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Old 05-06-2004, 12:46 AM
  #21
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1) My personal opinion is get rid of the MSD ignition, if the engine is properly tuned, you don't need it. I don't have it on my old 900's (572 cid/w2 750 HOLLEY'S) and I don't have it on my new 1000's (615 cid/w2 750 HOLLEY'S).

2) You are over carburated/jetted. Today I wittnessed Tommy @ CHIEF ENGINES get another 90 hp out of an engine by just properly jetting the carburators.

The best money you will spend is to put BOTH engines on the dyno and set them up properly. If there's no one in the area, create them up and send 'em on down and we'll be glad to look at them for you. Call Tommy first to check the schedule.

Robert
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Old 05-06-2004, 09:14 AM
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What PSI did the stock blowers run ?
If you ran 5 psi on a small blower turning it fast , and 5 psi on a big blower turning it slow , you didn't really change anything . The only advantage would be less heat build up . If you don't change the heads or the cam or the cubic inch , you are not getting more volume in . Pressure is pressure if all else is the same . Adding more carb to the same mix may have just screwed up the air fuel ratio . Also 34 degrees is too much for blowers in offshore boats . You may be detonating ,slowing it down ..... Just my .02

Good luck !
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Old 05-06-2004, 09:26 AM
  #23
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Quote:
Originally posted by boot
What PSI did the stock blowers run ?
If you ran 5 psi on a small blower turning it fast , and 5 psi on a big blower turning it slow you didn't really change anything ...
Bingo
5 psi is 5 psi wether its a little Weiand or a Ginormous 14-71

Smaller top pulley time crank her up to 7 or 8 PSI with a 420 you will not generate as much heat pushing thos psi's as you Weiand. That engine only has 7.5:1 comp ratio wich is conservative.

Just with my very numble opinion with my very limited engine knowledge
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Old 05-06-2004, 09:56 AM
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How was it tuned to begin with? I'll bet you're running way fat and if you are it could easily cost you 90hp (as mentioned above).

If pulling the engines and sending them to a dyno is not an option then what about welding a bung in the exhaust for a wide band 02 sensor? Does anyone else use a wide band in the boat to tune? I haven't seen it before in a boat. Is that not really an option in the boat? I'm not sure where in the exhaust you'd have to put it. This may be a much less expensive option than pulling the engines. You can get a great wide band for around $700. Where are you located. I didn't look. If you're near Dallas I can loan you mine. You can weld in a couple of 02 bungs for $20 and find out what it is doing. I'll bet your A/F is way off.

You may also have too much timing. Retarding it may get you a few extra HP but won't make the difference you're looking at. The A/F ration may. Tune it. A proper tuning can easily be worth 100hp on a forced induction application.

I would, however, respectfully disagree that 5psi is 5psi. Pressure (boost) and volume are inversely related. Increase volume and you loose boost. I've seen a large volume centrigugal supercharger (Paxton Novi) make 60 hp more than a small volume (Powerdyne) supercharger with both at 10psi and no other changes. Increase volume without loosing boost and you will increase power. All boost is not created equal.
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Old 05-07-2004, 03:41 PM
  #25
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TTT - I am still curious to see if anyone has a wide band 02 bung in their boat exhaust and if so where it was mounted. Is this feasible? I guess on a dry exhaust it certainly would be. Just curious. I'd love to be able to hook mine up to my wide band.
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