KAAMA

Thanks for all the replies. I believe some of you here know that I have been working on an engine project. I have two 565 cubic inch naturally aspirated engines. I have bought some 357 AFR CNC ported heads USED unseen (long story) from someone I trusted and paid WAY too much for. The engines are short decks with 6.385" rods and have been freshly done (4.25" stroke X 4.600" bore). They have not been run or dyno tested yet. From what I am learning from some of you is that it sounds as if a 357cc head is too large for a 565cid N/A marine engine and that a smaller head would be a much better performer. And also that the 315 AFR cnc ported head would be a better choice than even the 335 AFR cnc ported head vs the AFR 357's I now have.

I too, am passionate about having the correct head size on these 565's besides the fact that I am a SMOOOOOTH idle freak when it comes to a cam profile---the SMALLER the cam I can get away with, the better! I have chosen a Reed hydraulic roller cam 232*/238* .578"/.578" lift on 112* lobes. I know that is not especially true with 99% of hi-perf boaters who like big cams that "hit hard" and sound BAD, etc. I don't like attracting attention with rough idling cams. If I could have my way I would have a cam that idles like the family van, and I am willing to sacrifice some top end power to get there---- but still runs up to 5600-5800rpm and yet SHAKES THE EARTH when you hit the throttles.

Being that my engines are naturally aspirated, I like to try and get the most out of a set of heads and a good exhaust system. And I am just trying to make the right decision as to what AFR CNC ported heads I should run on these 565's.

RLW

Not to get off base but what do you consider a good exhaust system for your application?

PatriYacht

Mark, I hope you run those beasts before you get a dfferent set of heads. Just so we can see how it works out.

Michael1

I'm with PatriYacht. Put them on and see how they run. "Bench dynoing" isn't anything more than guessing.

You still haven't told us whether you are using fuel injection yet. If it is injected, with a good set of injectors, I wouldn't worry about the big ports. You may just not gain anything, especially with that cam you have. If you want a smooth idle, the cam has a lot more to do with it than the heads. 112 degree lobe centers sound a bit tight, if you are looking for idle quality. I'd probably go with wider lobe centers, and more lift, if you are looking for "punch".

The whole situation is much more complex than port volume. As mcollinstn was eluding to, you are dealing with acoustics. Without modeling software, it is trial and error. Stick 'em on the dyno.

Michael

KAAMA

Okay gang, I will give some thought about dynoing one of my 565's with the AFR 357's, but I just may try the AFR 315 heads as well while the engine is still on the dyno. This is getting kinda expensive, but I gots to know! Anyway, carbs are HP-series 950cfm Holley's.

I am flying out to San Diego, and going to run around southern California for a week or so and visit my old stomping grounds as a U.S. Marine at Camp Pendleton. I was the M-60 machine gunner for my platoon and carried that dang thing all over the hills and mountains of Camp Pendleton. I also shot my way on the 1st Marine Division Rifle and Pistol Team. We also trained snipers at Division Schools while on the team. I am going to go reminisce with a old Marine Corp friend who was in my unit when we were both teenagers in the Corp back in the day. Tomorrow (Nov 10th) is the Marine Corps birthday. Friday my commrad and I are going to the Marine Corps Birthday Ball at the Marine Corps Recruit Depot in San Diego. I am kinda excited about going out there---haven't been there since I was released from active duty in 1981. Sorry for getting off track gang---I'm just looking forward to this trip!

mcollinstn

Yes, by all means, try both heads.

The 357's have a SERIOUSLY good exhaust port. Your single pattern cam is the right idea. Sure, a 114 center will both smooth your idle AND flatten your torque curve, but if you've already got the cam (and the pics I've seen suggest that everything is already together) then I'd run it. You may have MORE duration than those heads need for your purposes - dunno. Those big ports will have an effect on throttle response, but boats aren't short track racers or autocrossers so I don't know that it's THAT big of an issue.

You got two ways to encourage air into (and out of) a combustion chamber:
1) open the valves longer and hope that the pressure pulses are timed to be of benefit
2) give good flowing ports to allow more to come thru when the valves are open.

The 357s will flow like a moofo. Your cam, if the ramps are aggressive, may have more duration than you need for your rpm range.

Run em both. All it costs is a set of gaskets and more dyno time.


$$$

articfriends

Kaama,if you aren't dynoing motor for a month or two you might be able to persuade me to let you try my afr 315's i have on order when i get them ,I'm 2 1/2 hours away from you ,myself i love to try different things too because i'm always after the last possible power gain. Where would you dyno your motor at,ive chassis dynoed some race cars at baker engineering near you and they have a outstanding shop and setup,Smitty

KAAMA

Mc, I am running a dual pattern camshaft. The lift is identical on both sides at .578"/.578" but the duration is 232*/238*. On my AFR cnc ported 357's the exhaust ports start to flow funny around .500" to .600" lift. JimV flowed them withOUT a pipe. Flow at .500" lift was 261cfm and at .600" lift it only increased to 263cfm and we found this on all my heads and it may not be normal with these heads, but we're checking into it with AFR. You must keep in mind that I bought these heads USED from someone I trusted. Had I seen them before I bought them I would not have purchased them for the price I paid. I was deliberately decieved on the heads---it's a real joke for what I paid and what I was told was done to them!

Articsmitty, Thanks for the kind offer. I think you may have yourself a deal. Bring those heads over here and lets throw them on the dyno with my engine after we try the 357's---should be very interesting. I have my engines at Dave Wessledyke's shop called "WESCO" in Hudsonville just outside of Grand Rapids which might be a bit closer to you than Baker's shop. It will be on his dyno---he's a straight shooter. I will keep in touch.

mcollinstn

Jim knows his ports.
Yours sound "odd".

Sorry you got shafted. If I read between the lines I believe I may understand...

Michael1

Kaama,

I think you are on the right track now. Maybe your heads won't look so bad to you once you get the the engine on the dyno, and run a comparison.

Let us know your test result!

Have fun out here in California.

Michael