Whitey

Hey Mark have a good time at MCRD and Happy Birthday...I was there in 85, I was also a grunt...81 mm mortars. Dwight

Jmemoli

Kaama,
I am working on the same project as you , but have some history .
My 570 CI motor (4.25x4.620) was used in my 5900 lb magnum race/pleasure boat . Exhaust was CMI e tops with wet tailpipes . Compression is 9.3:1 .
This motor uses 300CC intake runners from a modified Merlin head . The ehads were epoxied to create a modified oval port . My cam is a 236/242 solid roller with .680 lift(1.8 ratio I, 1.75 exhaust ) 112 ls, installed at 108 .
From what I hear these ports flow around 370+ at .700 lift , and are super trick . I just talked to Jim V on these as I am trying to replicate them.
PErformance wise , the boat is incredible - The motor will turn a 25" prop to 5900 RPM for 80MPH, or will turn a 28 B1 like nothing to 5300 RPM . The torque and hp i this combination is incredible .
From my experience , you will be much better off with a set of heads with a cross sectional area around 3.5" or smaller as the cam you have is very mild . Your peak HP will most likely be around 5200 RPM . I would definitely stay with runners in the 305 to 315 range that can support flow in the 350 CFM range .
Theoretically , a 570 peaking at 5200 to 5400 RPM needs an intake runner flowing around 330 to 340 CFM . For a torque peak around 4000 to 4200 RPM, the cross section of the port only needs to be around 3.37 sq. in . at its smallest .
Not only will these high velocity , high flowing ports increase torque peak at lower RPM, they will also carry that torque higher in the RPM range for more horsepower .
Smaller ports , faster velocity , more torque, better acceleration- This is the secret of the MErc 525 .

KAAMA

Looks like you were able to dig this 2 year old thread out of the archives. A lot has happened since then!

Since the start of this thread, my 565cid engines were dyno'd that following May (2005) with the 315cc AFR CNC ported heads. Relating to my engines, you were pretty close with you above desciptions. Calling from memory, my engines made PEAK torque @ about 4200-4400rpm and peak HP stayed was about 5400rpm.

I didn't end up using the cams that I had orginally mentioned in this thread----as I also did NOT use the 357cc AFR heads either! The 357 heads would have worked "okay", but I was swayed into buying them USED from a smooth talking con. Anyway, I ended up consulting Bob Madara of Marine Kinetics for my head and cam combination, and was very pleased with the smaller runner 315cc head selection that Bob suggested. I must admit, I was a little reluctant at first, but I am a firm believer now.

I also know of another OSO member with some 565cid naturally aspirated engines who just a few days ago made some impressive HP/TQ with the same 315cc AFR heads as I have and some of Bob's cams on Dave Wesseldyk's dyno. I really can't say any further unless the owner decides he wants to say somthing about it on here.

With my engines in the boat turning about 5500rpm @WOTand running against my friend's 32' A/T (we both have the same exact boat...probably 8500 lbs with fuel and all) only he's got 556cid supercharged engines he cannot pull me from 3000rpm range up to WOT---I am right there with him so, something has to be said about how well the engines run/perform in the boat as well.

Jmemoli

Thanks Kaama ,
Didnt realize the post was so old - sorry -
Thats what happens when you drink and type .

Anyway , what kind of hp and torque did you see on the Dyno?
The reason I am back working on the heads is the epoxy started falling out . I am not sure wheteher I have these fixed , or go with another set .

KAAMA

Keep in mind that HP was not first on my priority list when we were drawing up the plans for my engines. I wanted to do someting different... a little experimenting with the heads/cams and try to see how small or little of a cam we could use without killing too much of the power---especially on top.

No doubt there is more power to be had with a longer duration cam, but I wanted to see how this would work out and see how low I could get the idle RPM quality and still make decent power---it wasn't the easiest thing to try and accomplish for what I wanted the engines to do when selecting a cam, but we had a lot of fun with the project.

In comparing the two 32' A/T's, I really thought my friend's boat with the supercharged engines would have blown me away...I think he did too! You must keep in mind that my dyno results were from Dave Wesseldyk's dyno...and his dyno is NOT a "happy" dyno and he won't fudge the numbers to show false power results...he keeps a crying towel for those who are not prepared.

I have heard it said that bragging rights on the dyno are best saved for the water! At Hardy Dam, against the current, into the wind, calm water and full fuel tanks I have hit 93.6mph on the GPS. As far as the HP is concerned, you wouldn't believe me if I told you---at least most would have a very difficult time with it. It was hard for me to believe myself and they are NOT as high as you may think, but I will say they made peak HP (within 5hp) between 5100-5400rpm.

Most of the time I have put too much emphesis on a HP figure...and that is why I wanted to experiment with these engines and see for myself. I am no expert...just a weekend warrior with my boat, but before building my engines, I had not heard of anyone putting a 315cc head on an engine with a cubic displacement of 565cid---and I just saw it again with another OSO member and his pair of N/A 565's/315cc AFR heads. He's got a little more cam than what I have and he's making A LOT more power compared to mine! And he's doing it at 5400rpm!

BTW, torque is something like 690-700 lbs. So far, I have about 112 hours on the engines since they were built.

GLENNS

KAAMA SPILL THE BEANS MAN!!!!!!!!!!!!!!!!!!!!!!! I was gonna start a new thread about my new motors shortly. Dont worry about me Im like a new proud papa anyway so type away.

KAAMA

Perhaps we should do it on a fresh new thread with a different title. Let me go take some pictures of your engines before I do. We'll name the new thread something like;..."It's Halloween and these are the GREAT PUMPKIN engines!"

GLENNS

Kaama I just put some pictures of the GREAT PUMPKIN engines up in the general boating discussion forum so chime in if you like