[Question] Boost / Intercooler / Ignition BBC questions
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Boost / Intercooler / Ignition BBC questions

  1. #1
    Member TOMSS1's Avatar
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    Default Boost / Intercooler / Ignition BBC questions

    I have a Sanger Ski Hydro lake boat that I am in the process of building an engine for out of parts I had and trying to keep the money resonable and reletivly dependable. I need a bit of advise on a few things. I know little about boats or Blown gas, The specs are:

    Gen VI 502 plus .030
    8.5 to 1
    Zero deck with 17046 Fel pro gaskets
    Iron merlin 320s w 2.250 intakes with a good valve job and some port work
    Crane solid roller Intake .737 lift, 274 duration @.050, Exhaust .726 lift, 284 duration @.050, 114 center, advanced 5
    Mert short manifold
    Old Terry Kell tube core intercooler
    Hampton big rotor 6-71 (No teflon)
    2 950 CFM Pro Systems carbs

    I would like to run Pump gas (midwest, No E10), Might consider mixing some av gas if it will help?

    I need to know :
    A blower overdrive and a boost number that is safe but not overly so?
    How do you recommend dealing with intercooler water temp on the Dyno?
    A Starting point on timing?
    A plug recomendation (14mm, .460 reach, tapered seat)?

    I had Cirello do me a Super mag 3 and I have a PSI rev limiter on it, But it looks like most of the blown gas folks running GN boats run MSDs so am I making a mistake here?

    I really appriciate all the info that that you all are willing to provide. It has been a big help so far

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  3. #2
    gn7
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    Quote Originally Posted by TOMSS1 View Post
    I have a Sanger Ski Hydro lake boat that I am in the process of building an engine for out of parts I had and trying to keep the money resonable and reletivly dependable. I need a bit of advise on a few things. I know little about boats or Blown gas, The specs are:

    Gen VI 502 plus .030
    8.5 to 1
    Zero deck with 17046 Fel pro gaskets
    Iron merlin 320s w 2.250 intakes with a good valve job and some port work
    Crane solid roller Intake .737 lift, 274 duration @.050, Exhaust .726 lift, 284 duration @.050, 114 center, advanced 5
    Mert short manifold
    Old Terry Kell tube core intercooler
    Hampton big rotor 6-71 (No teflon)
    2 950 CFM Pro Systems carbs

    I would like to run Pump gas (midwest, No E10), Might consider mixing some av gas if it will help?

    I need to know :
    A blower overdrive and a boost number that is safe but not overly so?
    How do you recommend dealing with intercooler water temp on the Dyno?
    A Starting point on timing
    A plug recomendation (14mm, .460 reach, tapered seat)?

    I had Cirello do me a Super mag 3 and I have a PSI rev limiter on it, But it looks like most of the blown gas folks running GN boats run MSDs so am I making a mistake here?

    I really appriciate all the info that that you all are willing to provide. It has been a big help so far
    the GNs are pretty much split about 50/50 on mags VS MSD. The really cool guys run the MSD, the wannabes run mags
    If you can just run a garden hose with 100% consdent loss thru the cooler on the dyno. Carefull, not to much pressure. But get a good steady flow thru it.
    I would hold the boost to 6 lbs unless the dyno shows different.
    Plug, start with a R5673-9 NGK. You may be able to go the a R5674-8 but with iron heads I would start with the 9.
    Start you timing at 28 degress and bump it 2* at a time. It may start losing power after 32.



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    Member TOMSS1's Avatar
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    Quote Originally Posted by gn7 View Post
    the GNs are pretty much split about 50/50 on mags VS MSD. The really cool guys run the MSD, the wannabes run mags
    If you can just run a garden hose with 100% consdent loss thru the cooler on the dyno. Carefull, not to much pressure. But get a good steady flow thru it.
    I would hold the boost to 6 lbs unless the dyno shows different.
    Plug, start with a R5673-9 NGK. You may be able to go the a R5674-8 but with iron heads I would start with the 9.
    Start you timing at 28 degress and bump it 2* at a time. It may start losing power after 32.
    Where should I start with the overdrive? and can you give me a bit more info on your unless the dyno shows different?, No experience with Blowers and dynos only blowers and fuel, Thanks again for the info, Tom

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  6. #4
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    Default over drive

    any where between 0% (1to1) & 7.5% over. that should be about 5.5lbs to 7.5lbs. i would think you could push it a little bit further than 6lbs, but the dyno is the place to figure that one out. start at 1 to 1 and do all your base line and break in there. then go up until your comfortable with everything.

    i ran break bleed water through my intercooler on the dyno at Westech. it wasnt real cool, about 80+* if i remember right, but it was the best we could do. on a good note, it just means i should be that much safer with lake / river water.

    my pump gas tune up is with 11lbs of boost, and i could have gone a bit further. but thats with a lot of head work and other goodies to help fight detonation. i run a 14-71, and a super chiller.

    the smaller the blower, the more heat it will make as you increase the overdrive. you will start making more heat and it will make the extra boost worthless as far as adding power, and will make it detonate easier. with my 509 and a 10-71, it was maxed out at 25%/15lbs, and was barely making more (if any) power than when it was at 20%/14lbs. it was making a ton of heat. that was 15lbs on 100ll av gas.

    ive since made it a 540 with a 14-71, and am on pump gas at 11lbs & making pretty much the same power (with so much less heat).

    just keep the overdrive reasonable!! as you go up, your gains will get less and less, and with each increase, it will get harder on the engine than the last change, until it reaches a point at which it will be negative. of course, by that time it will be in pieces on pump gas

  7. #5
    gn7
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    the biggest reason I would hold it to 6-7 pounds to start is the iron heads, and because I don't know much about the intercooler, and how well the lower the intake charge. 6-7 pounds should be safe, unless the dyno tells you otherwise so let me explain,

    dyno testing is about finding what the motor wants. A good operater will have what is called a "loop" he is comfortable with. You start with a safe baseline like 6-7 psi and 28* timing, and good safe guesstimate on the jetting. You watch the A/F and get a HP reading. If the jetting is off, you fix that first, then maybe a little timing. You may go all the way to 32-34 degrees. Then you can go back to 28 and try 2 more lbs of boost and run it again. You may find that 7 lbs at 32* is pretty close to 9lbs and 28*, but the curve is different. The main thing is, if you over boost it on the dyno, it will lose power due to detonation. Same if you go over on the timing. when you find where the motor is happy, you may take a degree of timing out, or lower the boost a lb for a little cushion. The loop will tell you what works. It takes some time, but thats why you on the dyno. To find out what makes power and what doesn't.
    A good operater can be worth more than the dyno itself. they have seen alot of motors, and pretty much know what they are seeing.

    Then, if your good, like Steelcomp, everything you do from the base pull loses power, the A/F is dead on, your on the dyno for 1 hr, and go home. But those kind of guys are just showing off and try to make the rest of us look bad.



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    Then, if your just plain lucky, like Steelcomp, everything you do from the base pull loses power, the A/F is dead on, your on the dyno for 1 hr, and go home. But those kind of guys are just showing off and try to make the rest of us look bad.
    There...fixed it for ya.

    The 489 I did a couple years ago was a very basic blower engine with a few minor differences. Alum heads (unported Canfield 310s), custom hyd. roller 248/260, .661/.640 112 with (2) 850's, no intercooler, and a BDS 8-71 and intake. On straight 91 oct, 28*, 6# boost, it made 790hp @ 6400. With 110, 9# boost, 33* it made 853 @ 6700. It's sitting in a '68 El Camino waiting for the final touches, but it would have made a great marine engine. I think with an intercooler and pushing it just a little more it had close to 900 sitting there.
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