Engine knock

Waiting Falcon · #1 01/19/15, 07:01 PM

Half way interested in a 76 gmc motorhome. He said the engine has a knock.....
What would likely be the reason?Bad fuel? too low octane? or something far worse?
I have not had the chance to go see it yet....

HuskyBoris · #2 01/19/15, 07:37 PM

rod knock,probably needs an engine

FarmTechnician · #3 01/19/15, 11:43 PM

A rod knock is what you hear when a connecting rod "bounces" on the crankshaft as it moves up and down. This is usually caused by low-oil conditions. Eventually the rod will break and exit the crankcase in a violent manner.

Waiting Falcon · #4 01/20/15, 09:01 AM

I have not seen the rig yet. He said the knock comes from the top ,,He thought it was a lifter, wrist pin or maybe a piston but he thought definitely not a rod.
So how much does it cost to rebuild? do you have to get what is in the rig or would a newer motor /short block work?

Darren · #5 01/20/15, 09:26 AM

You can swap another engine in to the rid. Chevy drivelines are simple as far as compatibility. You shouldn't have a problem finding an engine. Finding a carbureted engine for a swap may be more difficult. A local junk yard that sells parts should have a set of Hollander manuals that will tell you which engines are direct matches.

I have no idea what it would cost to rebuild. That varies with the amount of machine work needed to prep the block which depends on the wear and where you're located. You could always buy a remanufactured short or long block like a Jasper and use that. Places that sell Jasper rebuilds usually have a prominent sign.

FarmTechnician · #6 01/20/15, 10:35 AM

I'm a machinist and I would charge about $200 (+/- $50) to resurface the deck, turn the journals, bore and hone the cylinders, etc... Some charge upwards of $500 depending on the type of engine (some engines take a couple of hours of set-up for a single pass).

Expect to pay about $800 for all the parts in a master rebuild kit (new gaskets, pistons and rings, connecting rods, etc.).

$1500 is a good ballpark figure to start with. Used 350s go for about $800.

Waiting Falcon · #7 01/20/15, 11:04 AM

This GMC has a 455 Olds
Does that make a difference?

FarmTechnician · #8 01/20/15, 11:10 AM

The 455 seems to be a rare engine, produced for less than ten years. I would expect to pay a bit more for that puppy. I would recommend finding a used 454 for less than a grand with 40k on it and pray the bell housing won't need to be replaced otherwise you will be into drive shaft/transmission mounting territory.

Darren · #9 01/20/15, 11:19 AM

Someone, somewhere would give their left you know what for that engine. Don't scrap it.

FarmTechnician · #10 01/20/15, 11:25 AM

Quote:

Originally Posted by Darren

Someone, somewhere would give their left you know what for that engine. Don't scrap it.

SHHHHH! How else am I supposed to restore a 70's Cutlass for cheap when I can't haggle? LOL!

He could almost buy a short block crate motor for what he could sell that engine for.

Darren · #11 01/20/15, 11:38 AM

That engine is a beast. A friend gave away a van with a 440 to a guy for junk. I wasn't the only one in shock when I heard.

fordy · #12 01/22/15, 05:29 PM

Quote:

Originally Posted by Waiting Falcon

Half way interested in a 76 gmc motorhome. He said the engine has a knock.....
What would likely be the reason?Bad fuel? too low octane? or something far worse?
I have not had the chance to go see it yet....

..............Is it front wheel dr ? Gm mfged. some really nice motor homes along that time period which utilized the front wheel drive engine and tranny from the OLDS Toronado and\or the Buick Riveria.....same thing I believe . They are very much in demand and sell quickly when you can find one that has been properly maintained . Not that many were mfged . , fordy

HuskyBoris · #13 01/22/15, 06:27 PM

ditto on what fordy said

http://en.wikipedia.org/wiki/GMC_motorhome

fordy · #14 01/22/15, 06:29 PM

Quote:

Originally Posted by Waiting Falcon

Half way interested in a 76 gmc motorhome. He said the engine has a knock.....
What would likely be the reason?Bad fuel? too low octane? or something far worse?
I have not had the chance to go see it yet....

............There are several vid's on these GM motor homes ! , fordy

Waiting Falcon · #15 01/23/15, 08:50 AM

This one sold which really needed to go to someone that could do their own work . The motor was going to have to be rebuilt...more info led me to believe it was the piston skirt. The windshield was also cracked and needed replacement.
I still want one and yes they are collectors items not the reason i want one but really as RVs go they are in a class alone .