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TR4/4A tr4a vacuum test

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grant tr4a

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I would like to do a vacuum test, but I do not see anywhere to connect to the intake manifold. Has anyone figured out how to do this test on a 1966 tr4a. Thanks Grant
 
If you have SU carbs, there should be an inlet pipe on the front carb. The other end, of course, goes to the distributor advance connection. On one of my cars, the prior owner left the line plugged at the carb and open at the distributor, and I have no idea why the car works so fine like that. It runs terrific. Someone else here on this Forum may have an answer as to why the carb activation for the vacuum apparently isn't critical.
 
The vacuum advance is almost entirely for fuel efficiency. It doesn't do anything at idle or at full throttle.

But because the port is closed off at idle, it also doesn't work very well for connecting a vacuum gauge.

One approach is to drill & tap the manifold for a 1/8" NPT to hose barb adapter. You'll need a cap to keep on it when you aren't using the gauge.
 
Will it be ok to drill and tap the manifold while it is installed on the car. What location? What about the metal filings from drilling and taping getting into the engine.
 
I wouldn't, unless you really have to. You can pack the flutes of the drill & tap with grease (remove, clean, and regrease frequently), but there is a significant risk of dropping filings inside, which will eventually get sucked into the engine. The aluminum is fairly soft, so there's a good chance they will pass through harmlessly, but I wouldn't rely on that.

I drilled mine in two different locations; couldn't tell that it made much difference. If you look closely at this photo, maybe you can see the black rubber cap for one of them, peeking out between the throttle linkage and front manifold pipe; plus the hex head peeking out from behind brass nut on the front carb dome, where I plugged off the other fitting. (Somewhat disgusted at that point, my experiment with water injection had gone sour when one of the makeshift water nozzles got sucked into the engine.)

P3170006.jpg
 
Grant, believe you could disconnect the PCV valve from the manifold and use this fitting. Remove the other end from the valve cover to avoid pressure build up
 
I thinking of removing the hose adaptor in the intake manifold. Get a spare locally (are the originals npt) and try to make a 1/8 npt tap into the side of the new adaptor. That way the pvc can be hooked up during the test and i can install the original when i am done. What do you think?
 
If you want do try the vacuum test with PCV installed, it might be easier to try a t-adapter using a third piece of hose where the PVC connects to the manifold.

There have been a number of threads on this PCV valve, its efficacy, and TR crankcase ventilation. You should try a search and review. I removed the PCV valve on my 4A and have a filter (temporarily)on the valve cover PCV outlet. This eliminates the problems with that PCV valve design and provides "just OK" crankcase ventilation.

If you want to install another fitting...why not..should be a strait-forward project and you could even have a vacuum gauge permanently installed under the hood.
 
I could use an education on why you're interested in testing the vacuum and why crankcase ventilation is an important issue. Wouldn't either the down-pipe or the PCV valve be adequate for an old LBC?
 
KVH said:
I could use an education on why you're interested in testing the vacuum and why crankcase ventilation is an important issue. Wouldn't either the down-pipe or the PCV valve be adequate for an old LBC?
Click to expand...
I believe the ventilation comment was about running the engine with the PCV valve disconnected from the intake manifold. If you leave it connected to the rocker cover, then pressure will build up inside the engine until the valve opens, which is probably not a Good Thing. If nothing else it tends to blow oil out of the joints and seals, especially the original non-contact rear main seal.
 
I took a vacuum measurement by connecting my gauge to the PCV connection on the intake manifold. The TR4A should have this port on the intake manifold. Worked perfect.

Bob
 
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