Quote:
Originally Posted by Bored&Stroked
The question comes back to the application and usage of the engine. In a performance built engine, a relief will help - especially if you have good port/valve work done, cam, heads, etc.. In a stocker type engine, it will reduce compression and there is not a huge amount of benefit. Also, what RPM do stock engines usually run at?
Pete, Ron and I probably relieve every engine we build - as we do not build stock type engines. I've not built a stock engine in 40 years.
If I was building a stocker or mild performance type engine, I'd probably do more of a blend of the transfer areas around the valves - more of a 1/2 relief to improve flow out of the valve pocket. Also, consider that stock type engines are already suffering from low compression - do you want it any lower?
Here are a few pictures of what I'll call a 1/2 relief - it was done for a 276 cubic inch street engine running dual carbs and a Potvin 3/8 cam. Stock valves sizes, street porting and guide work (on the tops). This is kind of a "tweener" - improved ports, a 1/2 relief - not a competition style engine, but surely an improvement over stock. It ran extremely well in a street driven Model A roadster:
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Dale,
Looks great, as usual. This is close to the type of relief that Barney Navarro used on his engines.
I've curious about the "eyebrow" above and 1/2 way between the valves. Any thoughts on if this metal impedes, improves or is indifferent to flow?
Jack E/NJ,
Thanks for posting the heads picts. Curious about head combustion chamber shape and how to improve that area as well.