camshaft size Vs converter stall Vs rear gears vehicle weight ? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 05-27-2012, 02:31 PM
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camshaft size Vs converter stall Vs rear gears vehicle weight ?

I have a question regarding the relation ship between all of the things above

Can you get by using a bigger than recommended camshaft in a lightweight vehicle that has lower than optimum stall but relatively steep gears ?

Best regards.

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Old 05-27-2012, 02:43 PM
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Choose the stall base on the range the cam makes power. Pick stall 500 rpm above the start of the power band. No one can predict how the engines power will turn out exactly. If you are familiar with a converter type and engine build I like about 1000rpm over stock. No affect on driveability, depending. A 3000 stall can useally be footbraked to 2000-2200rpm. Foot brake is not the best indictor, but fun. Footbrake below the stall to get a better launch and the most from torque multiplication. Not uncommon to get x3 or x4 the torque at start up from a stock unit. Big difference.

Even stock style cams dont enter the power band till 2000rpm, and will benefit from a 2400 type.
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Old 05-27-2012, 04:03 PM
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Can you get by? is subjective.

If you want to go fast at the track your besd to leave the start line quick fast and hard.

You want to launch at or very near peak torque. Often launching with a stall speed that is above peak torque is best , expecially with a light racey car.

Usually more stall speed is better if you want to go fast.

A light weight car is very forgiving as far as street drivability with a high stall race converter.

With big cams the rpm range is high(er). The engine wants rpm and gear and compression ratio.

You only need about 40 to 80hp to get back and forth to work.

If for what ever reason you want to or are forced to get by with a modest converter and or gear, you would want to tame the camshaft.
Bias the cam profile towards torque rather than peak HP and rpm.

The intake valve closing point is the biggest factor of the four valve events.
Idle quality drivability and easy tunability is a whole other discussion.

Its always a trade off. There is no free lunch.
Big racey cams tend to have a rough idle and like a loose converter to idle nice in gear with a auto trans. A too tight converter is a pain with a big cam.

Last edited by F-BIRD'88; 05-27-2012 at 04:14 PM.
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Old 05-27-2012, 05:20 PM
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Another way , not for the daily driven , is manually ratchet into 2nd use the increased trans load to boost the stall higher. This will cook the fluid , but give some incredibly high stall ranges. Like changing a 3600 stall to a 4200, but starting from second slipping down the way. I dont recommend this, but it is possible.
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Old 05-27-2012, 06:26 PM
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I'm no pro, by all means. But I have seen guys throw big cams in their engine, and not correctly line up the drive train, and fail horribly on the line. I ran a stock 350, 8.5:1 cr with an edey 600 carb, lunati voodoo idle-5000rpm cam and a tci saturday night special converter (Around 1800-2200), and stock gears. Car took off like a scared dog. I could burn rubber into 3rd gear. That combination was awesome because it was cheap and hassle free.
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Old 05-27-2012, 09:18 PM
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I'm asking this question because The transmission blew in my strip car, taking the converter with it to the trash bin,
I want to put together an engine out of a short block i have, and to do so i was thinking of using the heads of my race engine (215cc) because i know they mut be better than some crap #624 heads i have laying around, because the transmission and converter blew i have to use another transmission and converter i have th350 and 2400 stall holeshot converter. Some of you may say this seems odd to do. But i have to tear the race engine apart to look at bearings and measure crankshaft straightness, and to be able to drive my car this summer i'm going thiss odd route.... Also to work the bugs out of it while i can run it on the streets on pump gas !

Engine so far is a stock 350 short block. Performer rpm manifold, 215cc heads and 750 holley carb. 1.5/8" headers. I have figured out that with my heads compression will be around 9.1:1. And i was wondering if i could err on the bigger side when it comes to camshaft, because the car is pretty lightweight.... 2600 lbs empty weight, it has 4.11 gears and i drive on 275/60-15 tires.
With such lightweight car with low stall and big heads. Should i emphasize on a small torquey camshaft or go with one that's on the bigger side for street driven car like mine ?
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