This is hard to put into typing, so kinda bear with me on this...
I'm a little confused, so can somebody straighten out my thinking?

My car is not raced, but just used on nice days to zoom around, or go to work.

Mildly ported stock intake, headers, stock long block, MAF, hypertech, '87 305 TPI W/700R4 and 3.90:1 posi, in a '78 Camaro.

I read where camming loses some bottom end, and then you need to install a 2200-ish torque convertor to make up for the loss of TQ, down low. But with the gobs of tq that TPI has, I don't see how it can be that much of problem??

Also, I read where using anything over 3.73:1 gears is not desireable, (to most) but since it is not a daily driver and I don't race, and I have the OD tranny, isn't just having the 3.90's and a stock convertor, about the same as having 3.42's AND a AM convertor?

What considerations am I misssing??

 

One consideration that jumped out to me was 3.90 and stock converter vs. 3.42's an a higher stall converter. The gearing and converter you choose really depend on the engine, specifically the cam that you go with, and the ratio's in the transmission. Your motor is the 87 305 TPI, and if its all stock, it came with the real tiny cam. So, I wouldn't consider your car to be in need of an extreme converter because the power is going to come on in the loewr revs, especially with TPI. 3.90's are pretty steep as well, I'm sure the car jumps up off the line nicely. My theroy on a car that doesn't have to worry about fuel mileage is to give as much gear as possible and still achieve a fair launch (ie not blowing the tires off)

Now, using a longer duration and higher lift camshaft does tend to shift the powerband to the higher rpms, a converter is important because it allows the engine to get to those higher rpms quickly so the engine is in its most efficent power producing band. The gears will also keep the engine singing at the higher rpms, which is important as well.

Are you thinking of camming the motor. I would, there is a lot left on the table with the tiny little cam. 3.90's in the rear are plenty good enough for even a pretty wild cam, I would reccommend a higher than stock stalling converter if you go with a decent amt of cam. My 305 has a 204/214 (at .050) mild cam, with a 2500rpm stall converter and 3.73 gears, and I would say that gearing and converter is about perfect. I actually wouldn't mind a 3000rpm stall, as long as I continued to retain my factory lockup clutchs to keep cruising rpms under control.

 

I've considered camming the 305, or I have a mild port/polished NEW 355 with unknown 'RV' cam, inherited from Dad. Trouble is, the cost to cam the 305 vs. what I see in DD2000; TOTAL dollars per hp&ft/lb. aren't that appealing...with cam costs, associated 'other' costs, for about 15-20 hp-ft./lbs...

Sorta the same with the Gen 1 355, when I consider injectors, rechip (AM chip Or AM DIY programming initial costs), new flexplate, hassle to mount Gen2 tpi to Gen1 (early) heads, etc., and I get maybe 35-40 hp-ft/lbs...

It runs good now, and money is tight...

I've about decided to just leave it alone, mechanically, and just tune it with an Autoprom...

But I've never understood the whole low number ratio vs. higher stall TC deal...maybe it's the 1/4 milers that feel that 3:90 is too much due to trap end R's, or mileage for daily drivers, but I mostly just putt and then mash it...

 

I would think that a good cam in the 215-230 duration would yeild a healthy increase in power, espeically with good tuning. Its a roller motor, you can get away with plenty of adt'l duration without going insane on the lift and running into problems with the heads. I would think 240hp would be easily achievable, a good deal more with decent heads. Fabbing the TPI onto the oldschool 350 might be trouble, but would be more rewarding in the end.

Or, you can just leave it alone...

TPI motors do like the numberically lower numbered gears for that very reason, to much rpm at the traps sucks with TPI, and you need unstreetable gears to use all 4 gears in the 1/4 mile.