Why Is This 400 SBC Junk?

[bigsbetter]

My cousin bought a 400 SmallBlock off of craigslist. It's sopposed to have 1000 miles on a rebuild. Guy says he got a rod knock. He started it up for my cousin just for about 15-20 seconds. Anyways, we tore it apart, no spun bearings, but they look like crap. Lots of scoreing and copper. You can tell it was just rebuilt but very poorly. The cylinder walls show an OK cross hatch, but I removed 1 piston and there is some SERIOUS piston scoring going on! The pistons have .007" clearance in the cylinders! I measured the cylinders , just with my dial indicator, and they measure 4.152-4.155 witch would be a .030 over 400, as 400 are 4.125 bore. The pistons say 400 AP .030 on the top of them. And INDIA on the underside. Is the india my problem??? Were trying to do this cheap as his funds are short and its going in a 1969 Chevelle. The 400 had vortec heads on it with no steam hole drilled and it had a blown head gasket. Here's a pic of the piston and I think all the pistons are going to look like this.

 

[Old Navy]

Blown head gasket=water in oil=ruined bearings. Cast piston to wall @.007 and water in oil=ruined pistons. Start over....

 

[bigsbetter]

You know, I said blown head gasket and it was blown, but in a different way than a normal head gasket blows. Normally a head gasket would blow into a water jacket. This one blew between the center 2 cylinders, where the 2 exhaust valves are close to each other. The gasket was TOTALLY GONE , not just leaking but gone, about 1/2 inch of it! I've seen this before on my 21' Scarab 350 and it ruined the head between the 2 cylinders. It ate away the iron and put a groove about 1/4" deep into the head. That's where this motor was going. The was no water in the oil. The gasket did not blow into a water jacket.

 

[Big Red]

You know, I said blown head gasket and it was blown, but in a different way than a normal head gasket blows. Normally a head gasket would blow into a water jacket. This one blew between the center 2 cylinders, where the 2 exhaust valves are close to each other. The gasket was TOTALLY GONE , not just leaking but gone, about 1/2 inch of it! I've seen this before on my 21' Scarab 350 and it ruined the head between the 2 cylinders. It ate away the iron and put a groove about 1/4" deep into the head. That's where this motor was going. The was no water in the oil. The gasket did not blow into a water jacket.

I seen a gasket due what you said water would get into one cylinder and as the piston travled up it would blow it into the next cylinder. This kept the engine from locking up when you where cranking it. It was playing musical water

 

[robwkamm]

the may have NOS the motor before you got her. or really bad detonation can blow a gasket that way also.

 

[ezstriper]

sounds like to me was just a junk rebuild, maybe never got the block/parts cleaned ?? had that happen on the original engine in my checkmate....better off starting with a decent machine shop..also head that they don't drill the steam holes any more to use std heads, but ck on that to be sure....Rob

 

[rhmapes]

If the cylinders look good, have them honed and rechecked for size and taper. Have block cleaned, make sure the galley plugs and cam bearings are removed before cleaning. The crank will need to be turned or at least polished. Depending on your budget, you may want to pick up a set of 5.7 rods instead of the 400 rod. You have to buy pistons anyway. The heads deffinently have to be drilled. This is where your problem started, that and it sounds as if was assembled dirty. The India piston is no big deal I believe Speed Pro has their's made in India. If and when you get it back together the 400 with vortec heads make a nice combo.