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**jocko** · 07-30-2013, 10:50 PM

I'm assuming you have a grann4 or 3 ott? If that's the case, the one thing I would focus on, rather than the carb, is the trans. 1:1 final trans ratio will kill highway mileage. If you drive it above 55 mph much at all, you'd probably see more gains by swapping in an o/d trans, such as a T5 if you prefer manual or 2004R or 700R4 if you prefer autos. Might be more than you want to spend - but since you're looking for a fairly BIG improvement in gas mileage, I'm afraid you won't get it just by changing to a 2 bbl (or from a 2bbl to a 1 bbl, vice versa).

Only other realistic option (but it would cost you bottom end acceleration (I'm not talking drag racing here, but basic bottom end torque "feel") would be to swap out the 3.73's for something lower numerically.

50% mileage increase is a lofty goal - and, as you've seen, you're getting roughly what everyone else is getting with your combo, so it would take a major change to get what you're looking for.

Great question - I'd still like to hear from others that may have swapped 1bbl vs 2 bbl on a similar setup just to learn.

07-30-2013, 10:50 PM	#8
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 18,001	Re: Sgl or dbl brl carb? I'm assuming you have a grann4 or 3 ott? If that's the case, the one thing I would focus on, rather than the carb, is the trans. 1:1 final trans ratio will kill highway mileage. If you drive it above 55 mph much at all, you'd probably see more gains by swapping in an o/d trans, such as a T5 if you prefer manual or 2004R or 700R4 if you prefer autos. Might be more than you want to spend - but since you're looking for a fairly BIG improvement in gas mileage, I'm afraid you won't get it just by changing to a 2 bbl (or from a 2bbl to a 1 bbl, vice versa). Only other realistic option (but it would cost you bottom end acceleration (I'm not talking drag racing here, but basic bottom end torque "feel") would be to swap out the 3.73's for something lower numerically. 50% mileage increase is a lofty goal - and, as you've seen, you're getting roughly what everyone else is getting with your combo, so it would take a major change to get what you're looking for. Great question - I'd still like to hear from others that may have swapped 1bbl vs 2 bbl on a similar setup just to learn.