Jeep CJ AMC 401 Engine Failure

DesertCamaro · 01-15-2014, 09:43 AM

My buddy picked up a pristine '76 CJ7. The past owner had swapped in a 401 motor last fall, "freshened up 401 in it" he said. Well, test drive went smooth and he bought it. Less than 500 miles later, developed a knock in the motor. Back cylinders rod bearings failed completely so we tore it apart. It also seems the PO had swapped in pistons that were a fraction too tall, and they were hitting the head.

Luckily the crank looks ok, just needs a quick polish, and the cylinder walls seem good, hopefully get away with a light hone.

He's on the fence whether to go performance build or repair. Performance build, quoted between 2 and 3K. Repair, could probably get away under a grand. I know how everyone likes pictures

toesuf94 · 01-15-2014, 10:02 AM

Wait? They aren't supposed to do that?

ChrisBlair · 01-15-2014, 12:23 PM

If the previous owner had been so careless as to install those, I would not consider a performance build unless I had a good machinist give the block and crank a real once-over and align hone, etc. Who knows what else the previous owner didn't do right.

DesertCamaro · 01-15-2014, 12:48 PM

Quote:

Originally Posted by ChrisBlair

If the previous owner had been so careless as to install those, I would not consider a performance build unless I had a good machinist give the block and crank a real once-over and align hone, etc. Who knows what else the previous owner didn't do right.

Haha seriously. I'm surprised he got 500 miles out of it before it grenaded. Funny thing is, chunks of some pistons are missing, but there's no evidence on the valves. Strange.

JasonK · 01-15-2014, 10:31 PM

Bearings like that,.... and the crank is okay??? No way, I'd get it checked out by a machine shop, the bearing on the left has spun. Whomever "freshened" that motor had no clue what they were doing.

I really really want a vintage CJ. Tell your buddy congrats on it!

01-15-2014, 09:43 AM	#1
DesertCamaro Drives: Fast Join Date: Mar 2011 Location: Phoenix, AZ Posts: 785	Jeep CJ AMC 401 Engine Failure My buddy picked up a pristine '76 CJ7. The past owner had swapped in a 401 motor last fall, "freshened up 401 in it" he said. Well, test drive went smooth and he bought it. Less than 500 miles later, developed a knock in the motor. Back cylinders rod bearings failed completely so we tore it apart. It also seems the PO had swapped in pistons that were a fraction too tall, and they were hitting the head. Luckily the crank looks ok, just needs a quick polish, and the cylinder walls seem good, hopefully get away with a light hone. He's on the fence whether to go performance build or repair. Performance build, quoted between 2 and 3K. Repair, could probably get away under a grand. I know how everyone likes pictures Attached Images __________________ 2014 SS

01-15-2014, 10:02 AM	#2
toesuf94 Drives: THR #11 E-force supercharged Join Date: Jul 2008 Location: Cedar Rapids, IA Posts: 4,746	Wait? They aren't supposed to do that? __________________ Cars and women are both going to give you problems...but you can pay somebody else to fix your car!

01-15-2014, 12:23 PM	#3
ChrisBlair Buick 455 Fan Drives: 1970 Buick, 2012 1SS LS3 Join Date: Jun 2010 Location: Boston MA Posts: 5,957	If the previous owner had been so careless as to install those, I would not consider a performance build unless I had a good machinist give the block and crank a real once-over and align hone, etc. Who knows what else the previous owner didn't do right. __________________

01-15-2014, 10:31 PM	#5
JasonK Drives: 2010 Camaro Join Date: Aug 2010 Location: Topeka, Kansas Posts: 713 View My Garage	Bearings like that,.... and the crank is okay??? No way, I'd get it checked out by a machine shop, the bearing on the left has spun. Whomever "freshened" that motor had no clue what they were doing. I really really want a vintage CJ. Tell your buddy congrats on it! Last edited by JasonK; 01-16-2014 at 08:33 AM.