I am going to reseal and locktite my pump, install a longer fuel screw, new fuel filter, and switch to a 4200 gov spring this week. is there any difference in the 3800 and 4200? indexing should be the same right? any tips?

 

If you didn't clip your current 3800, then the 4200 should fit right in.

 

Never clipped it... Think ill see a defference?

 

Were you smacking the gov limit already? I don't and that is because I don't have an adequate lift pump.

 

Iv got tons of fuel : )

 

I have the 3800 in now (untrimmed)and i have my fuel maxxed. only hitting like 3100 or 3200 rpms.... when i put the 4200 in how do i get it to turn 4200 rpms. i have the fuel to push it i know.
others with 3800 or 4200 springs how did you get it to turn that rpm? can anyone with these springs shoot me a pic of there indexing and the spring after its trimmed.
need help please.

 

Is the back of the throttle plates hitting the fuel line going into the pump?

In neutral I can hit 4200rpm really easily. Under load, I have gotten to 3500rpm but no power whatsoever.

I cut 1.5 coils from where the sharp 90* bend is at where the coils go to the hook. Then I took 1/2 a coil to bend the same 90* to get the hook part.

 

mine will hit 3500 rpm at ease with a load. If I lock it in first or rev it up in neutral I'm not sure what mine will reach, haven't really tried it. I got 60 lb springs so I feel more comfortable spinning the R's then I used to be. I am running an unclipped 4200 and love the quick response it has since its a much tighter spring. It takes right off after about 1200 rpm. I'm thinkin about clipping it though.

On a side note I had to re index my throttle one notch to get my truck to idle when I went from my 3200 to my 4200.

 

I got a clipped 42 in mine and have hit 4400 on the dyno. Made good power up til 35 or 36 then slowly tapered off.

Not sure what it would free rev to but I don't want to find out.

 

my stock 3200rpm spring will rev 4200 rpm on the road... id be afraid to know what a clipped 4200rpm spring could actually rev.

 

I forgot to mention i have a make shift spring and washer thing for my top hat assembly. I have new bosch parts to fix it all. Mew spring and washer. Lol. I will be installing the 354(4200) spring untrimmed, new tophat spring and washed, locktighting pump top seal, longer fuel screw, drilling out banjo bolts to 3/16(herd of this on 1stgen.org), new fleetguard fuel filter, turning fuel pressure back up to 16-17psi(maybe), and an m&h timing spacer. Hope the untrimmed 4200 will underload het me atleast 3800ish rpms. Any ideas or comments?
Anything else i should do?

 

take your high idle screw out and make sure your throttle cable and lever are getting full travel. sometimes this requires modifying the pedal

 

I have denny t pump top(no high idle screw).... And tight shortend throttle cable (full travel).

 

Who makes valve springs stiffer than 60's and would they be better? What do they go 2?

 

www.hamiltoncams.com

I talked with the owner face to face. He says that the springs he sells are made for the Cummins. Unlike the dual-valve springs that people sell for the 24v which is a Japanese car (I am thinking S2000 or something like that) valve spring.