GMC 305 V-6 Big Block????

[70C10Step]

I picked up my $250.00 Craig's list truck today and it has a 305 GMC V-6 Big Block with a 4spd in it. Before anyone trips I found a website about the engine... I just need to know if anyone knows more or had any personal experience with this engine...

http://www.6066gmcguy.org/gmcv6b.htm

[Longhorn Man]

it's not a big block... it's just the GMC truck engine V-6.
They run forever
love to drink gas like mad
parts are not avalible at the corner auto zone
Most parts store guys will tell you there is no such thing as a 305 V-6 (tell them it is a '66)
More torque than you'll ever need unless you are dragging houses around
don't like to rev much at all
Neat lookin old monsters that will get you a lotta looks at the cruise in

[67_C-30]

That site is pretty the authority as far as internet info goes on them. I have 2 of them, and I'm a big fan of them. They are very reliable and last forever, and they have tons of low end torque. They aren't a high revving engine and usually geared low, so they aren't the best highway engine in stock form. With higher gears, they do fine.

[67_C-30]

Originally Posted by Longhorn Man

parts are not avalible at the corner auto zone
Most parts store guys will tell you there is no such thing as a 305 V-6 (tell them it is a '66)

All of the standard tune up stuff, starter, alternator, water pump, fuel pump, carb kit, etc. can all be bought at Advance Auto Parts. I know they they list them up to '67 in the computer. I've never had any trouble getting parts for mine, but I'm sure internal parts would unavailable there. They do list all the parts in their Federal-Mogul book, but I'm not sure if they can order them.

[powerdriver 1958]

years ago i drove a dump truck that had a 401 v6,Everything LHM said is true.put 21 ton of wet sand on it and go(way overloaded).it would pull down to 500 rpm and just keep chugging.It had two 50 gallon fuel tanks on it and needed them.in the 10 years i was around it the only parts I can remember it needed was a water pump and the carb rebuilt.

[Spray-Bomb]

The website you found has about all the info you will find for them on the internet

Dont twist it over 3400 (I liked to shift mine at 2800)

They have dual thermostats & are supposed to maintain no more than 4 degrees difference between cylinders & they last forever, just dont buzz it at high RPM for long & you'll be ok

They like big exhaust like a diesel, I had 2-1/4" on mine & I think it was fine for a stock carb, but if you were to put a bigger carb on it & take it apart & have it balanced & find a way to put a harmonic balancer on it so you could twist it higher, I think 3" would be better

Over Drive trans & some different gears in the rear to keep the RPM low would be a great addition... A NV-4500 would be what i would put
behind it

And my truck got rather decent mileage, Unlike what Andy said... But I drove mine slow & it was a 1/2T 3-speed

[lilred67]

i have a '68 gmc 3/4ton with one in it. 4 speed, dana 60 rear. i use it around my place hauling and moving stuff. it's not street legal but it makes some cruises on the old black top country roads behind my house. not real fast but it pulls good. as mentioned above,parts aren't at every parts store but can still be found with a little seaching. i bought a carb. kit, valve cover gaskets and a fuel pump for mine.

[70C10Step]

Thanks for the good education!!! Keep the info coming... I am at a point where I have to decided to clean it up or go in another direction... I think for now I am going to clean it up and see how well it does... The thing runs like a sewing machine...

[paisaloco67]

Wow, I didnt know GMC made V-12s...... Thats some good info...

[67_C-30]

They are truly unique and are quite a conversation piece. I have the 351 Magnum version in my dump truck, and it is a Beast!!! I also have a 401 Magnum out of a 2 1/2 truck that I hope to use in a pickup someday.

[WIDESIDE72]

Originally Posted by paisaloco67

Wow, I didnt know GMC made V-12s...... Thats some good info...

I went to the Texas Early Days Tractor and Engine Association (TEDTEA) Show in Temple earlier this month. The V-12's were used on irrigation pumps.This engine was there, the owner started it occasionally. I sounded WICKED. I grew up in the 70's/80's on the Texas coast near Port Lavaca and there was only one of these still in use that I knew of at that time. It was near Francitas, Tx ran on propane or natural gas, I forget which. It was used to irrigate a rice field. You could walk right up to them where they were running. If memory serves right, I think the GMC I saw was running around 3k rpm. It was under a metal shed roof (no sides) to keep the weather off. It was hooked to a well with a discharge pipe around 18" and threw a solid stream of water about 25 ft.! My friends and I used to swim in the canals in the summer when it was around 100 degrees outside. You had to be careful to to get too close to the discharge. We were told tales of people drowning when they got into the "undertow" from the pump discharge. We believed it, as the discharge made a whirlpool around 10 ft in diameter and sucked down about 3'-4' in the middle. We weren't stupid enough to test the warning. You also had to keep an eye out for Water Mocassins (snake) HAHA Now, everything is way to safe.HAHA As far as I know, all of these GMC's have been replaced by Caterpillar engines that are diesel, but run on natural gas. Boy, the good old days...

[WIDESIDE72]

In original use, the engines did not have the "zoomie" headers. There were cast iron manifolds with mufflers. They were still pretty loud, though. I think GMC also made these to be used in tanks in the late 40's / early 50's as well.

[Lugnut64052]

Originally Posted by paisaloco67

Wow, I didnt know GMC made V-12s...... Thats some good info...

I didn't either. I went and hit the website and surfed around for a while. Quite interesting!

WIDESIDE 72, those pics are great.

[PanelDeland]

Met a guy years ago who had a business.His clients(old Farmers) used the V-12's for irrigation like above.His business was to tune/maintain those pumps and engines.He claimed most needed points,condenser,plugs and an oil change a couple times a year.He also kept a couple rebuilt for replacements.

[streetstar]

cool engine --- i'd clean it up and roll with it

fits right in with the current "dare to be different, newstalgia" vibe thats floating around the auto scene now (a vibe that i like -- bring on the 6's, W motors and other asorted niceties)

[factorystock]

The V6 was designed for rugged low rpm torque and long life. They ranged from the 305 in pickups to the 478 in larger trucks.

[68GMCCustom]

I don't know about the term "big block"...but it appears to me a 305 V6 (and 351, 401, etc) is "physically" bigger then a say a 305 or even 350 sbc V8.

it's no hot rod motor...but a great, low rpm, long lasting, torquey, "truck motor". dang thirsty though compared to a I6.

[paisaloco67]

Originally Posted by WIDESIDE72

In original use, the engines did not have the "zoomie" headers. There were cast iron manifolds with mufflers. They were still pretty loud, though. I think GMC also made these to be used in tanks in the late 40's / early 50's as well.

WIDESIDE, those pics of the v-12 are defenetly worth saving in my computy
thanks a lot !!!

[67_C-30]

Originally Posted by paisaloco67

WIDESIDE, those pics of the v-12 are defenetly worth saving in my computy
thanks a lot !!!

Here's a few more you find interesting. The first the B-702 a totally custom built car based around a GMC V12.







This a GMC V12 Powered IH TD-18




Lastly, here's a few V12's running.

YouTube - GMC 702 V12 Engine

YouTube - GMC V12 powered car

YouTube - 12 stacks GMC v-12 702cid...

[pitt]

wonder if i could wedge one of those v12s into my gmc???>>