at that time to compensate.

Let me know how you did this - pictures obviously help a lot!

 

[Downey]

Rick, I might suggest that you are over-thinking this. With universal joints on both ends of the drive shaft to eat up most abnormalities, and considering the only time the two drive shaft flanges might be parallel to each other is when the rig is parked, I've never found this issue too be very important.

 

[Cruiser Corps]

Reading through, I was like, " You are way overthinking it."

Acceleration, deceleration, and cruise are all going to have different pinion positions in relation to the output. Especially with a V8. The U joints should be smooth and vibe-free in all of those conditions, especially with SUA and stock springs. The U Joints give you a decent margin for error.

A 2.5" lift would bother the angles more than setting the drive line and body on, and I've seen a lot of 2.5" lifts where no pinion correction was done, and they rode and drove fine.

Set the Chevy up at the recommended 3-5 deg. tilt. You're going to have to measure for drive shaft length once the drivetrain is situated, anyway. New shafts, or modified stock ones will be balanced, as long as you use a reputable shop, so you should be good there.

- Josh

 

[RWBeringer4x4]

Rick, I might suggest that you are over-thinking this. With universal joints on both ends of the drive shaft to eat up most abnormalities, and considering the only time the two drive shaft flanges might be parallel to each other is when the rig is parked, I've never found this issue too be very important.

Damnit Jim, I was hoping to NOT bug you with this one! I totally see your point - just went down a rabit hole reading last night on a couple other forums and everyone was saying if the flanges were not within 2 degrees of parallel there would be problems.

Reading through, I was like, " You are way overthinking it."

Acceleration, deceleration, and cruise are all going to have different pinion positions in relation to the output. Especially with a V8. The U joints should be smooth and vibe-free in all of those conditions, especially with SUA and stock springs. The U Joints give you a decen margin for error.

A 2.5" lift would bother the angles more than setting the drive line and body on, and I've seen a lot of 2.5" lifts where no pinion correction was done, and they rode and drove fine.

Set the Chevy up at the recommended 3-5 deg. tilt. You're going to have to measure for drive shaft length once the drivetrain is situated, anyway. New shafts, or modified stock ones will be balanced, as long as you use a reputable shop, so you should be good there.

- Josh

Thanks Josh, overthinking is what I do...appreciate the feedback! If you and Jim both think that the U-joints will deal with some subtle pinion misalignment without vibrations or premature wear, that's certainly good enough for me...



So (probably not) last question: should I weld the front mounts in "level" (with the ground) and let the mount cushions absorb the 3-4 degree tilt, or should I weld the brackets in with 3-4 degree rearward tilt?

 

[pb4ugo]

I'd level the frame, either by jack stands under the frame or by stands under the axles w/the suspension loaded. It gives you a "0" reference point. When 1 mount is tacked in the other mount needs to be in the same location opposite the the 1st one. I prefer loading the suspension because at some point you will be looking at the pinion angle, engine angle or caster angles. If you're using the angle iron type mounts then I wouldn't tilt the frame mounts, the engine sits on rubber pucks w/bolts going thru them and will allow for some tilting.

 

[Cruiser Corps]

Damnit Jim, I was hoping to NOT bug you with this one! I totally see your point - just went down a rabit hole reading last night on a couple other forums and everyone was saying if the flanges were not within 2 degrees of parallel there would be problems.



Thanks Josh, overthinking is what I do...appreciate the feedback! If you and Jim both think that the U-joints will deal with some subtle pinion misalignment without vibrations or premature wear, that's certainly good enough for me...



So (probably not) last question: should I weld the front mounts in "level" (with the ground) and let the mount cushions absorb the 3-4 degree tilt, or should I weld the brackets in with 3-4 degree rearward tilt?

If it were me doing it, I'd be using the engine hoist, C-clamps, vice-clamps, and jack / stands to get the drivetrain in place. Bolt the mounts to the engine first, then spend time positioning, measuring, clamping, measuring, nudging, measuring, tilting, measuring, stand back, eyeball it, measure again... you see where I'm going? Haha

As suggested by @pb4ugo (dig that handle lol) level the frame, making sure it's plumb before you get started, otherwise your measures might not be as accurate as you'd like.

Once I'm positive the engine is exactly where I need/want it, lock in the mounts to the frame via welding. I would definitely bolt the mounts to the engine, then set the tilt, then weld mounts. I wouldn't rely on the rubber to absorb the rear tilt, because then you're putting uneven load on the rubber mount, which could lead to premature mount failure. That's my $0.02, as there are many ways to skin this cat.

- Josh

 

[RWBeringer4x4]

As you all know, the frame is not a flat surface - so I level it at the front and rear "flat" points?

 

[reddingcruiser]

The mid-span between the wheel arches will work as a level reference point. You'll need to use a couple of equally thick blocks about 3/4" thick at each end of the level to span the rivets. A couple short bar clamps, a level and two blocks on the bottom side of the frame will work. Doing both sides and leveling across the front and rear cross-members should get you dead on.

 

[reddingcruiser]

Use at least a 2' level. Torpedo levels are, IMHO, pretty useless.

 

[RWBeringer4x4]

This may be a stupid question - but is "fine tuning" the leveling by adding/removing air from the tires a bad idea? Seems to me this would accomplish the goal of leveling the frame but might be prone to shifting as the truck starts to take weight during the install...

I've got a couple of levels laying around and some scrap 3/4in ply, which is hopefully level enough to use as blocks.

 

[Cruiser Corps]

This may be a stupid question - but is "fine tuning" the leveling by adding/removing air from the tires a bad idea? Seems to me this would accomplish the goal of leveling the frame but might be prone to shifting as the truck starts to take weight during the install...

I've got a couple of levels laying around and some scrap 3/4in ply, which is hopefully level enough to use as blocks.

That'll work, because you want the frame level to measure for tilt back, clearance, and whatnot, but the engine won't be sitting in the frame at that point. The jacks, hoist, stands, etc... will be supporting the weight of all of it. Once you get the mounts tacked into place, you may unbolt the engine from them, remove it, and burn them in real good. We like doing stuff real good, cuz that makes it more better!

Edit- once you do get it level, I'd raise a jack or stand to just barely support the frame at each corner, so if you do put some weight on it, it won't move.
- Josh

 

[Cruiser Corps]

A waist-height frame table would be ideal, but we're not building a race car here! Well, V8 Land Cruiser, so maybe...

 

[RWBeringer4x4]

A waist-height frame table would be ideal, but we're not building a race car here! Well, V8 Land Cruiser, so maybe...

Haha yeah...this is getting done in a 2-car garage in MD...next to a lawn mower... A frame table is not in my future so I'll need to make do with what I have...

It's currently in a bit of disarray (the truck and the garage).

 

[Jdc1]

Haha yeah...this is getting done in a 2-car garage in MD...next to a lawn mower... A frame table is not in my future so I'll need to make do with what I have...

It's currently in a bit of disarray (the truck and the garage).

View attachment 1393107

Looks familiar...

 

[RWBeringer4x4]

Thanks for all the feedback!

I do have a crane and a load leveler which should make adjustment easier.

So the plan is to level the frame - either with blocks/jacks etc. or deflating tires to get it level. Then I'll block it/Jack stand it to prevent frame movement.

Next I'll load the driveline in, mounts attached, and finagle it all into position following the standard rules of thumb:

~19.5in back from front crossmember
~1/2-1in toward driver's side
3-5 degree rearward tilt, measured off where the intake mounts to the engine.
~level with the top of the (level) frame

Then I'll check fitment of all the various components that might interfere - PS pump, steering shaft, exhaust, driveshafts, transmission shift tower, balancer-to-axle

From there I'll tack the "L" brackets to the frame, and lock in the side-to-side adjustment on the block-mounts, then pull the engine and burn in the mounts.

 

[Tin basher]

Easiest way of setting the angle of a small block Chevy is to level the carb mounting flange
The angle is built into the manifold

 

[cult45]

Easiest way of setting the angle of a small block Chevy is to level the carb mounting flange
The angle is built into the manifold

This. When I did my conversion I bolted the box up and dropped it all in. Measured a few times, ensured the carb mounting flange was level and blazed the mounts in. KISS.

 

[RWBeringer4x4]

Easiest way of setting the angle of a small block Chevy is to level the carb mounting flange
The angle is built into the manifold

This. When I did my conversion I bolted the box up and dropped it all in. Measured a few times, ensured the carb mounting flange was level and blazed the mounts in. KISS.

I've heard of it done this way - the issue in my case is the manifold likely won't be attached when I test fit the engine. That said once he front mounts are burned in maybe I'll bolt the fronts down and support the trans/transfer from underneath so I can reinstall the intake and fine-tune the angle.

In either case - The manifold mounting flanges Should provide a decent reference point.

 

[Cruiser Corps]

Thanks for all the feedback!

I do have a crane and a load leveler which should make adjustment easier.

So the plan is to level the frame - either with blocks/jacks etc. or deflating tires to get it level. Then I'll block it/Jack stand it to prevent frame movement.

Next I'll load the driveline in, mounts attached, and finagle it all into position following the standard rules of thumb:

~19.5in back from front crossmember
~1/2-1in toward driver's side
3-5 degree rearward tilt, measured off where the intake mounts to the engine.
~level with the top of the (level) frame

Then I'll check fitment of all the various components that might interfere - PS pump, steering shaft, exhaust, driveshafts, transmission shift tower, balancer-to-axle

From there I'll tack the "L" brackets to the frame, and lock in the side-to-side adjustment on the block-mounts, then pull the engine and burn in the mounts.

You've got a game plan, and it sounds like a pretty good one! You can do it! I once swapped a big block Ford 460 into a Ford Fairmont in a 10' x 20' storage unit. No room for a lawnmower!

- Josh

 

[RWBeringer4x4]

You've got a game plan, and it sounds like a pretty good one! You can do it! I once swapped a big block Ford 460 into a Ford Fairmont in a 10' x 20' storage unit. No room for a lawnmower!

- Josh

Sounds like the first few years of this project...working out of a borrowed, 10x20 garage where the truck had to be driveable at any given time in case the owner wanted to put her car in it, mine would get kicked out! Always a challenge having to button up a big project by the end of a weekend and have it back on all 4 wheels, running and driving.