1972 GMC "the beast" c20

[Wideopenracing15]

Yeah mines blue too. Server must have updated or something.

[292farmer]

well found out (after being pulled over by cop) that no light in rear of truck work well except for drivers side taillite, reverse license lamp and passenger taillite are dead, and i found out all the wiring from rear to cab is melted seems just the drivers side wiring survived, im pretty sure its from when the previous owner skipped over the external regulator when he wired the alternator, the wiring from headlites alternator and battery caught fire second week owning truck, and found out that was the cause so obviously should checked rear wiring? doh! oddly ive never drivern the truck at night (ive had it 3-4months) so that's why i've probably never noticed the lack of lites. so ive decided to do all new wiring harness front to back, once the wheather warms up, in the mean time im getting a 1975 gmc w454v8 does anyone know who sells a good harness that comes with good directions? thanks

[Wideopenracing15]

If you want to get a really easy one I'm pretty sure pain-less makes a wiring harness for our trucks but they don't exactly come cheap.

[84 400]

cool project and a 454 75 should be fun also. I actually ran the trails in Troy in May. Some fun stuff in there but I was the only full size Chevy in the group.... The shop down in the town center does some pretty slick fab work also I am forgetting the name Doctor or custom or something..... Anyway keep up the good work and love the screaming six idea!!

[292farmer]

thanks! the company is DR customs they are actually two buildings down from me! lol its either the 75' 454 or a 83' 6.2l diesel, was playing in my works garage yard today we use road salt and it melted all the snow and made mud so had to test the trucks ability to play in mud, that 6 is pretty quick! do u know where in troy u went? glad to hear someone lives close by and familiar with the area!

[geremy]

is your truck 2 wheel drive or four wheel

[292farmer]

two wheel drive but it does have insane gearing and traction ive taken it down alot of trails and threw the woods, as u can see in some pics.

[84 400]

yeah I am actually part of this group.....

http://www.exploringnh.com/

http://forums.exploringnh.com/showthread.php?t=7099

Like I said mostly jeep and yota guys and gals but there is some cool rigs. I can't remember off hand what all the trails where most was class VI roads tho. Had a blast tho and can't wait to get back out again. Pretty cool group they are all about legal responsible wheeling . mostly trail riding from stocker friendly to extreme

[292farmer]

u know looking at those pictures i remember u guys all at the dragon palace parking lot i remember wishing i could join! i think i recoginize the trail too i've taken my 72' down it and i only got two wheel drive as long as its dry out that truck does most the trails, it does some mud pretty good but 2wd is well...2wd btw i went to high school with some of the guys that run, dr customs it was pretty cool seeing those pics thanks!

[Wideopenracing15]

Did you ever get that big block truck?

[292farmer]

i went to go look at it from the photos looked mint, he said it was good wanted 1800 but when i got their the floor rugs sagged when u stepped on them, looked under neath no rubber on body mounts and floors were gone and i mean gone the rug was the only solid part and the rear frame was twisted i could see it from underneath and it was on level ground, and he wouldnt budge from 1800 so long story no so im looking again...

[Wideopenracing15]

Well good thing you didn't. If the floors are saggy I can only imagine what is under neith.

[292farmer]

yeah now i'm looking at either a 77 impala w/305v8, or a 77 trans am w/301v8
hoping to get a new harness soon and some garage space so i dont have to rewire truck in the snow and cold lol

[Wideopenracing15]

Yeah wiring in the cold would just suck. Hope you find something to drive soon. Wiring harnesses will be easy to find, hard to afford.

[292farmer]

well it hit 38degrees today so i decided to at least pull out the old harness from the firewall back to the tailights, found about 3 random wires twisted around the old harness not connected to anything, one went to fire wall right below fuse box? three sections fell apart as i was unclipping them from frame guess thats why they dont work found that both ground on the sidemarker lamps were broke off, so i know that was another problem overall was surprised how easy it was to undo the harness, just hoping i can afford a new harness soon and that it goes in as easy

[292farmer]

pulled out the radio someone stuffed in, and found out that they were using the power wire off the wipers to power it, after pulling it and all the speakers out, i tried the wipers and they actually work smoothly now not jerking, and wiper pump works too!! thought i was gonna have to replace that guess not now now im just trying to undo the antenna anyone know how? i tried unscrewing it but no luck, i didnt try too hard i didnt want to ruin it or the paint. also tucked the tach up closer to the dash and strapped the tach wires out of sight. thinking of finally getting the passenger mirror on later this week, and maybe cutting the rotted muffler off and making it a straight pipe right back to rear axle i don't like my neighbors' fart can honda, figure instead of listening to his honda i might as well drown it out, instead ahh music to my ears lol

[Wideopenracing15]

Haha I like the exhaust idea. As far as the harness goes, you might be able to go to a local junkyard and swipe one off a truck there, but after 40 years of use I doubt you can find one that hasn't been spliced, rotted, or just messed up.

[292farmer]

yeah right now i'm using the old sockets and connectors and installing new wires see if that works, that's assuming all the old sockets and connectors are good. hopefully that works. now im playing with the idea of dropping in a 2002-2006 4.2l inline 6 motor out of a gmc envoy. right now im looking for trans adapters to see if using the sm465 is feasible. but that will be a few years in making probably so still building the 292 up.

[Wideopenracing15]

Yeah I'd love some specs on that stuff!

[292farmer]

heres the respective bores and strokes
305v6--4.25x3.58in 130hp 240tq
351v6---4.56x3.58in 190hp 305tq
379v6--4.56x3.87 170hp 266tq
401v6--4.875x3.58in 178hp 350tq
432v6--4.875x3.87in 190hp 336tq
478v6--5.125x3.87in 225hp 410tq
twin six 702v12--4.56x3.58 250hp 650tq (governer limited to 2400rpm creates 400hp at 4000rpm)
637v8--5.125x3.87 185hp 560tq
their were magnum series of these engines, which were basically the same motor but had bigger ports in head. usaully a couple more horse power and torque, these are averages for power varied slighly year to year. check out thunderv12.com they have a dyno video of the v12 hitting over 500hp and 700lbs torque,

i have tranny specs and models let me look for them

[Wideopenracing15]

Man those things made torque like diesels. Did the 702 v12 rev out to 4000 in stock form?

[292farmer]

yes but gm installed a governor in it for longevity issues, they wanted it to last forever. they were used in buses and semi trucks mainly ive seen one used as a genarator, had something like 300,000plus hours! put that into road time at say 1mph = 300,000miles! and it didnt smoke! these motors are a little hard to find but not to hard, the bad part is they dont make replacement parts for them u have to find part motors, or have them custom made, the c-60 we own originally had a 351v6 but a 401v6 got dropped it in. the b-60 mack has an inline 6 gas motor which if i remember is 450ci would love to drop a 450ci inline 6 in my truck but dont think it will fit has like 4 7/16 bore and 5 in stroke and it weighs like 800-900lbs

[292farmer]

got some updates on the mack motor 464ci 170hp @ 2800 370tq @ 1000 sae so believe gross is like 200-225hp 400-450tq

and they were 5 speed transmissions (6if u count reverse) so my bad. but here are some specs, there were a couple overdrive equipped ones and some still had the 1:1 5 gear ratio they just added a gear between the low and second, to spilt the difference so they isnt such a large gear reduction gap like in the sm465 better for towing and hauling i believe was the idea
i just listed some major ones there were like 15different models
np 540 series 6.05 to 7.41 first gear options. 540-gd wide ratio 540 gl close ratio 540 go14 had an overdrive of .82
the np 541 had either a 6.15 ot 7.25 1st gear ratio one wide and one close ratio
clark 264VO had a 6.06 1st and .8 overdrive
spicer 3153c 6:1 1st .79 OD 6853c 5.71 1st .86 OD

i have all the gear ratios if you want them i just didnt feel like typing it all i got this info a couple years ago so if some one sees a mistake, please correct me im open to being corrected, i just try to pass on what ive learned, im not trying to be a know it all. im just fascinated with these old trucks and since i cant own them all i read up as much as i can thanks and enjoy!!

[292farmer]

im trying to get the price on this c20 has 350v8 plus sm465 flatbed with tool boxes. think itd be a cool addition to my collection the cool part is think it used to be used by a concrete company my dad used to work for. oh yeah its a dually rear wheel too!!

[Cw72gmc]

Hey there, Just skimmed through your thread and looked at pictures. When I have the time to read it I will. I just thought I'd say I'm glad to see another 1972 Gmc k20 In Here!

Looks Like Its A Great Start. My Thread is "Jack Lallane". And If you need any help or advice Feel free to ask anytime!

Best of luck with your project