[Lucky161]

From what I understand one of the things that helps make the Racesaver series more affordable is the spec Brodix aluminum head. Aside from being $1200 fully assembled, it uses soft valve springs. Apparently the valves will float at 7000rpm. I can see where that could save the bottom end as well as lower costs by allowing more stock parts to be used in the short block. People say they are getting 2-4 years between rebuilds on these motors. My question is, does floating the valves hurt the valve train itself? I can also see soft valve springs requiring less frequent and less costly head overhauls. Would that be correct?

[Tim]

Originally Posted by Lucky161 From what I understand one of the things that helps make the Racesaver series more affordable is the spec Brodix aluminum head. Aside from being $1200 fully assembled, it uses soft valve springs. Apparently the valves will float at 7000rpm. I can see where that could save the bottom end as well as lower costs by allowing more stock parts to be used in the short block. People say they are getting 2-4 years between rebuilds on these motors. My question is, does floating the valves hurt the valve train itself? I can also see soft valve springs requiring less frequent and less costly head overhauls. Would that be correct?

Lucky,

The softer valve springs are also needed due to the engine rules mandating flat tappet cams, no roller or mushroom lifters. The roller cams will allow much higher spring pressures and valve lift and, therefore, more engine power and stress on the lower end. I believe the rules also mandate a maximum valve lift.

I'd steer away from most "stock" parts in the engines. The crank should be forged rather than cast. Chevrolet/GM put forged cranks in some pickup, and maybe other, applications, but I don't believe they had a forged 305 crank. If I'm wrong someone please correct me. You also want to have better rods than stock, as well as pistons (the hypereutectic may be OK, but I'd go for forged pistons myself).

Floating the valves is never good. As far as head rebuilds, I understand the RaceSaver rules to require re-certifying by Brodix after any head work, which indicates to me the heads will need to go to them for any rebuilds. Also, don't forget there is a compression rule and crank weight rule. The engines will need to be certified by Smiley (or the organization you're racing with), and sealed.

Tim Simmons

[Lucky161]

Thanks for your reply. However, it didn't really answer my question. My question wasn't about the advantages and disadvantages of different types of cams. That variable has been taken out of the equation.

I'll try to restate it so that it makes more sense. What is happening to the valve when it floats? Is it hitting the piston? If so does it always do that, sometimes do that or never does that? On the other end, what is happening? Can the valve damage the lifter or can the lifter damage the valve? Or is this just a temporary loss of power and rpms that will go back to normal when the rpms drop enough for the valve spring to catch up?

The other things you bring up, while probably pertinent to a general engine question don't seem to me to be important considerations concerning my question. Whether or not the heads go back to Brodix for rebuilds shouldn't matter in the context of this question.

The reason I am being so specific is that I don't want this topic to just bounce around with little tidbits of information here and there, but never answering the specific question.

I plan on starting a thread to discuss pistons too.

[badcoupe]

Valve float is when the spring can no longer hold the valve closed because of the speed of which the engine is turning. It isn't hitting the valve. While it's not the best thing on a lifter it doesn't nec damage it either. REV valve springs and components has a good video that shows valve float on a actual running engine it's pretty neat to watch. You the tip of the valve bouncing a little as the rpm go up.

[Lucky161]

Thanks for the reply. That does answer my question. I'll try to take a look at that video.

[speed9]

Check your valve springs after every 2-4 races for opening presure replace them when they get weak, you will need a valve spring lbs tool for that. The lower the presure and RPM the longer the valve springs last. Midgets get 4-6 races out of a set at 9,000 RPM (maybe)

[LEADERS EDGE]

As the others said; when the springs are soft they float and basically the spring cannot control the opening and closing of the valve. Soft springs make turning RPMS hard to do and basically pointless as the motor has become less efficient and it doesn't make as much horsepower. Excessive valve float damages the seats and makes the valves sharp.

Speed9 is right about neding to check springs constantly, but in the racesaver series you should be able to go a long time before changing springs.

As a side note: Spring life has alot of determining factors. Proper spring selection,cam design,proper oiling,harmonics,proper valve train maintanence and spring material.

An example from my experience is our midget motor. We had a Ford that we turned 8600rpms. We had been using Crane springs. After 15 races we changed them and all we could get was Iskys. We put the ISKYS in and only got 8 races. After two changes, we switched back to the Cranes and went back to getting 15 races. Our motor was built by Brayton. Motors built by other manufactures would only get 2-4 races because of the cam design and parts used.

[Lucky161]

Thanks