[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.

[GTOLou]

Thanks freek - great info. No, the piston skirts look okay in this motor.


I'll do what you said about cleaning, inspection.



Thanks.