Reply to "Suggestions on 4V Head Rebuild"

tomsealbeach posted:

Stock 4V Exhaust Seats vs. Hardened Seats?

The shop I found who is likely the one to do my 4V head machine work (valve grind, clean the head surfaces) on my heads is recommending replacing the OE Exhaust Valve Seats with hardened seats. What is the consensus? Is this needed?

This gentleman has a lot of experience racing 351C's in drag racing so is well versed on them. He says due to the unleaded fuel we run, he recommends this?  

Hardened seats on iron Ford heads are unnecessary and actually redundant.

Here is why.


Ford uses a harder cast iron in there castings then GM does. It's called nodular iron.

Originally insertable valve seats were invented for use with aluminum heads since you really can't keep an aluminum valve seat functioning for very long if at all.

One of the compromises with using an insurtable seat in any head is that the area you are going to install them in has to be thick enough to seat the insertable ring without weakening the valve pockets and the combustion chamber.

Some can't before eventually cracking down into one of the port walls.

The original Ford iron 351c heads seem thick enough if the cast in "velocity" ring has not been removed by "porting" the pocket opening.

That ring kind of reinforces the pocket walls.


The material used in the insertable valve seat (it's an unfinished ring) is cast iron. It likely will be the same as in most if not all of the current aluminum aftermarket heads.

It is actually softer then the original nodular iron in the Ford head. The original Ford iron seat is BETTER. Therefore you should only use them to repair an existing seat to save the head.


The ONLY exception to the cast iron seats that I ever saw were the stellite seats that Ford used in the aluminum 427 heads. Those were never intended to have street use and were used just for the race cars like the GT40 where ultimate dependability was done at a "cost is no object" basis.

You can't break those things with a jack hammer but the trade off is they are terribly difficult to cut the seats on.

You will go through an entire set of stones and will be going nuts resurfacing the stones.


SO, any knowledgeable engine builder is going to know this. So if he is trying to sell you a set of insertable valve seats, he's trying to just make you spend more money with him because he needs it.

Save your money. You don't need them UNLESS the existing ones have been cut so many times that the valves sit too deep or if you have a seat damaged to the point where it can no longer be cut properly.