[buds56]

I have my 59 389 heads at a machine shop and they need new valves.

The Intake valves have an odd step machined in the stem, looks factory, I've never seen it before..

Does anyone know the reason for this and is it really necessary?

Thanks, Bud

[pfilean]

Don't remember for sure what year but it was about 59. Pontiac had a small hole in the side of the head and a passage to the intake that was supposed to relieve vacuum in the intake valve guide to prevent using a lot of oil at idle. Didn't work well and most had the holes plugged by the dealer when customer complained about idle quality. I can't say for sure but maybe those intake valves were used in that system with the step in the stem.

[Bill Hanlon]

'57 Pontiacs had that vent hole to the intake guides. So did '57 GMC (Pontiac V8s) like mine. Cross section drawing including cut down valve stem here: http://chevy.oldcarmanualproject.com...5559mm403.html

[buds56]

Thanks for the info.

They had some unique thinking in those days.

I have to get new valves and probably guides too and wanted to be sure I wasn't missing anything important.

Thanks again, Bud

[Teej]

Originally Posted by Bill Hanlon

'57 Pontiacs had that vent hole to the intake guides. So did '57 GMC (Pontiac V8s) like mine.

My '58 370 also has these vent holes.