Re: McCulloch VS57 on a 359 Straight Eight

Posted by Anthony Pallett On 2013/5/25 15:07:41

Absolutely stainless are better than stock steel.
I cut my teeth in the racing world working at a high performance machine shop from the ages of 15-21 or so. We would use a stock style steel valve in restoration or pretty much stock engines, with the basic modifications low rise dual plane intake, RV style cam, reasonable compression (as in 9.0 or below on a modern OHV engine) pretty much the car show standard engine 5500 RPM or below.
Saying that a Packard L8 would be screaming its guts out at 5500 RPM but a flat head is a bit of a different animal than an OHV. 9.0 compression is extremely high on a flat motor and they do run hotter so when we built say a V8 ford for racing we tended to over build them. Its almost like 300hp on a flat head is as brutal on components as say 600 on a modern OHV engine.
I have seen a lot of engines run just fine with a stock style valve, so I'm not saying they are bad; however, the number of failures be it burnt valves, excessively worn valve stems ect were mostly on the stock style.
Stainless valves or the more exotic materials such as titanium are not indestructible by any means but they will take more of a beating.
Look at the header design on some bleeding edge performance engines most are made of stainless because it can take more heat before failure. The same is true in valves.
In most modern engines a set of stainless valves can be had pretty cheap the last set I purchased was around 200 dollars for a small-block Chevy engine, in that arena its cheap insurance especially compared to the cost of reconditioning a stock valve.
Sadly this isn't true for the L8 I contacted Manily for a guesstimate quote and with the race series blanks the estimate was around $30 a valve so almost $500 for a complete set and if i went with a more stout valve the price would go up quite a bit. With that you would have the option of going from the 3/8 stem diameter to say 11/32 lighten up the valve train and pick up a few RPM but it isn't a necessity.
With the engine plan I am working towards I will be getting the pricey stainless valves, but if you are staying stock or reasonably close to it the factory style valve should work just fine.
Back to the topic a bit Egge and the comparable restoration part companies produce a product that is adequate for
A) the driving that is typical of how classics are driven today.
B) An engine running well within the stock design parameters.
4psi of boost on the build refrenced in this post is not much roughly 25-30% increase of HP over stock so a 150 hp L8 Packard would be around the 185ish mark on paper with no other changes to the engine. But their will be increased heat in the intake charge and engine will be more detonation sensitive. If you are great at tuning and keep your A/F ratio in the safe range stock style valves might work fine for occasional driving and impressing people at car shows. Anything more than that I would highly suggest a quality stainless valve.