LZ23 connecting rods

[Sealik]

Was wondering who had their L20B/Z22 connecting rods machined for their LZ23?
Just realized that the Z22 rods are a little tight in the Z24 piston......only about .012 clearance
Z22s approx 2 mills larger than the Z24s

The clearance for the Z22/Z24 piston and rods is about 3mm.

Obviously my machinist had no clue....resulting in some (most or all) of my issues now.
Blow by...rings not seating...bearing wear etc.

You can see the wear on the side of the rod....from the limited movement (?) of the Z22 rod in the Z24 piston.
....where the pen is pointing in pic....

[q-tip]

as a machinist, clearance is clearance you have a thou(.001) you have a mile. that being said i dont machine engine parts and i dont know the standard clearance on L series rods.

[okayfine]

Con rod end play (at the crank) is spec'ed at .008-.012". I can't find a spec for small-end/piston clearance. I recall having more than .012", but I don't know how as little as .012" would cause any of the issues you suggest. The con rod end play being tight would be an issue with regards to the wear you see.

[Sealik]

The low mile Z22 block was bored to 89 mill.

A local mechanic suggested that if that boring was not 100 percent true from the crank.....or if a torque plate wasn't used (not sure if needed)....then there could be the resulting wear on the con rod, many possibilities I guess.

Just trying to get an understanding before I take the block back.... no doubt get the 'buck' passed to me from negligence and or.

1 theory of many....

Compression was 112 to 124 before I fired it up, with blow by (noticed after I flashed it up)
Never thought anything more about it until I started the motor without the oil fill cap.

http://youtu.be/1JR1onIaxRA

Assumed the blow by would 'get better' after the rings seated.....negative.

Compression readings slowly climbed to 175 across the board....3 percent loss with leak down test

Last check....the compression was 170....leak down tests also dropped to 14 percent
Lots of carbon on the backside of the intake valves from the PCV valve sucking the gases out of the crankcase.



About 5000 kms on engine

The machinist assembled/built the block.
New NPR pistons and rings, bore cylinders, re-size Z22 con rods, polish crank, new bearings etc etc.

[datzenmike]

End play on the crank (forward/backward movement) allowable is 0.012". All four con rods have to fit and their tops have to still fit the gap in the piston. Yeah the Z24 rod tops are way thinner than the Z22/L20B.

[Sealik]

Well...Just got the block back from the machinist.
He shaved .050 from each side of the con rod small/pin end



Now the Z22 rod has the appropriate clearance on the Z24 piston....relative to stock configs

[tristinGrind]

This is good to know... Im about to start this same build. Luckily I have the mills to do my own work for some of it to save a few dollars. Still in the research stages, but looking for a Z22 short block now.