Valve guide reamer size?

[sprint]

What size reamer is required to do the phosphor bronze guides on a SR head, 63 RGS.

Exhaust valves are Hepolite V128's, don't know what inlets are but I assume that they are reamed to the same size?

[wardleybob]

I'm sure there different sizes ? You need 2-3tho Clarence .

[muskrat]

I think your right Bob. In the book it says 0.310" for both but the new ex valve is 0.3095" to give a tad more clearance. 2 thou clearance max on the inlet will give 2 1/2 thou on the ex.
Cheers

[sprint]

Thanks for the replies.

A 5/16" reamer is 0.3125 which should give the right clearance of 2.5" to 3.0" thou? Assuming that you are referring to valve stem dia's of 0.3095 to 0.3100?

[Briz]

Yep; 5/16" reamer works great. Which I'm pretty sure is what the factory intended.

[trevinoz]

Just for the record, bronze guides were only used in the alloy heads until some time during 1957. Iron guides were used thereafter and were also fitted to the early A50/65.
Whether it was to save money by using the same guides in all heads or some other reason, I guess we will never know.
I have iron guides in my alloy heads with no issues, except for the '54 head which needs new guides.
According to the parts book, the change was from CA7SS 4025 & CA10R 5603.


Trev.