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Critique my build

  1. #1
    Senior Member Bigblockbill's Avatar
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    Default Critique my build

    So my boat is not as fast as I hopped it should be, crituque my build and tell me where I went wrong or maybe I am just wish full thinking. The boat is a 1991 24' Eliminator Deck Boat. My guess is it weights 4000 lbs dry. The other day I had 50 gallons of fuel and 5 people in it with a bravo 1 prop and 1.50 gears and only went 58 mph on GPS at around 4600 rpm or so (Tach has a bad connection right now and gets flaky over 4K, so I don't really know what the final RPM was. Now we boat at 4300 ft elevation and the density air was probably around 6000 ft.

    Last winter I pulled off some edelbrock perfomer RPM heads and installed some Merlin Iron heads that have been worked flowed around 370 on the intakes... thinking it would benifit, but with the tach not really working and I did not have prior gps data on it I have no idea if its better or worse. Did definatly loose some bottom end torque.

    So anyway here are the motor specs:

    523 inch bowtie block,
    flat top pistons (4.563 bore 4 in stroke) (could use a lot more compression at this altitude)
    merlin iron heads
    solid roller cam (.653/.660 lift and 248/254 @0.050),
    1.8 Ratio rockers and girdles
    Vr Jr intake,
    Holley HP-1000 carb (88 jets with PVs blocked off)
    Timing at 40 degrees (High Altitude),
    IMCO thru hull exhaust.

    I would think I could swing a 24 p prop at over 4600 but maybe its just wish full thinking. What do you think? Anything I really blew?
    24' Eliminator Fundeck

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  3. #2
    gn7
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    Altitude density and compression are killing you. You could have EASILY gone another point on the compression, maybe 2, even with the iron heads, and for sure with the Edelbrocks.



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    Senior Member md-11mike's Avatar
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    The carb intake and heads are for sure set up to breath at the upper end of the rpm range which will doesnt help the velocity of the air running into the engine at lower rpm which will affect the bottom end of the rpm and torque. Take a look at a carb CFM calculator (internet search). You would probably do better with a dual plane intake.

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  6. #4
    Senior Member Bigblockbill's Avatar
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    Quote Originally Posted by gn7 View Post
    Altitude density and compression are killing you. You could have EASILY gone another point on the compression, maybe 2, even with the iron heads, and for sure with the Edelbrocks.
    Agreed. I bought the boat with that bottom end on it, or else I would not have done it that way. I used to run an iron head 468 motor with 11.5:1 pistons on pump gas out here with out any problems and a full load of timing.
    24' Eliminator Fundeck

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    Senior Member Bigblockbill's Avatar
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    Quote Originally Posted by md-11mike View Post
    The carb intake and heads are for sure set up to breath at the upper end of the rpm range which will doesnt help the velocity of the air running into the engine at lower rpm which will affect the bottom end of the rpm and torque. Take a look at a carb CFM calculator (internet search). You would probably do better with a dual plane intake.
    Yes agreed the heads are probably to big and hurting bottom end and I am not making it to the top end so thats really no good. I have to disagree about a dual plane intake though as they do work better from idle to 2500 or 3000 rpm but other than getting on plane (of which I have no problem) the boat spends no time under about 2700, so if thats the case wouldn't the single plane intake be the better choice?

    The carb is one of the things I am really questioning right now. I found an article stating that an HP 1000 carb is really just a worked over smooth body 850 and 850 base plate and that Holley inflated the numbers to be more competitive with the inflated numbers from other carb companies, so I don't know what to think about that yet. The same write up said the HP950 was actually a 750 body and a 850 base plate. The other data point I have is we tired a HP950 or 1000 (don't recal which) on a 496 jet boat and the boat went 5 mph slower than it did with a 850 double pumper... (Note: The boat sounded crisp but we did not make any jet changes or do any tuning on the HP carb so maybe it was just really fat?) So with all that being said I do have plans to borrow and try a standard Holley 850 dp on the motor to see what it does. Anyone else have any compairsons of the HP series carb vs standard ones?
    24' Eliminator Fundeck

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    Quote Originally Posted by Bigblockbill View Post
    So my boat is not as fast as I hopped it should be, crituque my build and tell me where I went wrong or maybe I am just wish full thinking. The boat is a 1991 24' Eliminator Deck Boat. My guess is it weights 4000 lbs dry. The other day I had 50 gallons of fuel and 5 people in it with a bravo 1 prop and 1.50 gears and only went 58 mph on GPS at around 4600 rpm or so (Tach has a bad connection right now and gets flaky over 4K, so I don't really know what the final RPM was. Now we boat at 4300 ft elevation and the density air was probably around 6000 ft.

    Last winter I pulled off some edelbrock perfomer RPM heads and installed some Merlin Iron heads that have been worked flowed around 370 on the intakes... thinking it would benifit, but with the tach not really working and I did not have prior gps data on it I have no idea if its better or worse. Did definatly loose some bottom end torque.

    So anyway here are the motor specs:

    523 inch bowtie block,
    flat top pistons (4.563 bore 4 in stroke) (could use a lot more compression at this altitude)
    merlin iron heads
    solid roller cam (.653/.660 lift and 248/254 @0.050),
    1.8 Ratio rockers and girdles
    Vr Jr intake,
    Holley HP-1000 carb (88 jets with PVs blocked off)
    Timing at 40 degrees (High Altitude),
    IMCO thru hull exhaust.

    I would think I could swing a 24 p prop at over 4600 but maybe its just wish full thinking. What do you think? Anything I really blew?
    I have had two engines dynoed here in Colorado Springs, #1 a o49 headed 10.8 454 that made 567 at 6100 corrected and 34 degrees timing, #2 a brodix headed 572 with 10.4 that made 837 at 6300 corrected also at 34 degrees timing, the heads were kinda big for this build. Point being not so much the power but the timing. I ran both engines down in Missouri on pump gas at close to 32 degrees just to be safe with the cheap gas. Doesn't 40 degrees total on your build seem like way too much? Where is your cam setting at. I bet it will like 34 total and 4 or so degrees advanced on the cam timing if your hanging out at Navajo. I made the mistake of retarding the cam 4 degrees on the 454 and lost out on 300 or so rpm in my jet. Those Merlin heads porbably have 119 to 123, or so chambers(110 on the Edelbrocks) with a flat top will be pretty low, like 8.5 if your lucky. Now you have a reply from an amateur so NOW lets hear from the the experts!
    Last edited by jungledave; 05-23-2012 at 06:09 PM.

  9. #7
    gn7
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    Quote Originally Posted by jungledave View Post
    I have had two engines dynoed here in Colorado Springs, #1 a o49 headed 10.8 454 that made 567 at 6100 corrected and 34 degrees timing, #2 a brodix headed 572 with 10.4 that made 837 at 6300 corrected also at 34 degrees timing, the heads were kinda big for this build. Point being not so much the power but the timing. I ran both engines down in Missouri on pump gas at close to 32 degrees just to be safe with the cheap gas. Doesn't 40 degrees total on your build seem like way too much? Where is your cam setting at. I bet it will like 34 total and 4 or so degrees advanced on the cam timing if your hanging out at Navajo. I made the mistake of retarding the cam 4 degrees on the 454 and lost out on 300 or so rpm in my jet. Those Merlin heads porbably have 119 to 123, or so chambers(110 on the Edelbrocks) with a flat top will be pretty low, like 8.5 if your lucky. Now you have a reply from an amateur so NOW lets hear from the the experts!
    His compression works out right at 9.0 assuming a 118 chamber and .00 deck and a .040 head gasket. The Eddy heads would put him right around 9.6 at 110, more if he cut them.
    If I was running 10.8 or 10.4 compression, I might try 34 degrees myself. But with 9 to 1, its a little different game.

    You MIGHT gain from advancing the cam, but it depends on where the CL was ground by the manf to start. I wish I have a nickle for every cam ground 4o advanced out of the box.

    You MIGHT find a tiny bit with 1.7 rockers. The EDDY heads and 1.7 rockers will gain you the most with out having to tear down the lower end.



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  10. #8
    Senior Member EVILFORCE's Avatar
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    Did I miss it? What pitch is your prop?
    No Fool Like A Old Fool is there?

  11. #9
    gn7
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    Quote Originally Posted by EVILFORCE View Post
    Did I miss it? What pitch is your prop?
    24"
    try to keep up Evil.



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  12. #10
    Senior Member Bigblockbill's Avatar
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    The cam is a comp cams so yes it is ground with a 4degrees of advance and is degreed and installed straight up (106 Intake Centerline I believe).

    I believe the edelbrock heads have 118 chambers so compression is the same low number either way. Not sure the deck hight but doubt its zero so I am figuring its actually somewhere around 8.5. Tempted to throw some 13.5 pistons in it and find some E85, but there are no E85 stations at the lake where I store the boat, so I would have to carry my own fuel.... bummer.

    So reading the above posts I am gathering as you go up in compression you have to come down in timing? I am somewhat suprised in CO on the dyno it ended up being as low as 34 degrees. Did you make a pull with more timing and found that the power fell off? I ask only cause I am helping a guy with a drag car and 13.5 :1 pistons and trying to figure out where to set his timing.
    24' Eliminator Fundeck

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    Senior Member md-11mike's Avatar
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    Prior to the head swap what sort of numbers where you getting. RPM and speed?

  14. #12
    Senior Member Bigblockbill's Avatar
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    Thats what sucks... I don't remember. Never put a GPS in the boat till just last week. And the tach has always been flaky up there. I seem to remember 5100 rpm once with the eldelbrock heads, but think I had the drive trimmed waaaay to high. Also have a note that it ran 4500-4800 rpm with 5 people, bimini up, and a medium fuel load with the edelbrock heads so that is in the same range it is now, so I don't think much changed.
    24' Eliminator Fundeck

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    Senior Member md-11mike's Avatar
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    Quote Originally Posted by Bigblockbill View Post
    Thats what sucks... I don't remember. Never put a GPS in the boat till just last week. And the tach has always been flaky up there. I seem to remember 5100 rpm once with the eldelbrock heads, but think I had the drive trimmed waaaay to high. Also have a note that it ran 4500-4800 rpm with 5 people, bimini up, and a medium fuel load with the edelbrock heads so that is in the same range it is now, so I don't think much changed.
    Well I may be wrong here so please let me know but maybe if you tried a smaller prop (pitch or diameter) maybe you could get that set up breathing in the rpm range it will run best. That engine shouldnt really come to life till later in the upper end of the RPM range wihich I dont think in the md 4's your are reaching. What kind of rpm can you run thru and outdrive?

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    The iron merlin heads weigh what 75 lbs more then the aluminum's and the low compression is killing your power. With that low of compression a blower would be a good fix
    If your going to buy pistons you might as well add a 1/4 inch stroke while your in there

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