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I-6 Engines For GMCs that came with the Inline 6 Engines

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  #11  
Old March 14th, 2014, 07:31 PM
Vern Vern is offline
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Default Re: Blown head gasket vs. cracked block

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Originally Posted by quest View Post
Based on your earlier description of all the white smoke, leaks, no oil, no coolant(did you see any blue smoke in there or oil burning?) I wouldn't replace the head gasket without getting the head examined at the machine shop. see if your valves and valve guides are still serviceable and get the head magnafluxed for cracks first. It's not worth wasting a gasket set to seal up engine leaks if it needs a rebuild or replacement anyway, if it's worn out... it's worn out! It does kinda sound like it is at the of it's service life.

Sometimes you can get away with a budget rebuild such as saving your crank, cam, lifters, pistons, valve train, even the oil pump and water pump. If these parts are not excessively worn. you could possibly getaway with tank cleaning everything and put it back together with rings, bearings, gaskets and maybe valve guides. If you have not done this before and you like mechanical work just do a little research, ask for a little help here and you will do fine, it's easier than you might think. It will be fun to do!Hope it goes well.
I sit behind a desk all day, so I'm looking forward to digging in. It seems like the next step will be to locate a shop that can service the head.
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  #12  
Old March 15th, 2014, 06:31 AM
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Default Re: Blown head gasket vs. cracked block

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Originally Posted by Vern View Post
Is it possible to replace the rings without pulling the engine? It seems like replacing the rings wouldn't be too bad, but could be a nightmare if it's still in the engine bay? How about those rebuilt kits that actually include new pistons and rings?
Well not really because you should have the block and head tank cleaned and put new cam/main/rod bearings in with the rings. Doing rings also requires using a cylinder hone and probably a ridge reemer which would contaminate the inside of the engine too much.
Because of the transmission input shaft and flywheel, the crank cannot be pulled without removing the engine first. Lifting the engine out is very simple and makes it very very easy to do the engine work. You just have a few wires and hoses, engine mount bolts, trans bolts, exhaust pipe and lift it out with a rented or borrowed hoist.

You could get a full engine kit but if this is a real budget build I would inspect & measure your pistons/cam/crank first to see if they are too far gone. If you are getting an engine kit with pistons go to 10 - 30 thou oversize and bore the cylinders. The machine shop will tell you how big you need to go.
Now you are talking going full tilt rebuild for more $$$ and if this is not the original engine it just makes sense at this point now to look into the cost of a good quality used 6cyl of any year or buy yourself a an already built long block, see if you can save any $$$ and time.
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  #13  
Old March 15th, 2014, 03:10 PM
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Default Re: Blown head gasket vs. cracked block

before you do all that just change the 20.00 head gasket and see if it fixes it. if it dont fix it buy a new motor v6 for 200.00.
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  #14  
Old March 15th, 2014, 07:38 PM
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Default Re: Blown head gasket vs. cracked block

Vern,

As far as originality, it's a moot point....right..?

If you really feel like you want a project, then I would pull it and put it on a stand, take it down to the block.....find a good machine shop that understands what your intentions are and have a good time doing something new.
It's a hoot if you're not under any time constraints or other "pressures".
BUT.....if you were to call around and do some price and availability checking, you might surprise yourself.
I don't know if you can still buy a Mr. Goodwrench Crate motor....(long or short block)....but I'm sure someone on here will pipe up and let us know.
Both options are enjoyable, and even if it's the first time on an engine swap for you, you couldn't hope to find a more simple project than a GM I-6 in a mid sixties pick-up to cut yer teeth on.
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  #15  
Old March 18th, 2014, 03:28 AM
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Default Re: Blown head gasket vs. cracked block

Best Way I know is to tear it down. I did one today, a small block V8 and it had; a blown head gasket, a cracked block, bad piston, and spun bearing. This was because they overheated it and ran it out of oil.
Attached Images
File Type: jpg badpiston.jpg (106.0 KB, Multiple views, 8 clicks)
File Type: jpg BlownHeadGasket-1.jpg (100.6 KB, Multiple views, 8 clicks)
File Type: jpg CrackedBlock.jpg (115.3 KB, Multiple views, 7 clicks)
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  #16  
Old March 19th, 2014, 02:18 AM
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Default Re: Blown head gasket vs. cracked block

Quote:
Originally Posted by Rockdriller View Post
Vern,

As far as originality, it's a moot point....right..?

If you really feel like you want a project, then I would pull it and put it on a stand, take it down to the block.....find a good machine shop that understands what your intentions are and have a good time doing something new.
It's a hoot if you're not under any time constraints or other "pressures".
BUT.....if you were to call around and do some price and availability checking, you might surprise yourself.
I don't know if you can still buy a Mr. Goodwrench Crate motor....(long or short block)....but I'm sure someone on here will pipe up and let us know.
Both options are enjoyable, and even if it's the first time on an engine swap for you, you couldn't hope to find a more simple project than a GM I-6 in a mid sixties pick-up to cut yer teeth on.
One of the comments I heard when asking around is that it's not worth getting the head worked on without replacing the rings, bearings, and getting the driveshaft machined? Sounds like I either need to just replace the gasket only and cross my fingers or go all out on a rebuild?
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  #17  
Old March 19th, 2014, 02:22 AM
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Default Re: Blown head gasket vs. cracked block

Now that is what you call having a bad day!
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  #18  
Old March 20th, 2014, 01:55 AM
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Default Re: Blown head gasket vs. cracked block

Quote:
Originally Posted by Vern View Post
One of the comments I heard when asking around is that it's not worth getting the head worked on without replacing the rings, bearings, and getting the driveshaft machined? Sounds like I either need to just replace the gasket only and cross my fingers or go all out on a rebuild?
Hi Vern, a lot of mechanics claim that if a fresh head or heads are installed on a worn short block that it can cause the rings and possibly bearings to fail due to the increase in compression because of better sealing valves. I don't buy that, done it many times on race and street vehicles.

Just replacing a head gasket wouldn't change the compression and MIGHT solve your problem. Done that a lot of times too but it was usually obvious coolant was getting in a cylinder or leaking on the outside. It is definitely possible that the head gasket won't help. Just depends more about how much time you have to mess with it, not super expensive to try it.

Oh yeah, had to hit "edit"! I have no idea why you were told that the drive shaft needs machining while doing this work!!???

DAC
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  #19  
Old March 21st, 2014, 06:05 AM
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Default Re: Blown head gasket vs. cracked block

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Originally Posted by GMCDAC View Post
Hi Vern, a lot of mechanics claim that if a fresh head or heads are installed on a worn short block that it can cause the rings and possibly bearings to fail due to the increase in compression because of better sealing valves. I don't buy that, done it many times on race and street vehicles.

Just replacing a head gasket wouldn't change the compression and MIGHT solve your problem. Done that a lot of times too but it was usually obvious coolant was getting in a cylinder or leaking on the outside. It is definitely possible that the head gasket won't help. Just depends more about how much time you have to mess with it, not super expensive to try it.

Oh yeah, had to hit "edit"! I have no idea why you were told that the drive shaft needs machining while doing this work!!???

DAC
What you say pretty much covers what I heard. The idea was that you shouldn't fix "the top (head)" without fixing "the bottom (piston rings, bearings, crankshaft)". The guy I talked to was a racer. I just have to think about the trade off of putting money into an I6 vs the cost of buying and possibly rebuilding a V6. Might be worth the time to try the gasket fix and see what happens.

"driveshaft" was a typo for "crank shaft". The thought being that you should replace the bearings on the pistons, but not on an old crankshaft.
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  #20  
Old March 22nd, 2014, 03:45 AM
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Default Re: Blown head gasket vs. cracked block

Quote:
Originally Posted by Vern View Post
What you say pretty much covers what I heard. The idea was that you shouldn't fix "the top (head)" without fixing "the bottom (piston rings, bearings, crankshaft)". The guy I talked to was a racer. I just have to think about the trade off of putting money into an I6 vs the cost of buying and possibly rebuilding a V6. Might be worth the time to try the gasket fix and see what happens.

"driveshaft" was a typo for "crank shaft". The thought being that you should replace the bearings on the pistons, but not on an old crankshaft.
Yeah it is tough to make decisions on guesses, but that's all trouble shooting is anyway with experience mixed in. There is a cylinder leak down test that can be done also but that will still not tell the difference between cylinder wall or head cracks or a head gasket problem.

A used crank doesn't always mean it has to be turned either. In 1986 I built a 350 with a used, un-machined crank, new standard size bearings on mains and rods. I did check clearances and they were on the loose side of acceptable. Long story short, that engine is still running in my '72 GMC. It is getting tired again but it's only been 28 years!

DAC
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