vacuum pump?

fired the car again today to play with the vacuum pump.it's a moroso 3 vane pump with the moroso valve on the pump.i have 4"at idle and it looks like it stops at about 9"when i turn the rpm up.any you run one of these?and what kinda vacuum do you see at idle?thanks!

We never really look at what the idle number is. we set ours to be where we want it at WOT and that depends on the setup, size of motor, rpms, fuel and what type of motor it is.

I don't have a Moroso, but from what I understand that's normal. On gas it would pull more, but on methanol you will see much lower vac due to the volume of fuel compared to gas. I guess you get more fuel past the rings.

I have a Star vac pump. I've been told that on gas it will pull 16-18, but I will be lucky to see 10 on alky. We will find out in the next few days.

i dont want too much but what about not enough when rpm comes up?will it cause a leak?this is all new to me,thanks for the help.

David Cole wrote:I don't have a Moroso, but from what I understand that's normal. On gas it would pull more, but on methanol you will see much lower vac due to the volume of fuel compared to gas. I guess you get more fuel past the rings.

I have a Star vac pump. I've been told that on gas it will pull 16-18, but I will be lucky to see 10 on alky. We will find out in the next few days.

Never heard that. Good too know

whatbumper wrote:We never really look at what the idle number is. we set ours to be where we want it at WOT and that depends on the setup, size of motor, rpms, fuel and what type of motor it is.

526 on meth,7500 rpm max.26tooth crank pulley with 36 on the pump so it's driven pritty fast.

found it! moroso has instructions on their site i didnt buy this pump new so................. the valve has 4 washers in it,no washers in it =10"vac,1=12",etc,etc. maybe i'll have some video to share after tnt,or it could suck and i wont talk about it. thanks guys!

Dave which star pump are you using ? When I used Travis' 4 vane moroso If I just touched the throttle it would hit 15" and stay there on idle I had to do a lot of adjusting on the relief to keep it down around 10" on the throttle. I was thinking about buying a star pump and was just wondering.

I have the Star std pump. It's a 4 Vane. Their Sportsman is a 3 vane. Should be on the dyno very soon to find out if what I had been told is true.

KY JELLY wrote:Dave which star pump are you using ? When I used Travis' 4 vane moroso If I just touched the throttle it would hit 15" and stay there on idle I had to do a lot of adjusting on the relief to keep it down around 10" on the throttle. I was thinking about buying a star pump and was just wondering.

my worn out moroso 3 vane does about the same, the number down track is what matters, mine is at about 10-12.

FWIW I see the same numbers on alky as I did on gas...............but my shit is sealed up pretty tight................

Here is the deal on the Star std pump. Today on the dyno. First pull was on gas just to warm it up. Pump was pulling 10" @ idle and 16" for the pull (started @ 4500). The adjustable regulator was set about 2/3 to 3/4 of the way out.

We could have increased or limited the vac some more, but reducing it would have required grinding on the mounting bracket for the pump. The regulator adjustment port/nut was right up against the mounting bracket/motor plate. My engine has a short Boss style crank snout. Due to the short snout, the crank pulley is very close in to the motor plate. So close that we had to shorten the pump to bracket standoffs to the minimum. A 1" longer mandrel would have worked and solved the problem.

When we put the injection on the vac went to 6" at idle and 10" for the pull with no changes to the vac pump. We only adjusted the amount vac once. Got it up to 12" with more left, but it did not make any more power, so we backed it down to 10" for safety. The last couple of pulls the vac had dropped to 8-9". I think that was just due to the amount of heat that had sunk into the block and oil. It actually made the most power on those pulls when it was at 8-9".

great info David,thanks.this vacuum pump stuff it the shnit for alky engines,IMO.i was to see how much water i got outa the can after i run mine.