Engine/Transmission (1994 - 1998) 4k on a Stock truck?

[FDavid]

98 12v 5spd no engine mods. Would like more usable rpms. Would a 4k kit be ok to use?

thanks

Dave

 

[FordCummins]

Yep, but you will have to do the valve springs as well. Not a bad job at all. Might as well add a fuel plate, or make your own while you are at it.

 

[Matthug]

On a bone stock truck??? I wouldn't, it isn't gonna be breathing in them upper RPM's and won't have any power after about 3200 RPM anyway.

You have to remember a GSK isn't just more RPM's, the 4K kit shifts the power band to the right meaning you will have less low end power and more upper RPM as opposed to a 3K kit (besides 3K+ RPM power which on a stock truck is very minimal and not worth the low end loss).

Also, more RPM's tends to wear a engine out faster. Why do you think our trucks last so long compared to powerstrokes? I mean it not 100% the reason but the largest portion is cummins engines turn way lower RPM's.

Unless future mods are planned stick with the 3K kit.

 

[Forrest Nearing]

at least do a #10 or #100 even if you slide it way back so that the fuel curve will be decent.



I'd do a 3k, if you're not planning on spinning it. you don't need valvesprings w/ a 4k, but don't spin it over about 3400...

 

[RoadGoesOnForever]

You have to remember a GSK isn't just more RPM's, the 4K kit shifts the power band to the right meaning you will have less low end power and more upper RPM as opposed to a 3K kit (besides 3K+ RPM power which on a stock truck is very minimal and not worth the low end loss).

How do you figure this???

 

[biggy238]

The heavier springs mean the weights can't move out as low in the RPM band? I thought there were two sets of springs though, one for lower rpm and one to control the high rpm.

 

[Matthug]

The heavier springs mean the weights can't move out as low in the RPM band? I thought there were two sets of springs though, one for lower rpm and one to control the high rpm.

Thats right but there's still some tradeoff.

 

[RoadGoesOnForever]

The heavier springs mean the weights can't move out as low in the RPM band? I thought there were two sets of springs though, one for lower rpm and one to control the high rpm.

The flyweights defuel the engine, and tighter springs would keep the weights from coming out as fast which would not hurt low end at all. This is in line with the experience I have had on my truck with stock turbo, stock injectors, and even the stock camplate (slid full forward). Now I have a 0 plate and some modifications to the AFC to help rack travel, but even before that I did not notice any loss in low end fueling with the 4k gov. springs. I do agree that your peak hp moves up in rpm, but that would obviously happen since the engine would not defuel as early as stock.

 

[Forrest Nearing]

the problem is it takes your fuel curve (plate profile) and extends it, so it will hurt low end power because the lever arm is going to stay on the nose of the plate longer

 

[RoadGoesOnForever]

the problem is it takes your fuel curve (plate profile) and extends it, so it will hurt low end power because the lever arm is going to stay on the nose of the plate longer

I can maybe see that happening, but I did not experience it with stock plate slid forward, and I definitely do not feel it with the 0 plate.

 

[Forrest Nearing]

it's happening

 

[RoadGoesOnForever]

it's happening

I will take your word for it. I honestly do not know enough about P7100 governors to make an argument either way, I was just letting you know my experience.

 

[Forrest Nearing]

you don't feel it on the #0 plate, because the AFC is all that's limiting rack travel... that's why the #0 and #100 plates work so well w/ GSK's w/ the #100, you can play w/ the lever arm to dial in the lower RPM fuel to your liking... w/ the #0, you don't have to worry at all

 

[RoadGoesOnForever]

Yea, I understand why the 0 is not a problem. I was just saying that I have not felt a problem with a stock plate. Of course, this is only seat of the pants feel. On a dyno, it may have been obvious that the plate profile was holding me back at the lower rpm's, but I could not feel it. Either way, if he wants a 4k spring kit with a stock plate, he will more likely than not end up doing other modifications to make the spring kit more effective. Really, who with a 12 valve just stops with one modification. Now its a spring kit, next a plate, then injectors, turbo, etc. etc. Its an addiction

 

[FDavid]

Well, my main goal was to build a truck that would be a good daily driver and a great tow vehicle. But most importantly was to do modifications that would keep the truck as reliable or more reliable than stock. So sitting in my garage I now have a Banks Powerpack and an ATS exhaust manifold. I went with this combo since it would give a slight increase in power while keeping EGT's at a minimum. I also purchased a 5" exhaust and an BHAF, so if anyone wants a Banks air filter and banks muffler/tailpipe cheap let me know. And oh ya, I bit the bullet and ordered a 4k kit. I'll let you guys know how it turned out

Dave

 

[Matthug]

Well you're not gonna like the touchy throttle of the 4K kit. And with the mods you have planned the engine isn't gonna breath past 3000 anyway. Also if you want reliability and longevity of your engine, revving it past 3K won't really obtain that!!!



Edit-I hope you also ordered the 60# exhaust springs, if not I hope you don't bend a valve when you float it.

 

[Forrest Nearing]

my old 97...



got a #6 plate, 4k GSK and 370's right at 100k miles...



I got it w/ 200k...



at about 215k I ground the plate deep and flat... truck made 450rwhp, ran 42psi all the time, and I shifted it at 3400-3500 20 times a day.



it finally lifted the head at ~250k miles. put it back together and the stock valve springs are still doing fine.



I agree, don't get the 4k, if you're only going to rev to 3k, but...



Forrest