Not to be a buzzkill but those valves are real heavy. I have had the stock size F2 valves made up with 5mm stems (with the stock tulip)....they are still heavy. One problem I found was valve to valve clearance with a real big cam with a lot of overlap. Another problem was getting enough spring with Kibblewhite 5mm guides. That was for an LSR engine but drag racing is the same. If anything I'd go to a 36mm intake (changing the seat) and shrink the exhaust valve (changing the seat again). The F2 port could handle the 36 intake. But where do you get new F2 carb manifolds?
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Horses for courses I suppose Mike. I wouldn't know one end of a drag racing motor from another. The head combination we use, is cost effective, works well for us and they usually give a service life of around 80 to 100 hours.
This will really get you tearing your hair out mate.We use the cast guides with these valves as well.
Never had an issue with valve clearance we haven't been able to sort with the cams we have run.
As for valve train weight, your right it's not the lightest set up in the world, but I'm not a great believer in reving the tit's off these old motors anyway.
A quick overview of the setup used in our road race chair.
Inlet; evo8 S/S valve +1mm @35mm keeper grove needs to be machined, stem shortend, I use 6.5mm x1mm lash caps but you could stellite I suppose. Std seat.
exhaust; evo8 S/S valve std @30mm after .5mm machined off dia. the rest same as inlet.
Megacycle 125-70/75 cam. We run an Ivan Tighe monster in our B motor but I wouldn't wish that on anybody.
I think the spring pressure with Mega cam is around 60lb closed, 100lb open but I need to check.
We haven't stripped any cam tower bolts with this setup and we don't use the braced valve cover.
