alright Got some plans for my BBC C10 big block guys in here!!
 

I've got an 1984 C10 with a 427 BBC and a TH400 trans, and a shift kit. its a bit doggish off the line due to a .561 lift comp cam, but moves through the gears very well and spins like an animal once you take off the initial hit of the pedal and will rip the tires off in 1st and 2nd gear, but when it hits 3rd it falls on its face because of the tall rear gears.

the spec sheet says the truck has 3.08's in the rear, great for highways but any kind of take offs it sucks even with a BBC.

so I'm debating doing a set of either 3.90's or 3.73's for the rear, do you think the 3.90's would be too short with the torque of a BBC?

also i have a crappy old outdated Holley double pumper 650cfm carb, and its got mechanical secondaries, which suck for the street, i like vacuum secondaries, much better response.

so I'm looking at a quick fuel 750CFM slayer carb.

so what do you think how much of a difference will i get for my money? I don't want the truck to just roast the tires off constantly, (although it is fun) i want it to accelerate quickly but not fall on its face and not move in 3rd gear. obviously it spins pretty good now, but I'm still left with some more bite to be desired.

Re: alright Got some plans for my BBC C10 big block guys in here!!
 

Spinning 1st and 2nd, then dogging 3rd? Dogging 3rd gear won't have anything to do with rear gear selections. I'd say get it hooked first, get your 750 carb settled, then go after gear selection. Sounds like you could use more rear tire (height, width, or both) before you worry about gear too.

Also, what about the stall converter?

FYI, mechanical secondaries only suck for the street (daily driving anyway) because they require more tuning to contend with weather. Vacuum secondaries do NOT give you more response. 750 should be about right for your combination.

Re: alright Got some plans for my BBC C10 big block guys in here!!
 

i mean 3rd gear pulls good, but obviously with 3.08s and the 1:1 gear its going to pull very smoothly but i want a harder acceleration, i want it to keep you in the seat a bit more. and it has 285 wide tires on it, with practically new tread. and its winter time as well lol

Re: alright Got some plans for my BBC C10 big block guys in here!!
 

3.90's
Same gear I had in a '69 442 that I swapped a 396 bbc into, along with a very good Crane cam and it was a 4 speed too.