Thread: 390 Valve Upgrade?

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Rebuilding my 390 in a 67 Mustang after 20 years. My question for you is it worth upgrading to stainless, undercut valves? If it is, then I would need to go to larger valves as I can't find s/s intake and exhaust in stock sizes. I ported and polished way back when and don't want to switch to way to expensive heads if I'm not going to gain anything. Your input would realy help!

If it's a street car, probably not worth the expense of undercut valves. The undercutting would only marginally improve flow and you'd have to have the heads on a flow bench to see that little bit of improvement.....Just good stainless valves would work, but probably should also consider hardened seats for the exhaust if that hasn't been done yet.....

Hardened seats are part of the build. Looks to be stainless is the best way to go for a hot street set up. Thanks for the replay!

If you have any problems locating the valves you want, might want to get hold of either Pat McCarthey or Jerry Clayton here on CHR, I'm sure they can help you out.

Thanks for the quick reply. Hardened seats are in the build. Looks like stainless is going to be the best for a hot street set up. Will have to go larger. Thanks again.

Originally Posted by Parts-Geek

Hardened seats are part of the build. Looks to be stainless is the best way to go for a hot street set up. Thanks for the replay!

most of the stock EX valves are going to be a grade of stain less steel . parts should not to hard to get over all on them valves look like 5.435 and 5.450 with a 330 tip your machine shop that is doing the head work can get the valves for you .when i build heads i like to get the valve s most of the time. one thing i will add here is on the 390 heads putting hard seats in needs to be watch heads can get screwed up very ez