Vacuum roblems
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6th Gear
Joined: Sep 2013
Posts: 6
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Vacuum roblems
I need some help regarding a low vacuum problem I am having with the 1969 T-Top I am restoring. Originally a 350 C.I./350 HP 4 speed A/C car. The owner had the engine rebuilt to "LT-1" specs he says for more horsepower. When I bought the car the headlights were working intermittently and the wiper door not at all. Found one bad regulator, one bad relay, bad wiper switch and many cracked but not leaking hoses so I replaced EVERYTHING in both systems except the vacuum tank which showed it held vacuum perfectly when tested. Still couldn't get the both the headlights and wiper door to work at the same time. Finally checked the vacuum at the intake manifold and got a fluctuating reading of 8 - 10 lbs. My local shop says the cam is too hot not creating enough vacuum and I need to buy a bulky (4.5 x 6 x8") and expensive electric vacuum pump and install it in the engine compartment.
Please tell me there is another alternative. Thanks in advance for any help offered.
Please tell me there is another alternative. Thanks in advance for any help offered.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Eight to 10 in/hg is more than sufficient to operate those systems. The vacuum motors are fairly large for the job they do so there is a bit of over-engineering. Besides, what you're reading from the manifold is different from what the tank is holding. The tank will pump down to the highest vacuum that is present throughout the engine's operating range. In that regard, if you **** the throttle and allow the engine to return to idle, you will momentarily see well over 20in/hg, which is what the tank will pump down to and hold.
You still have issues with your system. Start isolating the pieces -to include the check valve- to find out where it's not working.
You still have issues with your system. Start isolating the pieces -to include the check valve- to find out where it's not working.
Thread Starter
6th Gear
Joined: Sep 2013
Posts: 6
Likes: 0
More checking and still not sign of the problem
Eight to 10 in/hg is more than sufficient to operate those systems. The vacuum motors are fairly large for the job they do so there is a bit of over-engineering. Besides, what you're reading from the manifold is different from what the tank is holding. The tank will pump down to the highest vacuum that is present throughout the engine's operating range. In that regard, if you **** the throttle and allow the engine to return to idle, you will momentarily see well over 20in/hg, which is what the tank will pump down to and hold.
You still have issues with your system. Start isolating the pieces -to include the check valve- to find out where it's not working.
You still have issues with your system. Start isolating the pieces -to include the check valve- to find out where it's not working.
Have checked everything 4 times or more.
Had the professional mechanic from the shop next door check everything again. All components good, no leaks. Headlights work if vac to wiper door is blocked off and vice versa. Only problem he could find is low vacuum from the intake manifold. Fluctuating 8 - 10 lbs.
Team Owner
Joined: Sep 2006
Posts: 31,221
Likes: 4,309
From: Westminster Maryland
Hi RR,
You won't want to read this but…….
The new vacuum system parts available are not too reliable…. sad but true! My inclination is that most of the original parts are likely better than those you bought.
If you have a small vacuum pump w/gauge like a mity-vac and a trouble shooting guide you can test the function of each individual component.
This will help you pin down whether it's an issue of low vacuum or not.
Would that be possible!
Regards,
Alan
You won't want to read this but…….
The new vacuum system parts available are not too reliable…. sad but true! My inclination is that most of the original parts are likely better than those you bought.
If you have a small vacuum pump w/gauge like a mity-vac and a trouble shooting guide you can test the function of each individual component.
This will help you pin down whether it's an issue of low vacuum or not.
Would that be possible!
Regards,
Alan
