Posts: 1050 Location: Greenbackville, Virginia, USA
Yes, KR heads will fit a KH, BUT you wouldn't get any benefit from them without doing all the relieving that goes with a KR. Check out Eric@Beauty of Speed's web site. He has the drawings, pics and specs on it, and also a copy of an article about Jerry Branch detailing the mods. And to avoid detonation the mods have to be done right. G
I run KR heads on my KH, and there is no real difference, other than they had no cracks when I started to run them, and have been pretty solid against cracking so far. (I am now knocking on my head, the one on my shoulders). I did get a small crack that I peened in the rear head. I like the brass inserts that the KR heads have, and as long as they have not been greatly modified, as is often the case should be a good substitute, but will likely not gain you any power. They look almost the same on the inside as the KH, combustion chamber wise. The brass threads seem to make it easier to put in, and take out the plugs, but the threads run all the way to the inside edge of the combustion chamber, so you have to use a longer reach plug. No big deal. I use NGK B8ES, or Champion N4C. The NGK's seem to be easier to find these days, and run a little cooler. They also have 6, 7, 8, and 9 in the series for you to play with. I just like the 8's.
kr heads r better than k or kh. they have relief around valvela for better breathing. also shelf angle is diffrent also brass insert. some people on krs cut cly. down and re did heads. lot of heads have had mod work done to them very hard to find stock ones. if u get make sure u check clearance over valves and piston. i have seen probbley 50 sets of heads lots of diffrence. i have several sets most diffrent. check kr manual for clearenances. try to keep com. down for better breathing and heat problems caused fron hi compression