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Engine Specific Info and Questions => IDI Engine => Topic started by: hippiekiller on January 30, 2012, 06:55:27 am

Title: Cracks in Pre-Cups
Post by: hippiekiller on January 30, 2012, 06:55:27 am
I found a fairly straight head on a parts engine, the only thing is these cracks on every PC, should I be worried enough to replace them before I get the head ground?  I've heard Giles can get them but they can be a B to remove.....Sorry for the picture quality....
Title: Re: Cracks in Pre-Cups
Post by: rodpaslow on January 30, 2012, 07:50:27 am
to each his own, I had 3 precups in the head I use and I replaced them.  The're not that bad to remove and you will likely find the new ones will be a bit loose.  This is normal.
Title: Re: Cracks in Pre-Cups
Post by: RabbitJockey on January 30, 2012, 08:40:36 am
looks normal, but u should remove them and cut them seperately on the top so that the face and whistle hole are never changed
Title: Re: Cracks in Pre-Cups
Post by: belchfire on January 30, 2012, 10:41:46 pm
I have found that some of the cups aren't interchangeable. Some are different volumes too. Unless you're cranking off a lot on a surfacing, I don't think that there should be any appreciable change to the whistle hole to necessitate removing them.
Title: Re: Cracks in Pre-Cups
Post by: RabbitJockey on January 31, 2012, 04:24:10 am
if you surface the head with them in the cracks can catch and they get chipped up on the edges, the pre cups are supposed to protrude a few thousandths, so if you're taking a few thousandths off the deck of the head, you're taking even more off the pre chamber.  they're supposed to be cut seperately and protrude a few thousands
Title: Re: Cracks in Pre-Cups
Post by: kevinm on January 31, 2012, 07:37:42 pm
dont worry. so as long as the cracks dont go into the fire ring.. you can see the imprint of the fire ring on the head