[GTOLou]

I've posted some other pics from this 76 TA that I bought a month + ago. Motor was rebuilt by a reputable shop in mid-south GA about two years ago. 455 +.030, forged pistons and rods.


I drove the motor 4 hours home - ran very well. Pulled it to change heads and to fix oil leak (never could figure if it was rear pan or rear-seal). Figured I do both.




I usually let the pro's do the short block work - so I don't have a decent depth of knowledge as to how these should look. I had hoped they'd look better.

Main journals look very clean - without all of this wear. Only seen a couple of the rod journals - they look pretty good also.

[GTOLou]

I don't know if the pics show it - but it looks like the copper part of the bearing on #2 and #5 is starting to wear through.


Abnormal wear pattern?

Need to replace them?


Anything else wrong?

[Formulas]

Lou .. copper is bad, replace.. Now real low miles makes one wonder why the copper. either starvation or too tight.. the wear looks uniform so i wouldnt suspect a main saddle problem.
check clearances. then go from there.

[gtofreek]

Agree with Formulas.

Also, it looks like it had some fine grit pumped through it. The main housing bore looks like it may have some taper in it on #'s 1 & 2 main caps also. Copper should not show for a long time. Something ate them up in a hurry. All the scratch marks on both rod and main bearings suggests to me that there was foriegn debris in it on start-up. I have torn apart Pontiac engines that have trashed the main bearing so bad that you could lift the crank up and down with the main caps bolted down and the rod bearings looked perfect so I don't think the rod bearings got damaged from the mains. The debris from the main bearings is going to be pumped out the sides of the bearing rather than be pulled into the pressure groove and pumped to the rods.

If you have a flat tappet cam in it, you may want to look at it. Cam lobe debris can do this also. You may have gotten a bad break-in on the cam. If any lifters are cupped or won't pull out of their bore, you have a bad cam.

[RAJNWDY]

I would pull them out, read the size on the back, ie. .020, .010 ect and then measure the crank. It actually looks like the mains and rods may have been over sized just one size. there is no wear to speak of on the sides of any of the bearings and all the loading seems to be up and down. A good oil film will keep a crank pretty steady side to side but the beating it takes up and down are a differant story. If the crank looks fairly good, I would have it mic-ed, checked for cracks, resize or check the rod ends and then buy the right bearings and clearance everything. I would chuck the oil pump for a new one and make sure all the oil galleys are clean and open. I would also check the plug by the distributer to make sure that everything is good there.

It didn't come apart because of the oil, it wasn't that noisy probably because you couldn't hear it but deep down I bet it was making a little noise.
Check your timing and fuel too. detonation will mess with bearings like this too.

[GTOLou]

Build sheet had .020 for the mains and rod bearings. / I did check the main bearings - they say .030 - so I guess that is the truth. Will look at rod bearing sizes.


*Car had very low compression - so I wouldn't think about detonation too much. (4x heads off of a 74 and 30+cc dishes on the forgings.)


*Car did have a HR cam - WITH a bronze gear (first thing I replaced). At least I THINK it was a bronze gear. I KNOW it's not composite.


*The cross-hatch in the cylinders still looks very good. (looks like a two-year old build in a car that was taken car of)


I'll pull the crank and have a good machine shop check the main and rod journal sizes and (I guess) consider a polish if they're okay. Also - I appreciate the advice about the oil pump.








Interesting - I don't really do this stuff.... .I guess I do now. So much for just changing the rear main seal..I APPRECIATE the help - keep it coming.

[GTOLou]

ALLRIGHT - got the crank checked/polished - am going to replace main/rod bearings (WITH the new rear seal - that got me into this).



I was able to REMOVE the crank with the rods/pistons in their bores still - the crosshatch/bores look great - WILL IT HURT the ring seal to remove some or all of the pistons/rings and rods when I put this crank back in???






I've got good access to a ring compressor - If I've careful and keep everything in same place, alignment, orientation, etc. - no problem right?

[gtofreek]

No, it won't be a problem. The rings rotate around the piston anyway so orientation really isn't that important either. As long as your careful and don't chip or break one, the rings will never know the difference. Just clean the bore real good and oil the rings with regular, nothing special 30 wt. motor oil. We like to clean the bores with laquer thinner and then follow up with tranny fluid or motor oil[tranny fluid works a little better I think] on some folded up squares of toilet paper and scrub the bores with that. This will clean them the best. Personally, I would take all the pistons out and inspect the rings for pitting or chips on the face. Also, check the wrist pin movement in the piston. If the grit got in there, the pins will be bound up and hard to move and they will need to be taken apart and lightly honed, and the pins miked and polished up if OK. They should pivot freely with no binding.

One more thing, if I remember correct, you said the piston skirts had scratchs on them? If so, look closely at the skirts for small pieces of metal embedded in them. You may need to pick them out and lightly sand the skirts with some 600-1000 grit wet sandpaper in a crosshatch pattern to tune them up. Scratchs in the skirt won't hurt anything but pieces of steel in the skirts will just keep wearing away at the cylinders. Unfortunately, that stuff gets everywhere and has to be cleaned out real good or it will happen again. I really think you should get the main housing bore checked. Something caused this damage if you didn't find any foriegn material in the oil. It looks to me like the front and second main bore have taper. Maybe .0005"-.0008" would be my guess judging from the wear patterns. This puts more of the load on that one side of the bearing and this helps start the wear cycle.