dodge350c

I just had a 4 k spring put in my truck cause m not big on messing up my daily driver lol but i was wondering if anyone has done one yet because it doesn't seem like its hitting 4k and I done have it turned back up with the power screw yet does anyone know Wat a problem might be with why its not winding out but i know they defuel at like 3600 or 3800 rpm and i was thinkin its cause i got it back to almost stock and the pump doesn't wanna give the fuel up at that high of rpm. Thanks for all the help Dominic

Onemoparnut

Did you change the valve springs also? Is the motor floating the valves? Is the high idle screw still in the stock location?

stillsmokin209

I just installed the 354 spring in mine. From the few WOT runs I have done I have seen 3200rpm as the highest, and that was at higher speeds. This is on stock injectors. Without more fuel I doubt I will see much more under load. It does run good though, I like it so far.

dodge350c

Yes I have springs and I like it cause half throttle is about 3 grand ha ha and my power range is different then like only 2500rpm as peak its now like 3k rpm. Dominic

sshort

Do you have a tachometer mine will pull to 4k with a 3200rpm screw if you manually shift it (auto trans)

dieselJon

Stock lift pump kinda limits it at 3400ish unless you do a no load rpm spike but I don't not recommend it.

In fact, after what I just saw this weekend and learned, 60lbs are good for sub 4k rpms with a stock cam profile.

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dodge350c

Oops ha ha I got an air dog sitting in my room I guess I should find some time to put it on and have any of you had any issues turning the power screw back up cause i done want it running away it's not fun trying to shut it down

dieselJon

It was turned all the way in before and after. Nothing really changed except for the ability to smoke my valves at a mis-shift.

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jimbo486

I just found out that even 60lbs springs aren't quite strong enough to prevent the valves from floating.

93flatbed

John, need the story.
Jim, also need the story.

dodge350c

I got them there decent they came with an o ringed head and studs and it was done the next day for 1500 bucks and thanks for all the help everyone. Dominic

92smokin blacky

the 4200 spring is much more touchy and is snappy to get the motor up and going quicker if you ask me. After 1200 rpm you better hang on. Thats the first thing I noticed after putting mine in. As far as topend and rpm it seemed to pull a little harder topend and have a hair different powerband. Mine will easily hit 3500 rpm if I leave my auto in 3rd and give it all she has and it will slowly keep climbing but i haven't really seen the need to go further. Under load it doesn't seem to go past 3300 rpm. i know with my 3200 spring I could rap it up past 3500 rpm as well if i manually shifted my auto and held it in 1st. I do have 60 lb springs and studs now...

My high idle screw is gone, linkage moved to inside hole and the throttle is re indexed one notch (wouldnt idle at all when i installed 4200 spring til I did this) I'm thinking maybe re indexing it some more and turning my full power screw down a bit. But I think my throttle lever is bottoming out inside the pump rather than in the linkage at full rpm.

Like stated you are probably running out of fuel supply pressure at high rpm. Get a different lift pump and make sure you have the high idle screw backed out and getting full travel with your linkage/pedal.

DodgeFreak

I had that same problem when i installed the 3800 spring, i could get it to idle really high with the full powerscrew all the way in or not at all, so i chose not at all and bumped the idle up but lost some throttle travel. so i think i'll turn it back to where it idles high and back the screw out.

jimbo486

While it may be just part of their sales pitch, I read it direct from Hamilton Cams' site...

"...Factory and “60lb” springs do not have enough spring pressure to adequately control the valvetrain in all conditions. In fact at 1.4” 60lbs springs have exactly the same pressure as factory springs! Trucks running over 3400rpm with stock springs or 3800rpm with 60lb springs are experiencing valve float. Beehive design to reduce valvetrain mass, increase initial acceleration of the valve, and to cancel spring harmonics."

dieselJon

I was told that by Zach face to face.

And my buddy. If you are on CumminsForum, look up WAYNES WORLD and ask for the pics of his truck. It either flared between 3rd and OD or he just kept in it when it wouldn't shift. The pics show a light outline of the intake valves kissing the pistons. He got lucky with only 1 bent push rod.

What Zach says makes sense. There is seat pressure and spring return rate. Spring return rate is what is the same.

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