BIGGER is BETTER.....RIGHT?

Here's the important question regarding cylinder heads and porting. Is bigger really better? The same could be asked about tires, carburetors, brakes, and bumpers, even sandwiches for that matter. This will be a short post now that I brought up sandwiches.

With heads here is the key: Everything in moderation. Bigger valves and ports breathe bigger air at bigger RPM. The question, however, is what does your engine need for the way it will be used? Make sense? The Ford 351 Cleveland 4-barrel engine had huge intake valves and runners. You could park a bus in those runners and still have a passing lane. And how did they perform? Terrible! They made very little power until 3500RPM. So they were sluggish at low RPM. The cure was to use the 2-barrel heads. The local dirt oval track racers that use 351C's never use the big heads. With valves, if you go too large, they will be shrouded up against the wall of the combustion chamber. Air will not flow in any volume in that area. With ports or runners some would-be porters just "hog" everything out as far as possible. Many times this will slow the air flow... not what we're after. We want velocity. Anything that slows the air flow is something we want to remove, not create. My next post I'll say some things about gasket matching and port matching. I can't wait. - Dr.Denny

Dr. Denny does custom head porting & polishing. For more information go to DR.DENNY.COM