Head rebuild problem, Is this guy a dick head? Options

[DavidSweden]

I am rebuilding my engine a 2.0 from 76. I took the heads in to be reconditioned.
The machinist told me that the valve stems needed replacing, the valves needed regrinding and the seats machined. He said this would be no problem.

He know tells me that the new valve stems are not at the same angle as the originals and after machining the seats the valves sit too low in the valve seats. He says new valve seats are required
As you will understand I am not happy especially when he reassured me that he could do the job no problem.

Is this guy incompetent dick head or is this a common problem,?
Appreciate feed back before I go to the shop on Wednesday.

[veekry9]

The first clue that the shop is not well versed with T4 heads was when they did not insist on replacing the valve seats as a standard service of the rebuild.

Get your heads and find someone who knows T4's

(IMG:style_emoticons/default/agree.gif)
So true,an overheated head will always be prone to dropping the seats.
I find it incredible anyone would consider flying an engine without new valves and seats.
Staking them is a good measure that if done correctly,is a margin of durability.

[HAM Inc]

The first clue that the shop is not well versed with T4 heads was when they did not insist on replacing the valve seats as a standard service of the rebuild.

Get your heads and find someone who knows T4's

(IMG:style_emoticons/default/agree.gif)
So true,an overheated head will always be prone to dropping the seats.
I find it incredible anyone would consider flying an engine without new valves and seats.
Staking them is a good measure that if done correctly,is a margin of durability.

I appreciate the agreement, but have to point out that staking is not an accepted method of o.e. seat retention in T4 heads.

The #1 contributing factor to valve seats dropping out of these (and most aluminum heads) is tired valve springs. All other issues are contributory but secondary.

A vicious cycle that comes into play as the engine ages and gets fatigued, losing power over time. As a result it's revved higher between shifts to compensate. While this is going on the springs are fading and no longer able to control the valves, especially the heavier intakes. They literally pound the seats like a hammer, loosening them. This is why intake seats drop, but rarely exhaust seats.

Heat plays a role, but it's more an issue of the aluminum softening as it heats allowing deformation of the seat bore, than actual expansion of the bore.

Excessive valve lash magnifies the issue by adding to the pounding, this is why hydraulic engines suffered this problem in spades with these engines.