Bigger valves for early 4.2 head

(Art Ford) #1

I am considering putting the larger valves in an earlier 4.2 head. Is this a problem to do? Someone wrote that the 1 & 7/8 valves had longer stems. If my head already needs new seats I wonder if changing the seats will help accommodate that. Or is there another size between normal and 1.875 that goes well with normal seats and has the correct length? Probably I am better off using std parts if they can be fitted.

(Skip Ohnmacht) #2

Go oversize for better flow, which also gets even better with larger camshafts.

(Art Ford) #3

C’mon people out there. Someone can do better than that.

(David Jauch) #4

I think they fit (if not they can be made to fit), but why not save the trouble and swap in a S3 XJ head and store the other one? I think all you need is to block the rearmost coolant passages and you can of course keep the head studs as long as nobody corrects me on that. You’ll be on the road far quicker, and you can work on the inlets of the foreign head without fear of destroying something, etc.
You can still rework your old head later.
Not sure about the seats but I’d do the inlets while at it. So all the work makes less sense to me.
If in doubt see for literature, or try calling a supplier that can check.