Re: 1934 vacuum wipers lube

Posted by Owen_Dyneto On 2012/4/17 14:04:52

Terry, an engine with rings and valves in good condition should give a manifold vacuum reading at idle of 18-20 inches, and the reading should be quite steady.

The main vacuum take-off at the manifold is hard-piped to the rear of the block, passenger side, where there is a fitting and it splits into two lines. The smaller, lower (nickel-plated) line goes tothe vacuum booster pump, the larger line changes over to rubber hose which crosses the back of the block and emerges near the starter motor where it changes back to hard pipe up to the power brake variable boost valve and then on to the brake control valve (under the brake pedal and power cylinder, There is a take off from a hard line at the inlet to the power brake variable valve that feeds the Bijur. Thus the vacuum booster pump on the fuel pump is only for the wipers as the brakes and Bijur don't need boost because the brakes are never applied while the engine is under hard accleration.

Problem is, there really is no convenient take-off to install a vacuum gauge. Though you could jury rig something, I think the easiest initial test is to, one by one, disconnect the Bijur, the Stromberg automatic choke, and the line to the brake system, hold your finger over the end, and see if the engine idle suddenly increases. If so, that would be the source of the vacuum leak.

Perhaps someone else with a 33/34 will see an easy place to hook up a vacuum gauge, the only possibility I see is a removeable plug at the inlet side of the brake variable valve, but it's a very small diameter so you'd still have to jury-rig some sort of take-off for the gauge.

When I mentioned earlier the most likely source of vacuum leaks (brake system and fuel pump booster), I should have also added the large diameter rubber hose that runs behind the engine block; if it's 80 years old, time to replace it.

Let us hear your findings.