[PLAY400]

Tearing apart a 400 I had done but not run. Assembly was done by shop. I have what looks like sprocket marks, uneven scuffing (chatter) on my rod bearing and full scuffing on different sides of the mains. Not even across the surface but one side side of 1 bearing, other side of bearing on next journal etc. It's like the mains were polished on an angle.

To me the scuffing looks like the engine was put together tight. engine has not been run and was well oiled.

I have never put together a new rotating assembly nor torn 1 down before. What gives? Thanks Alan

[wheelspin]

Need some pics in order to help determine the cause and the appropiate fix.

Les

[trim]

I am guessing that they put all of the rods on backwards and the scuffing is from the chamfer on the crank.

[PLAY400]

Try to post pics of main and rod bearings. Motor has only been spun by hand.

[PLAY400]

last of them. Normal or problems?

[wheelspin]

How much force did it take to rotate the assembled short block?

The minor scuffing does appear to be from tight bearing clearances or out of shape journals. First mic the bearing surfaces of the crank mains/journals/rod big ends and the assembled bearing shells to determine the existing bearing clearances. Some of the scuffing appears to be caused by poor housekeeping (debris) or mishandling the bearings. If in spec, clean the main and rod bearing shells, lightly Scotchbrite the obvious scuffs, assemble with a quality moly paste assembly lube, and be sure to prime the engine's oil galleries with a priming tool thru thru the dist. hole.

Les

[PLAY400]

Seemed to spin easy, major reason we tore it down was to 0 deck the block as the pistons were too far down the hole.

Mains are slightly out of round when checked with a bore gauge so we are now line honing the block, crank measures different any place you check it so it is now being .010/.010, and the big rods all measure different so we're redoing them. Every component has atleast 1 issue, even the block which was bored and honed has a .005 taper in most holes.

[pro-tour79]

.005 taper !!! that's more than the piston to wall clearance.

[Jack Gifford]

Doesn't sound like they got much of anything right! I'll bet you're glad you needed to deck it, and thus tear into it, huh?

[PLAY400]

Originally Posted by pontiac jack

Doesn't sound like they got much of anything right! I'll bet you're glad you needed to deck it, and thus tear into it, huh?

You bet!! Would have run it, blown it, either piston or crank, taken back to the original shop and been told it was abuse and "you know Pontiac is famous for weak bottom ends". If shipping and Canadian Customs weren't such a pain I'd get on a program with 1 of the US builders on this site. SD is up here but I get the feeling David doesn't wants to bother with the little dogs anymore.

[Jack Gifford]

Oh well, keep educating yourself on Pontiacs, and put it together right ("right"="carefully"). There's a wealth of good stuff on these forums!

[Geoff]

I cannot see that those marks would be made by the crank. From the pics, they look more like packaging marks. The soft bearing material is susceptible to corrosion & acid attack. Maybe other metal parts were in contact/rubbing during shipment? Galvanic action corrosion from unlike metal[s]?