6.2 precombustion chamber cups

[Greg6.2]

Is it OK that the cups have small cracks by the openings visable on the deck surface? Cracks are about .100" long. Should these cups be flush or raised slightly?

[Dieselboy]

This was dicussed thoroughly before the meltdown, and I think the general consensus was that so long as the cracks aren't large or long, then it was okay to reuse the pre-chambers. Many folks have removed heads to service other items like lifters and have found them to be cracked, so it's not unusual.

In my opinion, pre-chambers are one of the less expensive components, and I chose to go with brand new ones. If you're doing an R&R, then I would stay with what you've got. If you're building a new engine, then I would get some new ones.

smile.gif

[92gmc]

according to the GM 6.2 maunuals, as long as the crack does not extend into the gasket o-ring (past the fire deck) then they are ok

[Greg6.2]

Thanks for the info on the cracks in the pre-cups. But should they sit flush or slightly raised?. They are currently slightly raised up from the deck surface. (maybe .002")

[mpascino]

Service manual says as long as they are +/- .004 you're all set. Just finished puting in a set of T prechamber, they stick out about .002 also.

[5.7L oldsdiesel]

Prechamber inserts are not cheap......i paid over $100 bucks for one precup.Crazy as far as i'm concerned.Make certain they are flush.If they are dropped below the surface,or even above,you'll have trouble.2 thousandths either way is the maximum i do believe.

[92gmc]

they can protrude 2 thou or sit flush, but NOT recessed, this is because the flat of the chamber sits across the fire ring of the head gasket. If there is protrusion, the flat of the precup will simply compress the fire ring another 2 thou. If the precup is recessed, then there will be a section of the fire ring which is compressed 2 thou LESS than the rest, leading to a weak point

[Greg6.2]

Thanks for the info!