White Magic 1200 quest for more vacuum

I purchased an older White Magic 1200 (5.6 blower) recently because it was low priced and low hours. My hand built van powered unit with a sutorbilt 4L spanks it. I assume it is the exhaust restriction (4" outlet reduced to 2") on the white magic causing the issue, can anyone verify before we fire up the welder and cutting torch?

4" Blower exhaust reduced down to 2" sure sounds like a problem to me, from everything I've read and heard.

I'd say waaaay too much restriction is killing the blowers performance, and I would think causing excessive heat and possible damage to it.

Start Cutting!!!!   

That's what I thought too. Plumbed my 4L 3" in & out, then had to turn the rpms down because I could pull carpet off tack strips with a PC quad wand

Be careful with that. We have an 1800 and when we rebuilt it I found the reducer and plumbed it 4" to the waste tank. The problem was that the relief valve isn't built for that much vacuum and can't be adjusted enough to allow it. This in turn strained the belt which strained the pulley that stripped out.

procarpet wrote:Be careful with that.  We have an 1800 and when we rebuilt it I found the reducer and plumbed it 4" to the waste tank.  The problem was that the relief valve isn't built for that much vacuum and can't be adjusted enough to allow it.  This in turn strained the belt which strained the pulley that stripped out.

Yep, always one of the first things you check after making changes like that, wither it changed the inHg/vac amount.....if so, you have to adjust accordingly.......But I'm SURE ThaBeast knows that!    


"can't be adjusted enough" that's an easy fix, prob a foot valve and just needs a heaver spring......Or if not, just replace whatever it is with an adjustable Foot Valve, same type that's used on many other TM's.  

I want to figure out a way to install a kunkle valve. Right now there is a box on top of the tank that holds the filter and has the relief valve

ThaBeast wrote:I purchased an older White Magic 1200 (5.6 blower) recently because it was low priced and low hours.  My hand built van powered unit with a sutorbilt 4L spanks it.  I assume it is the exhaust restriction (4" outlet reduced to 2") on the white magic causing the issue, can anyone verify before we fire up the welder and cutting torch?

the pro 1800 we run has the same blower, its a true best once you open it up. Its still restricted by something.

procarpet wrote:I want to figure out a way to install a kunkle valve.  Right now there is a box on top of the tank that holds the filter and has the relief valve

Remove inlet elbow from blower, install a tee fitting there. One side of tee is plumbed to the waste tank, other side gets a kunkle or bayco valve. All blowers should be plumbed this way per the spec sheets but rarely do truckmount mfg. do relief plumbing this way.

Don't forget to weld your factory relief shut after installing a correctly plumbed relief valve

ThaBeast wrote:

procarpet wrote:I want to figure out a way to install a kunkle valve.  Right now there is a box on top of the tank that holds the filter and has the relief valve

Remove inlet elbow from blower, install a tee fitting there.  One side of tee is plumbed to the waste tank, other side gets a kunkle or bayco valve.  All blowers should be plumbed this way per the spec sheets but rarely do truckmount mfg. do relief plumbing this way.

Don't forget to weld your factory relief shut after installing a correctly plumbed relief valve

I'd have to see an illustration. I can't picture that

I'll see if I have a pic of that from one of our builds or mods.

I decided to change one of the sheaves on the white magic this evening and picked up about 70 cfm, I'm happy with that for now. I changed the blower sheave from a 64 to a 54, still within limits of the clutch and maximum blower rpm but the 3-400 rpm boost gave us about 70 more cfm at 100ft hose run. Once my Cobra has the rear axles back in her I'll change the exhaust on the white magic and do a bayco mod

Btw, I ran the blower at speed under load (15hg) for thirty plus minutes and the blower only temped at 150 degrees F

Sorry guys been busy this week my Dad had back surgery.
What RPM are you running at should bee around 1500 to 1700.
Second i'm with the other guys on exhaust size even if you have a blower HX I've never seen a outlet smaller than 3" most are the same in and out. Even with the HX. it causes it's on restriction to make heat.

Van engine 1700 rpm under load, which puts the blower at 2480 now. It is definitely a 2" exhaust. As I stated above after speeding up the blower a bit by changing the sheaves cfms are good for now.

If you have never seen severely restricted blowers you haven't taken many apart. PowerClean genesis was the worst I ever saw, 5.9 blower with a 'hidden' restriction down to 1"

Granted I haven't torn a blower silencer apart but I have never seen one with 4" on one side and 2" on the other. But as I have learned from this forum there are brands that are not many of on the east coast. But I don't understand how a restriction down to 1" although will creat heat but less air flow can work very well. Kind of like trying to breath through a straw you can but not very fast. But I have seen the pro 1200 and in working on it I have never noticed it having different sized inlet/outlet just trying to help.

The silencer is 2" in and out....but the blower itself has 4" inlet/outlet ports. The outlet is reduced to 2" right at the blower. Honestly since I changed the sheave it has been working well enough that if the blower case stays below 200 on a hot day on an all day job I'll leave the exhaust alone

I used to own a White Magic Pro 1700 and a
Pro 1500. Only difference is that one had the
Kaw liquid cooled 20HP and the other had an
Onan 24 HP. Rpms of the Kaw engine was I believe
3050 and the Onan rpms were around 2500 .
Blowers were both 2900 rpms. The plumbing throughout
the vacuum system was 3 inch except the silencers.
Too be honest I don't remember but I believe they were 2 1/2 inch. One thing I do remember about these slide ins compared to ones with same blower
which were 45 Roots Whispair is that they had better vacuum. I put it side by side a Steamaction Nike 22.
I was a distributor for both White Magic and Steamaction and also Bridgepointe. We had a Bridgepointe Lancer demo leased  which had a 22HP Kohler and a Sutorbilt 4MVL. All great machines! Easy to sell for sure.
These were all plumbed with 2 1/2" through vacuum systems. Even though the rpms were higher by a little on the Steamaction and the Bridgepointes
which we know is a Prochem Legend with a bigger engine the White Magics had a little better vacuum. The other machines did do better as far as heat however. So to hear about a 1200 White Magic which
of course has the 56 Roots had a 2 inch silencer suprises me. Only so many cfms can you get through a 2 inch silencer. But maybe there was a reason . I just can't think of one.

Because 4 inch silencers are freaking huge and expensive.

Fuzzsucker wrote:Because 4 inch silencers are freaking huge and expensive.

I think you hit the nail on the head right there!!!   

That would also be my bet, they went with a smaller silencer as a cost cutting measure.

can you take some pictures and show what are you talking about the 4" to 2" restriction