Hi guys!
This is my brothers cylinderhead that will be modified with 40mm intake valves and a 33mm exhaust valves, massive portjob is also included.....
This cylinderhead is made for a street/dragrace engine for my brothers datsun E10.
My question is!!?
I am planning to cut the valveguides against the top of the port, as done in Feral

Removing the valve guide will reduce any obstruction to the airflow that was caused by it's presence. Thats the good part.

The price that you pay for this, is reduced valve guide life, brought about by the reduced bearing surface. A small amount of wear will also result in more undesirable valve movement.

For a street engine, this may be a high price to pay. The guide wears faster, & the valve moves, or wobles more for a given amount of wear, which means that the service life of the head, before it needs work, is reduced.

By how much? I don't know. Shorten the guides, run the engine, & tell us in a few months time.

Quote:
Yepp, I will try it and I don

A good compromise is to machine a steep taper on the part of the valve guide that protrudes into the port. It gives the best of both worlds ie: you still have good valve guide length and the flow restriction is kept to a minimun.
It's funny but just removing the portion of the valve stem that protrudes into the port does lead to far greater wear of the guide.

It

Do it and replace guides every season. Guides are cheap.

Feral you are absolutely right, I just got sick of replacing valve guides every season. It ended up being a pain in the butt.
I went from flush fitting guides to tapered units and could not tell the diffierence. Thats just my experience
It is possible to port the runner prior to fitting the guides then very carefully mate the taper on the end of the guide to the port shape with an engraver. Die grinders are too agressive for this type of fine work.
If you are prepared to replace the guides every season then go for it

Tahnx guys, but I