Motor advice Pls!
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Motor advice Pls!

  1. #1
    Member HawaiianPunch's Avatar
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    Default Motor advice Pls!

    Heres a question to anyone with some knowledge, I am trying to put a solid motor together, I have a gen 4 block with 781 heads with some porting and seat work, comp cams RR, the cam I have is 224in 230ex @050 .456 .461 on 114 lobe sep. not sure about the cam but machine shop said it works for my set up?? I am running log exhaust, 12jc "A" 19' boat. Where should I go from here for the best reliability, power, etc. I have not yet got an intake or carb, and I still have all the stock pistons, rods and cast crank but was thinking about going to all forged rotating assembly? Any info is appreciated! I had a falling out with the machine shop and I got all my stuff back in boxes!!
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    New here Beer:30's Avatar
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    Quote Originally Posted by HawaiianPunch View Post
    Heres a question to anyone with some knowledge, I am trying to put a solid motor together, I have a gen 4 block with 781 heads with some porting and seat work, comp cams RR, the cam I have is 224in 230ex @050 .456 .461 on 114 lobe sep. not sure about the cam but machine shop said it works for my set up?? I am running log exhaust, 12jc "A" 19' boat. Where should I go from here for the best reliability, power, etc. I have not yet got an intake or carb, and I still have all the stock pistons, rods and cast crank but was thinking about going to all forged rotating assembly? Any info is appreciated! I had a falling out with the machine shop and I got all my stuff back in boxes!!
    Depends on HOW you want the boat to run, in my opinion. That cam is quite small - good STREET cam, especially on a 114 center. The pros will hopefully kick in here and give you some specs for how you want your boat to run. That cam will be good for staying low-RPM, but is gonna run out of leg on the upper band. If it's just a family boat that you don't want max top end, but more bottom end - you'll probably be advised to stick with that cam.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.
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    At this point I dont want to sell myself short, if I have to get a new cam I will, I would like to see around 70-75mph?? I think that would be fun! And I dont want to do it twice, so I'm asking first! Someone once told me measure twice, cut once.
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    I think you can probably find something someone else has put together much cheaper than doing it yourself, Machine work and good parts are very expensive and what you are tring to build is very mild. I would stick to a flat top or small dome piston so you have no worries about fuel, A forged bottom end is a good idea but not mandatory, more so for a jet boat as the motor works very hard. large oval port will give you good all around power topped with a dual plane manifold will work well over a wide RPM range.
    Good luck
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    Quote Originally Posted by varmit86 View Post
    I think you can probably find something someone else has put together much cheaper than doing it yourself, Machine work and good parts are very expensive and what you are tring to build is very mild. I would stick to a flat top or small dome piston so you have no worries about fuel, A forged bottom end is a good idea but not mandatory, more so for a jet boat as the motor works very hard. large oval port will give you good all around power topped with a dual plane manifold will work well over a wide RPM range.
    Good luck
    Thx! Most of the machining has been done, I really want to put this mill together, just want to do it right and not worry about blowing it up on the water! Any advice on using a 427 crank and pistons they are forged factory arent they? Any draw backs going that route?
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    Budget? This may help.
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    Quote Originally Posted by HawaiianPunch View Post
    Thx! Most of the machining has been done, I really want to put this mill together, just want to do it right and not worry about blowing it up on the water! Any advice on using a 427 crank and pistons they are forged factory arent they? Any draw backs going that route?
    427 crank is also a 396 crank and both motors are not necessarily forged. Base models (325hp) would be cast/cast.

    You need the casting number off of the crank and/or just post a pic of the crank. The seam along the center of the casting will tell if it's a forged piece or not.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.
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    Quote Originally Posted by BOOSTPOWER View Post
    Budget? This may help.
    Ok here is a list of what I have;

    - 2 bolt bbc truck block line bored, decked, 030 over
    - 781 heads ported polished exhaust, intake cleaned up, guides installed, cut for bigger valves
    - stock pistons, cast crank, rods
    - stock valve train, with guide plates and triple springs??
    - crane street/strip roller rockers
    - edlebrock gear drive
    - holley dual plane intake ( came with boat, willing to swap out to make it right)
    - holley 750 vac sec ( old and tired, came with boat)
    - A cam which is too small ( I was told it would work now deemed too small) What cam profile do I need?
    - berkley 12jc alum "a"
    - 19.5 boat

    Obviously I will have to buy new valves, springs, locks and keepers. Planning on going with some forged pistons, (what comp ratio??) and rods, still on the fence for the forged crank, hence my idea of finding a gm steel crank. I have most everything else, VC, exhaust, gaskets, stainless arp bolt kits, etc..the guy who MIGHT be putting it together said 2500 including any machining I will need and a dyno session is included in the 2500. So I was thinking 5000 would be my budget which includes the 2500, plus 2500 for parts?? Am I close?
    And will this get me;

    - 70-75mph
    - 500hp
    - reliability
    - solid platform to build upon
    - longevity
    - lots of fun?

    Thx for any advice
    Last edited by HawaiianPunch; 10-25-2011 at 09:30 PM.
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