I have a set of heads that I have been working on and about ready to take them to the machine shop and was wondering what size hard seats do I need installed and what size exhaust and intake valves do I need,my machine shop will do the work but he wants me to bring the parts. Any help will be appreciated very much. Thanks

If you supply the valves, the machine shop will know which size of valve seat is needed. Normally, the hardened seats are only needed on the exhaust side.  Are you doing a stock rebuild? You should not have any problem finding stock-replacement valves; you can start with RockAuto. All 57 heads use the same intake and exhaust valves ( 1.925/1.510). However, the exhaust valves are two-piece (welded) and not ideal for performance applications. John Mummert (ford-y-block.com). had stock-size one-piece stainless valves; they aren't shown in Valve Train, but they are still shown on John's price list. The shop that did my heads said that John's SI valves are quality valves.  

ECG-G or ECG-C?

Lorena, Texas (South of Waco)

ECG G

I have to apologize to the teacher who taught me to read; I have "ECZ-G" heads on the brain. 

According to John Mummert's cylinder head identification information, ECG heads are 55-56 272 heads that have 1.78 intake valves. The same size valves were used on 55-56 292 valves and 56 312 valves. All of the exhaust valves are 1.51. 

I'm not aware of any stainless 1.78 intake valves, but you should have no trouble finding stock replacement 1.78 and 1.51 valves. 

Sorry you are absolutely right ECZ G

If you want to install stainless valves, you probably should install manganese valve guides or liners. The shop that did my heads gave me a choice of manganese guides vs liners. I chose the liners, simply because the machinist had never had a problem with them, and it was cheaper than replacing the guides. Cost is always a consideration, but I won't sacrifice quality in order to save a few bucks. 

When I last serviced my head when they were off I installed positive seals and no longer use the umbrellas. I owned the tool from Comp cams and bought seals from Competition Products catalog. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I have the Comp Viton positive seals as well, but I had the shop install them. If you read some of the reviews, you'll find that it's not uncommon to break them during installation. Of course, having the right tool for any job always makes the job easier.