Changing Valve Angles

[Anonymous]

Hi Everyone,

Since the machine shop ruined my 300's head, I started thinking.

If you were to angle cut the Rocker Stud Bosses and install blank (solid) valve guides that would be drilled later, could you get the same effect as the 265 Ozzi Hemi 6 on the Ford head?

Now I'm thinking mainly about the intake side, the exhaust doesn't seem to have as bad a problem.

I think about 7* is possible, but is that enough to do any good?

Just a passing thought,
John

 

[xctasy]

Main issue is how do you accomadate it all? There would certainly be an improvement if there is no issues with the intake exhast margin between them.

The 7 deg cant will reduce valve shrouding, and will only increase power if the port flows more, off course, so you must reprofile it. Copy the 214/245/265 set-up. It works better than any other non-cross-flow I've seen. I think it may not be cost effective, but it may be the single best thing you can do with a stock head, as long as its done in conjuction with a reprofile of the ports. I am hope full there is enough metal to play with, because it sounds like a great idea.

David Vizard had seen a Mini head angle milled to 5 degrees, and it gained more power everywhere, but he felt it came from flame travel. It flowed less than some of his 0 degree flat valve heads.

Flatter angles in chambers work best. 90 degree Hemis work on top fulers because of the heavy fuels they use don't like rapid burn chambers. Ever since the first Cosworth four cam engines, the canted pentroof has been getting flatter. So have the stock block SBC and SBF non-porcupine headed alloy head replacements. They stated with something like 23 degrees, and have changed to shallower angles. Since the first BBC polyshperic heads, Ford and even Chev, with there Aurora heads, have flattened the valve angles to produce a better chamber and flame travel. BBC set-ups seem to work best in top full situations, where nitromethane and those heavier, fast burn fuels are used, although they are hampered by not being able to run huge bores like the Hemi and BBF 385 engines.

Horses for courses!

 

[80broncoman]

I have witnessed this very thing in winston cup engines about 12 years ago. It was very eye opening. The small block chevs ran better with the intakes tilted closer to the head. (multi angle like a clevland ford head)
The ford guys moved the exh valve angle closer to straight up, more like the chev heads (lees angle diference between intake and exh).

What really surprised me the most was in the area of rocker ratios.
Both GM and Ford teams ran mostly 1.6 on the intakes and 1.65 on exh.
This higher ratio on chevs and lower on fords.
Jim