Boats For Sale:
Which carb |
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lakedog55 
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Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
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 Topic: Which carbPosted: February-08-2014 at 8:50pm |
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What's up
question for you guys. buying new carb. 351w motor 20 over on pistons, cam research cam, intake, and gt 40 heads. what do you guys think 600 or 650. Thinking about the quick fuel or the demon, the demon looks like it has mechanical secondaries not sure how those work on the boat. thanks mike |
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Lakedog55
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Waterdog
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Posted: February-08-2014 at 11:17pm |
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I'd like to think my engine is a solid 300 hp
My engine is like yours with 1.7 roller rockers a Weiand stealth intake and ported GT 40p's and a 540 prop. I'm very happy with the Holley 4160 600 cfm I bought from Summit |
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TX Foilhead
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Posted: February-09-2014 at 9:46pm |
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Standard Holley works just fine, but if I had to buy another carb I think it would be a Quickfuel.
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TRBenj
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Posted: February-09-2014 at 9:53pm |
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You definitely dont need a 650cfm on a 351w unless youre going to spin it 6500. Thats what Joe runs on his 408w up to 6k. The stock 600cfm will be just fine.
Based on what Ive read, I'd opt for the Quick Fuel over the Holley as well. Price is about the same, and its hard to find people who dont like the QF stuff. Both of Joe's BG carbs run awesome, but there are mixed reports of quality issues coming out of that company. I think they ended up going out of business a few years ago, and then Holley absorbed the brand. Last I checked they werent offering marine carbs anymore... so if youre shopping used, it might be luck of the draw on getting a good Demon and not a lemon. QF is a safer bet. |
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lakedog55
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Posted: February-09-2014 at 10:05pm |
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Thanks
600 quick fuel . One more question what's the verdict on the plastic 5 degrees spacers? supposed to cool of the fuel. mike |
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Lakedog55
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Waterdog
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Posted: February-09-2014 at 10:32pm |
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A phenolic / plastic is good to cool the fuel.
In the 2001 Ski Nautique hull they don't use a tapered carb spacer. With a rebuild watch for hood clearance. With my Stealth intake I had to omit the 1in. spacer. I think it will fit with the Edelbock performer. |
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TX Foilhead
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Posted: February-09-2014 at 10:36pm |
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As far as do you need it? Depends on how the motor sits, if you had one before it was probably for a reason. I don't believe that most people are having issues with vapor lock and the original spacers were metal. The other thing is I'm not positive there is enough space left for a spacer on a DD.
Take everything you read from the car folks with a grain of salt, these are hot rod tractor motors. The only relavant advice I've seen comes from Bronco forums. |
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TRBenj
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Posted: February-10-2014 at 8:35am |
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Youre not going to get much good component selection advice from car forums- Bronco and Mustang alike. They all need off-idle power, unlike a boat. You can build for higher hp... everyone seems to think that boat engines should be built for "low end torque" but I have not found that to be the case.
Like Andy said, clearance will be your primary concern with any spacer- the 2001 box is particularly tight. PCM used a 1" spacer on all carb'd Ford windsors but it was not a wedge- so with proper float heights, you dont need one to address the engine angle. All additional height under the carb improves the intake charge, but all things equal, youre better with a taller (performance) manifold even if it means eliminating the spacer entirely. |
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TX Foilhead
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Posted: February-10-2014 at 1:12pm |
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I'm going to disagree with 2 things.
First, I've found some pretty useful info on motors on Full Size Bronco, they're building basically the same thing as we are. Second, we're building tractor motors not F1 motors. With any marine cam the design is made to pull throughout the RPM range, and to overcome the restriction of the wet exhaust. If you build for torque the HP will come since it's really just a math equation. We won't make numbers like the car guys because we don't spin the motors much past 5000 rpm. Since a boat is always under load spinning the motor another 1000 or 1500 RPM's puts exponetial stress on everything. I see a lot of the go fast crowd who need to freshen motors up at 4 or 500 hrs where ours are just breaking in, there's a good reason not spin too fast. A 351 with GT40 heads and a very mild cam (more or less a 302 HO) would be a dog at the dragstrip in a car. Ford put that same more in the original Lightning and it made 250 or so Hp, with a marine cam it made 310. Long intake runners and smaller heads are our friends. |
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TRBenj
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Posted: February-10-2014 at 1:24pm |
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Oh, theres a lot of useful info that can be gleamed from the car and truck guys... but boat (and specifically direct drive ski boats) are a different animal.
Stock marine engines certainly have a lot in common with their truck and industrial counterparts, but if you go and build a truck motor for your boat, it'll leave a lot of power on the table. GT40/GT40p heads on a 351w are a lot more conservative than you *need* to go on a boat, but its a nice step in the right direction. Single plane manifolds, high flow heads and big cams can be put to good use in our boats and improve every aspect of performance... which is not the case with a truck motor that needs to pull a heavy load around, tow, etc. There arent a huge number of people building these types of powerplants for ski boats, but that doesnt mean they dont work well. |
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lakedog55
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Posted: February-10-2014 at 8:45pm |
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Alright,
I think I won't bother with it. Seems like another place to get a leak anyway. I am still worried about clearance. On the 87ish boats they had a flame arrestor that was about 1 inch tall. I am going to try and get my hands on one. Or go with a k and n filter. Thanks for the info mike |
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Lakedog55
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8122pbrainard
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Posted: February-10-2014 at 9:32pm |
Mike, Careful to get the K&N that is USCG rated as a flame arrestor. |
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lakedog55
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Posted: February-10-2014 at 10:15pm |
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Yep,
only going that way as last resort. Mike Thanks pete |
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Lakedog55
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lakedog55 wrote: