I have a perry pump that works off of pressure from the crankcase. The question I have is, do I still need to pressurize the tank or just vent it? I am going to be using this on a ST3000 with an OS 7D carb and a slimline pitts muffler.

Thanks!

LOOPMAN

no pressure needed to the tank, just vent it.

Got a question, i am considering the pump also. Does it hurt to pressurize the tank when using the pump?

IIRC...The Perry Pump instructions say you should not pressurize the tank. You could take a look at their web site, I think they answer it there. There's a link on my Engine page.

Cliff
http://www.rcfaq.com

I ran the ST3000 today with the perry pump set up. It ran flawlessly. Throttle response was better than I had anticipated. The only thing I notice is that I get some fuel drainage through the carb when the engine is not running. Small price to pay for a great running combination. I did not pressurize the tank.

Happy Flying!

LOOPMAN :bananahea

LoopMan,

I have a ST 3000 for my H9 CAP 232 and am considering upgrading the carb to a 7D and getting the perry pump. Can you provide some detail about how the crankcase is tapped for pressure and how the pump is installed?

TIA for your help.

Cheers!

Galen

Did the carb siphon fuel before the addition of the Perry? Since the tank is not pressurized, it shouldn't make a difference?

I bought this engine second hand at the Perry swap meet two weeks ago. The first time I ran it was yesterday so I don't know if it had siphoned fuel out of the carb before. I may have had the tank above the carb line on the test stand. It's not that bad and if I close the throttle the siphoning stops.

The setup is very simple for the pump. Mount it on the firewall and try to keep it in line with the carb if at all possible. Set your tank up for three line operation, that means you have one vent line, a filler line and a fuel line. If you are running an uncowled engine you could just set up a two line tank. There is no adjustment necessary for the pump as it is pre-set at the factory. The OS 7D is a very nice carb and it appears to have been fitted on the engine with no modification. I drilled and tapped the center of the backplate for a standard du-bro pressure fitting, making sure I kept everything smooth and flush on the internal face of the backplate.

Happy Flying!

LOOPMAN

I use a Perry pump and a Perry carb on a OS160FX. THe tank is about 12" away from the carb. It works PERFECTLY. The attitude of the plane doesn't affect the rpm at idle or full throttle.

I was originaly going to use the pump with the stock carb but the Perry pump carb has a reduced venturi effect and won't run rich in the mid-range using a pump.

Ken

GalenB,
Before you purchase that OS 7D carb, I suggest you call Perry Pumps (630-858-3160) and ask them about the best pump / carb setup for your engine. They are very helpful nad knowledgeable. I'm betting you can purchase their pump and pump carb for about the same $'s as the OS 7D will cost you.
I put their pump and carb on my ST 2300 and have had great results with it.

The pump is supplied with a pressure fitting that is installed into the crankcase by drilling and tapping a 6/32 hole (usually in the center of the engine back plate). The pump instructions explain how to do it.

I have 2 3250's. Both had the all the midrange problems. I installed a 7D on one and a perry on the other. No pumps and no other modifications and they now run great.

True, the pump is not needed if the fuel tank can be placed in an appropriate position close enough to the carburetor spray bar. But in most planes large enough to require a ST 3000, if the tank is placed on the CG the clunk will be much more than 12" away from the carb. A pump in this situation is very beneficial for insuring a consistent fuel flow to the carb regardless of the attitude of the airplane, or the maneuver it is performing.

I've got an oscillating pump on my 1.6 FX. Stock carb, and I ran the muffler pressure. Fine so far, no dripping. I'm afraid to try it W/O pressure now because it is running so good.
RP

I don't know about the oscillating pump, I have never had one. But do not run exhaust pressure with the Perry regulating pump.

Why Not? I have always run muffler pressure with the regulating pump. I'm pretty sure that was the recommend method of venting.

The Perry should have crankcase pressure, but not muffler pressure. By adding muffler pressure to the existing crankcase pressure set up, you upset the operation of the diaphram in the pump housing.

Crankcase pressure is applied to the diaphram which pumps the fuel with the built in check valves. Muffler pressure is applied to the tank and push's the fuel thruough the check valves. The installation manual explicitly states that it is OK to use muffler pressure and they recommend doing so. I have never had a problem using muffler pressure.

Mine are about 2 years old. Maybe the newer ones are different?
It is the VP-30 right?

I really don't want to get into an online debate here. All I can tell you is that the instructions that came with my VP-30 (1 1/2 yr old) clearly states do not run muffler pressure to the tank. I also called the nice folks at Perry and discussed this with them. They said do not run the muffler pressure, and explained why. I have been running the VP-30 on my ST 2300 for over a year with the clunk 16 inches behind and 2 inches below the carburetor spray bar. Tank is vented to the outside air. Performance is outstanding at all throttle settings, and airplane attitudes.

For your own peace of mind I suggest you call the folks at Perry Pumps and ask their advice. 630-858-3160. They are very nice and knowledgeable and will be more than glad to help you and answer your questions.

I'm outta here

I'm Outta Here Too...