Is it possible to convert a low pressure 4k5 MaxFlow (175psi) into a high pressure (800psi) unit???
MaxFlow pressure change
- Thread starter AlexFarkouh
- Start date
and a HP guage, and if it was originally a LP Max Flo... a High Pressure PRV aswell (Pressure Release Valve - The Brass Valve) 
Actually, it's very, very tough to get an LP Max Flow up much past about 500 psi, even with a spring kit.
It's a simple matter of piston sizes- the "regular" (non-LP) Maxes have a smaller piston for a reason- so they don't have to have nearly as much spring pressure to balance and compensate for the supply-side pressure.
An LP Max with the stock Shocker/Impulse springs will go to about 250 or so. The brass overpressure poppet starts to vent at 220 to 230 or thereabouts.
With a stiffer spring, you can get the same LP Max into the 400 to 450 range, and if you don't mind having to use a spanner to turn the adjuster cap, you can probably squeak it to 500 psi.
However, at those pressures, you're looking at a loss in consistency and flow rates since the main seal simply can't open as far- the adjuster spring is very nearly in coil-bind (full compression.)
The Maxes with the smaller piston can easily do 900 psi with the right spring.
If you have an LP and need more pressure than about 450 psi, sell it or trade it. Or, if it's on something like a 'Cocker or Timmy, just yank the marker's inline reg and let the Max feed it directly. Max Flows are "pressure compensated"- the output is self-adjusted in relation to the tank pressure, and one in good service is more than capable of reliably single-regging any marker. (They single-reg the gas-hog Shocker, they ought to be able to keep up with a Timmy. )
Doc.
It's a simple matter of piston sizes- the "regular" (non-LP) Maxes have a smaller piston for a reason- so they don't have to have nearly as much spring pressure to balance and compensate for the supply-side pressure.
An LP Max with the stock Shocker/Impulse springs will go to about 250 or so. The brass overpressure poppet starts to vent at 220 to 230 or thereabouts.
With a stiffer spring, you can get the same LP Max into the 400 to 450 range, and if you don't mind having to use a spanner to turn the adjuster cap, you can probably squeak it to 500 psi.
However, at those pressures, you're looking at a loss in consistency and flow rates since the main seal simply can't open as far- the adjuster spring is very nearly in coil-bind (full compression.)
The Maxes with the smaller piston can easily do 900 psi with the right spring.
If you have an LP and need more pressure than about 450 psi, sell it or trade it. Or, if it's on something like a 'Cocker or Timmy, just yank the marker's inline reg and let the Max feed it directly. Max Flows are "pressure compensated"- the output is self-adjusted in relation to the tank pressure, and one in good service is more than capable of reliably single-regging any marker. (They single-reg the gas-hog Shocker, they ought to be able to keep up with a Timmy.
)Doc.
Cheers for that Doc, I had looked at the manual and it looked like it was a simple job to change a couple of components, but I'll take your advise and revise my plans.
-Sure, it's easy, but within a limited pressure range.
You can squeeze a "low" into the "mid" range, and a "mid" into the "high", but it's nearly impossible to push the "low" all the way into the "high" pressure range.
Same goes for the reverse- a "high" pressure Max will work adequately at mid to low pressures, but having the correct spring improves consistency and recharge by quite a bit.
Doc.