74 Lotus w/ minor/micro cracks in piston sleeves

While replacing the head gasget on a 74 Europa I notices some minor horizontal (going around the cylinder, NOT up and down) cracks that were visible about midway down the cylinder sleeves, they can be barely felt by touch. I checked the compression and it was around 150psi, is this a condition I need to worry about?

Re: 74 Lotus w/ minor/micro cracks in piston sleev

Are you sure they're cracks? Could they be better described as scratches, or even "built-up" deposits?

Re: 74 Lotus w/ minor/micro cracks in piston sleev

They seem to be something like stress cracks, they were so minor that I thought they were stains and rubbbed the cylinder with my fingernails to see if I could feel anything and I did in some spots, so I think they are some type of cracks, as well, they are jagged and not simply where you might expect the piston to have rested or rings to have rested and made a scratch, two other guys looked at it also and we all agreed it was some kind of cracking or something but none of us could figure how they got there or exactly what they are???

Sleeves? Are you sure there are sleeves? Its an Iron block with pistons running directly in the block, from the factory any way.

Re: 74 Lotus w/ minor/micro cracks in piston sleev

Regardless of sleeves or no sleeves it sure does not sound good. No coolant leakage?

Bruce

Re: 74 Lotus w/ minor/micro cracks in piston sleev

Any other items of note? For example, why were you replacing the head gasket? Has the engine overheated or otherwise misbehaved? Could the coolant have frozen at some time?

Re: 74 Lotus w/ minor/micro cracks in piston sleev

Oddly, I have this in one of my own. Back when I first saw it, in '75, I was in abject panic. Thought of delaminating, overheat damage (tho I'd never boiled it), poor casting due to lower than necessary temps to keep iron from "folding" when cast... the engine had done 80K to that point, we were befuddled. We're talkin' metallurgists, N.D.T. Nuclear Grade Inspectors, MetalMites all, here. Concluded there was aught to do but have it bored +.010, inspect and reassembled it. Ran it for 11 more years, nearly 100K, and will repeat the process again. Still suspect "folding" as the answer. The "cracks" are quite "tight" here. Evident, but it doesn't ~seem~ to matter to the overall running. It may allow a somewhat premature ring wear but not that I've noticed with a relatively stock engine ("SE" cams).

I've been into many, MANY kent engines in my time and only now have I heard anyone else with this, almost forgotten it! I'll check engine number and report back. Mebbe there WAS a batch run at temp's too low for homogeneity. Fascinatin' ain't it?!

Re: 74 Lotus w/ minor/micro cracks in piston sleev

Very interesting... I am interested in learning what you discover. Will be checking back a bit later. Thanks for the post.

Re: 74 Lotus w/ minor/micro cracks in piston sleev

Yes please let us know.

Bruce

Re: 74 Lotus w/ minor/micro cracks in piston sleev

The show so far: Like an archaeological expedition!

The engine number here is LP6073LB-A. Is that close to the unit you've got, Eric?

This unit had 24K Mi. (@ 8 years old) when rebuilt and I saw the "craze" cracks. Bored +0.020", ran for YEARS (60+ K ~hard~ Mi.), then cross-hatched the bores and installed new rings. Went roughly another 25K before it was yanked and is now patiently awaiting its turn, behind the MGB project completion, before it gets another renewal.

Have an earlier block, #LP4700LB-A at +0.040" (the way I got it) with NO evidence of the "crazing", and another (later, originally a Stromberg head) in the +2 I haven't checked the number on, but sure it had no cracking either.

Re: 74 Lotus w/ minor/micro cracks in piston sleev

Any block numbers Eric?