If you're worried about the compression use 2 or 3 barrel base gaskets. Each will give you about 5-8 thou. Or have a thicker head gasket laser cut there are plenty of firms around that can do that. That head will be fine, some didn't have much of a step on them anyway. It looks like the ports have been opened a bit so you may loose some of the small port advantage but if you're not racing it, why worry?
For normal use the head will be fine, plane as little as possible but also check the barrel for flatness as these can go out of shape too. Then make sure your head studs thread all the way in by hand without washers, thus proving that when your tightening your bolts down your not just screwing against the bottom of the blind hole.
All the 68-466 heads did not come from the factory with a balance pipe, this was fitted with the larger port heads. However that port looks played with. There should be a taper for the first half inch don the small port head, also the port doesn’t look central within the mating surface. They should start at 1 1/8â€ and taper within that first inch to 1 1/16â€. Then be parallel from there. It also looks like 40mm or bigger valves have been fitted, they should be 38mm. Some prefer the bigger valves but on a small port head I find you loose something at bottom end and gain a tiny bit at top.
In a nut shell. You could probably put some flat top/low compression pistons with it and it be fine. But personally I’d look for another head.
A65 heads can take quite a bit of planning......ive seen plenty which still have enough valve clearance left when they have been planed so much that the step is gone and the machining actually extends right out onto the bottom of the lowest fin ..........if you are not wanting to increase compression use a thicker head and or cylinder base gasket.
try to get your machinist to agree to do a MINIMUM clean up (good luck) if you are relay confident in his ability tell him you want a light "witness mark" left, that should stop him just hoeing into it ........i would use the one you have after planning just going by the pic with a min clean up done.
"There's the way it ought to be and there's the way it is" (Sgt Barnes)
You will need to drill the rearmost bolt holes to 3/8 clearance if you use a later barrel too. As for head bolts/studs, use the 71/72 type they have greater threaded length into the barrel, not essential but a nicer job.
Thanks. I think there is a slight taper at the first half inch or so. My measuring skills are not great. The port does look off center. Are people suggesting I have this head skimmed even more and if so, why? Alan - good eye on the exhaust port stub! Kind of a chunky weld there.
i would use that head, it looks fairly fresh, check the mating surfaces with a good straight edge , then with engineers blue on the barrel joint, that will show if its true or not. With provisos, all threads are OK? Valve seats not too pocketed? Guides in decent nick? CR is easy to adjust with gaskets, check the combustion chamber volume with some oil in a calibrated burette on trial assembly , do the math , then decide if its too high or not .
71 Devimead, John Hill, John Holmes A65 750 56 Norbsa 68 Longstroke A65 Cagiva Raptor 650 MZ TS 250 The poster formerly known as Pod