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CJ3B vacuum readings; some comments on engine vacuum reading
Topic Started: Jan 11 2013, 10:56 AM (732 Views)
Galen
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I ran a vacuum test on my Jeep and it stands at 23 inches of Hg. The "green" zone of the gauge ends at 20". Is the green zone a general - perceptible range and not specific to any engine? Since mine is higher than this is this a problem? I know that the "red" below the green indicates late timing and I did advance the timing and it runs smoother slightly advanced. The needle is steady in any case.

What is the spec.for the Hurricane 4?
1954 CJ3B -Transport Yellow-
1953 B4 Dodge Power Wagon
1941 Dodge WC 1/2 ton military
1967 Plymouth Valiant
Culpeper, VA
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oldtime
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Greg,
Do not confuse engine compression testing with engine vacuum testing.
This topic was initially about vacuum testing.
I'll try to "SPLIT OFF" the preceding compression posts later.

Galen,
According to W/O the ideal vacumm reading for the F134 is 18 to 21 inches of Hg.
About what elevation are you at ?
It's also possible that your vac gauge may be off.
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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Galen
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That makes sense in that those figures you mention correspond to the "green zone" of my gauge. I am at 300 feet elevation so I don't there is an impact there. However I mentioned that my engine is advanced more than the 5 degrees BTDC. At the time of static timing, I may be a tooth off regarding oil pump and distributor. This may give a "false" reading for static timing meaning that the number 1 piston really is not at the top of stroke when I show 5 degrees BTDC. I have the distributor is rotated fully and the timing shows to be more advance than 5 degrees with the light and the mark on timing cover but the Jeep sounds stronger at this timing advanced beyond 5 degrees.

If I really am more advance in the timing, will this have ill effects on the engine. I have not driven yet to listen for pinging.
1954 CJ3B -Transport Yellow-
1953 B4 Dodge Power Wagon
1941 Dodge WC 1/2 ton military
1967 Plymouth Valiant
Culpeper, VA
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oldtime
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Quote:
 
This may give a "false" reading for static timing meaning that the number 1 piston really is not at the top of stroke when I show 5 degrees BTDC.

If the indicator shows 5* BTC then the piston must be at 5* BTC unless the valve timing was messed with.
Valve timing cannot change unless the front engine cover is removed and the timing gears are incorrectly alighned.

The crankshaft will spin at faster RPM if the timing is advanced when engine is idling.
That is normal but advancing the distributor timing does not provide better operation.
I find 5* BTC to be near ideal as long as the correct distributor is working as it should.
Do you have a timing light ?
The timing should be adjusted with crankshaft velocity at 600 RPM.
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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div4gold
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OT, I was messing around with the timing after removing the distributor to access a model NR that was on the back side. Anyway I set the timing with a light and then hooked up a vacuum gauge to see what it had to say. At a pretty smooth idle it was bouncing rapidly between 18 to 20 inches of HG. I seen people talking about different vacuum reading indicating different problems. I just didn't see anything like what I'd call a smooth reading. My 18 to 20 reading was a very rapid movement between the two at idle. Is that normal?
Old retired fart living in Ione, WA. I have a 1964 CJ3B. Recently overhauled original motor, transmission and overdrive. 11" Bronco drum brakes on all 4. Needs a new coat of paint but that will have to wait till next summer, it's next summer and I'm working on that now :) UPS & FEDEX will continue to profit :)
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Don
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http://www.secondchancegarage.com/public/186.cfm

I found this an interesting link.
Don Norris
Southeast, NC

1953 CJ3B
1959 Jeep Pickup
195? M100 trailer
~~~~~~~~~~~~~~
The trail never ends
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If lovin' Jeeps is wrong,
I don't wanta be right.
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oldtime
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Quote:
 
Is that normal?

No.
Exactly where did you hook up the vacuum gauge ?
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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div4gold
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I checked out the different scenarios in the link posted by Don, my symptom mostly was what you see in the NR 5 scenario. But I couldn't really say that I had the gauge hooked up to the best spot. I didn't have anyway to connect it to the intake below the carburetor so I just pulled one of the line coming off of the fuel/vacuum pump. I've got the carb off now and into a shop for rebuilding. I'll get a proper hook up for the manifold and see what I get, It'll be a week or so before I get the carburetor back. That was a interesting link posted by Don. OT, if where I had the meter hooked up was satifactory would you say that the valves aren't working quite right? The timing could be a couple of degrees retarded. I really do need to know what line to hook up to and if anything needs to be plugged . Howard
Old retired fart living in Ione, WA. I have a 1964 CJ3B. Recently overhauled original motor, transmission and overdrive. 11" Bronco drum brakes on all 4. Needs a new coat of paint but that will have to wait till next summer, it's next summer and I'm working on that now :) UPS & FEDEX will continue to profit :)
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oldtime
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Quote:
 
I didn't have anyway to connect it to the intake below the carburetor so I just pulled one of the line coming off of the fuel/vacuum pump.

That's what I suspected because that can possibly give a bad reading due to the vacuum pump.
The vacuum gauge needs to be tapped directly into the manifold below the carburetor.
No other tube / hose plugging is required.
Vacuum test is normally performed with crankshaft spinning 600 RPM.
Perhaps someone scan and post the vacuum test procedure printed in the Universal Service Manual.
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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Rus Curtis
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div,
I was stumped on the fluctuation until you mentioned you hooked it up to the pump outlet. It is pumping rhythmically from the cam lobe.

Here are the directions. Get an adaptor if you need it but you need to tap in to the manifold as indicated.

Posted Image
Rus Curtis
Alabama
'54 CJ-3B "Green Gruntt"
Bantam T3-C
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div4gold
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Thanks for all of the information, now I just have to get the carburetor back on to check it out.
Old retired fart living in Ione, WA. I have a 1964 CJ3B. Recently overhauled original motor, transmission and overdrive. 11" Bronco drum brakes on all 4. Needs a new coat of paint but that will have to wait till next summer, it's next summer and I'm working on that now :) UPS & FEDEX will continue to profit :)
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div4gold
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Carburetors back on and all is well. I did get the vacumn gauge hooked up to the inlet under the carburetor. It may have been leaking a little bit but it holds a steady 19 in hg at 600 rpm.
Old retired fart living in Ione, WA. I have a 1964 CJ3B. Recently overhauled original motor, transmission and overdrive. 11" Bronco drum brakes on all 4. Needs a new coat of paint but that will have to wait till next summer, it's next summer and I'm working on that now :) UPS & FEDEX will continue to profit :)
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