351 V6 questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Americanrider · 10-20-2005, 02:08 AM

I'm trying to talk myself into or out of buying a 68 GMC w/ a 351 V6/Th350.
Pros & cons from those who own or have owned this motor? Are there any upgrades, re-buildable parts around? I'm a bit worried because it has about 170K showing and I'm not sure how much life is left in this engine.

shelby987 · 10-20-2005, 07:27 AM

I looked into buying one of these motors, there is a post somewhere that I will try to find....there doesn't seem to be much in the way of upgrades, and parts seemed difficult to located (at least when I ended up talking myself out of buying one). From what I gathered it boils down to what you are going to use the truck for, if you need a tow truck, stump puller, and something to haul stuff around in.....but just around town, its a good setup, if you want a highway cruiser at all.....3.08 gears (from what I am told) is your only hope as these engines don't like High RPMS.

http://www.6066gmcguy.org/ <---- this is the best site to find information about these motors.

hope that helps

Huck · 10-20-2005, 07:35 AM

These are low rpm high torque motors for pure "truck" type usage and have no appreciatable value especially with high miles. Forget about upgrades--. If this is a key part of your decision, if it runs and that is all you need--that's fine but don't buy it with great expectations. These trucks are primarly valued for the quality of the sheet metal, ease of repair and low cost of replacement parts. Buy accordingly--Huck

TP from Cntl PA · 10-20-2005, 09:26 AM

I'd buy it.............Not many are left with the V-6 still under the hood, and the 351 is EXTRA hard to find anymore. As long as you keep the block in one piece it will run a long, long time...........Most parts you can still get other than items like crank, block, cam, and heads, big stuff in other words.

My '69 GMC was a township truck, in other words who knows how many miles the 305 V-6 under the hood has on it, but it still is running hard. IMO, GMC's big blocks were some of the best engines ever put in a truck, they pull like h*ll and you can't kill them on a hill, they will lug like crazy until the cows come home. I use my truck for work, and I wouldn't trade my V-6 powered truck for anything else!

Americanrider · 10-20-2005, 11:11 AM

I had plans to use it as a parts runner until I finish an un-planned resto of my K20. You know... the brake job turned into a axle swap, power brake up gread and gee those motor mounts look tired. Why not pull the 283 and plant a 350, time to get rid of the rockwell transfer, so look for a new tranny, ect ect...

In the mean time I need to haul wood for winter, carry the scrap off, pick up a couch. The common everday uses we all have. Thanks for the input and the link.

Erl · 10-20-2005, 01:03 PM

I would be very interested in purchasing the heads, intake and exhaust manifolds off that 351. They are a good engine, but love the gas. If that is the original transmission, then it should be a TH400 or 2sp power glide. If it has p/s or AC those parts will sell. Sold an AC bracket for $200. The auto to 351 adapter is also worth some money, had a guy offer $250 for mine. Other parts on there are worth selling too.

Let me know.

**special-K** · 10-21-2005, 10:43 AM

They were/are very good motors.They use as much fuel as a V8.The 351 is a 409 minus 2cyls.The 302 is the 348.Parts are rare but available for those V8s and nobody runs away from those.You`llprobably never need a crank and,I believe the rest is the same internally.It wouldn`t make the best daily driver(same as all these trucks)these days,but a cool run around mill.

Fred T · 10-21-2005, 12:11 PM

I drove a bunch of the GMC V6 trucks when they were new. They were popular with the bean-counters that ran businesses. Most guys that drove them hated them, since you couldn't make one go fast and last.

GMC used a high nickel alloy for the block. As long as it isn't using oil and is properly cared for, it could easily go another 170K miles. The 351 is the best engine of the series. It will make you a good hauler, just don't get in a hurry. The crank has huge counterbalances, and does not like to be revved. GMC set the redline around 3,500 rpm, but running at high rpm for extended times will shorten the life in a hurry. Best to keep the rpm under 2,500 for the highway.

70rs/ss · 10-21-2005, 04:30 PM

Quote:

Originally Posted by Fred T

I drove a bunch of the GMC V6 trucks when they were new. They were popular with the bean-counters that ran businesses. Most guys that drove them hated them, since you couldn't make one go fast and last.

GMC used a high nickel alloy for the block. As long as it isn't using oil and is properly cared for, it could easily go another 170K miles. The 351 is the best engine of the series. It will make you a good hauler, just don't get in a hurry. The crank has huge counterbalances, and does not like to be revved. GMC set the redline around 3,500 rpm, but running at high rpm for extended times will shorten the life in a hurry. Best to keep the rpm under 2,500 for the highway.

Back in the day my dad and uncle ran a dirt car with 348's and he said they would replace one every race, and occasionally they would have one last two races, so I second the no high RPM's. These are great for what they were intended for and nothing else. My 1959 GMC truck had a V8 (guessing the 348) but it had been long since chucked. Try it, it should last untill your weekend project gets done.

Tx Firefighter · 10-21-2005, 04:47 PM

70rs/ss, I don't follow the 348 deal. What does it have in common with the 351 V6?

70rs/ss · 10-21-2005, 04:50 PM

Quote:

Originally Posted by Tx Firefighter

70rs/ss, I don't follow the 348 deal. What does it have in common with the 351 V6?

351 is a 348 with two cylinders whacked off. So they are pretty much the same.

Tx Firefighter · 10-21-2005, 04:54 PM

No way. You can't remove cylinders from a 348 and make it BIGGER to a 351. Not possible.

It would have to be smaller than a 348 if you chopped off 25 percent of the cylinders.

stllookn · 10-21-2005, 05:21 PM

Hmmmmm, a 409 with two missing cylinders would be a 306.75, V-6. I have had two of them and don't like them just because they are DIFFERENT...LOL! Ben, how about a '68 50th Anniversary C10 with a six...runs and looks pretty...$500!

Americanrider · 10-21-2005, 08:24 PM

Your holding out on me... where is it?

stllookn · 10-21-2005, 08:30 PM

Call me.

TP from Cntl PA · 10-22-2005, 09:44 AM

Quote:

Originally Posted by Fred T

I drove a bunch of the GMC V6 trucks when they were new. They were popular with the bean-counters that ran businesses. Most guys that drove them hated them, since you couldn't make one go fast and last.

Guys here that ran the larger ones in tandems and single axles loved them..............Guy who hauled alot of coal years ago ran alot of GMC's with them, they could haul 10ton legal on most of their trucks, but would run with 15+ out of the mines and they said those engine just ate the hills up. Maybe because of our hilly terrain keeping RPM's down they faired better.

**special-K** · 10-22-2005, 10:02 AM

They are strokers as in torquey/lower rpm.The longer stroke figures in to the displacement as well as bore.I don`t how it all adds up but I was always told the 351 V6 was a whacked 409/302 a whacked 348.Does not compute.So,it must be a 302 is a 6cyl 409(409-25%=302).Either way,they are the same tougher than nails overbuilt older technology(and slower times)motor.Like the later V6s being 3/4 of a small block V8(5.7-25%=4.3).
70rs/ss,I think your GMC might have had a Pontiac motor in it.That`s what they were doing back in the 50s.Maybe not by`59.

Americanrider · 10-23-2005, 01:05 AM

I have decided to pass on the deal. If anyone is interested just type in 68 GMC into Seattle's craigslist. It's the blue one for $950...... so many trucks...so little time! Thanks everyone for all the imput & info.

PS: I stand corrected, the truck has 130K miles on it.

**special-K** · 10-23-2005, 06:51 AM

It would seem a better deal has come your way.I guess that`s why you`re not stllookin.

70 shorty · 10-23-2005, 08:20 AM

I'd love to ride in one of these trucks with a 351 V6 after hearing all the discussion on this site about them. I'd like to see how they pull.

TP from Cntl PA · 10-23-2005, 08:32 AM

Quote:

Originally Posted by 70 shorty

I'd love to ride in one of these trucks with a 351 V6 after hearing all the discussion on this site about them. I'd like to see how they pull.

I couldn't imagine what a 351 would do..................I know with the little 305 in my 1-ton, the clutch and u-joints on the drive shaft could be the weak link. It just doesn't give up on a hill............We've been hauling firewood with it for some time this year and a few people have rode with me over to the woods and back to the house in it..............Acouple thought it was a diesel the way it hung in there, of-course being a smart A$$, I told them, "Naw, the diesel is in my other one that REALLY runs well loaded!"

JAKES 68GMC · 03-22-2006, 09:15 PM

Guys, V6 GMC's are completely different from 348-409 Chevys, GMC v6's were made in 305,351,379,401,432 and 478 inch engines. Plus there was a 637 V8 made from the V6's, and a 702 V12 which was 2 351's together. Read for yourself.

www.6066gmcguy.org

Longhorn Man · 03-22-2006, 09:40 PM

Jake is 100% right, there is nothing simalar between the W block motos (348 & 409) And the GMC V-6 motors. The spark plugs are on top of the heads by the intake instead of on the bottom by the exhaust, and in all reality, they are huge even compaired to a 409.

**Bob B.** · 03-22-2006, 09:50 PM

Even the oil pan drain plug is different!

JAKES 68GMC · 03-22-2006, 09:59 PM

Yup. 1 1/8 inch drain plug on mine.

10-20-2005, 02:08 AM	#1
Americanrider Registered User Join Date: Dec 2004 Location: NW, WA. Posts: 1,421	351 V6 questions I'm trying to talk myself into or out of buying a 68 GMC w/ a 351 V6/Th350. Pros & cons from those who own or have owned this motor? Are there any upgrades, re-buildable parts around? I'm a bit worried because it has about 170K showing and I'm not sure how much life is left in this engine.

10-20-2005, 07:27 AM	#2
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	Re: 351 V6 questions I looked into buying one of these motors, there is a post somewhere that I will try to find....there doesn't seem to be much in the way of upgrades, and parts seemed difficult to located (at least when I ended up talking myself out of buying one). From what I gathered it boils down to what you are going to use the truck for, if you need a tow truck, stump puller, and something to haul stuff around in.....but just around town, its a good setup, if you want a highway cruiser at all.....3.08 gears (from what I am told) is your only hope as these engines don't like High RPMS. http://www.6066gmcguy.org/ <---- this is the best site to find information about these motors. hope that helps

10-20-2005, 07:35 AM	#3
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,269	Re: 351 V6 questions These are low rpm high torque motors for pure "truck" type usage and have no appreciatable value especially with high miles. Forget about upgrades--. If this is a key part of your decision, if it runs and that is all you need--that's fine but don't buy it with great expectations. These trucks are primarly valued for the quality of the sheet metal, ease of repair and low cost of replacement parts. Buy accordingly--Huck

10-20-2005, 09:26 AM	#4
TP from Cntl PA Registered User Join Date: Apr 2003 Location: Central PA....In the Berg of Nisbet Posts: 790	Re: 351 V6 questions I'd buy it.............Not many are left with the V-6 still under the hood, and the 351 is EXTRA hard to find anymore. As long as you keep the block in one piece it will run a long, long time...........Most parts you can still get other than items like crank, block, cam, and heads, big stuff in other words. My '69 GMC was a township truck, in other words who knows how many miles the 305 V-6 under the hood has on it, but it still is running hard. IMO, GMC's big blocks were some of the best engines ever put in a truck, they pull like h*ll and you can't kill them on a hill, they will lug like crazy until the cows come home. I use my truck for work, and I wouldn't trade my V-6 powered truck for anything else! __________________ '72 K-20 EFI'ed 250 Inline/4spd stake body, Farm Truck '71 C-20 Cummins Diesel Powered, In storage thanks to $5.00 diesel! '69 3500 GMC 305V-6/4spd, Still under reconstruction.......... Inlines Rule! 6 soldiers standing is better than 8 laying down!!!!!!!!

10-20-2005, 11:11 AM	#5
Americanrider Registered User Join Date: Dec 2004 Location: NW, WA. Posts: 1,421	Re: 351 V6 questions I had plans to use it as a parts runner until I finish an un-planned resto of my K20. You know... the brake job turned into a axle swap, power brake up gread and gee those motor mounts look tired. Why not pull the 283 and plant a 350, time to get rid of the rockwell transfer, so look for a new tranny, ect ect... In the mean time I need to haul wood for winter, carry the scrap off, pick up a couch. The common everday uses we all have. Thanks for the input and the link.

10-20-2005, 01:03 PM	#6
Erl Registered User Join Date: Mar 2002 Location: Dallas, TX Posts: 555	Re: 351 V6 questions I would be very interested in purchasing the heads, intake and exhaust manifolds off that 351. They are a good engine, but love the gas. If that is the original transmission, then it should be a TH400 or 2sp power glide. If it has p/s or AC those parts will sell. Sold an AC bracket for $200. The auto to 351 adapter is also worth some money, had a guy offer $250 for mine. Other parts on there are worth selling too. Let me know. __________________ 1968 GMC 305 V6 3/4 4x4 Stepside 06 Corvette Daily Driver Dallas TX Last edited by Erl; 10-20-2005 at 01:04 PM.

10-21-2005, 10:43 AM	#7
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,852	Re: 351 V6 questions They were/are very good motors.They use as much fuel as a V8.The 351 is a 409 minus 2cyls.The 302 is the 348.Parts are rare but available for those V8s and nobody runs away from those.You`llprobably never need a crank and,I believe the rest is the same internally.It wouldn`t make the best daily driver(same as all these trucks)these days,but a cool run around mill. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

10-21-2005, 12:11 PM	#8
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: 351 V6 questions I drove a bunch of the GMC V6 trucks when they were new. They were popular with the bean-counters that ran businesses. Most guys that drove them hated them, since you couldn't make one go fast and last. GMC used a high nickel alloy for the block. As long as it isn't using oil and is properly cared for, it could easily go another 170K miles. The 351 is the best engine of the series. It will make you a good hauler, just don't get in a hurry. The crank has huge counterbalances, and does not like to be revved. GMC set the redline around 3,500 rpm, but running at high rpm for extended times will shorten the life in a hurry. Best to keep the rpm under 2,500 for the highway. __________________ Fred There is no such thing as too much cam...just not enough engine.

10-21-2005, 04:47 PM	#10
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: 351 V6 questions 70rs/ss, I don't follow the 348 deal. What does it have in common with the 351 V6? __________________ I'm on the Instagram- @Gearhead_Kevin

10-21-2005, 04:54 PM	#12
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: 351 V6 questions No way. You can't remove cylinders from a 348 and make it BIGGER to a 351. Not possible. It would have to be smaller than a 348 if you chopped off 25 percent of the cylinders. __________________ I'm on the Instagram- @Gearhead_Kevin

10-21-2005, 05:21 PM	#13
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	Re: 351 V6 questions Hmmmmm, a 409 with two missing cylinders would be a 306.75, V-6. I have had two of them and don't like them just because they are DIFFERENT...LOL! Ben, how about a '68 50th Anniversary C10 with a six...runs and looks pretty...$500! __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

10-21-2005, 08:24 PM	#14
Americanrider Registered User Join Date: Dec 2004 Location: NW, WA. Posts: 1,421	Re: 351 V6 questions Your holding out on me... where is it?

10-21-2005, 08:30 PM	#15
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	Re: 351 V6 questions Call me. __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

10-22-2005, 10:02 AM	#17
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,852	Re: 351 V6 questions They are strokers as in torquey/lower rpm.The longer stroke figures in to the displacement as well as bore.I don`t how it all adds up but I was always told the 351 V6 was a whacked 409/302 a whacked 348.Does not compute.So,it must be a 302 is a 6cyl 409(409-25%=302).Either way,they are the same tougher than nails overbuilt older technology(and slower times)motor.Like the later V6s being 3/4 of a small block V8(5.7-25%=4.3). 70rs/ss,I think your GMC might have had a Pontiac motor in it.That`s what they were doing back in the 50s.Maybe not by`59. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

10-23-2005, 01:05 AM	#18
Americanrider Registered User Join Date: Dec 2004 Location: NW, WA. Posts: 1,421	Re: 351 V6 questions I have decided to pass on the deal. If anyone is interested just type in 68 GMC into Seattle's craigslist. It's the blue one for $950...... so many trucks...so little time! Thanks everyone for all the imput & info. PS: I stand corrected, the truck has 130K miles on it.



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10-23-2005, 06:51 AM	#19
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,852	Re: 351 V6 questions It would seem a better deal has come your way.I guess that`s why you`re not stllookin. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

10-23-2005, 08:20 AM	#20
70 shorty Where's my beer? Join Date: Oct 2004 Location: Glen Allen, VA Posts: 1,772	Re: 351 V6 questions I'd love to ride in one of these trucks with a 351 V6 after hearing all the discussion on this site about them. I'd like to see how they pull. __________________ 70 C10, shortstep, .30 over 250,Hurst shifted 3 spd parts hauler. Holley 390, Clifford Intake, Header, ported cylinder head, unknown bigger cam. 79 Corvette L82, 4 spd, black, red interior, headers, flowmasters, and unkown bigger cam. '03 Grand Cherokee Laredo, 4.0 4x4 daily driver. 165K miles, and runs great '08 Tahoe LTZ 4x4 155K

03-22-2006, 09:15 PM	#22
JAKES 68GMC Aluminum slot wheels rule... Join Date: Jan 2006 Location: Maine Posts: 6,212	Re: 351 V6 questions Guys, V6 GMC's are completely different from 348-409 Chevys, GMC v6's were made in 305,351,379,401,432 and 478 inch engines. Plus there was a 637 V8 made from the V6's, and a 702 V12 which was 2 351's together. Read for yourself. www.6066gmcguy.org Last edited by JAKES 68GMC; 03-22-2006 at 09:16 PM.

03-22-2006, 09:40 PM	#23
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 351 V6 questions Jake is 100% right, there is nothing simalar between the W block motos (348 & 409) And the GMC V-6 motors. The spark plugs are on top of the heads by the intake instead of on the bottom by the exhaust, and in all reality, they are huge even compaired to a 409.

03-22-2006, 09:50 PM	#24
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,349	Re: 351 V6 questions Even the oil pan drain plug is different! __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.

03-22-2006, 09:59 PM	#25
JAKES 68GMC Aluminum slot wheels rule... Join Date: Jan 2006 Location: Maine Posts: 6,212	Re: 351 V6 questions Yup. 1 1/8 inch drain plug on mine.

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