The Stovebolt Site Forums The Parking Lot '60-'66 Trucks 1969 GMC 305 Engine

I know it's a little new, but hoping you guys can help me out.

I just picked up this 1969 GMC 2500 series "custom camper" truck.

305 V6 engine, long bed, 8 lug 16" aluminum wheels, 4 on the floor, power steering, power brakes, under dash AC (works), new starter, alternator, new gas tank (1 of 3), a tad rusty, especially the drivers floor board and rocker, a little in the bed, but structurally sound and the body is solid.

Has new brakes all around, but does have a loud engine knock. Think it might be a spun bearing or ????. Drives fine, but due to the loud noise, I brought it home until I find a mechanic who is familiar with this engine.
I'd like to pull the oil pan and inspect it, but the 1 foot cross member seems to be in the way. Thoughts?

What's it worth? (What are the 4 wheels alone worth? 8 Lug 16" aluminum)

I'm trying to decide whether to pay to have the bottom end of the engine rebuilt, rebuild the entire engine or ????

I'm not crazy about tossing a SBC 350 in it, as it will lose all of it's towing power.

This BEAST rides very nice and drives so easy, especially compared to my bare bones '58.

Any experts out there on this truck? Would love to know more about it. (HP, Torque, production, etc).

It does need a new windshield and seat covers, but the leather embossed door panels are SA-WEET!

Sorry, the system won't let me upload pics. I'll send them to photobucket and post a link.

I'm looking for parts suppliers....none of the truck websites I've looked at even list this engine??? (I've heard is 3/4ths of a common V8?)

Any help would be appreciated!

58stepside(at)gmail.com

Cool truck, I have the same motor in my '66.
I found alot of info on these motors at "The 6066 GMC Guy" website, all I know about parts suppliers is I got the rebuild kit at my local Carquest, and my friend and I rebuilt the motor.

Before you tear it down, try this: Dump a glass of water down the carburator while the engine is running. You could have a Carbon Knock. Dump it in slowly and rev it some so it doesn't stall.

My '66 305 V-6 was famous for building up carbon. A glass of water later and it was cured. Also had a 350 V-8 that had a carbon problem. Had to use the water trick on that engine a few times during the 7 years I had it on the road. There is no telling how many engines out there got thrown away because of a simple carbon knock.

Bill

Automatic transmission fluid also does a great job of cleaning it out and also freeing stuck valves. Apllied the same way as the water, rev it up and SLOWLY add the oil. It will also kill all the mosquitos in the neighborhood :-)

John,

The first time I ever tried it, we used half water and half trans fluid. It doesn't really mix well, but it did the job. It did create a great smoke show. I had to warn my neighbor first, lol.

But when I was sure it was just carbon, I then switched to just water.

I like the idea of it freeing stuck valves. I'll have to remember that one.

Bill

Thanks, I'm willing to give just about anything a try!
I have heard of tranny fluid before...that seems similar to using a commercial product like Seafoam, but I haven't heard of using water.
I thought that would cause hydrolock and crack a piston?

Drizzle the water in SLOWLY with the engine at a fast idle, 2,000 RPM or so. The water breaks up into a mist as it hits the carburetor venturi.

Before you try the water trick, try to isolate the knock to a particular cylinder by disconnecting spark plug wires one at a time. A cracked piston skirt or a loose wrist pin bushing will quiet down with the ignition disabled, and a rod bearing knock will sometimes change to a double-bump sound without a firing load on the piston. If you can change the noise by disabling a cylinder, better do a teardown to find the source of the problem.

The GMC V-6's are TRUCK engines, not similar to Chevy V-8's at all. They have a 60-degree angle between the cylinder banks, and fire on a 120-degree rotation sequence just like an inline six. They are low-speed, high torque engines, and they burn gas like it's going out of style. Don't even think about getting good fuel economy, but they really excel at pulling heavy loads for a long time.
Jerry

Jerry,

Believe it or not, with a fresh super tune I was getting 15 1/2 MPG Hi-way with my 305 V-6 that I had in a 1/2 Ton Pick-up.

Now I also drove a 478 V-6. Not bad for what the truck was, but I believe that one was getting an all around 7 to 9.

Also drove a 637 V-8. We figured that one around 5 to 7.

Bill

I just bought a 1962 GMC 4x4 3/4 ton with the 305 v-6, I have no current use for the motor,but the previous owner loved it. I had one back in the early 80's when I was in high school, my buddy's and I put that truck through more abuse than Geraldo's nose, and it never even missed a stroke.

Bogiebuddy

Too bad it's across the country...shipping would be difficult to arrange.

Just took a 305 v-6 out of a 1963 GMC. 140# compression on all cylinders. Runs Great. Complete motor, carb, clutch, alt, water pump, ect...
If any one is interested in it.

Scott Moffit
Union, Oregon
Home 541-562-5134
Cell 541-910-0445
[email protected]

The engine inhaled coke by the pound? Yep, it must have been tough!

Jerry