the stock gsk starts defueling the motor at 2200rpms whether you have the plate removed or not. the 4k spring allows you to run more fuel in the higher rpm range so the truck wont fall on its face. it wont hurt nothing by running a 4k. hell the motor wont turn 4k even with the spring in unless you have some pump mods done cause i dont think the turbo nor the stock p-pump will fuel it that high. you can prob get 32-3400 out of it.
Well, I can get the revs as high as I want, (I once
saw it as high as 3500RPM when my mechanic drove it, but I'd never go over 3200). It was smooth as silk at 3500, but the noisy part was me yelling "SHIFT YOU A$$HOLE!"
What Doidge was saying is that you can do a 3k GSK if you don't plan on valve springs, but I'd never do a 3k - it's a waste of time. It starts defueling earlier than 3k and with advanced timing (mine's at 17º) and injectors, a 12-valve is good til 3200 at least. I need those last 400RPMs.
I just know that I won't push the revs to the point where I will risk exhaust valve float. You can free-rev it to 4k all day long and get no valve float, since it's the boost + high revs that cause the exh valves to hang open.
I plan on doing valve springs ASAP, but it's not risky at all in the meantime.
My point (in response to Doidge's warning) was that I doubt he knows what all is at risk if he's issuing warnings not to install a 4k kit w/o valve springs or your engine will blow up.
12veg we need a timing section. i am trying to learn about that. if the timing is advance, that will cause better response and lower egts correct? what is stock timing usually at? where is a good spot to put the timing if you are only running a stock turbo and no plate? thanks again man, keep up the great work
The stock timing varies, from around 11.5-12.5 depending on year. The earlier 94/95 160/175HP engines were timed lower and the later ones higher.
Mine was at 12º or 12.5º.. can't remember - don't care.
If you advance the timing, it shifts the powerband UP in RPM's. Going from stock timing to 17º, I lost a LOT of low-end power (below 1700RPM) and gained a LOT of upper end power (2500-3200RPM). My spool suffered from loss of low-end.. but hopefully the 024's that are in the mail from Mathews8PT will help (he's now running my old 191's - we just traded).
But I didn't notice any change in EGT's. My low-end smoke was more after timing. Could've been a tuning issue, which I've resolved as good as possible with the stock DV's. When I get the 024's in, I'm sure I'll have to tune the AFC s'more to get it dialed.
You need to match the fueling to your turbo. And you need to advance your timing based on what injectors you have and what you're planning to do with the truck.
With stock injectors, 15º is probably a good number for DD'ing and you're not going to gain anything by putting it past that with stock injectors.
With my 5x12's, 17-18º is good. Even 19-20º would be good, but I'm on the stock head bolts/gasket.
If you have studs and 5x16's and you're looking to make like 600-700HP, you may be better off going with 20º or higher timing.