My GMC, a little update

[Gunfreak25]

Just a little update. Still making progress! Thanks to Hippiedude for the new toolbox. I got it installed and my running board back on finally!

It appears the stock motor mount brackets for the 302 that are riveted to the frame, are setup for biscuit style mounts. They already have a large 1 1/4" hole for the rubber mount. That will save me lots of drill work and metal play. So i'll need to fab up a piece that extends from the 6.2 motor plates, forward about 4 inches to the stock frame mounts. Should be real easy.

Got my hood sanded, primed and reinstalled with new hinge pins.

Ordered all my transmission seals, filters, etc. All I need now is my adapter plate and I am ready for the installation.

I am also drawing up plans for a custom hard top that all GMC owners can make very easily and for under $150. Modeled after the M220 hard top.

 

[Tanner]

I'm lookin at those headers and I'm seein an easy turbo upgrade with there shape and size

Any turbo upgrade would be easier to perform by simply getting the factory 6.5 turbo exhaust manifolds...

'Tanner'

 

[Gunfreak25]

The only upgrade i'll be making to this engine later is a main girdle for the bottom end. At $175 it's cheap insurance against web cracks and I hear they work well. Although lots of people do it, I don't like the idea of a turbo on a stock 6.2. The 22:1 compression ratio is only increasing the changes of detonation and it seems the turbo'd engines don't last nearly as long. They were designed NA and I think they should stay NA. And I really don't need or even want the extra power. For the cost, i'd rather put a whole set of 11.00's on the truck.

 

[Tanner]

Stud girdle, while a band-aid, will buy you some time. And the 6.X could be built later if you wished with
18~ish:1 pistons & then turboed. Longevity comes down primarily to quality of what you start with, maintenance,
and how hard you run it. I've seen 6.X motors go 300K & some only make it to 50k before breaking...

But they're so cheap...

'Tanner'

 

[big block 88]

6.2 with 5 psi would perform very nice, and make sure it is gated and a BOV is a good idea. If you were around the early diesel pickups when banks came out with a side winder setup for the 6.2 the 6.9 and 7.3 IDI trucks even with turbos couldn't touch it and it even gave the NON incooled cummins a run for there money. The 6.2 can rev pretty high and a girddle will halp alot with bottom end issues. There are alot of farm trucks runnin around here 300k miles and those are hard miles they ARE good motors if taken care of and not hot rodded.

Just my .02

 

[Gunfreak25]

My new 60 gallon tank. When I have time I'll be cutting off the legs and moving my brackets down. I'll be reforming the old tank straps to fit the new round tank. It already has a half dozen fittings for stuff. This will be my fuel cap. Amazon.com: Vibrant 2.75" OD Mild Steel Weld Bung w/ Polished Aluminum Threaded Cap: Automotive The tank is thick, so it makes welding on it very easy. It was made in 1978 by the Manchester tank CO of Texas. Still have to clean it out, but a 1/2 gal of evaporust should do the whole inside. And of course it will be painted and stenciled properly.

 

[Gunfreak25]

Well I am glad I decided to remove the front pump and replace the seals. 40 year old rubber is crunchy! I found a lot of sludge build up in the pump fluid passages. Upon cleaning it down I also found the front pump bushing that the TC rides on was missing chunks of metal. No damage to the torque converter, thankfully. I just have to get a new bushing pressed in and the pump is ready, got all the seals replaced.

My adapter plate arrived today. Looks great, and $20 off my next order from Summit Racing. Will be using that coupon for my dual electric fans I have yet to order.

I just need to get the pump bolted back in, bolt the tranny up and throw the new drivetrain in. I also decided against the air tank as a fuel tank. It's just too nice to cut up, and I need to build a large at home compressor. Stock tank will have to be cleaned out.

 

[Gunfreak25]

I woke up with a nasty headache and feeling like I caught the flu this morning. Took a few tylenol and 2 hours later I was outside preparing the hoist my new engine in. Borrowed some plywood from the neighbor for my "temporary road" since a hoist doesn't travel well on soft clay.
Got them both hoisted in and it's currently sitting on top of a flew blocks of wood under the crank pulley. Surprisingly, everything lined up great and is darn near perfectly level. Pics tomorrow. Oh, and 1 problem presented itself pretty quickly. The mechanical lift pump will hit the motor mount, so you must use an electric pump. Plenty of oil pan clearance with the HMMWV deep pan, and the HMMWV headers fit great too. But as expected I will have to cut the flanges off of them and weld some downpipes on to move the flanges down lower.

Other than that, it fits great. I have about 6 inches of room to spare between the water pump pulley and the radiator. Fits just as good as that old 455 that was in it.

 

[m1010plowboy]

Never too sick for the M135

Get better man because I caught what you have and now the two of us are working sick. 104 temp in the fetal position won't stop a good man from workin' on his deuce.


New Drive Train threads for these trucks are really valuable because I'm seeing 'savers' with no power. Watching it come together is the best.
Thanks for keeping this going.....vitamin "C" and tea.

 

[Gunfreak25]

All balanced out, front to back and side to side. It's right where I want it and the last step is to fab up the brackets to connect the biscuits to the motor plates. The motor plates sit lower than I thought, so the brackets will sort of "step down" from the biscuits and then will be welded to the motor plates with triangular gussets. The passenger header needs the flange cut off and a 40 or 90 degree elbow welded on to move the flange down lower. The drivers header doesn't even fit without hitting the frame rail, badly. I will have to make an angled cut to remove the flange and weld on a downpipe hugs the block 2" closer. Fuel pump will NOT work. Use your stock in tank fuel pump, it will work just fine. I will need to modify (with a big hammer) the HMMWV oil pan or get a civi one, this pan sits 2" away from the differential.

Those are all the clearance issues associated with a HMMWV 6.2 in a M211. You can use a civilian 6.2 or CUCV 6.2 and get around all the above issues except for the fuel pump. I like the HMMWV motors since most have been recently rebuilt and they are 100% 24 volt.

If anyone has questions, just ask!

 

[Oldfart]

It looks like it is coming together!

 

[hendersond]

Looks great!

 

[Gunfreak25]

I appreciate the PM on engine alignment, OF! You actually got me thinking about raising the motor/tranny. It sits pretty low. The reason for that is the tranny crossmember is what is currently dictating where it all sits, height wise. If I remove the crossmember/frame bushings, put those bushings instead under the th400 tailshaft mounting holes I would have effectively moved the powertrain upwards 2.5 inches. That would not allow me enough room to get by without modifying the headers, but it would allow for a good 5" of oil pan clearance and the motor mounts would sit up a little higher.

Driveshaft angle wise, I believe you are correct in that it would be fine. You should see the HMMWV's. They are canted WAAAY over towards the passenger side. Those are some weird vehicles.

 

[Gunfreak25]

Well I couldn't wait until tomorrow. You are quickly turning into a superfriend OldFart, with all the info and tips you have given me. I can do this work, but I would have never thought to raise the powerplant up higher. I hoisted the engine up again, removed the crossmember bushings, bolted the crossmember back up, this time I put the bushings between the tranny tailhousing and the rubber mount for a total height increase of 3 inches. Boy did it make a difference. However, both manifolds will still need to be modified. Tis just the nature of the beast, they were designed for a very very unique vehicle, the HMMWV. It's no big deal though, I have acres of room now to work with. The good thing is the oil pan now has 5" of clearance to the pumpkin, I think that is just right. The fuel pump however, will never clear anything. I never realized how low it hangs. And I have no more room to raise anything without cutting the floor panel for the bellhousing.

 

[armytruck63]

Excellent work Gunfreak. I'm wondering if CUCV exhaust manifolds would give you more clearance. Either that or exhaust manifolds off of a 6.5 civilian engine.

A few years ago I saw a sweet M211 in Nevada. It had been a fire department truck. The owner of the yard where it was sitting said that someone "stole" the engine and transmission - which I find hard to believe. The rest of the truck was in great shape and it would have been an excellent candidate for a re-power like your project.

 

[Tanner]

GunFreak... work looks good thus far. However, you might want to look into this info regarding driveshaft angles. I know that the trans tailshaft to T case input is fixed, and you shouldn't be seeing any movement in fore/aft plane with new engine/trans/t case mounts used.

Driveline 101

Tom Wood's Custom Drive Shafts - Driveline 101

I would recommend balancing any chopped/welded/rotating shaft, even if it is only seeing a low-speed spin RPM at top 58mph. It's cheap insurance & keeps your seals & bearings happy in the trans & tcase...

'Tanner'

 

[135gmc]

"Stealing" the engine and transmission out of a junkyard 211 doesn't make any sense - unless the FD re-engined the truck with a different power train. The junkyard might have bought the truck on a bid and never opened the hood to see if it even had an engine..... Lots of volunteer FDs used the GMCs for water tankers, and they all wanted a faster truck than they had, so a FD installing a larger power train probably happened fairly often.

 

[Gunfreak25]

Thanks for the link Tanner, great reading! I won't have any issues here, since the centerline of the Tcase and transmission remains unchanged. The only difference now is the slip yoke on the back of the transmission sits 3 inches above the Tcase input. Angle wise, they are both parallel with the frame as they should be. My shaft was made professionally by Simmons and was already balanced when I got it. It's around 13 inches long yoke to yoke. Old Fart also mentioned the fact that your bearings tend to last longer with a little angle in the driveline since the grease in them gets distributed better compared to if the shaft was perfectly parallel between the two gear boxes. Always learn something new everyday with this project.

 

[Gunfreak25]

I also picked up my material today for my motor mounts. Little did I know the motor plates I made for the block were 1/4 plate. I thought they were 3/16". So I made sure to pickup more 1/4" stock. Total for all the needed metal was $8. It's great too, very professional business. Just walk in to the counter with a drawing or cardboard template of what you need, take your receipt out back and they cut it right there for you. I can't wait to mount the air compressor. I've become so competent in my fabricating abilities I feel like I could tackle most anything.

 

[Tanner]

Not sure about the slip yoke issue in the driveshaft... unless I'm totally missing something here, the motor/transmission are stationary, and the t-case is stationary, so I can't see a need for a slip yoke...

And The more metal you cut and stick together, the more proficient you get at it!

'Tanner'