2.06 and 1.66 valves in a 348 head?

[Gofish]

I’ve got a rebuilt, never-fired 348 with some interesting parts. The basics are the 3755011 block, 9.5:1 pistons, but the valves are giving me a big question. The heads are 379 and 256, but they both have 2.06 intake and 1.66 exhaust valves (as I measured them while installed). Everything I’ve read says the valves should be 1.94 and 1.66 from the factory. I’m guessing someone had the larger intake valves added somewhere along the way, but if so, why not the exhaust valves too? Any thoughts or corrections?

 

[Don Jacks]

It's possible that someone put hardened seats in for the exhaust valves.Due to the ease of ruining the heads some shops[Day's automotive for example]will only put the stock size seats in.One of our members runs a set of home ported 333's on his stock stroke 409 and is making over 470 hp with the stock 1.67 exhaust valve in there.I'd be more curious about if they blended the bowl area just below the valve seat for the larger valves.If they didn't,there's not going to be much gain especially on a 379 head anyway.You're right about the stock intake valve on the 379 being 1.94..

 

[1964SuperStocker]

What is the max size valves for the 379's int/exh anyway?

 

[Don Jacks]

I've never heard of more than 2.06 in a 379 head.1.72 exhaust can be used,but that's getting close to trouble.These heads are thin and crack prone as it is.I wouldn't want them on anything but a stocker with a mild cam.You can get 333's as cheap or even cheaper and you'll have a MUCH better core from which to work.