Would a tool like this work below to push old guides out without pushing/destroying seat.
If welding a socket to rest on valve seat and other side weld a ebay valve removal press tool.

My usual method is to drift them out , then drift the new ones in using a shouldered drift and a spacer around the guide to get the correct fitted height before recutting the seats . Sometimes helps to leave the guides in the freezer overnight before fitting .

They can be pretty damn tight in some heads, in which case you'd need a very sturdy G clamp.

As R-N says, drifting them out is the way to go. Buy or make a suitable sized drift that fits nicely into the ID of the guide with a stepped section that just a little less than the OD of the guide. I use a pneumatic air chisel to provide the encouragement rather than a large hammer, more control and less chance of accidentally hitting it at an angle and bending/breaking something.

I was thinking about a industrial g-clamp and extending the handle for extra torque.

The technique you described: Anychance of ripping the seat out if there it no weight supporting it from the other side?

Decent drift, but be careful you don't damage the head

Might be worth speaking to a local machine shop who might be able to press them out for a small outlay ?

your engine looks epic.

what max temperature can you go a head with a butane gas/flame gun.

[Edited on 11/10/15 by bikecarbfred]

So I'm practicing on a spare head.

I used a the correct drift and managed to move the giude about 5mm. Hard hits with hammer then gave up.

If your suppose to freeze a guide to help install it then why warm it up when trying to get it out.

I had a heat gun on it. It's hard to warm the seat it sits on without warming the guide aswell.

You need to drift it out from the cam side of the head into the port as the guide may have deposits on the port side that can jam it. When i worked at an engineering company we used to put the head into an old oven and heat it to 150c before drifting them out of alloy heads to make sure they didnt pickup. If its a cast iron head then just drive them out cold.
Paul

Thanks , that's why it got stiff abit. was hammering it from cylinder side.

I'll do it from cam side.

You may well have to get the valve seats recut to suit the valve guides