'68 gmc cummins project

[Str8-6-68]

Hey guys I'm new to the chevy/gmc forum but my project truck is a 68 gmc long box 2wd. hopefully this project keeps me busy for a while as i want to shorten the frame for short box and swap front cross member for a 98.5 24valve 5.9 cummins turbo diesel with lots of work done, I was also thinking of closing in the open channel frame for a box frame. my goal for the motor is in the 800hp range give or take on a single turbo so I would love some feedback on some of the best rear end gears and axel shafts to use, as the engine to be built will put out estimated 1200ft.lbs. I was thinking of doing a 2wd chevy 2500 front and rear 8 lug conversion including rear diff but i would rather keep as much off the '68 as i can except drum to disc and beefier suspension. any and all information on the suspension and rear diff to handle the added weight and high torque the engine will put out. I would rather find gears and axel shafts for the '68gmc to handle the power than swapping for 2wd dmax setup. Thank you in advance for all info.
-Allen

[tanman722001]

Hi Welcome.There is a few guys here that has done a diesel swap.Looking forward to see some pics or you truck.

[Str8-6-68]

ill post up pics along with build details right now i just pulled the front clip and fenders off and today im puling the 350 and transmission out. then cab and box off next days off.

[Str8-6-68]

In the beginning...

[tanman722001]

Nice looking truck

[Str8-6-68]

thanks it needs some tlc but its not the worst ive seen. a bit of rest to repair but frame first. then suspension and brakes, then rear axle and gears. that should keep me busy for a bit. well today i pulled the engine out and found out it is a 1968 283 from mexico, it has a edelbrock high rise intake manifold with a richmond quadrajet 4barrel carb on it. but her new power plant it long and tall. I took some measurements of placement and the cummins will be a tight fit but ill see how it looks after the new front cross member.

[502ms]

Enjoy. It is a great fit.
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[Str8-6-68]

i got around to some more tear down and the cab and box are off for the frame chop to make a short box frame. shave the drivers side of the frame and box it in, and replace front frame cross member. the frame will prob see sandblasting and powdercoat in a few months.

[rideharder]

take a look at my build, nothing to detailed but will give u a idea on the swap,
ps, the 800hp mark will be verry hard with a single... twins at a min. and 800 hp is closer to 1500-1600 tq

[Str8-6-68]

thanks for the advice but i have a set of twins on my 02 vp powered truck and i liked my older single 62 more than my 357/475 kit. I want to run a bullseye batimo 66mm single plus i like the room the single turbo leaves under the hood. in my theory "single is simple" ill prob see egt issues but i plan on having a snow meth controller to help cool.

[Dieselwrencher]

Cool project! If you're planning on going 8 lug, I'd use a Dana 80. None of this half ton GM stuff is going to hold up, period. If you want 5 bolt, build a ford 9" for it. You have more parts available to purchase and get the final drive rpm's where you need. Why don't you like the 57/475 combo you have now? I'm guessing the 475 is a box stock unit and has a 1.32 exhaust housing with the big turbine wheel. That would be your problem if you think they spool slow. Also, a 66 on the street won't be very snappy. IMO I'd stick with twins. There's no comparison when they're set up right for a fast spooling street rig.

[Str8-6-68]

thanks for the input diesel, my 57/75 spools good i still need 250s and #110 valve springs and hd pushrods before i make up my mind but for my 68 i was thinking of going with the batimo bullseye 66, 13mm ppumped with big sticks, mild cam, meth, ported and oringed head,valve springs, push rods, and studs in front of a billet extreme race nadp 47re. Also i was thinking of keeping the 5lug, and doing yukon axles with a 14bolt rear end. this winter ill save for suspension and in the early spring ill shorten the frame for a short box.

[Str8-6-68]

Updated pics. This is how it sits, frame is ready for the chop and I still need to max out this injection pump and get a conversion kit for the vp44 to p7100.




goodbye vp44

hello p7100




Before + After


Some scarred up pistons

[1970/327/c10]

Somebody that shares the same thing as i do; diesels and old pickups, i have a 72 chevy long bed c10 and i thought about dropping a cummins in it but i dont know how to go about it. I will be following this post till the end, i cant wait to see how this project turns out!!!!!

[HSkinner]

I've put a couple cummins into 1 ton square bodies and worried I would break something. Are you concerned with the suspension under that motor?

[Str8-6-68]

HSkinner yeah I am a bit concerned with front suspension mostly but ill be doing a fresh 4/6 drop and if the front has a tough time keeping fenders off the rubber ill have to upgrade to hd springs. I also plan on boxing in the the frame where I can on the front section of frame. Im sure I will come across a few issues along the way during this build though.

[Str8-6-68]

1970/327/c10 right on, thanks. If you have a 4x4 the front cross member makes this conversion alot easier where you can drop it down a little to clear the oil pan than the 2wd where you cant just drop the cross member to clear this somewhat tall engine. besides that i heard the 5.9 fits like a glove after a little frame shaving on the drivers side. Im just waiting for funds to get a new hamilton 188/220 cam, ppump conversion kit, 191 dv's, 4gsk for now then suspension goodies and disc conversion.

[Str8-6-68]

I got bored so i decided to chop the frame its just tacked for now ill finish it up in a day or two with some reinforcement steel on the inside of the frame.

[Str8-6-68]

Well I got a quick estimate on sandblasting and powder coating and I have other places to put that cash. So I have decided to just clean up the frame and degrease it really good myself then paint it with a gloss black marine paint. Does anyone know of a really good degreaser that would work great for cleaning the frame?

[bigyellow]

i like it, i have a 71 c10 in my pic and a 99 cummins for the daily driver.these cummins are pretty quick considering how heavy they are, i can't imagine driving an old c10 with a built 5.9.

[Str8-6-68]

Thanks bigyellow, I cant wait till I get into building the motor with my wish list of performance parts and obviously the first fire up. but im still a while before I get to even fitting the engine and making mounts.

[Str8-6-68]

Alright I got around to getting the chop completed and I stripped the frame off the axles and degreased the frame but I need to degrease more before I paint. I got a quick quote on sandblast and powder coat and I decided to put that money somewhere else. so either rustoleum or marine grade paint for me.





I will never have to worry about this weld failing



And this is how it sits until i get around to degreasing more.

[bigyellow]

if you've got any performance left over goodies for a 99 24 valve let me know

[bigyellow]

or even the old vp44 if it's good

[Str8-6-68]

the only performance parts i have left are a set of 80hp injectors (tips on bosch bodies) for the 24 valve. I already sold everything else at this moment, sorry bigyellow.