My engine currently has the 3k springs, but they have about 150,000 on them and I can tell that they've lost a little over the years. Now that I'm freshening up the engine, I was planning on just adding the 4K inner springs. I'm not really looking to anywhere close to 4000, but I want it to pull strong thru 3300-3400. Will adding just the inner spring work, or will things be out of sync a little with the combo of old 3k plus the new inner springs? A net result of 3.5k would be perfect.

 

just get the new set of 4k's i got mine from diesel_pap. they are a very reasonable price. and it helped my pickup out alot when i did it. if you want to go to that rpm i was recommended that i got 60 lb. valve springs to keep my valves from floating above 3200 rpms.

 

It wont hurt a cummings to turn 3500 or 4000 with 60v springs and nothing else done.

 

hey zach just because you put 4k springs on there doesn't mean it'll fuel up to there right?

 

CUMMINS!CUMMINS!CUMMINS!CUMMINS!CUMMINS!CUMMINS!CU MMINS!CUMMINS!CUMMINS!CUMMINS!CUMMINS!CUMMINS!CUMM INS! there is no G!!!!!!!!! sorry man that just drives me nuts

 

 

Some tweaking of the pump and it will fuel to 4k noprob. With the 4k springs of course.

 

Oh sorry about that my bad i will proof read next time. But can you turn a CUMMINS that fast without hurting it.

 

Guys you're kinda missing the point to my post. First, I already have 60lb valve springs, so I'm not really worried about hurting the engine by reving it high. But, the stock cam's power curve drops off after about 3500, so unless you're running a lot of boost (twin turbo range) or spraying it, above 3500 is wasted RPMs.

My goal is to get the most out of the engine with the stock cam in it. I don't really want 4k springs because of their touchy driving characteristics (my wife will drive it some). But my current 3k springs are a little tired, and I've lost about 75 rpm at idle and about 200 rpm off the top end. So, will adding the 4k inner spring help restore some of what has been lost, or should I just get a fresh set of 3k springs. I've also thought about maybe tightening down my current springs by a click or two. Like I said earlier, a net result of 3.5k springs is what I'm actually looking for.

 

yes, but a upgraded damper would not hurt.

Most of the time on a DD your motor is turning less that 2500 rpms, short pulls above 3500 will not hurt.

i think its more of a head issue than a cam issue in the upper RPM range. The stock 12v head is very restrictive.

As for the most power with a stock cam in a 12 valve, I know of a truck that made 800+ at the wheels with the stock cam ... good bit of head work tho

I think you should buy either the inner spring or a set of 4k's. They will pull harder in the lower rpms and you will have a bigger top end range as well. There not as touchy as most say.