im taking my pump appart soon to reseal my leaky fuel pin and i want to put a spring in it while im there. i pretty much know i dont need a 4200rpm spring but what about a 3800? do i need valve springs at that point or not? also is it that much better than a 32? this is my dd so i want it to be reliable but still make all the power i can get out of it.lastly will this help me any with top speed? i top out at 79 and would like to at least get to 100. thanks guys!

 

I vote for a 3200, and yes it will help out the top end.

 

if you happen to decide on the 3800, yes, you will need valve springs. both intake and exhaust. the valves on our beasts begin to float around 3500-3600RPM.

 

with a 12mm head will our pump even flow that well at those speeds? I can tell you with the 3200 spring i can hit 100 mph in my old pig...

 

i think i've heard they give their best until about 3300RPM with a 12mm head. i could be wrong though.

 

3200 spring all the way

 

I'd say 3200 also, but don't you need to back out the "stop" screw to make it go that far?

 

I remember David's (BC847) made peak hp I think around 3600rpm based on a dyno sheet he posted I think over on CF a little while back. I can't remember. I was shocked in any case.

Typically our trucks don't make a lot of power north of about 2800rpm though.

 

What are the downsides of running the 3800 or 4200?

 

I've read valve float occurs around 4000rpm, not 3500. 32, 38, and 4200rpm is a close suggestion. Mine turns 2950 or so with the stock spring, I just turned up the high idle a little. So a 3200rpm spring with the high idle turned up should yeild 3500rpm anyway.

I've heard the throttle is way too sensitive with the 4200rpm spring for normal street driving. 3800 I've heard of, but not much feedback.

Throw the 3200 in there and you can play a little higher for free with the high idle screw.

 

i dont understand the high idle screw at all, could you explain this please?

 

It's called the high idle screw. It's really the full throttle stop. Adjust it out until the pump bottoms out internally, then turn it in just a hair so the throttle is stopping on the high idle screw, not mashing internal parts together. You'll probably have to do some linkage adjustment after that, but basically you're allowing the gov spring travel further this way, so you'll get more RPM and more room to run without defueling. I know I was over 2700rpm on my dyno run and the operator kept telling me to keep going, my HP was still climbing. Sadly, the dyno chart is vs wheel speed, not RPM, so I can't tell exactly since there is TC slip. But I was watching my tach occasionally during my run, and I think I was 2900-3000rpm or so, stock gov. spring.

 

I run the 4200 spring and love it. The throttle is very responsive almost to the point of being touchy. I dont have a tach so I dont know the peak rpms I've run, but I havent had any valve float problems that I've noticed yet.

 

So if you do get a 3800 or 4200 rpm governor spring, the throttle is more touchy and responsive??? I was wondering about this. I'm thinkin about upgradin in the futre from my 3200 rpm spring. Just with my 3200 rpm spring it seems very touchy. I can hit 3800 rpm with my 3200 rpm spring and maybe even higher but haven't dared go past that! For just a DD I would recommend the 3200 spring.

Where do you guys get the 3800rpm or 4200 rpm governor spring???

 

Going 4200 rpm in my project.