currently building a 598CI Dart Big M, Tall deck. Merlin 319CC heads. 9.6 to 1 compression. looking for a Hyd roller Cam for max power at 5000RPM. Going to use about 950CFM carb. Any sugestions, or advise?
currently building a 598CI Dart Big M, Tall deck. Merlin 319CC heads. 9.6 to 1 compression. looking for a Hyd roller Cam for max power at 5000RPM. Going to use about 950CFM carb. Any sugestions, or advise?
Hell your in New York get hold of Scott Shafiroff Race Engines there in Bohemia @ 631-218-7530 and see what they say.
Small head for 600 inches. Contact Cstraub69 for camshaft design here on the boards.
with the single 950 carb id say the head should work great matched with the right cam. should be a torque monster. especially if your looking at the 5000rpm range.
That head/CI combination is leaving a lot of power on the table. No sense going 598 if you're going to choke it with a 950 and those heads. You should be looking at a BIG dominator as a minimum and bigger heads. Yes the smaller heads will keep the throttle response super crisp, and make the motor really torquey, but you definitely won't have the optimum setup.
To give you an idea, I run 100 fewer cubes, run a similar sized head that flows much better than those Merlins, and run dual 850s. My peak torque is at 5400 RPM, but runs within 3 ft lbs of peak from 5100-5700. HP peaks out at 6500(cause thats as far as we pulled on the dyno, but the curve is pretty flat at that point).
If you managed a similar HP to CI ratio with your 598, you'd be looking at somwhere around 730-800hp at 5000-5200 RPM!!! Get a pro to help with your parts selection. It can make all the difference in the world.
Additionally, the low end torque that motor has the potential for could considerably shorten the lifespan on your drive. Its not like a blower motor where you have to build boost to get your HP. You'll be pushing a lot of torque right off idle. Make sure to budget enough money to make the drive capable of living behind the new motor.
Chris
great info chris. but remember that he is running this motor in a 31' hull. the larger heads and fuel delivery would be great, but he may not be able to get the hp to come up there with that much weight. think of the 502 crate motors. the 502 hp has large rectangular ports and great flow for getting high HP but the truck motors use a very small round (not even ovals) port to keep the torque curve up high to push/pull those heavy loads. that motor in a boat like mine or yours would create some amazing rpms, but im betting he will be maxed out at 5000 if he can even get it there with that motor in that size hull.
Thanks For All The| Great Info Guys..
currently building a 598CI Dart Big M, Tall deck. Merlin 319CC heads. 9.6 to 1 compression. looking for a Hyd roller Cam for max power at 5000RPM. Going to use about 950CFM carb. Any sugestions, or advise?
Here's a dyno sheet from a 598 that was tuned to make peak power around 6k rpm or a little higher using 355cc heads and pump gas. If you're looking to stay at 5k then I think you're about right on the heads and carb, maybe just a tad on the small side but not much. My motor was pulling 844 cfm at 5k. Yours should need a little more if you're tuning for peak VE at the lower rpm. The 950 would be close, maybe a 1050 would be ok but no bigger. I don't think you'll make the 800hp suggested in another post but you'll make a lot of torque, definitely more than your peak hp number. Just a guess would be a very flat torque curve around 800 ft-lbs/700 hp. Good luck!
-Brian
http://www.***boat.com/image_center/...13dyno-med.JPG
great info chris. but remember that he is running this motor in a 31' hull. the larger heads and fuel delivery would be great, but he may not be able to get the hp to come up there with that much weight. think of the 502 crate motors. the 502 hp has large rectangular ports and great flow for getting high HP but the truck motors use a very small round (not even ovals) port to keep the torque curve up high to push/pull those heavy loads. that motor in a boat like mine or yours would create some amazing rpms, but im betting he will be maxed out at 5000 if he can even get it there with that motor in that size hull.
Vic,
I agree 100% on what you're saying about the heads. I disagree however on the size & weight of the boat playing a factor in what RPM he will be able to pull. That is a function of his prop and gear ratio in the drive. The bigger issue that IS related to weight is the load that is placed on the drive. Even with the proper ratio and prop setup, the motor will have to work harder to make everything happen. Not a problem for the motor as the gearing and prop selection can allow it to get to the RPMs it needs. It is a problem for the drive though, because it sees heavier loads getting on plane and sustaining speed when you compare the same engine/drive setup on a smaller boat.
When folks are setting these things up, they need to look at the big picture. This guy is heading in an alright direction with his engine build, but care must be taken with that drive. The torque numbers he will be generating even at say 3500 RPM (he's gonna be spinin that much easy to roll the thing over) are going to stress a Bravo.
Chris
Doghouse,
What cam are you running? I have Dart 355 CNC heads on my 10:1 598 and run a 264/270 duration solid roller .740" lift. My carb is a Nickerson stage 5 1250 Dominator that flows 1400.
Craig
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