Slant Six Forum :: h1291 ring gap

: Since I can't get the KB268 in 0.5mm os, I may
: have to use the H1291 pistons. This piston
: has an off-set pin hole, and since a 2.2's
: valves are canted the wrong way (to a 6
: head layout), is it OK to reverse the piston
: so the valve notches match a 6 head? Mopar
: showed doing this in the V8's and GMC also
: has shown this trick on their engines.
:
: Also want to mill the piston tops on the
: H1291's to lower the comp ratio down to
: about 10:1. How thick is the piston top, and
: how close is the top ring to the top of the
: piston? The KB268's had very thin top lands
: but the H1291's appear to have the top ring
: well down on the piston. Expect to take off
: at least 0.100" or more. Also going to
: increase top ring gap to 0.030"
: minimum.
: Thanks
: Smith

Author:	69dart [ Sat Jul 13, 2002 9:06 am ]
Post subject:	h1291 ring gap
I have been reading the posts on ring gap problems and wonder if the H1291 have the same problems as the KB's. Does anyone know what is the recomended ring gap for these, I did not get any paperwork with them. Thank Steve

Author:	Doctor Dodge (Doug Dutra) [ Sun Jul 14, 2002 5:35 pm ]
Post subject:	Re: Sil-vo-lite H1291 ring gap (& H1290)
Quote: : I have been reading the posts on ring gap : problems and wonder if the H1291 have the : same problems as the KB's. Does anyone know : what is the recomended ring gap for these, I : did not get any paperwork with them. : Thank : Steve I set-up an 8-1 CR engine a while back at .020 on the top ring and left the 2nd ring at .014 (out of the box measurement) The engine before that got .018 and showed some signs of top ring butting, but nothing broke. My 12 to 1 CR race engine that broke was running .024 on the top ring and they were butting. I think I will play it safe and run more top ring gap on the the next build-up. Somewhere between .028 & .030 on a high compression race engine is what I'm thinking at the moment. DD

Author:	Smith [ Mon Jul 15, 2002 7:33 am ]
Post subject:	Using H1291 Pistons
Since I can't get the KB268 in 0.5mm os, I may have to use the H1291 pistons. This piston has an off-set pin hole, and since a 2.2's valves are canted the wrong way (to a 6 head layout), is it OK to reverse the piston so the valve notches match a 6 head? Mopar showed doing this in the V8's and GMC also has shown this trick on their engines. Also want to mill the piston tops on the H1291's to lower the comp ratio down to about 10:1. How thick is the piston top, and how close is the top ring to the top of the piston? The KB268's had very thin top lands but the H1291's appear to have the top ring well down on the piston. Expect to take off at least 0.100" or more. Also going to increase top ring gap to 0.030" minimum. Thanks Smith sgw041454@aol.com

Author:	Doc. [ Mon Jul 15, 2002 12:04 pm ]
Post subject:	Re: Using H1291 Pistons
Quote: : Since I can't get the KB268 in 0.5mm os, I may : have to use the H1291 pistons. This piston : has an off-set pin hole, and since a 2.2's : valves are canted the wrong way (to a 6 : head layout), is it OK to reverse the piston : so the valve notches match a 6 head? Mopar : showed doing this in the V8's and GMC also : has shown this trick on their engines. : : Also want to mill the piston tops on the : H1291's to lower the comp ratio down to : about 10:1. How thick is the piston top, and : how close is the top ring to the top of the : piston? The KB268's had very thin top lands : but the H1291's appear to have the top ring : well down on the piston. Expect to take off : at least 0.100" or more. Also going to : increase top ring gap to 0.030" : minimum. : Thanks : Smith The top ring grove on the H1290 & 91s is at .320 (top of the first groove) so there is some room to machine off additional material. If you make a cut off the top, most all of that 2.2 valve notch will be gone, I would keep the pin off-set in the proper direction. DD

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