mike tkach

iTrader: (3)

so now you have a 335 cc intake port?

getrdunn

iTrader: (7)

Just a guess? I'd hope not. Looks like they cleaned up well anyway. For tims sake I sure hope they work out. 305/315

Full Force

iTrader: (5)

According to cam people all of them, the heads are very nice heads and will be great, with the cam choices in front of me.... all 5 were very close in comparison, and every one of them homies what boat and how heavy it is, if it don't perform it will get boost lol

MILD THUNDER

iTrader: (3)

Its really not about port volume per say, its about CSA vs Flow and Velocity (FPS). For example, a Dart 325 head, will have a smaller avg CSA than the GM 990 325cc head. It also flows more air as well. That is why, when you bolt a Dart 325 head, in place of a GM 990 head, you see power gains. The port volume itself, means zero. It is simply a way to sell heads. Same for flow numbers. Anyone can hog out a port and make big numbers on the bench. But its the overall architecture of the cylinder head, that determines whether or not its gonna make power out in the field.

As a very general statement, yes, it is always better to use a smaller head, that flows as much if not more air, than the larger head. A 320CC head that flows more air from .200-.700, will make a better combo, than a 345cc head, that flows the same numbers on a bench. But, on the flip side, bolting on a 265cc head, that flows less air, but has a higher FPS, may, or may not, make more power than the 325cc head, if it simply cannot deliver the required amount of CFM, to reach the goals. This is why, you don't see anyone running a 6000rpm 800HP 572, with a 265 AFR head, or a 781 GM oval port. The head just isn't gonna get it done. If it could, everyone would be doing it that way.

MILD THUNDER

iTrader: (3)

A 4900 RPM 454, certainly does not "require" a cylinder head, with the CSA, or port volume, of the GM Rect port head. It is way off, from modern design. However, it is not like it didn't "work". Its what they had to work with back in the day, at the factory. The 454 mags were great engines in their day, and with the dual plane, quadrajet, and small cam, they pulled lots of skier's up out of the water, and powered many big boats. Especially considering they were low compression as well. Big ports, low compression, and they ran pretty decent. heck, that 990 head, has too much CSA, for even a 454 turning 6000RPM. But, there were a ton of those at the drag strip racing for the past 50 years.

From a comparison standpoint, what do you think a 5000rpm 454 mag with a 325cc head would be comparable to, if you were comparing CSA/Volume per ci, to say, a 540ci? It probably be like bolting on a 380+cc head on a 540 that turns 5000rpm.

I think most of us here, are looking for a combination, that makes respectable power, and runs well. Nobody is building competition engines here, where 12ft lbs of torque, or 14hp , is going to make or break the build. Its not nascar, or any class limited stuff here.

Is Tim's AFR 325 head a bit large for a 6000RPM 540ci marine engine by textbook standards, yes, they are. Would an AFR 305, or even 290, be better suited for the combo, yes, they would. But, what are we talking here? 80ft lbs of torque? 75HP? Heck no. If he swapped his heads as they are right now, for a set of 315's, with no other changes to the build, I really doubt he would see any seat of the pants difference in a 35 Mistress.

Full Force

iTrader: (5)

The goal was to maximize the parts I ALREADY have, I agree the 325 may be larger then needed, that being said that's what Bob sold me for my goals that were not met, so I maximized my parts for best possible case, new Intakes, portmatched, cams will be a huge change over old ones, and having actual flow numbers and more importantly WHERE the gains and flow is, that will help us chose proper cam and not guess...

All 5 cam companies we taked to spec'd almost identical cams, for heavy boat, and to push 5800-6000 IN THE BOAT, is the goal... to spin my props that I have to 6000 or as close as possible, the changes I am making should absolutely make some sort of difference and will be dialed in WAY BETTER then before and more then most combo's I see, my buddy helping me looks into every little thing and is very sharp..between him, Joe and myself I think combo will be as good as it can be.

This is by far not a hack job, or a guessing game like the recent Big Johnson story going on on FB...

My goal is decent power, and reliable, stable valvetrain and such...

Recent research shows me the ENDURANCE PAC springs that Bob sells with AFR heads are just hot rod street car springs, when my buddy called PAC yesterday to see what they actually are good for they said toss them and buy 1200 series endurance springs... again never will I buy a head assembled... good thing some guys been lucky but I was not, and now have some REALLY EXPENSIVE AFR heads...

MILD THUNDER

iTrader: (3)

I was on the phone with a friend the other night, an oso member, and one who has been around many hi perf offshore engines, for many years. He had a set of AFR's on supercharged engines. After not very long, he had some valves sticking in the guides. The guides were simply too tight for the application, and needed to be sized. That , along with better valve seats (his were very worn), were installed in the heads.

MILD THUNDER

iTrader: (3)

I'd like to see an engine Like yours Tim, that will make more power , with a 305 "as cast" out of the box, vs the CNC ported version of that head, the 315 AFR. or, in your case, the 325 "as cast" vs, the CNC ported version of that, being the 335. Even thought the port volume has increased, typically, the additional air flow overrides that.

Also, just because a head is labled a "325" cc, doesn't mean thats what it actually pours at. From Tony Mamo

Regarding the other posters question about the CNC bowls, whether you opt for the chamber or not (Can't stress enough how much you should), the bowls come CNC ported either way. Its simply included in ANY of our as cast product which is a nice plus about the AFR as cast offerings.

The AFR 325's are just the opposite of the 345's in the sense they run on the small side and usually pour in the 317-320 cc range. When you CNC port the chamber it explodes the low mid lift side of the intake port, and usually peaks earlier (a good thing) around .650 lift in the 375-380 CFM range. The low lift flow looks very similar to a 315 head as well, fattening up 10-15 CFM's across the bottom. Exhaust is up 10 at .200.....15 at .300, and carries 15+ CFM thru to you cant open the valve anymore.

mike tkach

iTrader: (3)

how can you make a 325 port a 315?surly not from making it bigger.

veloc410

I have a Set.