JPM head drilled to 101.6 (stud pattern question)

[fastbus]

Hi Loungers,
                 I'm slowly building an oxyboxer and i'm planning on using a set of JPM heads which look like they have 94mm stud pattern spacings.
These heads have been apparently cut for the 101.6 cylinder liners and are now showing through on the the stud inserts, where the liners meet the chamber in the heads.

Is this common practice or should the stud spacings have be drilled from a blank head to accept the correct pattern?

Any helpful and grateful advice is appreciated.

Cheers
Paul
 

[richie]

Not exactly sure what you mean? they are either 94bore or 101.6 bore, 94 bore opened up to 101.6 would have the stud holes in the cylinder sealing area

This is what the chamber side looks like on my JPM head

[richie]

Just to be clear, that is a 101.6mm head

[fastbus]

Hi Richie
Cheers for the pic. Your head chamber is showing more
metal against the barrel. Can this be a weak point to the head barrel sealing point?

[richie]

Hi Richie
Cheers for the pic. Your head chamber is showing more
metal against the barrel. Can this be a weak point to the head barrel sealing point?

Shouldn't be, mine have been opened up slightly more since that pic so they fit all the common available cylinders, before we cut the cylinder to suit

cheers Richie

[spoolin70]

Hi Paul

Mine have broken through slightly more than Richie's in his pic - the top couple of mm of the wall has gone and the rest is pretty thin. A good poke with a screwdriver and it would all break through completely. Sorry, no pics though, they aren't with me at the moment.

I did question this and it was pointed out that the cylinder seals on the top mating surface to the head so any area that does break through (on the side) is effectively covered over by the cylinder.

Hope that makes sense
Darren

[fastbus]

Cheers guys. Your answers are very much appreciated.
 

[neil68]

I was recently looking at some 101.6 mm MS230 heads for sale.They appear to have broken through at the stud holes, but the cylinder sealing should be fine: