Hollow stem valves

[Ed Wright]

Originally Posted by Rob Wright

It generally just didn't look as smooth with more deflection near the nose and a little bit of drumming at the closing point. 150 lb less spring Force cleaned it all up and made it look beautiful.

High spring force is definitely not your friend all of the time.

Wow! I don't have to lose 150 lbs on the seat for my valves to start hitting the pistons. How much did you originally have on the seat?

[Greg Hill]

A smart guy told me one time that the lighter you make it on the valve side and the stronger you make it on the push rod side the better off you are. That being said the lighter the valve the less pressure you need.

[James L Miller]

I was watching a video with Billy Godbold and Scooter Brothers and they said they built a system for a restrictor plate NASCAR engine that had 70 pound spring pressure on the seat and something like 140 pounds over the nose. I'd like to know the rest of the details on that build.

[SSGT Mustang]

Originally Posted by James L Miller

I was watching a video with Billy Godbold and Scooter Brothers and they said they built a system for a restrictor plate NASCAR engine that had 70 pound spring pressure on the seat and something like 140 pounds over the nose. I'd like to know the rest of the details on that build.

The NASCAR guys use 6mm and 7mm hollow stem titanium valves, high rocker ratios, and perfect valve train geometry, which helps them run lower spring rates. Though I'm not sure that they are as low as 70 lbs on the seat.

Nevertheless, those low spring pressures and rocker ratios don't seem to work for drag racing.

[rx dealer]

Originally Posted by Ed Wright

Wow! I don't have to lose 150 lbs on the seat for my valves to start hitting the pistons. How much did you originally have on the seat?

Ed. that was my thinking originally throw the biggest valve springs but once again the spintron proved me wrong. Went from 850# to 700# ...Luke SS 311

[V M Kauffman]

Ed
One thing everyone forgets is the results on exhaust side can be questionable because in the real world the exhaust valve is trying to open against cylinder pressure on the spintron there is no cylinder pressure!

Originally Posted by Ed Wright

Wow! I don't have to lose 150 lbs on the seat for my valves to start hitting the pistons. How much did you originally have on the seat?

[Kevin Panzino]

Originally Posted by V M Kauffman

Ed
One thing everyone forgets is the results on exhaust side can be questionable because in the real world the exhaust valve is trying to open against cylinder pressure on the spintron there is no cylinder pressure!

Correct. But that force goes away the moment you lift at the stripe and the engine is still at high rpm for a few seconds....

[Ed Wright]

Originally Posted by V M Kauffman

Ed
One thing everyone forgets is the results on exhaust side can be questionable because in the real world the exhaust valve is trying to open against cylinder pressure on the spintron there is no cylinder pressure!

My intake valves are the close ones. I run both as close as I have learned I can get away with. I run my intakes at .040". Have gotten by with .036". Lose 100 on the seat, they hit.