1967 GMC V6 - 351E on a Camper Cruiser

[Blue Sage]

Hi GMC and Chevy Truckers,

I'm brand new to the site and am hoping for some guidance and info on rebuilding a 351E. I bought the truck with the original Camper Queen camper on it - which were bought together in '67 by a military man who kept extensive maintainance records and receipts. The engine was completely rebuilt in 1998 and various things added - power steering, dual battery charger and AC.

WHen I got it in 2006, it had the wrong carburator on it and only got 5 MPG. In the process of putting on a different - used - carburator - a 1/4 inch bolt fell in the spark plug hole for which I will surely go to mechanic's hell for a few seasons. The bolt banged up against the head about 20 times before I just abandoned the truck in my driveway that Autumn thinking I'd thrown a rod. In Spring I took the corresponding head off the V6 and found the bolt had bounced around the head a few times and settled next to the cylinder wall scoring it but just barely. A diesel mechanic told me that because the score is above the rings it will fill in with carbon and all will be well. Right?

So, my job initially is to put it all together again and then start from the beginning to analyze the engine for 1. leaking cylinders and 2. leaking rod bores and 3. out of round journals on the crank shaft.

I realize that because the piston cracked up against the head (away from the valves) that despite there being no visible cracks under the bolt, it still could have micro cracks that could ultimately break up the piston so that that piston should be replaced with new rings and bearings on the journal. But my logic is that the piston could withstand going back into the cylinder for a brief period so as to test the entire engine for efficiency, then take it apart again and replace the piston with new rings. Sound doable?

On the other hand, I could buy a new piston, rings and bearings (where would I find such things please?) and THEN test the engine in the event the engine is OK, and then I wouldn't have to do it over again. I have some mechanical skill having done a Dodge slant six rebuild in '84 that still runs!

Any help I can get on this deeply appreciated. I'd love to the that Camper Queen on the road again! Thanks, Blue Sage

[Ol Blue K20]

First of all. Welcome to the site. I wouldn't trust the scored cylinder wall myself. I also want to see pics of this truck and camper.

[Blue Sage]

Hi Ol Blue - The score is about 1/32" deep. It's pretty slight. The diesel mechanic seemed totally confident about it filling with carbon. I know though - sounds like a vulnerability. No pics just now.

One thing I need is specific info on the 351E. The manual I have covers everything BUT that so I need torque figures and everything else. The other option may be to have the frame altered and get a more modern V8 with higher efficiency. But the V6 has a such a great sound I hope to keep it.

[MJN]

This site should be of some help, he has torque values listed and other specifications. I can also check my old old Chilton's manual if there is any info in there as well.
http://www.6066gmcguy.com/EngineData.html

[Blue Sage]

Hi MJN - Nice! Thanks!

[MJN]

Not sure what all you need, here are some torque specs and head bolt sequence.

[Blue Sage]

MJN - That's great thank you a lot. That's basically what I need - head, rod and manifold torques. I'm going to just hone the one damaged cylinder with a bottle brush and put it all back together and test the compression and see what I learn. I have my doubts this engine can ever get decent mileage - the cylinders are 4 and a half inches wide! and the intake feeds two cylinders at once - so, pretty inefficient.
Hey! Thanks!

[WorkinLonghorn]

As for the 5 MPG mileage; My '69 came with a 12 1/2' (~2000+ Lbs) camper from the original owner and with a 350 V8 it got 8 MPG. I've always heard those 351s got lower than the V8 350. Somebody with one will be along soon I'm sure as long as this thread stays active.

[Blue Sage]

WorkingLonghorn - Soooo . . . . maybe I should think of putting a more modern V8 in the old truck. If I can't get 15 mpg then the truck is just a plaything that I can't afford to run!

[WorkinLonghorn]

With the camper? No way. With a fresh rebuilt 350 V8 empty on the freeway I get 15 MPG holding 60 steady. Most people on here talk about driving 75+ MPH and wondering why their RPMs are so high and their mileage so poor. Personally I don't think these old trucks are anywhere near safe over 55, but that's another discussion.

There are guys on here with the 351E that can give you real info. -BA


Edit: Oh, that is with 3.73-1 rear and 31" tires ~2500 RPM @ 60MPH. What rear axle do you have?

[WorkinLonghorn]

What did the diesel mechanic say about your piston? I would take a very good look at the top, clean it off really good first. Are there visible dents in it?

[5Tractorguy]

From a small engine mechanic standpoint... I had a late 80's Briggs 8hp engine that got the screw treatment, someone dropped one down the cylinder and it imprinted itself in the head about a dozen times. Cylinder was a bit scored bit it still ran great.

If the scoring is only 1/32 and minimal, personally I'd just run it! You wouldn't believe some of the scoring in tractor engines that I pull apart and they still get used on a weekly basis.

I have a 351 V6 in my '61 5000 flat bed. Nearest I figure, it's gets about 7-8 MPG loaded or empty and not being conservative with the gas pedal. Has the 2 barrel Stromberg WW.

From what I gather, 351's are hard to get internal parts for vs. the 305's. I thought there was someone reproducing pistons, but don't hold me to it. There are guys that have adapted more modern carburetors to them... 4 barrels and what not. You could try that to improve efficiency and power.

Anyways, it would be pretty cool to see that engine remain in the truck being original. But if you do decide to replace it, I may be interested in it...

[Blue Sage]

Hi Jake, Thanks for the thorough analysis. Apparently even a modern V8 with electronic ignition and fuel injection isn't going to give me 15 plus milage without which I can't really use it being on a fixed income etc.

I changed out the transaxle to a more efficient ratio and dropped the old transaxle in a clump of sage. I live in a sea of sage in New Mexico.

We need to haul our water from a community well a few miles away so I nothing else I'll use the truck for that as then I could just leave a 300 gallon tank on the truck.

The Camper Queen camper was bought at the same time in 1967 as the truck and is in fair shape. Thinking now about alternative trucks - a more modern 2500 for instance.

I hate to give up on the truck - it has the strongest frame I've ever seen. there's a plate between the front wheels that must be an inch thick. And the cab has a nice homely look, like a ten year old would draw a truck. I'll get a pic and send it to ya.

Thanks! Clint

[Blue Sage]

Originally Posted by WorkinLonghorn

What did the diesel mechanic say about your piston? I would take a very good look at the top, clean it off really good first. Are there visible dents in it?

The diesel mechanic said the fairly slight gouge would fill in with carbon as it's above the rings. I think I need another truck that will give me decent milage. Parts ARE hard to find for the 351E to begin with.

I changed out the transaxle ten years ago to a higher ration and before taking off and traveling. Don't know the numbers off hand.

I'm going to get new gaskets and just put it all back toghether and see if mayber I want to use it for a water hauling truck as i live in the desert and could put a 300 gallon tank on it and then just leave it parked while I use up the water.

[5Tractorguy]

Originally Posted by Blue Sage

Hi Jake, Thanks for the thorough analysis. Apparently even a modern V8 with electronic ignition and fuel injection isn't going to give me 15 plus milage without which I can't really use it being on a fixed income etc.

I changed out the transaxle to a more efficient ratio and dropped the old transaxle in a clump of sage. I live in a sea of sage in New Mexico.

We need to haul our water from a community well a few miles away so I nothing else I'll use the truck for that as then I could just leave a 300 gallon tank on the truck.

The Camper Queen camper was bought at the same time in 1967 as the truck and is in fair shape. Thinking now about alternative trucks - a more modern 2500 for instance.

I hate to give up on the truck - it has the strongest frame I've ever seen. there's a plate between the front wheels that must be an inch thick. And the cab has a nice homely look, like a ten year old would draw a truck. I'll get a pic and send it to ya.

Thanks! Clint

You betcha... Glad to hear it's going to stay together. That would be great! When you have a chance to take one, post a pic here or send me a message, would be interested to see it!

[Blue Sage]

Darn. I meant to take one today. I'll get one up. I don't know what I want to do with the truck - I want a truck is all - if someone wanted this one as an antique or something at this point I'd be interested. I have a thick pile of garage receipts from the military guy who originally owned it until about 2006. I've got the original receipt from '67 when camper and truck were bought together. In '98 there was a major rebuild - don't know if it got rebored or just had the rings replaced. He added AC, power steering, dual charging device. Has three gas tanks! One used to be for water but someone put gas in it.

[WorkinLonghorn]

Originally Posted by Blue Sage

The diesel mechanic said the fairly slight gouge would fill in with carbon as it's above the rings. I think I need another truck that will give me decent milage. Parts ARE hard to find for the 351E to begin with.

I changed out the transaxle ten years ago to a higher ration and before taking off and traveling. Don't know the numbers off hand.

I'm going to get new gaskets and just put it all back toghether and see if mayber I want to use it for a water hauling truck as i live in the desert and could put a 300 gallon tank on it and then just leave it parked while I use up the water.

That would be so cool to have your own water truck. I've always thought about doing that if I relocate to Arizona.

I hope I didn't discourage you with the dismal mileage figures. If you take off the camper you will get substantially better MPG for sure. I really like those big v6 engines and especially the 351 (which is pretty rare I think). Anyway I doubt that you will be putting so many miles on it that it would be cost-effective to go out and buy a newer truck with it's own set of problems. I would fix it up and use it and be really happy about driving such a cool truck. JMHO, Brian

[Blue Sage]

I live in Taos, New Mexico where a lot of the local Hispanics love the old trucks. When I've driven through town in the Cruiser, heads turn to hear the big cylinders of the V6 thumping! Yeah . . . water truck. But I would like to actually be able to go camping in the Camper Queen!

[Ol Blue K20]

I really wanna see pics of this rig!

[WorkinLonghorn]

Originally Posted by Blue Sage

I live in Taos, New Mexico where a lot of the local Hispanics love the old trucks. When I've driven through town in the Cruiser, heads turn to hear the big cylinders of the V6 thumping! Yeah . . . water truck. But I would like to actually be able to go camping in the Camper Queen!

Yeah I get that here all the time even with my 350 v8. Young guys come up, with that look in their eyes of wonder and respect and always ask "What year is it?" Sesenta y nueve Then they just stand there staring at it, drooling almost, and my truck is NOTHING to look at!

I tried the camping in my original camper that came with the truck when I bought it in '97 but the little woman didn't go for it at all. Shame really. Ended up selling it to a neighbor and putting my truck to a life of hard labor.

[Steeveedee]

I never camped as a kid, but my wife loved it, and went all over the western states with her parents. Still not big on it, to be honest. I go because my wife wants to. It's going to be about a year before we go again, due to health issues that I'm having that don't allow heavy lifting.

[factorystock]

The V6 was all about ruggedness and high torque at low rpm's, similar to the characteristics of a diesel engine. These engines got fairly good gas mileage in a 1/2 ton with standard 3.07 ratio. When in a 3/4 ton with 4.10 ratio, gas mileage was average, when in 3/4 ton or 1 ton with 4.56 ratio, gas mileage was poor. IMO, a 351 with the 3.54 ratio would be a great performer with good gas mileage. The biggest problem is that these engines have been out of production for over 50 years and parts are difficult to find. The cost to rebuild will be very expensive. If you really want to keep a V6 for the uniqueness, I would be on the look out for low mileage good running V6 truck being parted out, maybe out of a fire engine.

[Blue Sage]

Hi Factorystock, Thanks for the informative email. It's encouraging what you have to relay about the different ratio transaxles. I did change mine out to an axle more in line with a regular pickup truck for the milage - but forgot the ratio - it was ten years ago. I think I'm going to hone the scratch on the cylinder and just put everything back together and see what I've got. I put in a different carb - Rochester - but it smoked. Now to find a new needle for that. At this point if I can get ten to the gallon I'll use the truck close to home.

[Bob B.]

My 4 speed 351E with a 4:10 rear axle and LT245/75R16E tires gets 8-10 m.p.g. unloaded. I did replace the Stromberg WWC carburetor with a 500 c.f.m. Holley 2bbl.. That was a common swap back in the day and usually resulted in better performance with slightly better fuel economy.

As for the 351, pistons and head gaskets are particularly tough to find, but they do show up on Ebay from time to time.

[mike16]

valve train was never very durable at sustained highway speeds. there were new fix it solutions to the valve train every six months for almost the entire life of the engines. The did al right as water well pump motors.