Cylinder Head Swap?

[Shuriken]

Are the 1978 and 1980 (standard) cylinder heads interchangeable?

Ben

[skids]

Re: Cylinder Head Swap?

I believe that there is a difference in the intake valve/seat diameter.

Originally posted by ae7f
Are the 1978 and 1980 (standard) cylinder heads interchangeable?

Ben

[Shuriken]

So that would create piston clearance problems (?) and the answer would be "not interchangeable" then, right?

Ben

[skids]

The valves certainly are not interchangable from head to head. I would be inclined to try the complete head though, Ben. Take caution as I have not done it. Has anyone out there done it?

Originally posted by ae7f
So that would create piston clearance problems (?) and the answer would be "not interchangeable" then, right?

Ben

[sixtysix]

I know they changed some stuff on the cylinder head for 1980, valve size was changed, combustion chamber shape. I think the 80 got bigger valves to try and make up for the HP lost due to other emissions regs. Like the non-adjustable vac advance. I am not sure they would interchange.

[Shuriken]

The reason I am inquiring is because I have a 1978 for parts. It has a good set of carbs I cleaned recently and good guages. If not much else I need is interchangeable I'll get rid of the partzer.

Ben

[fusionking]

Of course they will interchange! Just swap out ever else it takes like pistons etc... Sounds Like more power could be on tap though. Older heads (smaller chambers) newer valves (bigger) newer pistons or big bore which would already have bigger valve notches. You can bet this has already been done. Garry

[Shuriken]

Thanks for the replies everyone.

So.... I use my existing 1980g cylinder assembly. I bore it to fit the Wiseco kit. Install the new pistons. Use of the '78 head is okay because it has smaller valve dimensions and won't interfere with the new pistons, which already give more valve clearance?

Correct or not?

Would the reduction in power due to use of the '78 head be enough to justify just rebuilding the '80 head instead and using it? I'm power hungry and want this bike to get the 95hp back and be able to run as fast as I've heard they can.

On a different note, I also went through the carbs that came off of the '78. Would there be any performance difference between different years of carb banks?

Ben

[Dennyz]

My experience has been that '78-'79 carbs are easier to tune for performance over the '80-'81. That said, both sets of carbs can be dialed in to do what they were designed to do.

The '80-'81 set has emission considerations that the '78-'79 set does not.