kpeterson

I’m trying to figure out what RPM an LSX 454 crate engine could lug down to in overdrive. The standard choice in gears I have are 3.25 or 3.50. I’m using a TKO600 with a .64 overdrive. The engine has the LSX/LS7 single plane intake and a carb (probably going with a 950 cfm). The LSX cam is 236/246 @ .050” with a 110 LSA. The car is a Factory Five at about 2400 pounds.

I’m pretty sure the 3.50 ratio would not be too tough to live with on the street. 1500 rpm would be 53 mph and 2000 rpm would be 70 mph. 50 mph would be 1420 rpm.

The 3.25 would be 57mph at 1500 rpm and 76 mph at 2000 rpm. 50 mph would be 1320 RPM

Any thoughts on the 3.25 option? Will it pull cleanly at those low loads/rpm? I’d like to be able to grab 5th gear by 50 mph. In my sbc cars that extra 100 rpm at 50 mph can make a big difference in how happy the engine is when you’re cruising. I don't want to have to stay in 4th gear above 50 mph.

Thanks for any input.

redtan

iTrader: (5)

With the size of the engine and the weight of the car there will be no problem to lug it down low as it won't have a lot of load on it.

Heck, I lug my 3800lb car with a 364 @ 1200rpm all day and it's fine, yours won't break a sweat doing that in a 2400lb car.

99Bluz28

iTrader: (35)

Between those two I'd go with the 3.50 gears.

JakeFusion

iTrader: (7)

I'd do the 3.50s as well. I don't think that's a great engine for lugging around. Single plane, 950cfm carb, and a cam with 21 degrees of overlap... being in a lightweight car and having 454cid helps, but I don't know. EFI it would probably be fine.