V6 easy to work on?

[Phillip]

I'm going to look at a 66 LWB, fenderside tomorrow. I know it's not running - the lady said "something broke in the engine" and it has been sitting under a barn since.

Question is: Is the V6 fairly easy to work on? For a mechanic, I mean -- not me. (I can build a house, but mechanic work... not so much.)

Are there common items that need to be replaced when the engine is torn down?

[TJ's GMC]

Engine is easy to work on yes, but parts are getting hard to find.

[Funky61]

Welcome Philip!
I'd say they're pretty easy to work on. It just depends what is actually wrong with the engine. If it's an internal problem and you would be asked to source certain parts, that would be your challenge.
However once you have a GMC V6 in great running condition , they run "forever" and are a unique piece.

[TJ's GMC]

There's a guy in Medford, Oregon with a GMC V6 that has 600,000 on it...still running to. Mine only has like 120,475 so I gotta ways yet. haha

[FetchMeAPepsi]

Originally Posted by Phillip

I'm going to look at a 66 LWB, fenderside tomorrow. I know it's not running - the lady said "something broke in the engine" and it has been sitting under a barn since.

Question is: Is the V6 fairly easy to work on? For a mechanic, I mean -- not me. (I can build a house, but mechanic work... not so much.)

Are there common items that need to be replaced when the engine is torn down?

Welcome to the forum


Hey man i didnt know anything about motors before I got my GMC. If you can change your oil and have a 1/2", 3/4", and 9/16" wrench you can dang near take the whole truck apart and put it back together without too much trouble. They're super easy to work on if you decide to try yourself, and if you get stuck just pop on here and ask. There's people from all over the country that'll walk you through just about anything you need.

It's a great "hands on" engine. Heck, even the spark plugs are right on top.


For most people "Something went wrong in the engine" is code word for "It won't start". Here's what I'd do with your old motor, but only after you get her home. No sense in driving the price up! Take a jumpbox or a spare battery (or even jumper cables) with you and a can of gas. Get in the truck - but only after lookin under the seat for snakes - then try to turn the engine over (not start!). If it turns over, you might have hope. Check the oil and if that's OK pour about 1 oz of gas in the carb and pull the choke halfway out. See if she fires up. If she does, listen for noises. If you hear anything funny, turn her off. If she doesn't start, at least she still turns over so that greatly improves the chances that it's something small you need to fix.

Though with these motors you can buy a whole spare engine for about $200 on a good day.

Anyway, take lots of pictures and come show us your new baby!

[tommr]

Our 401M has more than 400,000 miles. travelled 625 miles from Myrtle Beach SC to Phila on July 1. Uses no oil but has a leak. Noticed oil residue around valve cover fill cap. Ordered a breather cap to replace it. Factory breather on block is clean. Thinking it may need more crankcase venting. Oil is being pushed out of lifter valley area and down the back of the block. Used less than a qt on the 1400 mile trip.

[TJ's GMC]

Originally Posted by tommr

Our 401M has more than 400,000 miles. travelled 625 miles from Myrtle Beach SC to Phila on July 1. Uses no oil but has a leak. Noticed oil residue around valve cover fill cap. Ordered a breather cap to replace it. Factory breather on block is clean. Thinking it may need more crankcase venting. Oil is being pushed out of lifter valley area and down the back of the block. Used less than a qt on the 1400 mile trip.

That's cool to hear! My V6 burned a quart of oil through the course of like 9 months. haha And it smokes a tad upon a hot start up, but nothing to be worried about. Runs like a top. Driven everyday to.

Now what 350 chevy could last to 400,000!

[FetchMeAPepsi]

Philip, where ya go? Did you get the truck?

[tommr]

Actually my daily driver 86 Monte with a 4.3l FI turned 400k a few weeks ago. valve guide seals and head gaskets is all the motor has seen. Heads had no machine work. Have seen several 350s with nearly 500k--ex police and taxi with tons of idle hours. None of these are pushing 20k lbs down the road like the 401 does though. Ditto though on the parts availability issue. Allison transmission in the bus modernizes that aspect. Next is front axle and suspension conversion to modern axle with air disc brakes and air beam suspension--hopefully this winter. Have to upgrade engine/rear axle/rear suspension at the same time to get all the mount and driveshaft angles worked out. Bus is loaded with 50 and 70 year old components for which very little or no replacement parts exist.

[TJ's GMC]

Originally Posted by tommr

Actually my daily driver 86 Monte with a 4.3l FI turned 400k a few weeks ago. valve guide seals and head gaskets is all the motor has seen. Heads had no machine work. Have seen several 350s with nearly 500k--ex police and taxi with tons of idle hours. None of these are pushing 20k lbs down the road like the 401 does though. Ditto though on the parts availability issue. Allison transmission in the bus modernizes that aspect. Next is front axle and suspension conversion to modern axle with air disc brakes and air beam suspension--hopefully this winter. Have to upgrade engine/rear axle/rear suspension at the same time to get all the mount and driveshaft angles worked out. Bus is loaded with 50 and 70 year old components for which very little or no replacement parts exist.

That is a sweet bus. I've put like 2500 miles on my 305 through 2 years without issues. Planning on a long trip with the truck soon. Gonna take it easy the whole way. haha