Hi, Just finished swapping out the peanut cam in my 88 T/a 305 Auto. I have 2:73 Gears and I notice that the cam lets the car rev much more freely into 5000 rpm, but I have lost a bit of torque off the line. Which stall speed would be good for me? the car really comes alive at about 2500 rpm
Thanks, Jeff

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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

just get some 3.73s or 3.42s that would help off the line

 

The proper stall speed depends completely on the power band of your engine. This means that if you have an engine that starts to "pull" at say, 2100 RPM and you have a 1600 stall converter, your performance off of the line will not be at it's best. On the other hand if you put in a 2400 or 3000 stall you will be wasting expensive power, since the converter won't be passing the maximum power to the tranny until later in the power band. In the example I used, a 2000 stall would be ideal since you will "flash" up a little bit on take off. You will then be at the optimum take off RPM. Sometimes too, people have the proper stall converter for the engine combo but have the wrong rear end gears to fully utilize the power. You are in the best situation since you have the cam in the engine now and can see what it does. What you need to do determine when the engine starts to pull strong. That is where you want you stall speed.

 

easy answer......
Vette verter with 2100-2200 stall.
This is on my 86 nut cammed (only year BTW!) 305.

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

 

I would love to put some 3:42's in there, but I don't have 1500.00 canadian lying around. 1st gear goes by pretty quickly, of course, but I find 2nd gear to be where I notice the dropoff in power @ low rev's. Would a torque converter help here? or just on launch? BTW, does anyone know what converter is in there now?
Thanks, Jeff

 

torque converter will help the most under and at the rated stall, past that rpm it doesn't do much. Gears would help you out alot. You won't need a converter then.


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

 

Thanks, 82 camaro, BTW, how do you like your 3:73 gears? are they noisy? did you install them yourself? if not, was it very expensive?
also, what is your rpm @60 MPH?

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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

Leo has some good points as always but I'll add a few more.
What is your cruising rpm city/highway?
This must be considered also when choising a higher stall converter. If your highway rpm @75mph or whatever your speed limit is, if it is at or below your stall speed this will cause your engine to use more gas and transmition life could be shortend. the same goes for around town driving also but it's not as important because the constant gear changes ect ect. So your best bet is to find the rear gears you want and then choose the proper stall speed. a good 1800 stall seems to be good for almost all aps if you want converter 1st and gears later.
SSC

 

Very good point, SSC. I think I'll save up and get the gears. I don't do too much highway driving, so what would be best, 3:42, or 3:73? wouldn't 3:73's make 1st gear redline at about 20mph?
Thanks


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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

I have bolth sets . Although my experiance with the 700r4 in my camaro was short and it had and currently has 3:42's and there great with the tb400. 3:73's would probably be fine with a 305/700r4. This could actualy help increase the amount of stall you could use. That 2500 range you talk about in your 1st post would be reached quicker and thats the point of the higher stall to put you in your powerband. But like I said I have a 3:73 posi rear but it had too much bite for my car and since you only have 2:73's now 3:42's might be a better compromise. Im very tempted to put the 3:73 into my firebird "current 2:73's" just for kicks
Someone more versed in the art of 700r4's and proper gears want to help this guy out or what?
Good luck Jeff!
SSC

[This message has been edited by SSC (edited August 28, 2001).]

 

With a Lock Up converter you will not have a problem at highway speeds since the converter will be locked, therefore no stall effect (slip).

The choice of stall and rear gears are two seperate things that compliment each other and require much of the same information for proper selection. The stall speed gets you to the start of your power band while the rear gears allows your engine to be IN your power band most of the time. For example, if you had a diesel that absolutely maxes out at 3500 RPM you wouldn't want 5:13 rear gears because other than moving ten feet in a hurry you wouldn't be able to get out of you own way after that. On the other hand if you have a screamer small block that STARTS to make power at 4000 RPM and goes to 7500+, you wouldn't want 2.73's because at 60MPH (if you ever got there) your engine would not allow you to pass anyone since you would be at the RPM's that the engine is still sputtering.

Bottom line is that the correct stall is just that. IF you have a more or less stock TPI it will start to fall flat by 5000 RPM anyhow so going too low on the gears will be wasted anyhow. After that you need to address what the car will be used for and whether initial acceleration or top speed is more important to you.

[This message has been edited by transfixleo (edited August 29, 2001).]

 

RPM at 60 mph is 2150(overdrive is a wonderful thing)
Gears aren't noisy.
First gear is more like 35 mph.
Going from 3.08's to 3.73's made my car a whole lot more fun.
Installed the 3.73 my self with all new bearings, and a powertrax locker--all probably about 4+ years ago.
Cost was a little less than 600 bucks.

A site you might think is useful:
http://www.f-body.org/gears/


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

 

You'd be better off with a 2500+ stall tight convertor than gears, just my $.02.

 

The problem with a 2500+ stall is that unless you have an engine that NEEDS it you will be wasting power/band. Your typical TPI will pull strong to @5000 or a little more. 2500-5000 is not a whole lot of RPM range. With that you would be better off with a 200-4R to keep the R's in that range.

 

Rule of thumb and this goes back years.

Most powerbands are about 2000 rpm wide. Pick where you want it.

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86 T/A 5.0 A4 & 2.77 gear
15.62 @ 86 mph
93 Civic 1.6L
13.5 @ 100 mph

 

Huh? I have driven cars that pulled from 2000 RPM to 6500+. Many TPI small blocks make power from @1800-5000, above or below that they are flat. I am not saying this is 'peak' power, just where the engine 'works'. Take advantage of it and don't waste it.