gov spring for pulling?

I am going to pull my WC in the 3 mph. class.  I have 12.4 28 on it, I have been told to run the faster spring but with 3mph. I would be speeding for sure. I think with the stock spring I will just hit 3mph. Is it still a good idea to put it on, some guys tell me once they start to slip they open the engine up more. Is it really helping to spin the tires even more once they start slipping? I would think letting the engine lug along at normal speed the gov should keep her throttled enough to keep going without trying to just power the wheels into a spin. I have not pulled yet, so I dont know what is best. What do you guys think?

here is my opinion and only a opinion  . lets say youre running the wc spring and youre high idle is 1575 youre engine loaded rpm is 1300  with the wc gov spring. now we go to a 175 gov spring my high idle is 2000 but my full load is 1800 rpm. So with the gleanor gov. spring cover and throttle placement from the start through the middle of the track I can keep my high idle down for my ground speed and yet have a spring trying to keep my engine rpm up under the load of the sled trying to slow me down.  also if you were on 38 rubber spinning the  tire would help some because of the  more bars in the footplate.

Edited by mlpankey - 10 Apr 2010 at 2:29pm

Ground speed is helpful .  If it was mine and I was pulling it . It would have a bigger venturi and posiibly a bigger carb also.

If you put a larger venturi in don't throw the old one away. You can get more RPM's with a larger venturi but once the RPM's drop you loose lugging power. Of course it all depends on how much larger you go.
 
Think about what the job of the venturi is. It chokes off the air being pulled thru the engine to cause a vacuum where the fuel feed tube is located to draw fuel into the air stream. The smaller the venturi the more vacuum with the lower RPM's  Which in turn with the larger venturi you will have less vacuum at the lower RPM's. This will mean when you lug down with less RPM's you will not be able to have the needed fuel added to the air being drawn thru the venturi for the maximum power. (fuel mixture gets real lean)  In that case if you are on your game you could pull on some choke to cause more vacuum at the feeder tube if you could figure out just how much choke you needed.

Unless you have changed the engine to move more air thru the engine than what the carburetor  was (designed by Allis) to take for maximum power you might want to take baby steps in any changes to the carburetor.

I've been dealing with your issue as well...but here is what happens.  You get the stronger spring, your rpms want to go to 2500.  Bad if your rules are 10 - 20% over on stock rpm's.  So you want the throttle to have the full range so that you don't lose the early in the pull "snap" of the governor.  A stronger spring like the 175's mentioned earlier wants to hold your rpm's, but the spring makes it very sluggish, meaning that your carb will open up but it won't be until you've already bogged down at the end of the pull- happened to me today on my 45!  My suggestion, go with a new spring, even a better version of the stock spring, if available (??) and set your rpms's by the book like they're supposed to be.  You can probably still set them higher, but probably only within 200 rpms over stock by simply lengthening the rod on the carb side (taking out bend).  Be careful when you get into this governor thing.  I saw springs from the carb linkage to the block drain screw today on another 45 and still haven't figured out what that's for.  Good luck!