Carburettor too bg ?

[chookhen]

Hi from Brisbane,
I bought a 1972 DP 1600 super beetle just short of 12 months ago.
I noted an intake manifold port a couple of inches below the base of the carburettor which was uncapped and noticed if I capped it the idle became lumpyand the revs dropped.
I asked you all what I should do and as I expected and was the advice given to adjust the mixture and cap the port.
To get a reasonable idle the mixture screw had to be almost seated and despite this the spark plugs were heavily sooted.
I absent mindedly uncapped the manifold port and the idle speed increased and smoothed out against all odds.
I omitted to say, and I appologise for this, but the po installed a Stromberg 97 carby,these were widely used on Holdens here which were 6 cyllinder cars with capacity up to 3.3 litres.
Could it be that with intake manifold leak the venturi effect is lessened and the overly large carby becomes more suited to the smaller vw engine.
That is my theory which may not be right and I welcome any imput with those with more experience and knowledge than myself.
Looking forward to replies.
Many thanks, chookhen.

[Cusser]

That port would be sucking in unfiltered air.
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[Starbucket]

Your symptoms indicate your idle jets are way too large, try replacing them with a smaller number jet.

[chookhen]

Thanks Starbucket, good idea.

Hi Cusser, if I leave port open I plan to let it breathe through the air filter via a hose.
I haven't driven it outside the garage as yet as I was aware it was drawing unfiltered air.
Thanks to you both for the replies and suggestions.
chookhen.

[KTPhil]

Vacuum leaks can burn valves even if it appears to be running well. PLUG IT!!
Then fix what else is wrong.
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[chookhen]

Blanket statement, true only if resultant mixture is lean.
chookhen.

[chookhen]

Surely only if final mixture is lean,I plan to check plugs after a steady run in a few days and will report back.
chookhen.

[heimlich]

Sounds like you have a manifold for an autostick. If you do not have an autostick that port needs to be capped.
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[KTPhil]

It's your engine. Choose to destroy it any way you wish.
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[chookhen]

Went for a 45 minute drive up a nearby mountain road and return.
Oil temp via dipstick was just on 80 degrees and a spark plug I removed and cleaned before the run was moderately sooty so the mixture is on the rich side.
This is my fifth ACVW and I am quite aware that if we are talking Solex 34 Pict-3 the port would need to be capped of course.
I have elected to drive the car as is as my other options would be to buy a Solex clone which may or may not be ok or fiddle with jets on the current carby which I've read could be hit and miss and at $45 a go I would prefer the first option.
The reflex reply "cap it" in this context is a non reply and not helpful at all.

[passionre]

Your jetting is too rich for normal operation. When you uncap the vent, it is leaning out the mixture to run better....this is NOT a fix....in fact, it dangerous.
I would suggest you put the proper carb on the car...they're dirt cheap on Amazon for a brand new re-make of the original carb and they work fantastic.

[vamram]

Having owned 5 ACVWs doesn't make you a master mechanic. I currently own 3, 9 in all since '85 and I'm still nothing but a shade tree mechanic, learning as I go thanks in great part to the smart and helpful folks here who know *a lot* more than I do.

The port a couple of inches below the carb needs to be capped if not connected to a working preheat valve on a factory oil bath or paper element air filter, like these two:

The engine is designed for this port to provide engine vacuum to the filter's pre-heat valve. To run w/it open is plain old stupid, and you're just trying to cover up the super-lean condition created by leaving it disconnected and unplugged. Even if you get it idling smoothly w/the super rich adjustment, ultimately you're just giving your cylinders a thorough fuel bath every time you drive it your way. Get used to pulling those sooty plugs and replacing them frequently, until you bugger up the threads on the head, then have fun w/that.

Your carb is wrong for this motor too. Get a proper rebuilt 34-3 or buy one off of amazon or some other vendor, as suggested, tune it per Bentley instructions.
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[chookhen]

Thank you passionre and vanram for your constructive replies.
I will heed your advice(s) an buy the correct carburettor, I was on the cusp of doing this earlier but thought that the car was telling me it was quite happy as it starts first key,idles smoothly and runs very well.
Point taken about the big dose of fuel at start up washing the cylinders of oil, that is enough in itself for me to do the right thing by the car of which I am very fond,thank you for that.
Guess you can't make a silk purse out of a sow's ear after all!
Cheers Bob.



,

[Starbucket]

You can buy a set of #drills and find the one that fits your jets then solder the jet closed and redrill to a smaller # until you get it right size hole for the proper mixture then either run it or buy that size jet it won't cost much if you keep your gasket in a dish of gas to keep it soft.

[chookhen]

Thanks Starbucket, I"ll give that a go as I have some very small drills, I have decided to buy a 34 solex 3 clone as well, I don't like being defeated and would love to get this set up operational as well.
Would just rejetting the idle jets be sufficient, I really don't have any idea of the stromberg carburettor, I do remember with an earliervw I drilled out the main jet ? maybe from125 to 135??(Solex pict 34/3) and it cured the flat spot (only had a centrifigal advance distributor) and gave the exhaust a throaty sound which was a nice side effect.
I will let you know how I go.
Cheers, Bob.