Volkswagen /Revmaster vacuum

[cholmondeley]

I am struggling. I have an early (un-used) Revmaster 2100D fitted with an early Marvel Schebler Carb and Leburg ignition. It starts and runs reasonably well. Static RPM is 3000 and rather lumpy idle (don't they all?) at 750. At full power vacuum is about zero which is correct and at 2000 it's about 7-8 which again seems OK. But at idle it draws only about 6 which seems ridiculous. I understand it should be 15-17. The compressions are good, timing is good, leakage is good, valve gaps are good, mixture is a tad rich and a second vacuum gauge confirms all the readings and all the readings are steady. The wife suggests "replace the gauge with a clock and go flying"!! Does anyone have any other ideas?

Regards

[Rob Swain]

...and rather lumpy idle (don't they all?)...

No.

If the Leburg is installed and set up correctly it should idle smoothly, as the ignition should have retarded itself to make it so. You say it runs 'reasonably well' which is rather suspect: it ought to purr contentedly.

Admittedly my experience was with an 1834, not a 2100, but I see no reason it shouldn't be the same.

As regards the vacuum I assume the figures are "inches of mercury".

If you know the mixture is too rich, then I'd suggest you fix that initially.

Given your wife's advice I'm guessing she has you well insured!

[Chris Martyr]

I say Cholmondleigh old boy,
Rather an unusual combination what ? Isn't having a Marvel-Schebler feeding a VW a bit like an 848cc Mini being fed by a 4-Barrel Holley ? No wonder she's a bit lumpy on tick-over.
Sorry to sound a bore , but how do Francis and his chums feel about this combination ? You may not generate many replies as I doubt if many UK VW protagonists are too conversant with this one. Same thing with the vacuum gauge , why do you need it , you haven't got a variable pitch prop. as well have you? Sounds like the best accessory you have is the missus, take her advice . She's spot on !
Rob's right by the way , most well sorted VWs tick over beautifully, especially with the LeBurg ignition system.
What are you building by the way ? I'm interested. Best regards , Chris M.

[cholmondeley]

Thankyou Rob and Chris for your comments. Yes the readings are in inches of mercury. I haven't bothered to adjust the mixture yet as the plugs were only a bit sooty and I reckoned that could be due to the stopping and starting and slow running. Mixture adjustment would involve filling and drilling of the main jets. Chris, the Marvel Schebler is a VHD as fitted to a McCoulough 45hp outboard. It was supplied as standard by Revmaster so I guess it is suitable. I failed to mention that I have eliminated all induction air leaks which would be the obvious cause of low vacuum at idle.

Regards

Ben