Ported Oval vs. JEG's Aluminum Rectangular Port heads
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Ported Oval vs. JEG's Aluminum Rectangular Port heads

  1. #1
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    Default Ported Oval vs. JEG's Aluminum Rectangular Port heads

    I'm new to the jet boat thing this year (21' Omega Open Bow, jacuzzi jet) and wiped out some lobes on the cam (Hydraulic flat tappet) a few weeks ago. I'm going to use this as a chance to upgrade. I have a BBC (468, mark IV, 2-bolt main) with a set of ported (bought them that way) large oval port closed chamber heads (milled to 96.4cc) with slightly dished pistons on there now. I also have a set of stock 781 casting (extras), a couple extra 2-bolt blocks, and stock forged crank. I have the opportunity to upgrade to Manley rods (+.250"), 30 or 50 cc dome forged pistons, roller cam and lifters, rev kit (the cam included is a new .726"/.720" lift 284/290 @ 50 with a 108 LSA), Weiand Team G intake, and a set of Jegs Aluminum 119cc rect port cylinder heads (2.30" intake, 1.88" exhaust valves) for a very reasonable price. These are used, but I am going to have all of the parts checked out at the machine shop prior to purchase to verify that the are all sound. The questions i have are: -Has anyone ever used these heads? feedback on them? -Max compression ratio for aluminum heads on this setup? -What is the minimum lobe separation angle LSA for logs vs. headers? (I think the one included is too low from what I have read) -Any other info that would be useful would be very much appreciated! Thanks!

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  3. #2
    cfm
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    Those heads are Canfields.

    Wowzer does that cam have a lot of duration. Need more info on what you are planning to build (rpm range, compression, how to be used, etc) but chances are with that small of a motor and even built for drag race only that cam should not be used. Logs way,way out of the equation.

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    just a ski boat with bark Carnivalride's Avatar
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    If I read this right you have a 21" open bow jet, if so I would think you would need power at or before 6000rpm. Is this a pump gas build or are you planning on running better fuel, because the 50cc dome pistons sound like way too much, the 30cc dome ones would be pushing the compression limit IMHO even with open chamber aluminum heads, probably 10.5-10.75:1 with a 119cc chamber. The cam you mentioned sounds like way too much duration for this build. What do you have for exhaust on this logs or something better?
    Quote Originally Posted by gn7 View Post
    Carnivalride, you really need to find some other hobby. You have no talent for this boat thing

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    Use the Jegs heads, Canfield made them and are very nice heads for the money.

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    Are the heads that Jegs sells now still Canfields? Not tryin to jack! WT


    SOMEONE SAID YOU CAN'T TAKE IT WITH YOU! SO,IM BURNING IT UP ONE GALLON AT A TIME!
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    I believe he said they were used heads. Jegs heads are no longer with the exception of any left in stock. The Canfields are coming back. Don't know if they will be supplying Jegs, but the heads are coming back



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    With the 2.300 valve you don't want to use the jegs heads. Your engine will be a dog unless you want to turn 8500rpm. Chances are they're the 350c intake, not the 310. Either way, the 2.300 valve is way too big for what you're doing. The 781's with 2.19/1.88 valves and a good bowl blend will be a much better choice.
    Last edited by scott foxwell; 10-13-2010 at 09:09 AM.
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    I believe the Jegs heads have 350 cc intake runners. I was shooting for 10.5:1 or so compression. I think the 50 cc dome with .060 head gaskets and .035 deck gives about 11:1 with 119 cc head if I recall the calcs right. The cam doesn't look like the best choice, but I'm especially interested in whether the heads will work for the application. I know they are really for higher rpm use normally, but it is a budget builld and I am trying to use what I have available without too much added work/cost. The feedback is great so far, any more is appreciated!

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    gn7
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    Quick Jets says the heads can never be too big. But when he said that, I don't think he was thinking about a 21 ft Omega with a jacuzzi.

    Like Steel said they are big and will never get anywhere near the flow velocity they were made for at the RPM you'll be turning. Add to that a cam that is way big, and it becomes a double boggie.

    and I don't recommend you running the piston .035 in the hole, plus a .060 gasket for a total fo .095 in the hole and then throw pump gas at a 11 to 1 motor. The combo is screaming detonation!



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    I also have a set of Icon IC 779 pistons (18cc dome) with like a half hour of run time, but could not run the +.250" long rods. Of course I can always buy a set of pistons to match the application if the heads will work...

  13. #11
    just a ski boat with bark Carnivalride's Avatar
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    Quote Originally Posted by uawrestler View Post
    if the heads will work...
    Will they allow a 468 to start and run......... yes

    Will they work well on a 468....... no

    You're not getting it that a 468 in front of a jet pump is not going to run in the rpm range where those 350cc runner heads or that 284/[email protected] cam want to run. In fact the combination you're proposing might run slower than what's in there now.
    Quote Originally Posted by gn7 View Post
    Carnivalride, you really need to find some other hobby. You have no talent for this boat thing

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    108 LSA is super tight for a cam that is pushing 290 degrees @ .050 That is a huge cam that will run like
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    Distinguished Member David 519's Avatar
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    Quote Originally Posted by uawrestler View Post
    I'm new to the jet boat thing this year (21' Omega Open Bow, jacuzzi jet) and wiped out some lobes on the cam (Hydraulic flat tappet) a few weeks ago. I'm going to use this as a chance to upgrade. I have a BBC (468, mark IV, 2-bolt main) with a set of ported (bought them that way) large oval port closed chamber heads (milled to 96.4cc) with slightly dished pistons on there now. I also have a set of stock 781 casting (extras), a couple extra 2-bolt blocks, and stock forged crank. I have the opportunity to upgrade to Manley rods (+.250"), 30 or 50 cc dome forged pistons, roller cam and lifters, rev kit (the cam included is a new .726"/.720" lift 284/290 @ 50 with a 108 LSA), Weiand Team G intake, and a set of Jegs Aluminum 119cc rect port cylinder heads (2.30" intake, 1.88" exhaust valves) for a very reasonable price. These are used, but I am going to have all of the parts checked out at the machine shop prior to purchase to verify that the are all sound. The questions i have are: -Has anyone ever used these heads? feedback on them? -Max compression ratio for aluminum heads on this setup? -What is the minimum lobe separation angle LSA for logs vs. headers? (I think the one included is too low from what I have read) -Any other info that would be useful would be very much appreciated! Thanks!
    Ok, since you asked, here's what I'd suggest. Freshen up the 468 as is, put it in the boat and have a blast skiing/tubing/hanging out. The boat you have is perfect for that. The parts you have are too mismatched and the boat you have isn't a good choice for high HP anyway. Best of luck to you....
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

    Quote Originally Posted by fuelinmyveins82 View Post
    .....I think people forget that racing is supposed to fun. Losing shouldn't be discouraging it should motivate you work on your pile to make it faster.....

  16. #14
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    Listen to David.
    That is really good advice he is offering you.
    Sometimes your money ahead to just say no.
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    with Schizophrenia.

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