Are M20B27's prone to piston slap?

[Adrian_Visser]

since i bought my 84 eta a couple monthes ago it has had what i initially thought was a loose rocker arm, i did a valve adjustment a week ago and it didnt fix the problem. no its not an injector, much too loud to be that. i havent nailed it down yet but i think it's the number 3 or 4 cylinder.
it's the worst at about 1500-2000rpm then it seems to go away. the sound is a knocking clackity clack, since it seems to be coming from nearer to the top/ middle end my first guess is that it's piston slap. it seems to be the worst when cold too.

[pdx 528e]

M20B27s make a hollow knocking/rattle noise from the bottom end, but when cared for this isn't all that common. You can pretty quickly rule out valvetrain noise by opening the oil filler cap while its running and putting your ear close. Your symptom sounds like either piston slap or a wrist pin bushing. Either noise might not cause your engine to give out for 50 thousand miles, however its definitely worth investigating.

To see if its caused by piston slap, fill the cylinders with a squirt of oil when cold and fire it up. Piston slap will be eliminated for a short time after startup, and will return when the oil is gone from the walls. A wrist pin knock will still be there, even if you put oil in the cylinders.

I had a rebuilt B27 with only 46k on it when it started making a lot of cold running bottom end noise last winter. It definitely sounded bottom end but I had my mechanic go through the entire thing anyway. They determined it to be a wrist pin knock. Best guess as to the cause was a cheap rebuilder possibly reusing the wrist pin bushings, or not measuring new parts for tolerance.

[AdamF 88iS]

Piston slap is common on them, yes. It should quiet down once it warms up.

[EtaSport]

I can attest, mine makes the same noise in the same spot. Ive got more miles than most of your etas will ever see. Kinda freaks me out in winter cause its pretty loud, but keeps on ticking away every day and runs strong.

[Adrian_Visser]

yah from what ive read piston slap isnt necessarily a sign of impending failure. and it does go away once its warm. but i hope it isnt a wrist pin bushing, it doesnt seem quite loud enough to be that serious though.

[pdx 528e]

yah from what ive read piston slap isnt necessarily a sign of impending failure. and it does go away once its warm. but i hope it isnt a wrist pin bushing, it doesnt seem quite loud enough to be that serious though.

You can quickly rule out a wrist pin bushing by starting the car with some oil in the cylinders. The oil will keep the piston slap noise from starting right away.