I've asked how to tell the difference from PSO heads and everyone cam through. But now, I am very close to pulling the trigger on a set of MC's, but can't tell the difference. I can only go by pics, since the heads are out of state. The only difference I know of is the valve sizes are 2.40"/1.81" on the MC's and 2.30"1.78" on the originals. The guy had a tape rule on the head in a fairly blurry pic and the intake sort of measured 2 5/16" which would roughly be 2.30". But again, lousy pic, sloppy measuring due to not getting rule against valve surface. I wish they would just put some sort of casting marks in the rocker area or something.

That's a 2.300 valve. B1 original.

Looks like that head pictured went through a failure of some sort..

Vavle spacing is the only difference, they moved the exhaust valve away from the intake I believe .050" (Moved Center Line).

That’s what I was thinking. Make sure you check the valves out real good and possibly pressure check it

Scott Koffel was kind enough to respond right back:

Center to center distance on int and ex valve guides would be 1.800 on original B1 and 1.850 on MCL heads. Also intake valve seat would be 2.450 on MCL and orig B1 would be 2.350.Regards,Scott Koffel

At least I was right on the valve spacing, it's been a long time since I messed with them so my mind isn't totally gone. LOL!

Well help me understand something. If the valves run parallel to each other, the center of the stems should measure the same as the center of the valve faces, when the valves are laid next to each other. If the intake valve is 2.40" dia. and the exhaust is 1.78" dia, then the distance center to center of the valve faces would be 2.09". How can the center to center measurement of the stems be 1.85"?

He probably meant inside to inside of the stems. I can check my originals tomorrow.

I was thinking that. I don't know the stem diameter on the B1 valves to calculate that. But if you can send me your measurement, that would be a big help.

Mine are 1.750 inside to inside with 11/32 stems. My heads are from 1996.

Thanks for the measurement. I hope these are the right heads that I am looking for. I'll find out. Hopefully, this will be a late Christmas present to me!

just to second this, my b1 originals are 1.756 inside to inside, with 11/32 stems

Great! So, are MC's 1.80" or 1.85"? Maybe it doesn't matter, as long as they are more than 1.75". Since the heads are on a pallet, I'll just let him measure the intake valve diameter. Shouldn't be hard to determine if they are 2.300" or 2.400".

IT takes about 20 seconds to remove a valve and measure it the right way

Vale dia. won't show stem centerline distance.

My B1MC heads are 1.850...

The MC heads came with Ti intakes so try putting
a magnet on the intakes 2.04 was the standard on
the MC heads

B1Maxx, you can total the distance between valves plus valve stem diameter to determine centerline.

Mr P, stainless valves will not be magnetic either. And I'm pretty sure that titanium was optional, not standard. Either way, I know that originals came with 2.300" and MC's came with 2.400".

Wedgefed, is that inside to inside?

When I bought my MC heads the Ti was the standard
valve