In answer to post 15
Which box, kindof depends on the engine. And on the intended useage.
With a smallish engine, and a heavy chassis, and the limited gearbox ratios, you are gonna have to pay particular attention to marrying them. This is not a slap it together and go deal.
Do you remember the 305 Chevies of the mid to late 70s? Those were small bore long strokers, too. And they put those engines in big heavy chassis, like 77 Chevelles, Big Oldsmobiles,1/2T pick-ups,and other assorted tanks; and they were a terrible match-up. Well your 342 is a similar deal. It would be a pretty good engine fora 73 Dart, and a great engine in an early A. But as the weight goes up, the engine will start to show it's true colors.
So how heavy do you think that Ram might be?and
What are you willing to give up, in terms of useage?and
How attached are you to that cam? and
Where in the rpm band are you hoping the power will hit?
If you are a city only vehicle, then you can trade away some torque off the line(to be made up for by torque multiplication), for some midrange. Top end is probably out cuz there won't be any if it is a 4400 pound tank. So these are all things you need to take into consideration, NOW, before the Scr is set in stone; cuz in your case you will want to walk the thin line between detonation and Dcr limits.
Now there are exactly 3 non-O/D boxes to choose from, and two of them are the same except for low gear. The standard, most available box is the 2.66-1.92-1.40-1.00 box. This box is available in a 3.09 low, but the only gear that will physically swap between ratios is the M/S low gear.The third box is the 1970 T/A box with ratios of 2.47-1.77-1.34-1.00. This is a close ratio box, and is getting hard to find.The gears are all different from the standard box. (not sure about 1st). This one you won't want;first gear is just too high.
So you are sorta stuck with the standard 2.66 box.The splits are; .72-.73-.71; Fairly nice, but not set up for a high reving engine. Out-shifting at 6000, the rpm will drop to about 4320;making a powerband of about 1680, which is very doable.( But outshifting at 6800, requires a powerband of 1900.)
So to optimize the engine to the tranny with,say, a 6000rpm shift,the power would like to peak at 6000 less 1/2 of 1680 =5160; also very doable.
But you will need to punch in your own numbers based on what you want to do with this truck. And of course putting the wrong cam in there,does not automatically spell failure. The combo will just be a little off somewhere.
If the truck is very heavy, rapid acceleration with this size of engine will run out pretty early, so there is no sense in gearing it to go fast. You will need some pretty good gears to get moving.
If the truck is 3400 pounds or less, then this is less of a problem.
The point here is; the cam will have to matched to the chassis-weight to satisfy your needs.And after the cam is picked, the rest of the package can be finalized.
That 284 cam,with 3.55s, 30 inch tires, and a 4400 pound chassis, is almost a guaranteed disappointment with a 342small-bore engine.I say almost, cuz gears can be a pretty good bandaid.
Without knowing the parameters to hit, it would be hard to estimate any gears or a cam.Do you want a ripper in the zero to 50mph, with no highway use. Or do you want it to have passing power at 55/65 or are you gonna use it to tow a boat, etc.
That 284 cam can be made to work, but then you will want to search for a 3.09 low box.And you can expect to make the wrong choice in the first selected rear gear ratio.
Here's what I know; My 360 likes a minimum starter gear of 10/1 with 27" tires. This maths out to 7.3mph per 1000 rpm in first gear, and this is with a 276* cam.
I will imagine that the 284 cam will want about 10% more gear. This is an inverse proportion so 7.3/1.1 = 6.64 mph per 1000rpm. This maths out to a starter gear of 13.5. Divide that by the 2.66 low, and you will need 5.13s.If you find a 3.09 low tranny, then you can get away with 4.30s. These 4.30s will cruise at 3130. While the 5.13s will cruise at 3736. Now the rpm drop on the 1-2 shift is a bit of a stretch, so you may have to rev a little higher in first before the shift into second. This is where the 284 will show it's heart as it may not accelerate the heavy truck at low rpm.You may find that you have to rev it to 4000, to drop in at 2480, and the 284 is not gonna like that. 4000 with the 4.30 combo is 27 mph. And the shift into second, still at 27mph, and dropping to 2480;well that 284 cam is gonna struggle to get back into it's sweetspot, somewhere near 4000/43mph.And as the speed goes up, wind-resistance makes it ever worse.So now you can perhaps see why I am looking at a cam to make a more powerful pull,lower in the rpm band.Of course I am assuming the truck is way heavier than 3400 pounds.
So how heavy is it, and what do you want the vehicle to do?
