. . . All things considered i'm amazed it ran.

So last night I tore my :almost: 400,000 mile 300 down for its 'post mortem'. It had gotten to the point that it would barely maintain 60 going down the interstate and once you got a load on it try a max speed of 35 in 2nd gear. It was a LONG 90 miles coming home from college. Anyway, I figured it had served me long enough so I read it its last rights and yanked that mother on out of there. I stripped it down to a basic shortblock and got it on a stand in the garage. It was just it, me and an impact wrench. So that motor flew right apart and this here is what all I found:

1st off- Main caps
The inserts that go into the main caps had NO trace of lead ANYWHERE on them Pure copper. The insert halves that go into the block had patches of lead at the very top, but the sides were shiny copper.
Clearance: .004-.005 (wear limit, .003)

2nd off- Rod caps
All of the rod bearings had absolutely NO lead anywhere on them. Pure copper all the way around.
Clearance: .0035-.0045 (wear limit, .003)

3rd- out come the pistons
With just a little tapping #1 piston slid right out. I caught it, held it up, and heard this 'tink' on the floor. I look down adn there's half of teh top ring. Think to self "A broken ring, no wonder it was down on power."

#2 piston came out with a little tapping also. However, when I held up that piston i heard a 'tink, tink'. BOTH rings were busted. Think to self "Broken rings in two cylinders, that REALLY explains things."

To make a long story short, every cylinder had a broken top ring and three of them had broken 2nd rings. 9 out of 12 compression rings came out in two pieces. Then I threw the intact rings back into the cylinders to check endgap, see just how wore out they really were. Any guesses? I'll give you a hint; I could accurately measure it with a tape measure.
Clearance: .125 (wear limit, .035- also explains the 65-75 lb compression readings and 30% leakdown on those 3 cylinders)

Mic'd the pistons and bores, surprisingly these came out fairly unscathed. Pistons measured to 3.997 across the skirt, bores measured to 4.001.
Clearance: .004 (falls in factory specs)

So from the 9 broken rings and the 1/8" endgap on the rings, i'm surprised it ran as well as it did and didn't have issues fouling plugs. All it did was have MASSIVE blowby and wouldn't get out of its own way. Can't wait to get a fresh motor in this thing, see how much power I SHOULD have always had.

Justin

 

These are my rod bearings. The truck has 109,000 miles on it. But it has a bad rear main and the guy i bought it from did not know how the check oil. It sat up in a barn for 10 years and all the gaskets dried up and leaked. so while i was putting a pan gasket on it i pulled a rod and saw that and replaced them all. Didn't make any noise but oil pressure was a little low it's back up now.

All of my cylinders are a 140psi even and the cross haches are still visible.

Just goes to see what the 300 will do.

 

DT 466man just curious if the rods were that bad what did the mains look like?

 

Also add to the carnage list 4 cracked pistons. I was cleaning the ring grooves on #3 out when i felt something stab the palm of my hand. I looked at the piston and a section of the skirt about 1.5"x1" was about ready to pop out in my hand. When I grab the skirt and wiggled it I could watch the crack get bigger and smaller. Further inspection showed one more piston with a chunk about ready to pop out and two that were just starting to crack.

A set is supposed to come in for me on wednesday, so hopefully i'll be running by friday.

Justin

 

Didn't check the mains. Probally should of but i was kind of in a rush so i'll get that done when i start driving my diesel. That's when i'm going to restore the whole truck.

The funny part is the crank was still shiney and no shallow scrapes or discoloring it still looked brand new.

DT