86GutlessCutlass

i just put a thumper cam part number 42-600-5 and a b&m 2,000 rpm stall converter and im trying to figure out what the best gears would be so i can still drive it everyday and not have to worry about very poor mileage. i know it is not something to think about when building a car. if need more info let me know. im not sure what the stock gears are. i know there either 2:14,2:29, or 2:41. Thanks, Frank.

Fun71

What engine and transmission do you currently have in the car?

86GutlessCutlass

opps, i guess that would be some good info i have a 350 rocket out of a 1978 delta 88 with the 350 turbo transmission

86GutlessCutlass

i also have an edelbrock performer intake on it. and flowtech headers. did you have any problems with your headers sitting on the frame on the passenger side of your car?

olds 307 and 403

That is a lot of cam for a 8.5 to 1 350. A 2000 stall is small for that cam if it actually stalls there. I say you need at least 3.23 gears but it depends on how much highway driving you do.

61Bat

Agreed, a 3:42 max depends on tire size also.

86GutlessCutlass

I was told that if I went above 2200 rpm stall that my transmission would begin to slip?

1BOSS83

-That is a big overlap cam with a lot of duration that requires a lot of gear for it to perform with any spirit. That said, without an OD trans I am in the camp of the other posts

-No issues with headers, different brand however, That said, the only time I've worked with flowtech headers we had clearance issues (Chevy car)

-These may be helpful if you havn't worked out your wheel/tire combo

To figure rpm: 168 * gear ratio * mph / tire radius
To figure mph: tire radius / 168 * rpm / gear ratio
To figure gear ratio: tire radius * rpm / 168 / mph
To figure tire radius: 168 * mph * gear ratio / rpm

86GutlessCutlass

No. It is in in a 1986 olds cutlass supreme

1BOSS83

I overlooked that previously, sorry about that.

olds 307 and 403

You will need thick gears for ratios above 3.08 if you use your current carrier. I have a 2200-2500 stall that flash stalls at 2300. It is very tight at lower speeds, pretty good for a cheap converter.You will be above the stall rpm even with your current gearing which should help with slippage.

Fun71

My car has a Hughes Performance 2500 RPM stall and during "normal" driving it operates the same as the factory converter. No issues with excessive slippage even at highway speeds when I had to temporarily put in the original 2.56 rear.

GEARMAN69

1. A "thumper" big ole lopey cam isn't going to get good mileage

2. 2000 stall is really not enough rather just a absolute minimum so it will idle in gear without stalling. You would really need a 2500-3000 stall , a big transmission cooler and as said a 3.23-3.73 gear to run good. A 200r4 OD transmission and the proper gear ratio is what you would need to make it run good but mileage is still affected since it is not a mild cam and if you had a lock up 2500 stall it would chug along below its cruise range of the cam.

3. Needs more compression by either milling your heads and doing big valves , pocket port and flat top W31 pistons , or if your running a dish piston run some early 68-72 350 heads, #5,6,7,7a with the smaller chambers