2500 STALL WITH 3.25 GEARS?

[danny clemens]

I'm building a 408 stroker for low end power and mainly street use. It'll very seldom see high revs and streetability is my main concern. It's going in a 66 Mustang F/B with a C4 and probably 3.25 gears. From what I gather a vehicle should cruise at at least the stall rpm. Is that correct? If I've figured correctly a 26.6 OD tire, 3.25 gears @ 2500 rpm would be 60.839 mph. Since most of my driving will be under 61 mph would a 2500 rpm converter work for me if I use a cooler? Would it be a comprimise with the 3.25 ratio? I'd rather stay with the 3.25s because I'll be taking a few long trips on the interstate.

If you see any mistakes in what I've figured let me know. Any advice is appreciated.

 

[D.Hearne]

I would think you could get by with less stall with a high torque (at a lower rpm) engine in a light vehicle.

 

[rbohm]

i agree. since you are not drag race this car, and since your engine is going to be making some monster torque, i would go with a converter that stalls at something more like 1800 rpm.

 

[danny clemens]

That's good to hear. I wouldn't have to worry about running lower gears then. Thanks.

 

[brianj5600]

What does "mainly street use" mean? What cam is in it?

 

[dodgestang]

Its hard to determine the optimal stall without KNOWing the torque curve. Do you have the motors dyno chart or are you going by 'feel' on this one to try and get close? Remember with a stroker all published cam rpm numbers are worthless to you.

 

[danny clemens]

I really don't know what the torque curve will be. I'm fairly sure the torque will be down low. I'm planning on buying my cam this week. Mainly street use means that it'll be mainly driven close to home on weekends for enjoyment and to cruises. I will let it go once in awhile and take it to the dragstrip occasionally. I want it to be street friendly. I don't want to have to take it out of gear while stopping.

BUILD SPECS:
351 block bored .030 over decked
408 stroker kit; Eagle cast crank, Eagle rods, KB -27.5 cc pistons (approx 9.6 CR)
AFR 185 heads with 61cc combustion chambers
Performer RPM intake
700-750 cfm carb (don't have yet)
Roller rockers; 1.6

CAM CHOICES
Comp Cams XE268H hydraulic flat tappet with 224 and 230 duration at .050 with .510 and .512 lift
Comp Cams XE 274H hydraulic flat tappet with 230 and 236 duration at .050 with .519 and 523 lift

I'd rather have the 274H if I don't have to have too much stall. I'm figuring the cam rpm numbers will be lower than advertised with a stroker but I don't know how much. I've gathered information and changed things along the way. The last pieces of the equation are the carb, cam and converter.

I appreciate you guys helping me with this. I've been working on this for some time now and have been gathering parts. I just want to get it right the first time and not have to repurchase some parts because they don't work right.

 

[rbohm]

use either cam. my recommendation still stands.

 

[brianj5600]

I would not sweat a 2500 TC. Mine is similar use and I have a 3200 with 3.08 gears. Cruising down the road takes little HP. A 2500 converter won't slip much.

 

[D.Hearne]

The stroker will tame the XE274 considerably, I say go with it. The choice of a dual plane intake will as well. Go with a vacuum sec carb. As for stall, I think a stock stall will be fine, but you might want to invest in a better quality unit with that torque output. I ran a Crane 272 degree Energizer in the 390 in my 68 Merc with it's stock unrebuilt C-6 and converter. This was a 4200 lb hunk of iron and had a 3.70 geared rear. Your car weighs in at nearly 1500 lbs less, it's gonna be a hand full with a 408 no matter how you build it. The Comp 274 is a bit more cam,(duration wise @.050) but my Merc would light up the rear tires on demand from a powerbrake start with the Energizer. Intake on the 390 was a factory 428PI/427MR high rise dual plane,. carb was a list 3310 Holley 750. All in all that 390 was pretty much equal to your build.

 

[Vinyl66]

BUILD SPECS:
351 block bored .030 over decked
408 stroker kit; Eagle cast crank, Eagle rods, KB -27.5 cc pistons (approx 9.6 CR)
AFR 185 heads with 61cc combustion chambers
Performer RPM intake
700-750 cfm carb (don't have yet)
Roller rockers; 1.6

CAM CHOICES
Comp Cams XE268H hydraulic flat tappet with 224 and 230 duration at .050 with .510 and .512 lift
Comp Cams XE 274H hydraulic flat tappet with 230 and 236 duration at .050 with .519 and 523 lift

I run the XE274H in my 347 and love it. It is definitely not too much for your much larger stroker. I would choose it along with a 750 vacuum secondary carb and a good quality stall converter. My car's performance was night and day difference when I changed from a 2500 TCI to a 3400 Edge converter! And I run 3.55 gears.