Secondary Metering Block Calibration

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JedIEG

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Thought I would ask here also.

I have a QFT slayer series 600cfm VS carb. I switched to a billet QTF 3 emulsion bleed metering block on the primaries, IFR moved to the bottom and the crab has been running pretty well except some light throttle stumble and rich WOT. I am considering putting the old primary metering block that came with the carb on in place of the metering plate. The base plate already has the secondary idle port drilled. I was wondering if anyone could suggest a calibration for the SMAB, SMJ, and emulsion bleeds for the plate?

I have the power valve blocked off already and am going to JBweld the constant idle feed under the transfer slot.
Current cal on the secondary block is 0.028 Kill, Top, Mid and Bottom for the emulsion. 0.031 IFR (upper)
Current Carb cal on the secondary.
SIAB- 0.073
SMAB- #31 (0.031)
Metering plate
SIFR- 0.043
SMJ- #74

Should I try to match the primary for idle circuit cal from the factory for this carb or try 670cfm Brawler with VS and 2 mettering blocks?
 
All I can tell you is, if the area you plan to use JB Weld on is exposed to fuel, don't use JB Weld. It is NOT impervious to gasoline and will break down. Lots of people make the incorrect assumption that it is, and it's not, I don't care what it says on the package. Just trying to save you some grief down the road.
 
If WOT is rich you can try a bigger HSAB. Those are the inner bleeds on the top of the carb closest to the discharge nozzle. That would add more air leaning out the mix. As far as jetting the secondary side which I believe you list as a 74 the original metering plate probably has a number stamped on it which you can contact QF and find out what it is jet sized equivalent to. That's all I've got.
 
Last edited:
JedIEG said:
Thought I would ask here also.

I have a QFT slayer series 600cfm VS carb. I switched to a billet QTF 3 emulsion bleed metering block on the primaries, IFR moved to the bottom and the crab has been running pretty well except some light throttle stumble and rich WOT. I am considering putting the old primary metering block that came with the carb on in place of the metering plate. The base plate already has the secondary idle port drilled. I was wondering if anyone could suggest a calibration for the SMAB, SMJ, and emulsion bleeds for the plate?

I have the power valve blocked off already and am going to JBweld the constant idle feed under the transfer slot.
Current cal on the secondary block is 0.028 Kill, Top, Mid and Bottom for the emulsion. 0.031 IFR (upper)
Current Carb cal on the secondary.
SIAB- 0.073
SMAB- #31 (0.031)
Metering plate
SIFR- 0.043
SMJ- #74

Should I try to match the primary for idle circuit cal from the factory for this carb or try 670cfm Brawler with VS and 2 mettering blocks?
Click to expand...


You have way too much emulsion. Block the middle hole and use .028 for the other two. It may like .026 even better.
 
66Valiant528 said:
If WOT is rich you can try a bigger HSAB. Those are the outer bleeds on the top of the carb. That would add more air leaning out the mix. As far as jetting the secondary side which I believe you list as a 74 the original metering plate probably has a number stamped on it which you can contact QF and find out what it is jet sized equivalent to. That's all I've got.
Click to expand...
Outer are idle circuit, inner are the main circuit.
 
Rat Bastid said:
You have way too much emulsion. Block the middle hole and use .028 for the other two. It may like .026 even better.
Click to expand...
I'll have to tap out the block since the emulsions are not adjustable on this metering block. Should I swap the IFR to the lower position or does it really matter on a secondary side? SIAB size seem ok?

66Valiant528 said:
As far as jetting the secondary side which I believe you list as a 74 the original metering plate probably has a number stamped on it which you can contact QF and find out what it is jet sized equivalent to
Click to expand...
The QFTs come with plates that are tapped for using regular main jets so it is actually a #74 jet out of the box.
 
JedIEG said:
I'll have to tap out the block since the emulsions are not adjustable on this metering block. Should I swap the IFR to the lower position or does it really matter on a secondary side? SIAB size seem ok?


The QFTs come with plates that are tapped for using regular main jets so it is actually a #74 jet out of the box.
Click to expand...


Yes, lower the IFR even on the secondary side.

Did you actually pin the emulsion holes? I’m asking because you can’t go by what the paperwork says. I’ve done enough of these to know they can say .028 on the paperwork but when you pin them I’ve seen them as big as .033. Just want to be sure on that.

Yeah, you’ll have to drill and tap those for a set screw. I always drill all the way through to the channel with an .062 drill bit and then drill for tap size. That way, if for some reason you may need a bigger than .028 emulsion bleed you can get it. If you leave the .028 hole there you will never get bigger than .028. FWIW, I can’t think of a time when you’d need more than .028, but I hate taking chances.
 
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