Best Trans for Swap
No way AJ I’m just asking ..,,
OK well, I questioned the need for the 2000 rpm cruise speed.
The fuel-economy difference is said to be about half the percent difference in mpgs. So from 2000 to 2200 is a difference of 10%, ergo fuel economy may change 5%. if you were getting 16 before the gear change, the new number looks like 15.25..
BUT this assumes; firstly, that the stall is lower than your cruise, and secondly that you are not trying to cruise with the intake in reversion.
OEM 340s are a prime example; Mine always got better fuel mileage at a little higher rpms.I won't say85mph is where it got the best mpgs.
The point is most of the time, your cammed up 360 will not get any better fuel mileage at 2000, than at 2200 or maybe even 2400. It's all in the combo.
Therefore, to sacrifice performance in the name of sticking to 2000, is, IMO, somewhat misguided.
After your engine is built, and tuned; rev it up in Neutral to about 3000,while watching the manifold vacuum. The vacuum will rise to a peak, plateau there, then begin to fall. The lowest rpm when it hits the plateau, is where you want to cruise at. Now start cranking in timing by pulling on the Vcan. Again the vacuum will rise to a peak. Put the light on it.That is the timing you will try to cruise at. You may find this to be 52* at 2200rpm. Or 56* at 2400. Or 48* at 1800. Every combo is different. The point here is that getting the timing right for your combo is far far more important than 200 cruise rpm.
The biggest deal is TRYING to keep the rpm down; BETWEEN 2000 and say 2600, rather than 3000 plus.
Now. having said all that, I can give you a combo that, for me, went 32mpg at under 1600 with timing approaching 60degrees, and at cylinder pressure approaching 200psi....... and still went 12.9/106 in the quarter, with zero tuning; and with a 60ft in the 2.4xs @3650 pounds.And it did it all with 87E10. It's all in the combo.
With ladder bars, and big sticky tires,and an overdrive;I would certainly exploit the 3.91 to 4.30 gears......... And keep the TC tame, to cruise 65@ under 2600.Then I would tune the chitoutofit. And the fuel economy will be what it will be. You will need a dash-mounted,dial-back,timing device, to sneak up on the cruise timing, because it is almost impossible to give the engine what it wants with the factory systems. Say you end up cruising at 2500. And say you end up with 25* mechanical timing,there. And say you finally find a 22* Vcan. And say your engine makes enough vacuum to fully bring it all in. Ok that totals 47*@2500. It ain't enough. The dial-back has a range of 15*. If you set it to full advance, the new total is 62*.
But more than likely you will try to run more than 25@2500, and more than likely you will not find a 22* can, or will not be able to run your 22* can at full timing; so say you manage only 42*, see what I'm saying? it's a long way from 42 to optimum.
Now one more thing, as you put more and more timing into it, it will be possible to take more and more fuel out of the cruise circuit. And this is where the true fuel savings will be.
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From 55* to 62* is where mine plateaued, that is to say the MPG was very hard to improve in that zone. So I just set it in the middle,about 58*, and called it done. During the following 10 years I tried it from time to time, but the results were always inconclusive.
So 42* will not be nearly enough, and 58* is about right in my combo. Your results may vary. My 367 likes a 2250 cruise rpm. It has a happy sound in the pipes. I have it geared for 65=2236 mathematically speaking,lol.