To Boost Reference or not to Boost Reference?
01-07-2003, 08:50 PM
#31
Did anyone try this?
If you really want good midrange fuel distribution try mounting the carb sideways. Can you guess why this works better?
BTW any method of power valve referencing, or any type of power valve has nothing to do with idle quality unless the fuel is bypassing a blown diaphram (ie. blown power valve). Think about it!!!!
Also remember a power valve is stupid, it only opens, to allow more fuel into the main metering system (bypassing the jets), WHEN THE VACUUM IS LESS THAN THE (powervalve) DESIGN.
Light boats may need below SC refrencing, heavy boats shouldn't.
BTDT, JB
BTW any method of power valve referencing, or any type of power valve has nothing to do with idle quality unless the fuel is bypassing a blown diaphram (ie. blown power valve). Think about it!!!!
Also remember a power valve is stupid, it only opens, to allow more fuel into the main metering system (bypassing the jets), WHEN THE VACUUM IS LESS THAN THE (powervalve) DESIGN.
Light boats may need below SC refrencing, heavy boats shouldn't.
BTDT, JB
Last edited by John B; 01-07-2003 at 08:57 PM.
01-07-2003, 10:02 PM
#32
Picture for above post
Carb mounted sideways= great fuel distribution in the midrange, because throttle plates can't direct fuel to their backside until they are open 90 degrees. Found this during part throttle dyno tests.. Think about where the fuel hits the rotors in either position. Standard position = end cylinders run lean!! at less than full throttle. Hummm
01-08-2003, 09:23 AM
#33
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Mr Anderson,
The check valve part number from NAPA is 207449.
There are others, but this one works and is usually readily available anywhere. Good Luck!!!!!
No matter what boat you have, there are times when the power valve is needed, no matter the size or weight unless it is a pure RACE piece, IT NEEDS POWER VALVE INDEX!!!!!!
We also try to run the carbs sideways except on Whipples which don't care which way the carb is.
The check valve part number from NAPA is 207449.
There are others, but this one works and is usually readily available anywhere. Good Luck!!!!!
No matter what boat you have, there are times when the power valve is needed, no matter the size or weight unless it is a pure RACE piece, IT NEEDS POWER VALVE INDEX!!!!!!
We also try to run the carbs sideways except on Whipples which don't care which way the carb is.
Last edited by blown1500; 01-08-2003 at 09:27 AM.
01-08-2003, 10:40 AM
#34
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I'm going to chime in here, even though I'm in the minority. Teaque has set up 6 750's for me, all running on blown 502's with B&M 250s. They are not boost referenced, although I don't know exactly what they do to them. They don't load up, they idle great, minimum black on the transom, I've never even had to rejet the carbs. Maybe my engine combinations are just good for whatever they do to them, but they work great for me.
01-10-2003, 08:45 PM
#35
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All of the carbs that I have seen are boost referenced on the primary side only.
Is this because everyone is running a p/v plug on the secondary side?
Just curious because I'm going to try to set-up a HP 1000 cfm carb to run on top of a 250 powercharger on my 502.
Any base line jetting recommendatios?
Thanks,Jeff
Is this because everyone is running a p/v plug on the secondary side?
Just curious because I'm going to try to set-up a HP 1000 cfm carb to run on top of a 250 powercharger on my 502.
Any base line jetting recommendatios?
Thanks,Jeff
01-10-2003, 08:50 PM
#36
Ginger or Mary Ann?
Charter Member
Yep, my sec. is plugged. Can't recall jetting, but they are around 112-115 all four corners. 1050 Dom, 250 blower, 502
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01-11-2003, 09:23 PM
#37
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If your carb came with two power valves, I would run them and have both ends boost referenced. If you do plug the secondary power valve, be sure to adjust your jetting properly and maybe do some metering block changes (Air bleeds, maybe?) or you will get a surprise!!
01-12-2003, 07:38 AM
#38
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I`ll jump in here also. When I first bought my Top Gun, with 750 Hawks, the carbs were sooo rich that just the short no wake from my house to the lake I`d foul the plugs badly, soaked with gas. Last April, I had sent all 4 carbs to Nickerson Performance. He had reworked the carbs and flowed them and ran all of them on a blower motor similar to mine on his dyno. I could not be happier with the results. The black transom problem is gone, I can idle all day, no problems and have not fouled a single plug in over 100 hrs. They are NOT boost referenced and my plugs look perfect throughout the entire rpm range.
How was this achieved without needing to boost reference????
Kurt.
How was this achieved without needing to boost reference????
Kurt.
Last edited by Biggus; 01-12-2003 at 09:51 AM.
01-12-2003, 12:38 PM
#40
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Okay, sp far we've been talking about DRAWTHRU setups. The need for boost-referencing is obvious for these applications.
Maybe I'm off topic here, but I'm curious as to what mods are useful in a BLOW THRU (carb box) application.
I know: floats must be "crush resistant".
power valves must be sized differently.
That's all I know of.
Surely there is a host of setup info applicable to a 502 8.5:1 Crane 731, rect port, 6 psi Procharger Stage 3, CMI Etop, holley 4150HP 950cfm...
Who does the best job on these setups? What is the appx cost? Does anybody know if the carb itself is modified (powervalve feed circuits, etc..) or if it is just a matter of proper air bleeds, powervalve sizes, and jetting??
Comments? RumRunner??
Maybe I'm off topic here, but I'm curious as to what mods are useful in a BLOW THRU (carb box) application.
I know: floats must be "crush resistant".
power valves must be sized differently.
That's all I know of.
Surely there is a host of setup info applicable to a 502 8.5:1 Crane 731, rect port, 6 psi Procharger Stage 3, CMI Etop, holley 4150HP 950cfm...
Who does the best job on these setups? What is the appx cost? Does anybody know if the carb itself is modified (powervalve feed circuits, etc..) or if it is just a matter of proper air bleeds, powervalve sizes, and jetting??
Comments? RumRunner??
