310 cc heads
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11-25-2015, 07:29 AM
#402
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Smaller the cam with big heads, the better the power "curve" will be. Big enough to make decent peak pwr, but small enough to keep port velocity up and still build some tq. The most common mistake we see in the industry is the "bigger is better" mentality where guys go big heads AND big cam. This never ends well.
11-25-2015, 01:00 PM
#403
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Smaller the cam with big heads, the better the power "curve" will be. Big enough to make decent peak pwr, but small enough to keep port velocity up and still build some tq. The most common mistake we see in the industry is the "bigger is better" mentality where guys go big heads AND big cam. This never ends well.
02-03-2019, 07:04 PM
#404
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I'd look at the Callies Compstar line, as I know you are on a budget dale. More than enough crank for what you're doing. I believe you'll tear up that Gen V production block long before the crank would be an issue.
As far as cam durations go, just for conversation. A couple recent roots blower builds we dynoed.
First one. 540ci, 7.5:1 static compression, Dart 345 Iron eagles, Crane shelf 244/256 114 LSA camshaft 8lbs boost. 10-71 blower. Peak horsepower was at 6400-6500RPM, torque peaked at 4500RPM.
Second one. 522ci (4.00x4.560), 8.25ish static compression, AFR 315 heads. 10-71 blower. Buddy ordered a custom cam from Bob M. Cam was 245/253 114 LSA. We did not see a peak. At 6700RPM, it was still climbing, but just about done. Torque peaked at 4500RPM also.
Another buddy of mine, had some 540ci N/A engines. Dart 320 heads (race series not pro 1s). Static was somewhere in the 9.25 range, flat top piston. He originally had some 250/260ish cams in them, dominator carb...they were not the best around the docks, but ran good. When freshening the engines, he wanted to focus on a more user friendly rpm range, he called bob for cams. new cams were around 240ish 248ish. Its been a while, and dont remember the exact numbers. Engines made 680-690hp at 6000. Now, his boat, didnt gain any top speed with the smaller cams (30ft vee straight bottom coupled to SSM drives running 90ish mph), however, what he did gain, was a better idle, and acceleration thru the rpm range, with less camshaft.
Something to remember, our boats aren't dynos. You want to look at the full picture. Losing 10HP at peak, might not be worth losing 30-40 ft lbs of average torque. I agree with what KVogt said earlier, about things being a compromise. In marine offshore, when it comes to cams and heads, usually erroring to the smaller side of things, is a better bet, than erroring to the large side of things.
Speed wise, a very rough rule of thumb, is it takes around 25HP, to gain 100RPM with your props. The average offshore boat, that might be 1, maybe 2 mph. The difference between a 675hp engine, and a 700HP engine, might not net you the speed gains you might expect. Most of the time, there's more to throwing HP at your boat, to increasing speed.
Dale, bigboat28, I would focus on reliability, after all the BS you've been thru the past year with engines. A mild camshaft setup, may cost you a little power, but it can pay off in the long run. How many hours would you be happy with, before replacing valvetrain components?
As far as cam durations go, just for conversation. A couple recent roots blower builds we dynoed.
First one. 540ci, 7.5:1 static compression, Dart 345 Iron eagles, Crane shelf 244/256 114 LSA camshaft 8lbs boost. 10-71 blower. Peak horsepower was at 6400-6500RPM, torque peaked at 4500RPM.
Second one. 522ci (4.00x4.560), 8.25ish static compression, AFR 315 heads. 10-71 blower. Buddy ordered a custom cam from Bob M. Cam was 245/253 114 LSA. We did not see a peak. At 6700RPM, it was still climbing, but just about done. Torque peaked at 4500RPM also.
Another buddy of mine, had some 540ci N/A engines. Dart 320 heads (race series not pro 1s). Static was somewhere in the 9.25 range, flat top piston. He originally had some 250/260ish cams in them, dominator carb...they were not the best around the docks, but ran good. When freshening the engines, he wanted to focus on a more user friendly rpm range, he called bob for cams. new cams were around 240ish 248ish. Its been a while, and dont remember the exact numbers. Engines made 680-690hp at 6000. Now, his boat, didnt gain any top speed with the smaller cams (30ft vee straight bottom coupled to SSM drives running 90ish mph), however, what he did gain, was a better idle, and acceleration thru the rpm range, with less camshaft.
Something to remember, our boats aren't dynos. You want to look at the full picture. Losing 10HP at peak, might not be worth losing 30-40 ft lbs of average torque. I agree with what KVogt said earlier, about things being a compromise. In marine offshore, when it comes to cams and heads, usually erroring to the smaller side of things, is a better bet, than erroring to the large side of things.
Speed wise, a very rough rule of thumb, is it takes around 25HP, to gain 100RPM with your props. The average offshore boat, that might be 1, maybe 2 mph. The difference between a 675hp engine, and a 700HP engine, might not net you the speed gains you might expect. Most of the time, there's more to throwing HP at your boat, to increasing speed.
Dale, bigboat28, I would focus on reliability, after all the BS you've been thru the past year with engines. A mild camshaft setup, may cost you a little power, but it can pay off in the long run. How many hours would you be happy with, before replacing valvetrain components?
