305 v6 GMC motor

[72addict]

Are these motors any good? is it worth saving or should I feel OK in scrapping it? thanks

[gulfcoast66]

I would save it, I might be wrong but i think its one of the biggest 6 engines made doing the 60's era, It would be great for someone going back original with there truck. my 2 $

[Stepside65]

Parts are a pain in the @$$ to get. You should just give it to me. I'll take that junk motor off your hands.

All joking aside from everything I've been able to gather these are great engines once you get them up and going. They came stock with amazing amounts of torque, and all with a little two barrel on top. What you do with it is up to you. If you don't want it send it down here. I'll find something to put it in.

[slorio]

Before you decide, you should read through this website:

6066gmcguy.org

Jolly Goodfellow has taken the time to create a wonderful site dedicated to these engines. Before buying my GMC I stumbled on his site. Once I read through it, I was hooked. If you have any inkling of doing something different, these engines are great fun. If not, please send Jolly an e mail and offer it to the folks on that website rather than junk it out.
Regards,
Steve
New Orleans

[rwgregory]

DO NOT SCRAP IT!!!!! The GMC V-6 was one of the coolest pure truck engines ever produced. Low on revs, high on grunt. Parts are getting a little tough to find, but wierdo's like me think the world of them.

[loosecannon39]

As a former Houston Lighting and Power mechanic, I worked on a lot of these engines. Previous posts were correct. It is a torque monster, and a workhorse, but heavy as an early hemi. 2 cautions. Never -Never, allow one of these to get hot. Every time it happens, they crack the heads between the intake and exhaust valves. Also, if you have a miss that seems to be a vacuum leak, pull the valve covers and check to see if the Donaldson valve has spit out its innards. It is their version of a pcv valve, and screws into the head,directly into the paired intake passages. The slow turning, long stroke engine caused major pulsations in the intake system, and the valve cycles to violently, it regularly breaks through the tabs that hold the innards inside. Also, I've seen people pull the valve, and just put a pipe plug in the hole. Don't be tempted to do it. Finally, the plugs are on the intake manifold side of the head instead of the exhaust, and you must be extra careful installing the intake manifold, and gasket, and retorque it regularly. They commonly work loose and allow the very thin gasket between the two passages to be sucked in to the passage. A little attention goes a long way. This is a true workhorse, if you give it a little attention
REGARDS
DAN

[ChaseDale3and8]

A friend of my dad's had one of them in a 69 GMC that he used to own. One tough engine.It ran well over 300,000 miles without a rebuild or so much as a problem. Definately DON'T junk it out!

If you don't want it there are people out there looking for one. They are a bit of a gas hog for a 6 cylinder, but they have a lot of torque. I never understood why they were only offered in the GMC line instead of GMC and Chevy.

My dad used to have a 69 GMC cabover with if I remember right a 351 V6. Same story. Tough engine. Couldn't seem to hurt it, and it ran forever. I considered taking it off his hands for use in hauling my show truck when he got done with it back in 91, but the thing was such a gas hog that I decided not to.

Both the 305 and 351 are strong durable engines and are kind of the oddball these days. You just don't see them anymore. My personal opinion is that they are worth putting in a 60's project truck just for the cool factor alone because not everybody has them. They sound different when you run dual exhaust and it makes people take notice and wonder what you have under the hood. ...Joe

[Stepside65]

Originally Posted by ChaseDale3and8

I never understood why they were only offered in the GMC line instead of GMC and Chevy.

Back then GMC and Chevy were two entirely different entities. They were remarkably similar but there wer a few select differences. Such as the v6 vs the chevy v8, and 63 and up GMC's have leafs in the back instead of coils. Just my .02 Sorry didn't mean to thread jack.

[truckn']

would love to know where to get one in east tennessee want to replace straight six but don't want to go to v8

[Stepside65]

Originally Posted by truckn'

would love to know where to get one in east tennessee want to replace straight six but don't want to go to v8

I know where there's one out here in New Mexico...

[slorio]

The V-6's pop on Ebay pretty often. Here are two on there now. The first is in Kentucky and the second two are in New Jersey. It takes a bit of looking, but they usually go fairly cheap. Check out these two auctions:

290131864958

230162334745

Both of these are for 351's rather than 305's. The 351M engines as opposed to 351E's were magnums and had larger intake and exhaust ports. They would be preferable. Check out this website if you are interested in the V-6's.
6066gmcguy.org

Regards,
Steve

[Tomsriv]

Did they ever make a V-12 out of that V6 for military use? That was my theory on the reason GMC made a V6 when a straight 6 would have easily fit in that engine bay. If it can be done, it would be way cool to build a V12.

[chevy_mike]

Originally Posted by Tomsriv

Did they ever make a V-12 out of that V6 for military use? That was my theory on the reason GMC made a V6 when a straight 6 would have easily fit in that engine bay. If it can be done, it would be way cool to build a V12.

Yep, there was a thread a few weeks back about it...

http://67-72chevytrucks.com/vboard/s...d.php?t=251706

[60ratrod]

yeah i remember reading the thread that jerry put out while i was on the boat. if anyone needs the v6 i'll keep my eyes peeled cause the junk yard just off base tends to get alot of 60-66 gmc's, which doesn't help me out too much since i have a 60 chevy. i'll keep everyone up todate cause i'm always looking at the crusher pile

[Oldgmc1963]

Hi Dan from Houston. I just bought a 63 gmc with one of these engines and it has a lot of oil in the air filter. Everything I'm reading is saying its the PVC valve. Are you saying it's under the valve cover on the 305 V6?

Thanks Rob

[TJ's Chevy]

There's a fair amount of GM v6's....

305A, 305B, (350E 125 hp and 260 pound feet of torque.)

351E, 351M

379

401

432

478 235 hp and 440 torque

478M 254 hp and 442 torque.

[Oldgmc1963]

thanks for the response. the tag in the cab says 305E Engine w/ Certified net H.P. 142 at 3800 R.P.M. I'm pretty sure my PCV is clogged but any help is much appreciated.

[Old Truck Man]

Yes those GMC V6 engines are real pulling working engines. that are slow turning and have heavy pistons rods etc. The big problem is they like to consume gas. Ive owned several and in a two ton truck about 4 MPG in a Pk about 7MPG. Remember they where manufactured in the sixties when gas was cheap.If its my daily driver I prefer 250 inline six. if its something that is being worked and need to pull heavy loads I would prefer a 292 inline 6. To me there like a 348 or 409 . Cool looking engines but not very practical and parts are super expensive.

[markeb01]

I got rid of mine over 20 years ago because a new 350 Chevy crate engine was under $1,000 and the only shop I found willing to rebuild the V6 wanted over $2500.

I believe it was probably the most over engineered engine ever produced in the US. Very unique design like having the crankshaft up in the middle of the block instead of hanging off the bottom. But my truck was being built to function as a long distance daily commuter, and the engine was too heavy and inefficient for what I wanted. The 800+ pound weight was also a killer with manual steering.

That far back I could find no takers, so we had to completely disassemble the engine just to take it to the dumps. If I had one now I'd try and find someone that wanted it, just because they are now so rare. But trying to be thoughtful with an 800 pound lump can be more trouble than it's worth if there's no interest in your area.

[imjeff]

Great motor! I had one in a 63 burb in the late 70s. Sometime in the early 80s I destroyed in input shaft on the granny 4 speed. It had 235,000 miles on it and the motor ran like a top. As I recall, it held 8 gallons of coolant and was heavy as a house, but would pull a mountain.

[Oldgmc1963]

again guys - thanks very much for the feedback. I'm new at this and the truck is not going to be a daily driver. Plus after learning a bit more about this engine, it's kind of cool to me. I just want to find out how to keep oil from blowing into the air filter. If anyone can tell me where the PCV is that would be much appreciated.

Many thanks. Great forum!

[nathankershaw]

The oil in my V6 was really sludgy and there was a decent lip at the top of the cylinder.

I advertised it for sale on the GMC forum (as my privileges don't let me sell things on her yet) and no one replied.

They may be great engines but I couldn't find any demand for them.

[imjeff]

Originally Posted by Oldgmc1963

again guys - thanks very much for the feedback. I'm new at this and the truck is not going to be a daily driver. Plus after learning a bit more about this engine, it's kind of cool to me. I just want to find out how to keep oil from blowing into the air filter. If anyone can tell me where the PCV is that would be much appreciated.

Many thanks. Great forum!

The 305 doesn't have a PCV and they came equipped with an oil bath air cleaner. There's a vent towards the back of the block that has a down tube on it for venting the crank case. Can you post a pic of your air cleaner?

[Oldgmc1963]

thanks Jeff - if you mean the thing that looks like a little oil filter and unscrews from the top, I found it last night. Have to get it open next and hoping that is what is clogged and causing the oil to make it's way into the oil filter. Will take some pics and come back. Can't thank you enough for your time and help.

Rob