Issues with using Aluminum heads on Iron Engines

[mylesm260]

Re: Issues with using Aluminum heads on Iron Engines

Tell ya what then.

You obviously have a IB/OB boat if you're in this forum.

If you're so sure it will more more bottom end torque, why don't you go buy some after market heads, and get a prop with 40% more pitch on it, load you're boat full of gear and people and tell us how you're boat pulls out of the hole.


BTW. The AFR site boasts "SMALL CAMS" meaning low lift/during meaning aiming for bottom end torque.... sounds EXACTLY like what marine motors are built for.

AFR CAM: Intake: .460 lift/218? @ .050, Exhaust: .470 lift/223? @ .050

 

[n2ostroker]

Re: Issues with using Aluminum heads on Iron Engines

Low lift doesn't mean marine and the duration they use doen't mean much without the opening and closing events of the cam.

I don't care what you do you're not going to throw 40% more pitch on and expect to run the boat without re-gearing the outdrive.

There are guys on on hear that have done builds with big aftermarket heads that just aren't responding to this thread. There are many others on other sites that are running much more than just a small cam and big heads that run more prop and bigger loads and pull out of the hole fine.

Me personally I run a 355 9.75:1 with heavily ported cast iron heads with bigger valves, a moderate cam 218/224 dur@.050 and .462/.477 lift, and a Performer RPM intake and a 750cfm carb. All the things that are supposed to kill my low end torque. I went from running a 19p to a 23p prop and pulling out of the hole very quickly even with a full load on board. When playing I run a 21p ss prop and turn 5000-5100rpm even with a full load of people, gas and junk.

This isn't a full throttle from the dig launch but it ain't shabby.
http://www.youtube.com/watch?v=naEEuAX0pqI

 

[wca_tim]

Re: Issues with using Aluminum heads on Iron Engines

ok, I'll play. want to go for a ride? I bet you can't stand up in the boat if I roll the throttle on hard from a 500-600 rpm idle, and that if you try you might wind up in te drink... even if i set the tabs to keep the bow down.

that's with a 383, 200cc runner heads a single plane intake (torker 2)750 cfm carb and pump gas. running a labbed 28" mach 4 sterndriver with the diffuser ring cut off and 1.8 gears. cammed / set up to run wot at about 5500 rpms with rev limiter set for 5600 (and will hit it with this prop on it - it's my tow and general use prop). I don't ever get past about half throttle pulling skiers or boarders.

the comparison above isn't a fair one. if an engine is built to maximize low end torque, then it's aabout air fuel mixture momentum from high velocity flow in relatively small ports. afr 180s would be the right head on a 350 for that coupled with a good dual plan intake with small port volumes and well designed runners. the set-ups in the vast majority of examples on the web are skewed toward peak horsepower numbers. the other major issue that hasn't come up that OI noticed is that when we're comparing the stock heads from an older 350 with any of the well designed aftermarket heads, the cumbustion chamber design and burn characteristics are a huge improvement and worth a ton.

just my two cents...

 

[Mkos1980]

Re: Issues with using Aluminum heads on Iron Engines

I think My combo is about perfect for my size boat + it was super cheap to build. All parts for just under a grand! Most of it used. Hot cam is spec;ed at 218/228 .525/.525 112 LSA I'm spinning a 21 Laser to 5400 RPMS and a 23 Laser to just about 5100 RPM's with full load. (Maybe 100 less with full load) but just as close. + I run 32 total timing with 89 Octane for a little safty. (10 initial and 22 module) Idles better with 12* though. This combo made the most HP per the build up with 92 Octane and 34 timing.

Moves pretty good for me. http://www.youtube.com/watch?v=L8YRUMqqDEI