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 Jet & rod sizes SMAB to dual MAB 
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Joined: Wed Oct 23, 2013 8:01 am
Posts: 113
What would be a good starting point? Started with a SMAB .085 or so to dual MAB .046 each.
It started with 73 jets & 51M rod.


Fri Jun 24, 2016 11:14 am
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Joined: Fri Feb 08, 2013 2:37 pm
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Large or small venturi? Brief engine description? Using WBO2?


Fri Jun 24, 2016 11:18 am
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Joined: Wed Oct 23, 2013 8:01 am
Posts: 113
Large, 530 hp 421, single plane intake & yes I have WB.


Fri Jun 24, 2016 12:29 pm
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Joined: Fri Feb 08, 2013 2:37 pm
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That's as good a place as any to start, with the wide band you will know what to do next after a couple of test runs. You are aware (?) that the two-bleed rods always have a .026" tip and the single-bleed rods have the larger .036" tip. On the other hand, a radical cam engine commonly needs a rod with very little difference between 'lean' and 'rich' steps. Some radical engines may not need a rod at all, just the jet. I see a trend that higher HP engines generally want smaller primary jet and less rod diameter change from lean to rich than a similar engine with less HP.

The Mopar carb advice for T-Quad includes a "club-foot" rod with a larger tip than shank, the "lean step" is small and the "rich step" is large, backwards from normal. The T-Quad has positive mechanical linkage to raise the metering piston so the "rich step" is positively in the jet at WOT. I have never done that with a QJet so ???


Fri Jun 24, 2016 1:08 pm
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Joined: Wed Oct 23, 2013 8:01 am
Posts: 113
I guess I should have taken your word, I think it's going to stay the same.
It's at 72 & 50 now & it's a bit lean under load.
I thought with less than half the bleed area I would need less jet area.
Maybe would if it still had a dual plane.


Thu Jul 21, 2016 5:49 pm
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Joined: Fri Feb 08, 2013 2:37 pm
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"word" LOL, it was just a guess. The single bleed large venturi usually needs a MJ in the .075" to .077" range so WOT is OK, like with a hard working 454 in a truck, so .072"~.073" is a logical step and usually near where they end up.

Do you have any headroom toward lean on the APT to lower the rod, so you could go back to the .073" jet and get some more WOT fuel?

You can reduce the tip diameter by putting the rod in a drill motor and using a good sharp jeweler's file or pinching it in some wet-or-dry sand paper between the jaws of needle-nose pliers. Take care to make them both the same size.


Thu Jul 21, 2016 8:04 pm
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Joined: Wed Oct 23, 2013 8:01 am
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I have some more rods too up 54M I think.
Here's my spec sheet.


Thu Jul 21, 2016 10:00 pm
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
That's a nice handy form for your notes.


Fri Jul 22, 2016 1:15 pm
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Joined: Wed Oct 23, 2013 8:01 am
Posts: 113
Only if I remember to write the right stuff on it. :O


Fri Jul 22, 2016 9:20 pm
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Joined: Wed Oct 23, 2013 8:01 am
Posts: 113
Why when changed to dual air bleed does it require a bigger jet? I'm at 75 & could go to 76 I think.
The dual bleeds are about 1/2 the area of the SAB .046 vs. .086 0.0033238128 vs. 0.0058088184


Wed Jul 27, 2016 2:56 pm
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