Alternator, serpentine belt and tensioner

So... Now that the motor is in the car there are all kinds of challenges to be addressed. Exhaust routing is going to be the biggest one. I'm still working that out and gathering materials to tackle that job soon.

I figured the best place to start sorting things out was getting the hood to close and getting all the engine driven accessories (A/C compressor, power steering, alternator, etc.) installed. The original GMC mounting of the alternator resented a problem. The alternator was about an inch too high to allow the hood to close. After considering a couple of options for relocating it I realized I could just rotate the alternator down on its main mount by modifying the alternator support bracket.

Original alternator mount

Lower mount

Moving the alternator meant screwing up the geometry of the serpentine belt tensioner. I made a relocation bracket to rotate the tensioner over and down to get it in the same position relative to the alternator as it was before.

Success! The tensioner works correctly and the original length belt still fits...

But just barely! Down at the power steering pump there's only about 1/8" clearance between the belt and the upper control arm pivot shaft. Not much, but it's enough!

The finished bracket with power steering pump reservoir.

Is it in yet...?

It's good to have the 6.5 off the engine stand and into the car. Yes, it's a tight fit! I figure at this point I've done almost all of the easy stuff - pulling motors, taking things apart, fooling with the motor on the stand. Now the real work begins.

Frame modification

To ensure plenty of front pulley clearance I Cut the chunk out of the front crossmember with a plasma cutter. Then cut a piece of 1/8" plate and pressed a few small bends into it one inch apart to approximate the curve.

Making individual bends is much easier than trying to form a smoothly curved piece. You can sharpen or flatten each bend until it matches up just right.

A little cleanup

Steam cleaning 30+ years of gunk from the engine bay and undercarriage. Yuck!

Motor mount spacer plates

I fabricated the motor mount plates

And bolted up them to the 6.5

Out with the old (350)

The 350 L48 motor comes out

There's nothing stopping me from pulling out the old 350 gas motor. Everything else I want to do with the 6.5 can be done just as easily with it in the Vette as on the engine stand.

A piece of channel is bolted to the frame
rails and runs under the transmission.

I made a simple brace to hold the TH350 transmission in place  while the 6.5 gets fitted to its new home.

Pulley clearance

The 6.5 diesel is almost 2.5" longer than the small block 350. This means the front pulley is going to end up over the crossmember rather than just behind it. One solution would be to cut a piece out of the crossmember and weld in a patch with more clearance.

Another solution would be to make spacer plates to raise the motor up at the motor mounts. Raising the motor would also give a little additional ground clearance.

The downside to raising the motor will be decreased clearance under the hood and decreased clearance between the bellhousing and firewall.

Here's a drawing for a motor mount spacer plate. Because it will sit at a 45 degree angle a 5/8" thick plate will raise the motor about 7/8".

I'll probably make both modifications. If raising the motor runs into too many unseen difficulties I can remove the spacer plates. If I've already modified the crossmember I won't have to pull the motor back out to do it later.

Which transmission?

Certainly not the TH350 that is in the Corvette now. To keep the diesel motor happy at freeway speeds it will need something with an overdrive. The GMC pickup has a 4L80E which is a very robust transmission. It's also quite a bit larger and longer than what's in the Vette right now. It would probably be possible to stuff the 4L80E into the tunnel but that looks like a really tight fit and a lot of trouble. Plus, I would probably lose about an inch of precious ground clearance.

The 700R4 would be a good choice. It has a nice low first gear for good off the line response and a nice tall overdrive for relaxed freeway cruising and good fuel economy. Then there's the 4L60E which is a computer controlled version of the 700R4. I would have to use a stand alone aftermarket controller which complicates the installation a little bit and adds to the expense. One nice advantage to the 4L60E with aftermarket controller is all the shift parameters can be dialed in without digging in to the valve body. The controller will also support the use of paddle shifters. I would like that a lot.

For the time being I can get a lot done without having the actual transmission I'm going to use. I'll leave the TH350 in there for now and bolt the 6.5 to it (no torque converter or flex plate). That will give me an accurate motor position and I can work on plumbing for the turbo, modifications to the thermostat housing, wiring, fuel supply, etc.

Almost time to get the motor out of the Vette

There's a bit more to do to the 6.5 before it's ready to be dropped into its new home under the Corvettes hood. Even so, it getting to be time to get the 350 gasser pulled out. There will be plenty of tidying up to do in the Vette engine bay.

The view under the Vette hood. Ughh... The first thing to do will be to remove the radiator shroud and intake snorkels so I can get in deeper with a tape measure. I want to keep the car drivable for a little while longer.

The 6.5 looks a little better now

 It is not a thing of beauty but at least it's presentable. The top half of the intake manifold is a snorkel that connects to the turbocharger that will be mounted to the right hand side of the motor.  I'm going to have to modify all the turbo plumbing to get the turbo to fit in the tight space under the Corvette hood. That top snorkel will have to either be modified or (more likely) replaced with a fabricated part. The same goes for the water outlet and thermostat housing. It looks like it is going to be a little bit too tall. I'll probably have to make a replacement that doesn't stick up so high.

More motor prep

I figure the Diesel Corvette is going to be a bit of a curiosity. Folks are going to want to look under the hood to see that big ugly diesel lurking in there. That means it needs to be made presentable. The oil pan is already looking pretty so I figure I better pull the valve covers and intake manifold and give them a good cleaning and a coat of paint.

 To get the valve covers off you have to remove the fuel injection lines. The get the injection lines off you have to pull the intake manifold. Here's pics of the injection lines. The lines have to come off in the right order or you can't get a wrench in where you need to. The same goes for putting it back together.Check out the cobbled up (rubber) fuel supply lines. That will get tidied up as well.

Shortening the oil pan

One thing I knew from the start was the 6.5 oil pan was going to have to be modified. The diesel holds a lot more oil than the gas motor and the oil pan is a lot deeper. The Corvette doesn't have much ground clearance to start with so the oil pan has to be shortened.

I measured how far the oil pump protruded down into the pan and marked a cut line around the sump. Off to the bandsaw! There's a little bit of a thrill to be had taking perfectly good expensive parts and running them through a saw. Now you're committed! It worked out fine. I cut a piece of diamond plate to fit the oil pan bottom and welded it in place. I made it about 1/8" too short so a quick trip to the hydraulic press put a dimple in it right below the oil pump body for clearance. The pan is now about 1 1/2" shorter than stock. With this modification and some mods to the motor mounts to carry the motor a little higher I should have about the same ground clearance as 350 gas motor. 


More reference pictures with the motor on the stand:

Pulling the diesel motor

During the motor-ectomy I tried to take a bunch of reference photos. I probably should have taken more. Photos are really helpful when you're looking at some parts and trying to remember how they fit together.

Hydro-boost hoses

waste gate actuator

Battery positive bus bar

WTF! There's no crank position sensor.
This motor doesn't need one but the hole
should be plugged.