Valves - size convo. Someone asked - 45 degree angle-not 35

[AdminGuy]

Someone asked so here it is. I thought it was common knowledge.
These are 45 degree angle cut NOT 35. 35 has better flow? does it? I know nothing. But would like to learn more. How about 30 degree? Why is this? Swirl pattern? Is there an intake swirl pattern to speak of? What sort of flow work would one recommend for a wee sport scout. Smooth out the intake manifold? open it up? cut/trim the exhaust guide? Open it up? Longevity VS effect? Is it worth it?

Pop-up piston, squish band? upper head pocket fill? Anyone messed around with this? Has anyone done any flat head flow port testing? Ultimately, does it really matter?

GM - Buick Bros., Louis Chev, Ranny Olds, Chief Pontiac ; 1973-80, 350 C.I. V8
Head dia; 1.875, Val L **4.667**, Std. Dia. 0.3428, over 0.3498, Manley PN- S1818

[J Wall]

Hello.
In my opinion and looking to common rules of thumb you will generally find that as the angle becomes less so does the multiplier for the size of a port. .85 is the size for 30 degree seats and .91 is the size for 45 degree seats. The size of the nipple in a sport scout cylinder is limited to something less the .85 before you hit thread and the nipple falls out of the cylinder. When fitting oversized nipples the .85 size is the limit for a 1 .750 valve. It is also thought that cams with lifts less than .400 will not benefit from a 45 degree seat. KR Harley uses a 35 degree seat as well as Pontiacs from the 60ies. Food for thought.
Jim

[AdminGuy]

Hey Jim, Thanks. Good info. I've always wondered about that.

I noticed that intake nipple appeared to be silver soldered in - so I better mic that up and see what's happening.

Have you ever repaired a cracked wall? Exhaust valve to bore. Should I just leave it alone?

Paul Edwards
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