VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 using vacuum gauge to check health of engine?

Hello Everyone,

I was looking at a chiltons manual, and there is a section on using a vacuum gauge to check the general health of the engine, (not a compression test where you put a gauge in the sparkplug hole a crank the engine) this one is supposed to be able to check for correct timing, sticking valve, weak valve springs etc... Has anybody used this method? And if you have, what have you used for a vacuum source? Could you disconnect the vacuum advance line to carburator and use that? I think this would be a great way to check an engine, and would like to know if anybody uses this diagnostic test. I'm a young pup trying to learn how these old engines run!

Thanks again!

Yes, I do at every tuneup. When you purchase a high quality vacuum gauge there should be a full set of instructions for it's use and the needed attachments.

The vacuum gage is an excellent tool for diagnostic work. It is normally attached to the windshield wiper vacuum port. Do not remove or use the vacuum advance port.

hello,

thanks for your quick replies. I just called NAPA and they said that all they had was a vacuum gauge part #7009573, but they said no fittings came with it. Could someone tell me where I could get a good vacuum gauge test kit?

Thanks

Steve

Here are several selling on ebay at this point of time:
eBay Motors> tools> is the catagory.
Item number: 280117064043
Item number: 290118901421

I have one very simular to this one
Item number
290120036966





-Read or write a product review
-Provide feedback on product information or image
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Our Price: $21.99
Availability:All items will ship within 24 hours


Professional quality at an affordable price!
Tests pressure up to 10 psi and vacuum up to 28° Hg on mechanical and electrical fuel pumps.
Vacuum gauge diagnoses improper valve timing, burned or stuck valves, sticking choke, leaking manifold, improper fuel mixture, more!
Gauge has large 3-1/2" diam. face with standard and metric calibration. Includes 2-ft. hose with fittings to fit most vehicles.


This one is from J.C. Whitney


Item Item # Unit Price Order

Vacuum Gauge & Fuel Pump Tester ZX473059Y Each $21.99 Will ship within 24 hours

I installed a vacuum gauge on the steering column of my 1968 pickup and I glance at it constantly while driving to check out my engine performance. The vacuum gauge came with all of the engine fittings. For a permanent mount vacuum gauge or for a vacuum test gauge you can tap into either a fitting or a vacuum line on the intake manifold.

:) :grin:

Steve:
Check the photos above and you'll see a "T" fitting. That enables you to tap into a vacuum line and still keep the engine running as it should. I use my vac gauge when I set the timing and advance...it's much more accurate then using my tin ears. You can also adjust valves using the vac gauge. It's an inexpensive but valuable tool for older cars.

Coach

thanks everyone for your posts!

Now I'm informed enough to get the right item! Maybe I should change out all my hissing vacuum lines while I'm at it!

Thanks

Steve

Vacum gages can also be used to time engines, detect a clogged muffler, tell you how bad your driving habits are and as stated are invaluable when you work on old cars. One item we often forget is that at sea level a chevy 6 at proper idle speed will pull around 21/21 pounds vacumn. An adjustment of about one pound less per thousand feet is needed. I am at close to 4500 feet and the vacum gage at idle reads in the area of 17 pounds.

Good morning. Couldn't sleep and this thread struck a chord with me as I explore VCCA Chat at 2:30 in the morning. It sounds like I really need to go this route and check out my 216 (39 Mster Dlx). I installed a combo fuel/vacuum pump from The Filling Station following the instructions from the books, Mr. Mack, and others. Thought it would solve all/any problems with my vacuum wipers at all/any speeds, up/down hills, etc. My wipers still don't work worth a darn except on deaccelleration. Then they wipe away like crazy. Gut feeling diagnosis - vacuum problem? Must admit, I've never checked. Any thoughts?

See if you can pick up a "Y" somewhere so you can put it in the vacuum line to the wiper and use the other opening for a vacuum gage. Now drive the car and observe the readings. With a functioning dual fuel pump the reading should be very high unless you have a vacuum leak somewhere.

Thanks Ray. Sounds like the next logical move. Couldn't sleep either?! :sleep:

I just like the late shift. I make up for it by sleeping in in the morning. Spent too many years of up at the break of dawn. Let someone else have that shift. HA!

I'm going to the accessories/radio forum to make a posting to you. Would be more appropriate there than here, especially since I don't even have a 1949-56 although my birth year is in that group.

There are as I recall two locations that allow air to move through the wiper motor, one is the Vacumn line from the manifold, the other is a small vent on the motor itself.If that vent is clogged from dirt and dust it would effect the operation of the motor because of restricted air flow. The extra vacumn provided by the closed throttle position could over come the problem. One other thing is just old age. I used a IV injection needle I got from my chemo nurse, loaded this with about an ounce of ATF, injected this in the vacumn line, and with a thumb over the line to prevent back flow, worked the wiper arms back and forth manually, I have done this twice, and there is a noticeable improvement in the slow speed low vacumn operation of the motor.

The amount of vacuum depends on the throttle plate position and engine rpm. The throttle plate is actually a valve on the inlet section of a vacuum pump. Without the reduced pressure no gas/air is drawn into the engine. So the higher the rpm the more air flow (vacuum) is produced. Any leaks are most troublesome at lower rpm and will effect the gas/air mixture to the cylinders. That includes the vacuum wipers also.

The wiper problem could be in the wiper also. Proper lubrication is important. Also adding a vacuum container or tank to the wiper circuit can improve performance.

Of course the intake stroke of the engine is the producer of the manifold vacuum, good valve action and piston ring sealing are major factors in producing the vacuum. The exhaust system of the engine is also a factor, you have to have good flow from the air cleaner out thru the tailpipe to maintain both RPM and manifold vacuum, the dual action fuel & vacuum pump supplements the vacuum to the wiper motor when the engine vacuum is low due to the throttle being open and good air flow going into the cylinders.