Zone 5

If you take a look at some heads that really respond well to porting, (and that someone spend big bucks to have ported) you will many times see that material is also added to shape them to make max flow. But that flow is not just raw flow. Some of it is gainned by the velocity of the flow. Anyone could just hog out ports, and then pop them on a flow bench and say that flow "x" flow numbers off a bench are not the be all end all.

MILD THUNDER

iTrader: (3)

I kinda think the 305 Vs. 315 runner size is splitting hairs. There are a bunch of variables. CNC or not, cam choice, etc.

What Im saying is a properly cammed 305cc can outperform a poorly cammed 315 with CNC. Have a guy like Bob Madera spec it out and be done!

Zone 5

You have just said the magic words. If you are used to someone specing your cams that doesn't know what they are doing, you are never going to take advantage of the heads. If a cam is too small, or wrong all around, smaller heads in many cases will hide this. But then when you put the correct heads on, the motor is a dog because its the wrong cam. Then you can't figure out why your engine won't perform to where it should. On a lot of basic builds, you can be very very close out of the catalog. Once you start getting beyond a certain HP level, you need to talk to someone who knows what they are doing. Bob would be on my very short list of people to talk to.

boatcrzy

Scott, Glad to see you posting your info here. Seen the crap thrown your way on the "other" site. Good info, keeep it coming Dave

ROTAX454

Variables you say. Does not the intake play a role in the delivery of fuel/air to the CC? My point is, everything from the carb or throttle body to the CC are important. Nothing should be overlooked or assumed. That is if your looking to extract the most from your motor build.

searaycer

My dyno numbers are in, Ron Potter built 540...factory 500 efi intake he ported..345 Merlins he ported...big solid roller...695 horse at 5600 rpm, 695 torque at 4950, makes 645tq at 4000rpm, and climbs from there. 5800 rev limit 5600 peak horsepower...plenty of midrange steam...I cannot wait for Key West.

ROTAX454

Do we assume that your motor pre-mod was a HP500efi Merc?

Your changes/alterations were the crank, rods, pistons, heads, cam, lifters, push rods, and intake modifications? Course, not forgeting the program was changed too. Throttle body changes/mods? 645 lbs. of TQ at 4000. Sweet.

searaycer

Yes, it was a 500 efi to begin with, we have a 525 throttle body on it, which is still way bigger than the ASM mono blade I bought thinking that was going to work just fine.