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GMC V6 and V12 Engines Engine repair and rebuilding

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  #71  
Old February 4th, 2016, 06:28 PM
POWERSTROKE POWERSTROKE is offline
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Default Re: SO who came up with the GMC V6's???

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Originally Posted by TJ's GMC View Post
And I'm scared to get mine past 3500! LOL!
If the valves don't float, keep your foot in it!
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  #72  
Old February 4th, 2016, 10:06 PM
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Default Re: SO who came up with the GMC V6's???

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Originally Posted by POWERSTROKE View Post
If the valves don't float, keep your foot in it!
I'm good. lol My V6 is running like a top and I wanna keep it that way for a long time. haha Have no doubt in the motor, but never hurts to be easy on them....occasional burnout or two works for me. lol!
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1964 GMC 1500 305E/sm420 4 barrel intake mod and dual exhaust.
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  #73  
Old May 4th, 2017, 05:15 PM
401bluebird 401bluebird is offline
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Default Re: SO who came up with the GMC V6's???

I found this thread from some time back this morning. I followed with interest when discussing driving in heavy haulers with the V6s, as I have a 1960 GMC 35' motor home conversion All-American bluebird Coach with a Clark 5-speed trans behind the original 401 V6 engine.

I drove it quite a bit after I purchased it in 1987, going to British Columbia, Canada. I got 6 mpg consistently, which I thought it was all it would get, but the previous owner told me he got 10 mpg on long trips. After several trips I did something I should have done after purchase--I pulled the plugs and saw that they were close to being gas fouled. The 2-bbl carb was spilling fuel into the air stream while running. After corrected, I was getting close to 10 mpg @ 60-65 mph.

My rig weighs 23000 pounds, which is a lot of mass to climb hills. The trans has a bad gap in the 3-4 shift, which becomes quite annoying when climbing long grades, which are numerous here in the West. I learned to simply be patient and stay in the lower gear at a slower speed.

I have plans to return this to the road after replacing the wheels and tires to eliminate the old rag 20" tires on split rims. I also have a new, old stock (2001) Holley pro-jection throttle body retrofit EFI system which I intend to install. It is 2-bbl sized which should ease the adaptation to the pre-magnum 2-bbl intake manifold.

Though slow on grades, the coach performs very well on the flats, and steers and rides quite comfortably. I recently had the opportunity to acquire a low-mileage 478-M with the idea I could swap it into the Bluebird, but I think I am going to stay with the workhorse 401.
Regards, Andy Carlson, Ojai CA
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  #74  
Old May 6th, 2017, 04:44 AM
BillT BillT is online now
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Default Re: SO who came up with the GMC V6's???

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Originally Posted by bigblockv6 View Post
The GMC V6 family of engines was prematurely phased out, I would have to say it was all a matter of dollars and cents with GM. You could see the trend from the late 60's of incorporating Chevrolet engines and more interchangeability lead to the final demise of the GMC V6 after 1974
Back around '74, I was talking to the parts manager at a GMC Dealership and he told me that the V-6 did better and was more liked on the East Coast with all the hills we have, but not that favorable on the flat areas in the Central and Western US. He said because of that, the demand was dropping off and they decided to phased it out, to my dis-appointment.

I had both a 6-292 and V-6's. I like them both, but really liked the V-6 in Heavier trucks. My '62 6500 with the 478 was a powerhouse. It would pull a full load of 20,000 lbs like nothing. Hills would not phase it either, lol.
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Drove:
-'60 GMC 2500 Dump, 305 V-6
-'62 GMC 6500 Flatbed Dump, 478 V-6
-'67 GMC 1500 Pick-up, 305 V-6
-'71 GMC 9500 Flatbed Dump, 637 V-8

Owned:
-'62 GMC 4000 Flatbed, 305 V-6
-'64 GMC 1500 Pick-up, 305 V-6
-'66 GMC 1000 Pick-up, 305 V-6
-'67 GMC 7500 Box, 6V-53 Detroit

Last edited by BillT; May 6th, 2017 at 04:50 AM.
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  #75  
Old May 6th, 2017, 05:07 AM
401bluebird 401bluebird is offline
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Default Re: SO who came up with the GMC V6's???

The economics of replacing a well regarded engine design with something cheaper has not been only with the GMC V6 family.

In the 1950s Chrysler produced many trucks under the Dodge brand which were fitted with the Chrysler double rockershaft engine, a highly regarded design which became popular for drag racing where they were known as "Hemis". These strong, well built engines were long-lived and very durable. But the complexity of the valve layout and the machined combustion chamber made this an expensive engine to produce--more than the other competitors in the luxury car market.

The replacement was a big block engine which shared a lot of design elements of the small block Chevy V8 and was used from 1958 until 1978. Though nice engines, they weren't anywhere nearly well regarded as what was replaced.

I look at the GMC V6 and I am impressed with the 100% great design incorporated into the engines. I guess 14 years was a good run, though. And here we are, all singing the praise!

-Andy Carlson
Ojai CA
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  #76  
Old May 6th, 2017, 05:18 AM
bigblockv6 bigblockv6 is online now
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Default Re: SO who came up with the GMC V6's???

What I would like to add to BillT's response is yes the GMC V6's were great for pulling uphills and I've mentioned this before on Jolly's site which is my Uncle drove prototype GMC Tow Trucks that wr given to the California State Automobile Association(AAA) in the mid 50's which were the 55-59 design trucks with the V6 engines. San Francisco was an excellent test bed as it has a lot of hills as well as real steep hills. As far the west coast and central parts of the country being flat I would say that's is really doubtful that let to the demise of the V6, it was all about dollars and cents from the corporate big wigs, It was just cheaper to use a Chevrolet engine, the GMC V6 was known for it's longevity so it was less prone to break down. GMC historian Don Meyer has even said that. Myself growing up in San Francisco in the late 60's and early 70's and being in a family that owned a grocery market I can say the GMC Trucks powered medium and heavy duty trucks by the V6 were very dominant compared to other trucks
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  #77  
Old May 6th, 2017, 05:27 AM
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Default Re: SO who came up with the GMC V6's???

I look at the GMC V6 and I am impressed with the 100% great design incorporated into the engines. I guess 14 years was a good run, though. And here we are, all singing the praise!

-Andy Carlson
Ojai CA[/QUOTE]

14 years not long enough, the V6's could have lasted longer if GM wasn' so cheap, anytime GM has something that's real good they tend to get rid of it. What was apparent though after the demise of the V6 was more Diesel engines were added to the larger Heavy duty series trucks, evidently the 366 & 427 engines couldn't quite muster the duties of the 432 and 478 V6 engines.
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  #78  
Old May 6th, 2017, 08:20 AM
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Default Re: SO who came up with the GMC V6's???

Quote:
Originally Posted by bigblockv6 View Post
I look at the GMC V6 and I am impressed with the 100% great design incorporated into the engines. I guess 14 years was a good run, though. And here we are, all singing the praise!

-Andy Carlson
Ojai CA
14 years not long enough, the V6's could have lasted longer if GM wasn't so cheap, anytime GM has something that's real good they tend to get rid of it. [/QUOTE]

The GMC dealer where my Dad bought the one ton Suburban new in 1965 once told him that one reason General Motors dropped the V6 was because so many of the GMC dealers were complaining that their repair shops weren't making enough money because the V6s were too reliable and long-lived. Switching to Chevy engines solved that complaint!
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  #79  
Old May 6th, 2017, 12:50 PM
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Default Re: SO who came up with the GMC V6's???

This reminds me of a great 305 V6 vs 350 v8 story a buddy of mine told me. He used to own a 65 GMC LWB C10 with a 305E/sm420 and 3.54 rear gear. He Loved that v6 and wouldn't have traded it for any v8.

Now here's the story:

He and a friend of his were ripping this deck down with their trucks.....his buddy had an early 70's or 80's Chevy 4x4 with a 350/th350. Well he backed up to the deck, and from what I remember hearing....in 1st gear that truck either couldn't spin the tires for it's life.....or they spun and the truck did nothing to that deck. Needless to say.....my buddy pulled up to the deck....hooked up...and in granny low, that v6 tore that deck apart without a thought.

And don't get me going on 305 v6 vs 305 v8 stories! Never will Any chevy engine beat the durability and performance of the v6. Best engine GM ever made, not many can claim an easy 300,000 miles!
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1977 Chevy C20 572 BBC/TH400
1984 Chevy C30 292/SM465

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