84 GMC C2500, V12 powered

[cayoterun]

Is it ok for a grown man, (72 yo at that), to cry or do we like new challenges?

The motor picked up a low rpm knock. Below 1,000 rpm, it sounds baad, increase the rpm and it goes away. Finally dropped the pan and one head. No cuttings, or chips of any kind anywhere. Has without a doubt been rebuilt, standard bearings in rods and mains. Pistons .30, and cylinder walls clean, smooth top to bottom. on the ones I've checked. While I have it open, I'll keep going and check all 12 cylinders. If I don't find anything, then will slide the tranny back and recheck the fly-wheels. It's possible I failed to torque all the bolts good, or a used auto flex-plate I used could have had worn bolt holes. I sure want to find the trouble if in the motor, because I don't want to ruin all the hard to find new parts in there.
I was lucky when I mounted the motor. I have room to drop the pan without having to pull motor mounts loose. V-12 tidbit: The pan has 40 5/16 bolts holding it on.

Cayoterun

[INSIDIOUS '86]

Seen these guys? http://thunderv12.com/
Posted via Mobile Device

[cayoterun]

Originally Posted by INSIDIOUS '86

Seen these guys? http://thunderv12.com/
Posted via Mobile Device

I've followed this link for some time. He has some great accurate info, especially about the "pitfalls of building/having a V-12". I'd like to hear his rebuilt and hopped-up ones turned up to 4-5,000 rpm. I'm sure it's would be quite a racket. They are loud enough at 2400.

There's 3 or 4 of us on this site that have one or more of them. Our goal is aimed at preservation, but like to package them in such a way we can let others see/hear them run. We'll never abuse the motors in any way, as we know if we break it, it may never run again, due to shortage of parts. They will make plenty of noise, throw rocks, and smoke the tires enough @ 2400 or less.

We're amazed at the number of people who never knew the V-12 existed and we enjoy showing them. They are sure a part of GMC's history, but they are a workhorse, not a hotrod motor.

Cayoterun

[dammitmitchell]

have you seen this?
http://67-72chevytrucks.com/vboard/s...d.php?t=547647

[cayoterun]

Originally Posted by dammitmitchell

have you seen this?
http://67-72chevytrucks.com/vboard/s...d.php?t=547647

No, I hadn't seen it. I'm sure all here knows that's Rap-em-Pappy's truck, a member here.

I'll pass it along to him, tho.

Thanks for letting us know.

Cayoterun

[dammitmitchell]

that absolutely blows!
good luck brother!

[Palf70Step]

and that's a LOT of bolts to take out.

[1985-GMC]

Best of luck my friend, I hope it's something minor!

[cayoterun]

Not really related to this truck, but an interesting story on a V'12 pump motor:
I was talking to a friend who I grew up with last night about this. He and his brother farm big a few miles from here. No way to tell how many of the 12s they wore out. He said they had put a new one on a well years ago. It had a vibration in it, that wasn't bad, but not right. They ran it serveral days that way. Dealer checked it, couldn't find anything, finally the dealer came, took it back to shop, and tore it down. Started pulling bearing caps. Pulled a main bearing cap, and the factory had left 1/2 of the main bearing out. Put both halves of new bearing in, and the motor ran for years.

So, factory will goof now and then.
Cayoterun

[cayoterun]

A WHOOPEE moment. Found my engine knock.

When I pulled #5 piston, finally found it. Never saw a piston break like this. Has anyone else? The piece was still in place and never made a scratch on the cylinder wall. It broke between 2nd and 3rd rings and about 1-1/2" long. The piston and piece were worn where they rubbed together when flopping around. Now the search for the elusive .30 over piston and rings.

Cayoterun

[cayoterun]

Originally Posted by 1985-GMC

Best of luck my friend, I hope it's something minor!

I like your "fingers, truck" sayin'!

Each time I read it, I smile.
Cayoterun

[1985-GMC]

Originally Posted by cayoterun

I like your "fingers, truck" sayin'!

Each time I read it, I smile.
Cayoterun

Haha a long time ago I saw that on a car at a local classic car "dealer"(for the lack of a better word), I thought it would make a good sig. Right now I couldn't care less if someone touches the paint on my trucks but eventually they will be painted nice and I might have to make a sticker for my back window saying that.

I'm glad you found the source of the knock and it just was a minor problem.

[cayoterun]

Hit paydirt!!
I found a new .30 piston in a neighbors shop. Now, if I can get the rings off the old one on the new one without breaking one, I'll feel like I killed a bear bare handed.

Cayoterun

[locomotive breath]

Glad you found it and the crank was ok. I've seen that before and it was caused by the ring end gaps being too tight. They get hot, butt together, and bind up in the bore, the ring grooves become the weak link.

[Palf70Step]

Glad you found the knock. Good luck with your search.

[1985-GMC]

Awesome job!

Do you have any plans for a speedo?

[cayoterun]

Originally Posted by 1985-GMC

Awesome job!

Do you have any plans for a speedo?

Maybe sometime in the future. Having driven road-rigs years ago, we depended more on our tachs, than speedos, as you soon learn speeds from what gear, and rpm.

I do have a nice dash insert that I can swap in with a speedo, and add tach. For now, plan to work any bugs out which I'm sure will show up with some use.

I'm ready to enjoy it for awhile and add a few miles on it. I've run it about 120mi. so far, within 10miles from the house. Sure sucks up the little propane tank in a hurry, so a larger one will probably be swapped in before long.

Cayoterun

[6066gmcguy]

Nice Job on tht truck Marvin.

[cayoterun]

Originally Posted by 6066gmcguy

Nice Job on tht truck Marvin.

Welcome aboard over here, Jolly. Now you can help me keep the V-12 running. I'll probably be bugging you for pointers and advice pretty often. You've offered a wealth of knowledge since I've been working on both trucks.

Long live the GMC V-6/V-12s. and You've been a great help to us to do that!

Thanks,
Cayoterun

[cayoterun]

Probably only ol' Geezers will remember when this model pickup beds looked like this, except those who lived in farming areas where they grew grain crops in the '40s and '50s. They'd haul 60-70 bushels. They'd load them up, the wife, and kids would head for the grain elevator. 65 bushels @ 60# per bushel, meant these old flivvers had 3900# on their backs.

I've run the pickup about 400mi. around here locally, and it's doing good. Still have to keep my eye on the temp gauge, tho.

[Telecasterjoey]

too cool! sounds nuts, Good job, Looks awesome.

[cayoterun]

Temperary 80gal fuel reserve tank added. I'm looking for a 30-40gal propane tank to replace the 16gal tank in front. With 2-3mpg, 16gal don't last long. Old truck doing ok for my purposes.

[Rubble]

Just read thru your build thread,that truck is awesome!!! Not something you see everyday. I am glad you went with that body too,it really suits it.It's really something to be proud of,great job man!!!!
Posted via Mobile Device

[cayoterun]

Originally Posted by Rubble

Just read thru your build thread,that truck is awesome!!! Not something you see everyday. I am glad you went with that body too,it really suits it.It's really something to be proud of,great job man!!!!
Posted via Mobile Device

Thanks for your comment.
This truck probably should be in alternate tinkerings, but still really don't fit anywhere.
I've always enjoyed watching the old car/truck hobbiests preferences and how they change over the years. This is what we were tinkering with 50 yrs. ago during the "Jalopy" days, when bits and pieces were put together from the salvage yards. No one had any money, so learned to make do with scraps.
Would be interesting to look in a crystal ball and see what they'll be building 50 yrs from now.
It's really all about a great hobby, self-expression, personal preference, and enjoyment anyway, so room for all, imo.


I've hauled lots of watermelons, coffee beans, and all kinds of produce to Sask., Man. and Ont. back in the early 60s. You Canadians always treated us great, and welcomed us while we were in there. Eight day turn-around from Ark.-Gulf coast/southern Florida-Regina/Winnepeg-back to Ark. $.04 cents a mile. Big bucks back then.
(Two drivers, and run 24/7, except for fuel, food, and showers)
Thanks for your hospitality.

[Vernski]

We think it belongs here just fine Cayoterun...Vernski