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Engine woes!! Got a big paper weight!

Section8

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Has any one out there got any knowledge on what engines diesel or gas that will mate to the hydromatic tranny. the best i can find on the net is another 302, or a 270. the M135 i just bought from and old man has a big paper weight in the engine bay. the old man told me it ran, yet when i got it home found he had stripped the engine of all the goodies including the radiator and most wiring. I am going to have to swap the whole engine for a newer one since i have nothing to work with. I will search the archives in here some more to find dimensions and compatibility of the old 302. Looks like i am not gonna have a restoration but a abomination. Any thoughts and info would be greatly appreciated!! I am new to all of this even though i have researched lots but until you own one, one never truly knows.
 

hndrsonj

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You missed a stripped engine and radiator? I'd look for another 302 personally. You could PM Gunfreak, I think his has a 455 in it.
 

NDT

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The parts to build up your 302 are not hard to find. Nothing else will bolt to the Hydramatic. An easy swap is a GM 366 with Allison from a school bus or Ryder truck.
 

Section8

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I saw the radiator was missing. took the old mans word that the engine was a runner. didnt get a chance to give it a good look over. seen it sitting as i went by going to work. the old fella has lots of parts and other trucks on his lot, assumed he knew it was a good motor. I am gonna start my search for parts as the battle begins and check out that 366 with allison option but not holding my breath. At least the body ie in great shape and most other parts are there along with extra blackout lights!!!:eek::)
 

Gunfreak25

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The list is endless. But remember the engine compartment was not designed with length in mind. So rule out most all straight diesels unless you want to make a small doghouse in the cab. There are a multitude of good gas V6's and gas/diesel V8's that will all fit very easily. It ALL depends on what YOU want.

You wanted insight on clearance issues and common hurdles involved in GMC engine/tranny swaps. Here they are. Yes, this is all of them. :D


-Clearance is usually a non issue. SOME oil pans may hit the differential. SOME exhaust manifolds (right hand) will hit the large cast iron casting on the right side of the frame that connects the torque rod to the top of the front axle. It can be trimmed but the usual procedure is to cut the manifold short and weld on a 90 degree downpipe.

-Brakes. You will need to fabricate a new mount to remount the GMC air compressor. It's the cheapest option and by no means a bad one. Lots of advantages to on board air. It's the simplest option, the air compressor can be plumbed into virtually any engine you can think of for the oil/coolant. Just a matter of fittings and hydraulic hoses from NAPA.

-When you ditch the Hydramatic, you have lost low range. If your an asphalt queen, it's no biggie. High range is still low enough to move 10,000lbs on level asphalt. Forget offroading with a load. If you want low range back the easiest option is to use a 2nd Tcase to drive the STOCK GMC Tcase. It's "special" to the GMC series as it drives the front axle shaft backwards. Part of the design.


-With the Hydramatic now gone, so is the original shift linkage and shift tower. The original shifter did two things. One, it shifted the Tranny into the selected gear, but it also simultaneously shifted the Tcase into forward or reverse. It basically had to tell the front sprag inside the Tcase which way to turn so it wouldn't bind. I had no need for front wheel capabilities so instead of fabricating new linkage/levers to manually shift the Tcase, I just dropped the front prop shaft, drained the axle housing and pulled the shafts. So the front is free wheeling. Also eliminates the chances of gear oil leaking into your knuckles.
Not recommended if you plan to drive in snow, mud or do offroading.


Oh. And make sure you have the tools to cut and weld 3/16" steel regularly. If you can't weld you'd better start quick. :D Let me know if you need anymore info and i'd be glad to help.
 
Last edited:

hole

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Has any one out there got any knowledge on what engines diesel or gas that will mate to the hydromatic tranny. the best i can find on the net is another 302, or a 270. the M135 i just bought from and old man has a big paper weight in the engine bay. the old man told me it ran, yet when i got it home found he had stripped the engine of all the goodies including the radiator and most wiring. I am going to have to swap the whole engine for a newer one since i have nothing to work with. I will search the archives in here some more to find dimensions and compatibility of the old 302. Looks like i am not gonna have a restoration but a abomination. Any thoughts and info would be greatly appreciated!! I am new to all of this even though i have researched lots but until you own one, one never truly knows.
Just curious, but how do you know the engine isn't a runner? What I read by your post is that it needs a radiator and "goodies" What's missing exactly, the crankshaft or the carburetor? If the engine is at least a complete long block, it could very well be a runner disguised as a "paper weight".
 

nattieleather

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That was my thought too. What is missing on the engine. Carb and distribitor? Generator? If you wanted to do a restoration then I would look into finding the parts that are missing and looking to get those parts. The 302 was a hard motor to kill so I bet if you find out what is missing and replace them I'd say you have 90% chance or better that the motor will run. First thing firts. Is the block sound? Are the pistons hanging out? Is the head missing and it's a rusted hunk of steel? If the block is sounds and it's just missing the bolt on things to make it go varoom then will the motor turn? Can you crank it around by hand and see if it moves. Again if it moves that's a good thing. If it won't budge that's not so good, but doesn't mean it wont move again with just a little work. Making a big truck move again is like eating an elephant. Just have to take one bite at a time. Assess what you have and then make a plan from there to make it go varoom again.

If you decide to a motor swap then you have many many options to go with and the advice of Gunfreak is very good!
 

Gunfreak25

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I just thought about that too, I'd keep it if you can. As much as I preach about motor swaps, I could only justify modifying a truck if the original motor/tranny was FUBAR or it was gutted. These very rarely break. They will run like garbage if not setup properly, but I don't think i've seen more than 1 or two members here with actual broken 302's.
 

Gunfreak25

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Radiators can still be obtained without too much trouble, as for the "stripped out wiring". When it comes to the GMC wiring it doesn't get any simpler. I wish I lived close by and i'd be happy to show you. Just 1 wire going to the distributor, 1 to each sending unit on the motor. If you mean the headlight harness that wraps around the top of the grill, it can be picked up from Vintage Wiring of Maine for $150 brand new.
 

hendersond

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Can we get some pictures of what you have? UPS, FedEx all ship parts fairly reasonable. Well, maybe not a complete 302.
 

m1010plowboy

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M135 save

Nice saves aren't always perfect but you get to appreciate the pieces you have.

There are a few guys out west that might know where some original parts are so when you put a shopping list together I'll pass it around.

The 302 lets you drive through puddles if you can keep it original. cha ching
 

spicergear

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The Big Block and Allison combo is a pretty decent set up. Also, the chances are really pretty good that the Big Block will have an air compressor on it already. And...seeing how you need to get a new radiator anyway, now would be a good time to upgrade power plants. You still *may* be surprise that your low gear will be decent as usually an automatic torque converter is considered another 2:1 when inputting it into crawling formulas. Heck, the NP205 is only 2:1 reduction.
 

135gmc

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Engine parts for the GMC are fairly common - Bryan Asbury in Canada or Memphis Truck & Equipment would probably have most of what you need. Don't rule out a junkyard - if they have any GMCs, engine parts should be very reasonable since they don't have a lot fo call for GMC parts. The radiator will probably be the priciest thing you need due to the price of copper now, but you can see if it runs (and how well) with a garden hose shoved into the engine. Mufflers for the GMCs don't exist any more - you will need to find something civilian and make it fit. The exhaust manifolds also tend to crack, so they are also getting scarce. When the GMCs engine is running correctly, and the trans is A-OK, the trucks are fun to drive.
 

Section8

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Little Fort, B.C., Canada
Wow! Thanks for all the tid bits of info! I never expected to get so much info and helpful hints!
Ok! Here is the low down. The engine bay is completely devoid of wiring and hoses. Due to scavaging for the copper and getting ready to be scrapped. The 302 is still there minus distributor, plugs, carburetor, air intake, belts, brake boost, exhaust rotted away typically, just off the top of my head. The 302 is also seized solid, as well as the air compressor, which I was surprised to see was still there.
Most brake lines and air lines are either missing or rotten to the point of being only held together by dirt and rust!
The tranny and Tcase seem good since I can push the old beast around the farm with the tractor and nothing binds.
All gauges are there in the cab, which is in really decent shape, except the typical weather strip rotting. Seats are decent, windows all there with only the rear cab window cracked.
I haven't torn into the drums yet to see how the brakes are since I don't have a boost anyway to feel for any drag when stepping on the pedal, which is just loosely sitting there.
All in all I think I either have a complete restoration on my hands or a modern make over coming up.
What to do, what to do?!
Got lots of time to ponder this winter and putz if it doesn't get to cold.
 

Section8

Member
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Location
Little Fort, B.C., Canada
Newbie M135 adventures/ engine woes.

Wow! Thanks for all the tid bits of info! I never expected to get so much info and helpful hints!
Ok! Here is the low down. The engine bay is completely devoid of wiring and hoses. Due to scavaging for the copper and getting ready to be scrapped. The 302 is still there minus distributor, plugs, carburetor, air intake, belts, brake boost, exhaust rotted away typically, just off the top of my head. The 302 is also seized solid, as well as the air compressor, which I was surprised to see was still there.
Most brake lines and air lines are either missing or rotten to the point of being only held together by dirt and rust!
The tranny and Tcase seem good since I can push the old beast around the farm with the tractor and nothing binds.
All gauges are there in the cab, which is in really decent shape, except the typical weather strip rotting. Seats are decent, windows all there with only the rear cab window cracked.
I haven't torn into the drums yet to see how the brakes are since I don't have a boost anyway to feel for any drag when stepping on the pedal, which is just loosely sitting there.
All in all I think I either have a complete restoration on my hands or a modern make over coming up.
What to do, what to do?!
Got lots of time to ponder this winter and putz if it doesn't get to cold.
 

hendersond

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Wow! That is a tough one. Looks loke you have 3 choices, from my perspective.
1 Buy another and use this for parts.
2 Restore it.
3 Swap in a modern engine and trans.

How much money are you willing to dedicate?

If you are leaning toward 2 or 3 start with the brakes. You will need a power pack, compressor, and pobably a master cylinder. There is a used compressor on ebay right now. It is buy it now for $80+>100 shipping that is a max cost of $180. Then a master cyl will run $150. I just purchased one for that shipped. The air pack will run $450 + shipping. Buy a power bleeder for $60. You may be looking at around $860 just for this alone if you are buying rebuilt. Then can you get the 12 wheel cylinder bleeders open and are the wheel cyls good?

Maybe you can find a good used airpack if you are lucky???????

Wiring is fairly simple if you are willing to cut, twist and solder. Is the regulator and generator still there?

You will need a radiator. That is heavy, will go freight. I think there is one listed in the classified?

I also wouldn't assume the transmission is good. That seems to be the weakest point in these trucks. Maybe that is why it was sitting? If you are going to swap in a modern engine, swap in a modern trans. Buy you won't have low range.

Here is the way I see it, Start with the bleeders. get them open. Find a person with a parts truck. You need parts. get an airpack and radiator. Put your pencil to the paper and make a plan. Add up the cost so you know wher you are going. Nothin worse than getting in and running over budget!

How about more pictures?

And seriously, It gets cold. :p

Dan
 

Gunfreak25

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Personally, I would forget about all of the small stuff for now. Brakes, wiring, hoses, lines, it's enough to drive you insane if your working on a budget. Wheel cylinders, air compressors and brake parts are still easy to find. As said above, wiring is the easiest. No special tools needed other than a soldiering iron and the materials. If you need help with any of the above, myself or other members here are more then willing to help through PM's.

Based on your previous posts, the current state of the motor, unknown tranny condition, I would start searching for a new powerplant. For $1000 or less you could have yourself a Military 6.2 diesel and a good Th400. Great fuel ecomomy, cheap repairs, excellent driveability.
 
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