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I have 1975 Q-Jet 7045250 which comes with an aneroid and auxiliary power piston & rod/jet shown in the picture with the blue arrows.
It came with .067 jets & .041 rods. Today I put new .071 jets with new .044 rods to make it a little more rich at cruise & WOT. I'm running lean because of my engine mods.
With the auxiliary piston first in the primary circuit, will it allow more gas through to the primary dual rods when needed?
I read that these 1975 carbs are a pain to tune because of this set up.
Can I remove the aneroid like they in 76 & 77 and remove the aux. piston & rod and plug both cavities?
I would like to keep the same carb if possible.
Very difficult to find info on the any help would be appreciated.
I know Cliff Ruggles mentions it can be plugged in the book. I believe he said it can be plugged and eliminated. I believe the rod adds fuel throughout the whole rpm range. It makes sense .067" is tiny jets for a 350, even 71 jets are probably a bit on the lean side. Contact Cliff Ruggles if you are unsure. I can't see why a plug can't be made and the assembly removed.
Thanks for the response. I bought Cliff's book, it talks about it briefly. It says they can be very hard to tune. It doesn't say how to remove the aneroid and how to plug the aux. piston and plug the aux. rod.
I want to test my set up when the weather breaks in a few months with .071 jet & .044 rod. Like you say, I may need to go to .072 jet. I'm .001" closer to range that Cliff wants between the jet & rod at .027 from .026" .
Plus I'm more rich at low end and WOT, it still may not be enough. May have to go the .072 jet with the .044 rod. Would put me .028" difference 15% more fuel at cruise and 18% more at WOT.
I was worried the Aux. rod was restricting the fuel with the new jet/rod set up? I thought I read somewhere the aux. rod meters the fuel at low RPM. I have a slight hesitation around 1300-1500 rpm and it clears out runs real well even at idle.
I may yet. I know this carb was working great before the engine mods. It was rebuilt 4 years ago. The throttle bracket is modified on it as well on this carb for the 200R4 piano wire attachment. I didn't really want to spend another $400 for a carb or more without tinkering first. I don't want to give up that easy yet...
January 13th, 2019, 05:48 PM
