Douglas Brown

Question???? can vacuum be increased with a smog pump????
It has to get air from some where??? can you tap into it and increase the vacuum in the system???

Tonio

Sure. Instead of pulling air from the engine bay, it can pull from a tank, thereby creating a vacuum within the tank.

Big2Bird

Have you looked to see where a smog pump intake is?

NewbVetteGuy

I assume you're talking about using a smog pump as a crank case vacuum pump; yes, this can work, for a while. These pumps are not made to deal with all the oil in crank case windage, though and will usually die fairly quickly; although some folks report them lasting quite a while before dying.

The difference between a real crank case vacuum pump and a smog pump is the ability to deal with oil and combustion gasses while still living a long life.



Adam

CanadaGrant

How are you going to plumb the air intake? It's the entire front of the pump behind the impeller and pulley. Then there are the diverter valve ports. It would be easier to just hook up a vacuum pump instead of trying to turn a pressure pump into one.

Tonio

I'm assuming that you're talking about increasing vacuum pressure within your vacuum system, right? Not increasing the vacuum within your intake plenum.

Douglas Brown

Ok , that's the easy answer. Sure hookup to the suction side of the pump and suck from a tank.....But can I increase the present vacuum by connecting to one of the existing 1/4" tubes that already connects to the main tank in the front of the car. With out causing a problem for the rest of the vacuum system???? answer is NO, has to be separate tank. Because If I connected to that tank, Then i would be working against the manifold vacuum??
So I would have to isolate one of them????
The cars manifold Vac. is not strong enough to pull and maintain needed vac. for cruise control servo. Question I should be asking is how much vac dose the smog pump pull???
CC needs 15-20 " of vac.

It's an idea to get around buying a vac. pump.
I can not increase Manifold Vac. due to cam (mild) vac. is 13-16 "
Throttle springs seem to strong for vac. operated servo.?????
I'LL need a Vacuum pump.

CanadaGrant

13 to 16 inches of vacuum is enough to run anything on your car. If something isn't working you can't fix it with more vacuum. The air intake on your smog pump is open, wide open and is at the front behind the pulley. There is no place to run a hose to or from. It's like trying to attach a vacuum hose to the outside of your air cleaner. If you have 13 to 16" of vacuum, fix the real problem instead of trying to up the vacuum.

Douglas Brown

OK..good and thank you for the advise...
I was under the impression I did not have enough Vac. due to the (mild) cam; I had read it required 15-20 " of Vac. to operate the CC.
When i checked the vac. before it was with nothing connected. But I would like to see what it is with all the tubes connected.
I am not sure of the real problem w/the CC...
I will start trouble shooting the issue testing Vac at the different components at different rpm's.
Then the electrical connections.
I just know it does not work It did not come with the car, I added it. So good chance it is the mechanic (me) who missed something. Thanks again for insight.
DB

calwldlife

an 81 with computer carb and advance?
no trouble light?
every sensor still hooked up?
did you lower the thermostat?
damn little info

Douglas Brown

What else would you like???
350 ci 300 hp w/ mild cam. Manual Trans.
currently 600 miles on new motor.
If you have a question, Ask,

calwldlife

ok. someone put a computer on a 78.
clue, they didn't come that way.
see ya

Douglas Brown

I posted - 78 C3 Vacuum reading- awhile back. I at that time had the following readings. At the manifold.
1,000 rpm 13.5 "
1,500 " 15.0 "
2,000 " 16.0 "
2,500 " 15.5 "
At that time I was told it was a might low.
This why I thought I needed a Vac. pump to increase Vac. to operate the systems.
What do I know?????

calwldlife

3 different threads ain't doing you no favors.
don't count on people knowing about the others.

i have gone from thinking running issues to bad vacuum can on cruise to cruise works but speed aint' right.

if it engages and holds it ain't vacuum issue
hard to check facts when 3 threads are about cruise control
with different info.

is the cruise from a vette that had it?
then the drive cable from tranny thru transducer is one to one.
when you hit an indicated speed and engage Cruise,
DOES IT HOLD THAT SPEED?
if yes then it is a tranny gear issue.
Bad speedo
IF not, then a transducer issue, vacuum?, maybe. but you said it held higher and higher speeds but was off from the chase car.

Douglas Brown

OK...
Cruise from another Vet..NO...Transducer new, Servo and mount used, rod linkage I made (Orig. too short), Elect. harness used, peddle switches new.
Speed-o-cable new Tranny to transducer to speed o meter
I used chase to check my travel speed not to check CC.
I have tried to engage that since then dose not engage.
The higher and higher speed was in the 1500-2000 rpm range when coming to a stop, clutch engaged...turned out to be a misalignment of the CC rod and servo causing a hang-up. That has been corrected and car dose not over run, ideal drops as it should.
I connected a manifold vac hose to servo to see if it would pull throttle springs back, it did. I jumped from start ideal to full speed before I could shut it down. Manifold vac 20 cm hg. or 8 in hg.
rechecking vac line hoses and electric.
I find I have a possible connection error. Manifold vac connection is 1/4" then steps up to the larger 3/8" that connects to the transducer. In effect staving system of vacuum.??? I think???
Sunday 1/7/18 found manifold fitting loose. tightened same, replaced vac. lines. one size now.
Vac release switch at peddle looks to be improperly adjusted.. No Electrical power at Transducer, will follow this closer.