How much boost can you run on a msd 7al before you need a Mag
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How much boost can you run on a msd 7al before you need a Mag

  1. #1
    Senior Member blownsouthwind's Avatar
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    Default How much boost can you run on a msd 7al before you need a Mag

    I have a Blown 548 with brodix big 2 heads ,and a BDS stage 4 8-71. I am switching to injected on alcohol with a Big & Ugly hat. I am using a msd 7-al box. How much Boost can I run before I need to switch to a mag. and what is the max timing on the 7-al with alcohol?

    Thanks

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    RAT PATROL rich s's Avatar
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    I am just a hack, with a opinion.I am putting similar combo together
    just less c/i and a bird.I think it is more of LIGHTing the fuel charge.
    A decent mag will put x2 the amount of spark at the plug than the 7al
    plus the msd will use at least 1 amp per 1000 rpms , so alternater may be needed.
    alternater not needed with the mag,it makes it`s own
    on the timing thing I want start out conservative and sneak up on it.
    note:I am a new to some of this stuff.and I don`t know what your intened use is
    we would like to see some pics.

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    i'm back!! 1QuickCP's Avatar
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    been there done this on many motors...forget the msd 7,8,10 or whatever...do yourself a HUGE favor and stick a msd 25 or 44 amp mag in there and be done with it if your on alky. you might get away with 10 lbs or so before you have tuning problems and shootin ducks ....but you will be chasing pills and nozzles forever when the only problem is the ignition.

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  6. #4
    gn7
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    I am a die hard MSD fan. If this was gas deal, I would tell you you could build enough cylinder pressure that deal that the 7 couldn't deal with it. But the alky is the clincher. You need a mag. And maybe a Hunt, or Zig etc. Vertex could get it done, But like 1 QUICK CP said, get some power. I wouldn't think you need the 44. But you aren't going to get it done with an MSD 7.



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    Last edited by gn7; 10-06-2010 at 09:44 AM.

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    Gas likes the MSD, (big gap, quick rise time spark)because it lights easier. Alcohol needs the big mag (lower voltage, smaller gap, LONGER DURATION spark), at much over 6 to 10 psi depending on other factors, because you have much more quantity of fuel and it is harder to light. You can light paper with a match, a log requires a lot more heat to ignite it, but the log will make more energy in the end. TIMINATOR
    MODESTY IS A CRUTCH FOR THE INCOMPETENT!

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    Senior Member wagspe208's Avatar
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    I am no expert on the max either, but I know for sure.....
    This assumes you mixture is somewhat close.... if you are 30% fat God won't light it.....
    You.. well, I have no idea what "you" can run... but "I, or We" ran 20# at The Cove. No evidence of misfire... either sound, or showing up on the data acquisition. Now, the mixture was good, plugs were showing a little heat, extended tip plug, etc. Your results may vary.
    My big bitch especially with the mag thing and drag racing is they are more sensitive to idle mixture. Any hack can get an MSD piece to start and not touch the barrel valve. With a mag (especially a vertex if you call that a mag) they are much more sensitive. River runner... well, no big deal.
    I run an alternator with a 7AL-2. The alternator was worth .1 ET. No shit. We had alternators fail, and sure enough we slow down .1. I'd not have believed it if I had not had it happen to me a few times over the years. Just a voltage thing I guess.
    Wags

  9. #7
    gn7
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    You disconnet the alterater from a MSD or HEI and you will pay for it in power. Unless your running a FULLY CHARGED16volt battery, you need the alternater.
    Saying you can't light a overly fat misture has some merit, but do you have any idea what is going on, on the inside of a top fuel motor, or even a TAD/ TAF for that matter. Twin MSD 44s can start a forest fire in a down pour.



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    Last edited by gn7; 10-05-2010 at 07:50 PM.

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    Senior Member bp298's Avatar
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    Quote Originally Posted by wagspe208 View Post
    I am no expert on the max either, but I know for sure.....
    This assumes you mixture is somewhat close.... if you are 30% fat God won't light it.....
    You.. well, I have no idea what "you" can run... but "I, or We" ran 20# at The Cove. No evidence of misfire... either sound, or showing up on the data acquisition. Now, the mixture was good, plugs were showing a little heat, extended tip plug, etc. Your results may vary.
    My big bitch especially with the mag thing and drag racing is they are more sensitive to idle mixture. Any hack can get an MSD piece to start and not touch the barrel valve. With a mag (especially a vertex if you call that a mag) they are much more sensitive. River runner... well, no big deal.
    I run an alternator with a 7AL-2. The alternator was worth .1 ET. No shit. We had alternators fail, and sure enough we slow down .1. I'd not have believed it if I had not had it happen to me a few times over the years. Just a voltage thing I guess.
    Wags
    yeahyeahyeah... but you got that double top secret triplewhammy delay box that does everything for ya...

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    Senior Member wagspe208's Avatar
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    GN-- oh I am with you. A 44 will light anything. Fuel guys are around what?? 100 gpm pumps now?? Something around there.
    I think a 7AL is an excellent ignition. A mag is needed is some situations. Well, many applications. But is the "average bad ass" river boat, or under Pro Mod stuff, it is just overkill. If a guy wants to spend the money, go for it. Just not "necessary".

    BP-- I forgot to mention the small reactor I had build into the black box to light the fuel. LOL
    Wags

  12. #10
    Distinguished Member David 519's Avatar
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    Quote Originally Posted by blownsouthwind View Post
    I have a Blown 548 with brodix big 2 heads ,and a BDS stage 4 8-71. I am switching to injected on alcohol with a Big & Ugly hat. I am using a msd 7-al box. How much Boost can I run before I need to switch to a mag. and what is the max timing on the 7-al with alcohol?

    Thanks
    We're kinda new to blown alcohol and running a similar combo, 565 BBC w/8.71/Bird in a flat. We're using a MSD12 with great results but only run about 5-6 lbs boost. We set our timing to 33-34 degrees and never change it.
    Also, I agree with Wags on the big mags. Anything below 1500 HP a 44 is way overkill unless you need to do some welding between rounds. However, on the flip side, usually you can find 44's easier in the used market on sites like inside top alcohol dot com....
    Last edited by David 519; 10-06-2010 at 08:45 AM.
    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.....

  13. #11
    gn7
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    Quote Originally Posted by David 519 View Post
    Also, I agree with Wags on the big mags. Anything below 1500 HP a 44 is way overkill unless you need to do some welding between rounds. However, on the flip side, usually you can find 44's easier in the used market on sites like inside top alcohol dot com....
    Besides the fact that the 44 is down right lethal, if you don't need that much power, all it does is eat spark plugs. Like David said, the thing is nothing more than a mini arc welder.



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  14. #12
    Senior Member bp298's Avatar
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    Quote Originally Posted by gn7 View Post
    Besides the fact that the 44 is down right lethal, if you don't need that much power, all it does is eat spark plugs. Like David said, the thing is nothing more than a mini arc welder.
    my digital 7 does a real good job doing that.

  15. #13
    gn7
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    And it doesn't use 44 amps primary current. More like 1 amp per 1000 Rs



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    Last edited by gn7; 10-06-2010 at 11:46 AM.

  16. #14
    Senior Member bp298's Avatar
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    Quote Originally Posted by gn7 View Post
    And it doesn't use 44 amps primary current. More like 1 amp per 1000 Rs
    true. all i know is, it eats 'em up a whole lot quicker with the dig 7/trigger/hvc, than it did with the 7al2/blaster/billet dist... don't care to buy plugs by the crate...

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