Carb

[rust_prone]

Hello everyone,
I have a question. I am bringing a '63 beetle back to life. I have discovered that it as a dual port 1600cc engine and a Solex 28 PICT-1 carb. Someone it its past used an adapter to fit the older carb on its upgraded manifold system. So my question is this, How much will increasing the size of the carb to a 32 PICT, improve the performance by maximizing the air/fuel flow? Any assistance is recieved graciously.
BTW this motor is not put back together yet as I am honing the cylinders and cleaning up the crank. Thank you.
Dman

[Aussiebug]

The 1600 engine will run on a 28PICT carb, but it's seriously under-carbed with that. You'll be losing maybe 5-8 hp with that carb and it would run out of breath at higher speeds.

The 30PICT/1, /2, /3 or H30/31 is better (all have the same sized throat), and will fit straight on the adpator the 28 is sitting on now. Only about 2-3hp less than using the 34 (below) - hardly noticable around town.

A 34PICT/3 is the "correct" size for the 1600dual port engine, you remove the adaptor and it will then fit straight on to the manifold.

Jetting comes into it too - the smaller carbs have to be rejetted for best performance on a 1600 - they will tend to run lean with the "small engine" jets.

For example - any of the 30/31 sized carbs on a 1600 should have a 55 idle, 125 (just maybe 127.5) main and 125 air correction jets. That's with a vacuum distributor - for a 009, increase the main just one size (to 127.5 or just maybe 130).

The normal jetting for a 34PICT/3 with vacuum distributor and 1600dp engine is 55 idle, 127.5 main and 60 air correction jets. New carbs are usually delivered with very lean jetting - small main jet (an emissions thing) - makes them very hard to tune right.

Cooling may be an issue with the 1600dp and solid engine lid - the dp engine has a larger fan and runs short of air with the solid engine lids. If you can - find a cabrio engine lid with the two sets of slots - that will fix the problem. Other fixes are to use standoff hinges (ugly!), standoff licence plate with hidden holes in the lid underneath, crack the BOTTOM of the engine lids open with a 1/2 tennis ball or similar over the catch (easily removed to lock the lid), weld in sections of slots - the front air vents from a Kombi work well and are still VW , or even have slots cut in the sides of the engine compartment - into the rear wheel area, though this last one can result in a dirty engine from all the road grime and dust pulled in by the fan.

Regards,

Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970/

[rust_prone]

Thank you for the detailed comparison. Your response was most comprehensive. As it happens, I purchased a 34 PICT 3 from a salvage for $20US yesterday. I disassembled it lastnight and will be kitting it myself.

Further advice is welcome as I much work to do.

[keifernet]

When you get to dissasembling the 34, be sure to remove the TINY jet next to the idle pilot jet (right side of the carb behind the choke area, but in the main body of carb) it requires a TINY screwdriver to remove the outer brass block off plug, then the little bugger is in there. Failure to remove this jet and clean the passage and the tiny hole in the jet will result in... problems, it's not really a rebuild unless you get this jet out and alot of people over look it. good luck.... K

[rust_prone]

Could you speak to the distributor compatibility for a moment. I have heard that I cannot use a 009 with this unit. I do not know what I have currently has I learned this may be an issue just today. What are the limitations of the stock unit & what is a good aftermarket recommendation.
Thank you so much for the input.

[Aussiebug]

The distributor decription number is on the side of the body which faces the fan shroud - difficult to see. They mostly have two numbers - a VW number and a Bosch number. The VW numbers mostly end in 205A, 205Z etc (205 means distributor, and the letter tells you the model of the distributor).

VW used a LOT of different distributor models, some of which are interchangable (performance wise) and others are not.

Generally speaking the 34PICT/3 works best with a vacuum distributor - the SVDA (single vacuum double advance) as fitted to 74+ beetles is considered the best, but other vacuum distributors will work fine too. From 71 to 73 the double vacuum distributor was used on 1600dp engines (two vacuum lines to the carby), but it's not necessary to use these.

All vacuum distributors have a vacuum canister on the side of the distributor body, so they are easy to pick from the 009 distributor, which has a plain cylindrical body - no vacuum canister attached.

The 009 does not get on especially well with the 34PICT/3, but they can be made to co-habit reasonably well. You adjust the distributor to feed more fuel through almost the entire rpm range and this helps replace the missing "shot of advance" which the vacuum distributors provide on acceleration but which the 009 can't provide (they don't provide ANY advance until about 1200rpm).

Increase the 34s main jet to a 130 or 132.5, set the accelerator pump to max stroke, and set the 009 to between 28 and 32 degree at 3000+rpm - use as much of the 28-32 as you can without the engine detonating/pinging. If it still pings at 28, do NOT use less than 28, use a higher octane fuel instead. That will usually get it working with the 009, but occasionally you need to block the air bleed hole in the throttle plate as well. All this means worse fuel consumption and sometimes still does not elmininate the 009 stumbles completely.

Vacuum is best.

Regards
Rob
Rob and Dave's aircooled VW pgaes
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970

[keifernet]

The thing about the 009 is you have to drive it like a drag car... most folks who just wnat to cruise or baby their ride need a vacume style. If you rev it right and wind it up (drive THROUGH the flat spot) it's an okay dist. But as Rob pointed out milage is sacrificed along with some drivability (dependend on what your seeking)
I am at sea level so I'm sure that has some effect on how I have tuned cars in the past. I usually have no problem getting the 009 to work with the 34, I also have the fortune of being able to try multiple carbs out to see which one works best as it IS NEARLY impossible to tune that flat spot out of some carbs or get the correct smooth idle.... I have had some people complain til I took them on a drive and showed them how drive their bug with a 009, they either got it or they wanted to know if I had a good used vacume dist laying around!!!

[rust_prone]

Thank you for all the great advice folks. I am printing off this thread right now. I'll keep you posted as to the success of the tweaks and trials.