I just completed, and worked the bugs out, of my smog pump to vacuum pump conversion. it seems to work quite well..although I don't have a vacuum gauge to stick on it...yet.

I've heard of dangers running too much vacuum in the engine. Something about it hurting oiling by pulling oil the wrong way or something...Is this true? if so, how much vacuum is safe to run?



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Jester,

What exactly are you evacuating? (How is the pump connected?)

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Vader
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It's sucking air out of one valve cover..the other is open to a breather for now (just a hyped up PCV). But I plan on blocking up the other valve cover to create state of vacuum inside the engine.

 

how were you able to remedy the noise problem?

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Yes I was. I put in a larger intake port, from 3/8" to 3/4", that helped a bit. Then I cut the stock output tube in half, right over the header. Clamped a rubber elbow on the end, and stuck the muffler I stole off the stock diverter valve on the end. Can just barely hear it now, with your head stuck under the hood.

 

Jester,

I must be missing something. If you evacuate the crankcase, you may prevent a lot of external oil leaks but I would expect that you would tend to encourage blowby and may affect the oil control - not by pumping up too much oil but stripping the necessary oil on the cylinder walls.

I understand that the lower density of air in the crank area will theoretically reduce air friction on the crank, pistons, and rods, but I'm guessing you'll get a lot more combustion gasses in the case.

What kind of vacuum do you intend to maintain with the pump?

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Vader
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Vader:
The idea is to help with ring seal. Obviously rings are designed to seal when pressure is applied downward. The idea of a vacuum pump is to assist that by creating less than atmophereic pressure on the bottom side of them. It's a trick used in some racing classes. They use either a vacuum pump (~$400), or they have ports welded toward the bottom of thier headers with hoses leading up to the valve covers. Since it's not cheap either way, and the gains are small (20hp or less) it's not commonly used in normal cars. But, I made one for pretty much fre...so what the hell


However, my concerns over oil control are why I posted this

[This message has been edited by Jester (edited October 03, 2000).]

 

yeah- istead of breathers on some of the race motors i have seen, the guys route them to the headers... weld a fitting in at an angle such that it creates a vacum and there for causes a negative pressure in the crank case... all too many times though you see them blowing oil smoke from suckin oil up...you probably dont really want to create much of a negative pressure in the crankcase, however, it does show small hp increases...

Steve

 

I've got a Moroso catalog and in the section under vacuum pumps it has a tech note recommending no more than 17" H2O.

I'm glad to hear you have the bugs worked out. I hope to be using my converted smog pump this weekend!

By the way, are you getting any oil carryover through the pump and out the muffler?

 

17" huh...sounds good. I don't think the pump is pulling that much..but I'll stick a gauge on it to be sure.

 

We pull 20" on my friends Cuda. You will also need to add a catch can and a separator. You should also have a safety valve on on the opposite valve cover.

It's a lot of stuff and money for a small gain. It only starts to help above 6000 rpms. And then it was only good for ~20 hp both n/a and on n2o and this is on a motor that makes 800hp on the motor and over 1200hp on the juice.

Miles

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