3200 vs 4200?

[bgilbert]

Even if it doesn't make any extra power at a higher RPM, which is pretty likely, why wouldn't one use the 4200 RPM spring?

Sounds like it works fine with 5 minutes of trimming, no downside unless one is in the habit of playing ring-around-the-rosie with their tachometer...

Well if defueling below 3000rpm isn't enough to not run one, price is a factor too. The 4200 spring cost more last I seen on PDR's site.

[Begle1]

So the controversy is over where the springs actually defuel at... Some say 3400 and some say 2700...

I turned my high idle screw plush against the pump; I guess it fuels up to 3200 RPM now.

But my tach starts wiggin' a bit that high, too. Around 2600 RPM if the foot's floored the tach needle starts jumping in 50-100 RPM segments instead of being smooth. Anybody else see this with the Autometer 2888? I figure it's either a bad belt tensioner, or a bad gauge, or a bad electrical thingy somewhere...

[gman07]

Try moving the sender around on the alternator until you get a non-jumpy signal. Mine jumps at low RPM (<700), but it's fine after that, all the way up to 3400, which is as far as I have taken it.

[Begle1]

I wouldn't think that the sender is the problem; it's rock solid throughout the entire RPM band as long as I'm not accelerating quickly, so I know it's capable of getting a good signal at any speed. It's just the fast change of rate that throws something off.

I think that what's sending the signal is stuttering; either the alternator starts to miss when I'm accelerating past 2600 RPM, or the belt is whipping around a little bit.

How much is the belt supposed to whip around at idle? Mine has always fluttered about an inch, is that a sign that I need a new tensioner? Or an adjustment on the tensioner?

You could very well be right, but it's not really an annoyance enough to be a problem. Although my old Autometer pyro had a similar problem with jumping in segments; if it's the gauge that's bad, then it's annoying enough to do something about. Of course, if that's the case I can't do anything but send it back to the factory.

And driving a vehicle without a tachometer's like making out with a women without any eyes...

[KTA]

My truck does not have a tach, and it doesnt bother me a bit, of course neither does making out with a good looking woman I can't see, heck I can always feel my way around. LOL

[seeker1056]

anybody wantsa cheap reliable tach
Tinytach, $60 US, is digital, clamps to a fuel line - reads to 10,000 rpm, and has an hour meter, and service reminder built in
It works greta

Only downside is that it isnt lit for nite viewing

[Cschafer]

If I understand it corectly all the govener spring does is put tension on the lever inside the pump and pull it untill the flyweights overcome the spring and pull back. Mine has the stock spring and defueled around 2500. I did some messing around and broke a little plastic stop out from the go pedal and adjusted it to sit up off the floor alot farther thus being able to pull alot farther. The truck does not defuel till after 3000 with a stock spring. On my last dyno graph, (on a dyno jet Bill). The truck hit 300 hp at 70 mph and didn't go back below 300 hp untill 103mph with a max of 319hp (pretty flat graph). Sombody will have to refresh me on what rpm's that is with a 5spd, 3.54's and 34in tires but it was still about 280hp at 108mph when it broke. I believe this is why everybody has a difernt situation of when there truck defuels with the differnt spring. I know I will have 60lb valve springs before I put in the 3200.

[dpuckett]

My 91 would pull hard to about 31-3200 with the stock spring. 92 pulls to 3500 real easy with the 366 spring (I havent gone any higher than that on the street- by 3300rpm in 3rd, I am running out of speed limit). I, too, think it has to do with other settings than just the gov spring. Max fuelling, timing, and injectors will play a part. Mine would start its "runaway" at 1700rpm with the marine injectors; it wont do it til 2000 with stockers and a dialed back pump.

Daniel

[Rampower]

At this point in time I wont say where mine defuels. We are going to be puting the truck on a Mustang dyno,{ I hope the Mustang's results are ok,} on the 15th of September. Will make a run with the 4200, then one with the 3200. I will post the results. I to am with most people in that the 3200 vs the 4200 can depend heavily on the pump in your truck. We will see after the dyno.

[bgilbert]

Will make a run with the 4200, then one with the 3200. I will post the results.

Josh Ayers beat you to it, he dynoed with the 3800 (same length as 4200) and the 3200 spring at Scheid's this past weekend. Results were very different. Where's my hat?:D

[2muchtq]

But what were the results?

[JAyers]

About 55-60hp and 75-100ftlb. The reason I dont have exact numbers is because I also changed the timing on the truck but the different spring deff made a difference. On the way home I put the timing back where it was before and noticed a gain in boost of about 4-5psi. Now dont ask me why because I have no clue, someone else who understands the pump alittle better will have to comment on that.

[Begle1]

So the bigger spring and advanced timing gave those power increases?

That seems like quite a gain... Almost to the point that I'd be strongly suspect of the dyno...

[JAyers]

Well we also messed with the throttle linkage, gained another 1/2in of travel. The timing advance was about 4deg. We also adjusted the valves to 6/10 vs. 8/18. And I dont know if this helped any but I also removed the air filter. It was also 7deg cooler than the first day and it wasnt as humid. Maybe I changed to many things at the same time for these numbers to be relevant as far as the 3200rpm spring goes.

[Begle1]

Unfortunately, I think that your test was contaminated by the donkycart of variables that fell in.

It's a good show of how little things add up, though.