Small Block Jet Boat engine ?
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Small Block Jet Boat engine ?

  1. #1
    Resident Ford Nut Sleeper CP's Avatar
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    Default Small Block Jet Boat engine ?

    If someone was going to build a 18' (light weight) River Racer and wanted a very quick boat would a strong SmBlk on nitrous be a good choice ?

    Regardless of the brand of engine used, Ford, Chevy or Mopar you could build a 650-700 hp Smblk at 6,750-7,000 with a 300 hp nitrous shot to get you 1,000 hp at 7,000 how would it stack up against a Big Block ?

    It was raining yesterday before the game, so I had sometime to put this together. This is a 409" Smblk Ford that Danny Crower and I built for the 2004 Engine Master's competition. We made some good number's considering how little time we had to get it together and run it on the dyno. The custom rotating assembly was delivered 6 week's behind schedule. It's a long story that I can add later if you guy's are interested.

    In any case, here are the dyno sheet's from the two combinations that we ran. This engine had to run from 2,500-6,500 on 91 octane. I dropped off the lower scale so it would fit better on the sheet's. I think (know) this engine with a few changes could make 700 HP at 6,800 to 7,000 with a single 4 barrel. Something to think about.....

    Edit: I should add that the head's are cnc ported AFR 225's w/58cc chambers they flowed 306/201 cfm's. The heads intake stalled at .600 should flow closer to 325 but on the 4.00 bore there was just to much shrouding of the valve.

    The engine made 1.61 hp per cubic inch and produced 2.15 hp per cfm.

    Edit: The small cam that we ended up with had a .438 & .414 lobe lift and was 258/266 @ .050 with a 106 lobe seperation we ran 1.6 int and 1.5 ex. rockers. the lift was .701/.621. The Victor Jr. made the most HP and Trq the RPM Air Gap made the best power under 5,000 rpm. And the Super Victor was just too big for this application it was down on power and trq. from bottom to top.

    With an .060 over bore to make the engine a 421 incher, and to unshroud the intake valve and a couple of tweaks the intake should flow 325. 325 x 2.15= 698.75 hp Should be in reach.

    This is the engine with the Eldelbrock RPM Air Gap Dual Plane:


    This is the same engine with a Victor Jr. Single Plane:



    Here is a hand graph on the two engine's compared to each other:



    Of these two combo's the Dual Plane RPM Air Gap was the better choice for the competition. Even though it was down 37 peak HP 620 vs 657 it was up on trq all the way from 2,500 to 4,900 and it stayed ahead on the Average numbers which is what the Engine Master's Competition is scored on.
    Last edited by Sleeper CP; 02-05-2008 at 03:13 PM.

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    Senior Member mwjsone's Avatar
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    Check out white water alloy hulled tunnels with out NOS some pushing into the 100s range
    http://www.jetboatracing.com/phpbb/index.php

    http://www.outlaweagle.com/forum/

    and somewhere Xero may pipe in here he is the Alloy Advocate

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    Ya know,I have wondered this as well. You could do a turbo small block also and make some serious HP. Brian Macey is making huge HP with small block turbos. A well thought out small block on nitrous should do the trick with a light weight carbon hull.

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    cfm
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    Can't answer the question directly since I'm not that familiar with jet pumps and what would work better big block vs small block, but I can say - as your strong SBF build shows - small blocks are putting out more tq/hp than ever. Gotta' love good ol' USA technology and heavy R&D. Oh yeh, Australia (ahem, CHI) too.

    Here's (below graph) a healthy SBC build (LS PLatform 427cid) Katech conjoured up for street cars and reliable long event road racing. With the advent of the LSX blocks 480cid (500 with tall deck) SBC with 12-15° cyl heads with offset + garguantuan valves with flow ratings being mega from even OEM, the small blocks are going (and have started too) to start replacing many big blocks. The marine OEM's are allready diving in head deep. Example: here is a 'basic' OEM head that cost less than $900 complete for pair - add another $200 for the offset rocker arm system.
    http://www.gmhightechperformance.com...ads/index.html

    These are going to be some very exciting years a head of us.

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    The big Smblks are just another way to go rather you go NA or supercharged.

    I think a Pro-Charger on a smblk jet boat would be cool.

    Sleeper CP

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    Distinguished Member David 519's Avatar
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    I've only had one jet boat and it was a long time ago. Great lake/ski boats though, if a bit rough on gas. Not all that long ago, I'd have said a SBC can't make enough torque for a boat. Now a day's that's definitely not the case. I don't know a lot about Ford/Dodge power, but a 23 degree 434" SBC is really easy to hit 650 hp without getting to crazy as to effect durability.
    That said, I'm just to used to looking at BB engines in boats and a SB from any mfg looks "wrong" to me.

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    Check out what Brian is getting out of these turbo small blocks at horsepower connection .com.
    Last edited by Oldelmn8tr; 02-06-2008 at 02:11 PM.

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    Amm
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    If you are into this type of thing, build your own out of plywood. http://www.glen-l.com/designs/inboard/rampage.html

    The weight advantage of carbon fiber without the cost. An 18' 750 lbs hull would fly with the kind of power you are talking about.

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    Quote Originally Posted by Amm View Post
    If you are into this type of thing, build your own out of plywood. http://www.glen-l.com/designs/inboard/rampage.html

    The weight advantage of carbon fiber without the cost. An 18' 750 lbs hull would fly with the kind of power you are talking about.
    750 lbs ? My open bow 19' weighs 780 bare, I know of a few sub-500 lb 18' Gullwings.

    None of the racer's want to chime in...... hummmmm ?

    Sleeper CP

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