The Dodge Challenger Message Board

Can anybody tell me the valvespring pressures of the Mopar Performance #P5249847 valve springs? Cause I'm looking for springs for my new MP 528" solid cam to put in my 340. The part# above is recommended for the 528 cam but I wanna go one step stiffer so I can turn more RPM's...

But If I go one step stiffer with MP springs that will be dual springs and then I have to work on my heads and I don't want to remove them. So I want to check out some other brands for single springs with enough pressure but to compare the springs I need to know the pressures. Understand? thx

But the cam decides the rpm range the engine works at. So why are you talking about using more rpms? If you want more rpms than the cam is designed to work in you should use another cam and the springs that match. You want the least stiff springs you can get away with to get the most power and valve/rocker/pushrod life.

Or am I missing something?

And you should know what I think of MP cams...

Yeah Dave...Hughes! I know, but I want a solid cam and to use the ones Hughes sells I have to modify my heads. (for the recommended springs) And at the moment I don't want that, they're already ported etc. Maybe later on I will work on other mods. And they're aren't that bad, my mate has run 10.99 with a 340 challenger with the 528 cam... (and some other parts)

Right now I have the cam from the edelbrock package which has a RPM range from 1500-6500 with matching springs which I also have. But the engine won't rev any further then about 6200; higher then that and it goes faster when I shift to next gear. (Yeah, the carb fully opens) From the 6200 they start floating which it wouldn't do with a little stiffer springs. (not too much cause of the wear as you said) And the 528 cam has a RPM power range from 2800-6900rpm; you think with the recommended springs I should be able to go till almost 7000rpm Dave?

It was just a thought Dave 'bout those springs because of the bad experience with the edelbrock cam & springs...

You need to know where peak power will be on your engine with this cam. The rpm you want to shift at will be about 500 more. If they are saying its full range is 2800 to 6900 I would guess the peak power would be about 6200 rpm. But you cannot really tell without seeing the dyno results from a 340 with the same setup. I would use the springs they say to use.

I was just looking at the Hughes web page and they say shift 300-500rpm above the rpm range that they give.

It depends on how steep the power curve is. You need to shift at a point past peak power so that when the next gear engages you are at the same power level before peak power. So if the power peak is a more shallow curve you need to shift at a much higher rpm past peak and if a steep narrow power curve (narrow power band) it would only be a few rpms past.

I will start with the recommended springs and see how they'll work