Valve Seat Angles

When does an engine builder decide to go with a 55* compared to a 45* is it all dependent on the cam ??
also what is the comparison of longevity between the 2 Valve seat angles ? ....and all things being equal how much airflow/hp is it worth ?

Boy oh-boy,

Watch me go off on this one! IMO the engine builder doesn't decide, the cylinder head guy decides. However the cylinder head guy needs to work with the engine builder and know the cam specs and etc.. The most important thing to be learned here, is that NOT all cylinder heads are compatible with a 55* valve seat angle. This is due to the shape of the combustion chamber and the chamber design. Does the 55* seat angle work with BB Ford ProFiler # 205 heads? Absolutely! Will a 55* seat angle work with BB Ford Pro-Comp heads? Never!

It's too easy for the uneducated to assume that because Pro Stock racers are using 55* valve jobs, then I want to use a 55* valve job on my generic XYZ head for bracket racing. For those wanting to learn more about steep angle valve jobs, may I suggest you attend a cylinder head porting seminar being hosted by ProFiler and conducted by Darin Morgan this October in New Carlise, OH. The cost is a little over $1,000. I'll have to look up the link and post it. Also, Jeff Jones of Jones Engineering gave a good talk at our 2008/2009 Winter Tech Seminar on steep angle valve jobs. If you missed the seminar, then buy the DVD form Damon Sea (Phantasea 466) and study it.

As for wear, yes the steeper the valve angle, the faster the valve job wears out. Jeff Jones alluded to this also. Furthermore, he mentioned a way to reduce this fact was to do the DLC hard coating on the titanium valves, at a cost of about $38 per valve. So at some point the question becomes, have you got deep pockets???

Hope this helps,
Charlie

No ...the engine builder should make than call . It is the builder that "should" know the customer's needs and maintaince habits [or the lack there of] . A racer should not knowingly be present with a package that is clearly over the owners head relative to maintance .

What if the engine builder IS the cylinder head guy ... ?

As Charlie eluded to though ... this is a bag of worms that customers want to have a say in but, they have no idea what the effects will be.
Some ports LIKE steep valve angles more than others AND some even like a 30° or 37.5° seat even more. It depends upon how THAT port acts with a different angle on the seat throughout the lift curve as to whether or not it will be beneficial.

"What if the engine builder IS the cylinder head guy ... ?"
That's an easy one.....tell him/her what they really need...which probley aint what the guys down at the bar told them

I've found things always work better and go faster and smoother when the owners are "hands off" at least in my trade. Tell me what you want, or what your budget allows.. let me do the rest.

Here you go guys, click on this link for Darin's cylinder head school.
http://www.profilerperformance.com/powertechclass.html

Hope this helps,

Charlie Evans