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exeric
06-22-2008, 04:34 PM
I have 2 sets of 1948 OHV heads. Like anything that's 60 years old these days, there are problems. Broken fins on some heads and recessed valve seats on a front head. I have heard that recessed seats will not affect performance and that it's okay to do a valve job on them and run them. I'd like to get other opinions because I'd rather not replace the bronze seats with hardened seats. I have a '51 that has the original Ampco bronze seats and it's been just fine.

bmh
06-22-2008, 07:09 PM
If the valves seat too deeply in the head it will cause at the very least that the rocker arm geometry will be off. That can cause pushrods (especially those with hydraulic units on top) to rub inside of the tubes. It can also cause extreme side loading of the valve stem at initial opening and accelerated guide wear. This pressure will also transfer to the gear case in a fashion and generally make a noisy and sometimes rough running motor. I have also seen were if they are really deep, the upper collar will start beating a hiloe in the cover. My advice is if it excedes the factory service wear limits it should be redone. It may actually run even though it is out of service limits but why do it? Why spend money on replacing fins so things look nice and ignore the mechanical portions? I know some people think of wear limits as guidelines, often these are the same people who consider a rebuild to mean it was disassembled, bead blasted and painted, and put back together. After all it ran before, right? Personally, if i have to take it apart for repair, anything even questionable gets replaced. I guess for me it boils down to $200 now or $2000 later.
Brian

T. Cotten
06-22-2008, 07:28 PM
Stick some oversized valves in it and ride.

....Cotten

koanes
06-23-2008, 09:50 AM
Rowe makes valves that are .060 shorter than stock to correct stem protrusion.

Jack_Hester
06-27-2008, 10:07 PM
I'm with Cotten. You can recut an new seat at the top edge of the old. Then, have Manley or one of the other valve companies make your valves to the head width that you need. They are not terribly expensive to have made. The last I had made were stainless, so I installed Rowe cast iron guides to be compatible with the stems.

Jack

Rubone
06-27-2008, 10:40 PM
Harley-Davidson sold a valve (18082-60) that was 5/32 larger in diameter than stock. It was sold as a fix for deep valve seats and allowed the valve to sit at the original assembled height. It was not for performance, merely to help save all the early heads that were showing problems with deep seats. Those valves restored performance in stock motors and no other changes were needed. You can purchase 1/8 in oversize valves that do the same thing. Run them and enjoy your ride. If the motor is otherwise stock it will perform just as before.
Robbie