R90/6 Heads on a R75/5

[Deleted User 62]

Hello all, question: I've got one head on my '73 doing the disappearing lash thing, and the only spare heads I've got to use are off a '76 R90/6 engine. I know the part numbers are different for these heads. Are they a direct swap, or are there squish band or other fitment issues I should be aware of? TIA

[Garnet]

The two combustion chambers should look the same. I think the only differance is the rocker mounts. That will be very obviuosly different if the R90 heads are the very late /6. Then you woll need to use the rockers from that head or a /7.

[Garnet]

More on rockers here: http://www.largiader.com/tech/rockers/

[Deleted User 62]

Thanks Garnet, that's the link I was looking for.

[wirewrkr]

Ummm, no one has mentioned the difference in valve sizes.
You may need to screw around with jetting, maybe not

[wirewrkr]

Then you woll need to use the rockers from that head or a /7.

actually, that's not true.
The early slash 6 rockers are inferior to the 76-84 rockers ( no hardened tips) but they will still bolt right on to the little elephant foot blocks, they will just need to be centered more carefully, just like on the early /6.

[Motorhead]

I'd think any jet adjustments will be needed just the setting on the carbs fuel mix screw most likely