piston pin bore and rod bushing wear - suggestions?

[A_VAS]

I tore this down recently and found some things with the pin end of the rod that didn't appear happy. Looking for some suggestions on how to rectify this since I don't feel comfortable re-assembling it with same parts and have a repeat.

engine:
4.125 bore, 4" stroke forced induction application <15 psi
427 cu.in. LS based engine
~1050hp
10w30 oil, engine has less than 3K street miles since first assembly. Many of those under boost and not cruising around I imagine
Rods are Compstar "shelf units"
Pistons are Wiseco forgings, I did not order them and have no p/n on them. They use a Total Seal ring set, and pin upgrade to the ".200 thickwall pin" .927 diameter x 2.25
engine is dry sump factory LS7 oiling system

Looking at the pics, the pistons do not show signs of detonation to me really...rings looks good. Bearings were OK.
The piston bores are being galled by the pins
The rod end bushings are getting hammered. The lower 45* or so of the bushing is being extruded out the sides of the rod if you look closely.
it was assembled with a quality assembly lube, on rod and piston bores before the pins were installed (not put together dry)


questions:
-- would this indicate a lack of oil problem? or a too much power / cylinder pressure problem for the components being used?
-- pin oiling is done with 2 scallops on the sides vs. a drilled passage from the oil ring groove
-- For the rod bushings...if not oil related and it is force related...is simply re-bushing to a harder material a common option?
-- recommendations for pin to bore clearance of rod and piston in this application? tighter side or looser and why?

Pin fit to the bushing and the pistons was not measured initially...the pins slide freely but I do not have measurements to say whether it had .0005 or .0015 clearance for instance.
I plan to set the pin fitting closely this time around.
Do pin to bore clearances need adjustment for dry sump vs. wet sump? seems to me it should not matter there.

Thanks for any comments

[blownzoom440]

I am just guessing but I think the lack of oil.

[Roundybout]

That pin wall thickness doesn't seem to be lacking. How much vaccum is that dry sump producing? In my opinion you'd want to open up the clearance a bit instead of tightening it. Anything that helps get lubrication to the pins is a plus with a drysump/vaccum pump. DLC coated pins would help a bunch here too.

[pamotorman]

don't LS-7 blocks have piston cooling squirters ??

[GOSFAST]

You need to be at a minimum of .0015" pin/piston, even a bit more maybe??

Same for the rods!

Thanks, Gary in N.Y.

P.S. Also need some "pin-oilers", if they are there in the pistons I can't make them out from the pictures. You want the holes on the bottom of the rods (where they are shown) and the tops of the piston pin holes! These are the two highest load points.

[oldjohnno]

The piston and rod looks like it has been awfully hot, perhaps because of blowby. Hot enough to affect the lubrication of the pin?

[MadBill]

How do the upper rod shells look?

[A_VAS]

Replying to all in random order:

my pic of the rod bearings came out blurry...will get another. I did not see serious detonation looking damage to the upper bearing. Some grooves from trash (the center 3 mains were chewed up).

this Ls7 does not have the squirters for piston cooling, early engines did not have them.

I think the colors in the pics are a little off from the flash...the parts don't appear like they were hot in looking them over.

I too like the idea of a passage direct from the oil ring groove to the pin...not sure why these were produced without the holes.
I also noticed the bushings in the rods, are not perfectly lined up to the feed holes in the rod. So about 1/2 the passage is blocked.

So I'll check with Wiseco, see if that missing oil channel is a 'mistake' or if was ordered that way. Unfortunately no part no. order no. or anything marked on the part.
I'd like to get the oil holes drilled, and will look at running extra clearance on the pin fit.

I really don't know how much vac the dry sump creates...from what I see the system is not a true dry sump, sort of a hybrid..so I'm guess it is not much of a vacuum generator.

Thanks for all replies

[hoodeng]

Piston pin deflection??? maybe? , is the rod pin bore waist-ed in the middle compared to the area just inside the extruded part of the bush in the vertical plane?
Did you have to drive the pins out or did they slide out ?

[MadBill]

I think it's all down to load vs. lubrication. You need major pin oiling enhancement.

[Mark O'Neal]

There are no forced pin oilers because the oil ring is in the pin hole. Oil supply is not a problem, unless there is not enough oil on the cylinder wall. Pin fit should be a minimum of .0008 and a maximum of .0015, is suspect it was shipped at .0005.

15 psi isn't enough to cause this in and of itself.....but I wouldn't hazard a guess without having the parts.

[A_VAS]

Piston pin deflection??? maybe? , is the rod pin bore waist-ed in the middle compared to the area just inside the extruded part of the bush in the vertical plane?
Did you have to drive the pins out or did they slide out ?

on the last pic, you can see the galling in the pin bore, I'd say it is pretty even all the way from the inboard side of the bore to the spiroloc groove, on the upper half.
The lower half of the pin bores also have some galling, but not as much. I was wondering if the piston or pin is flexing too...but with the even looking wear I don't believe it is.

The pins on 3 of the 8 had to be driven out...5 of the 8 seem to float ok but still have some early signs of the galling/wear. Worst one was cyl. #1 which is pictured

[A_VAS]

There are no forced pin oilers because the oil ring is in the pin hole. Oil supply is not a problem, unless there is not enough oil on the cylinder wall. Pin fit should be a minimum of .0008 and a maximum of .0015, is suspect it was shipped at .0005.

15 psi isn't enough to cause this in and of itself.....but I wouldn't hazard a guess without having the parts.

ok thanks...makes some sense on the pin oiler drilling...although I think if they were drilled it would better put the oil where it is needed, vs. having to migrate from the outside to the pin interface.

To try and salvage these pistons, I need to have the bores honed a few strokes and see if we have less than .0015 after cleanup. If too loose, I guess new pistons or see if an oversize pin is available

[mag2555]

What do the plugs look like in terms of heat range and detonation?

[pamotorman]

I always pre lubed my piston pins, rod end bore, and piston pin bore with moly kote and oil mixture on assy.