Sanity check: my Weber IDF's don't obey the installation manual

[AlteWagen]

I have always set them with the plate just covering the progression port so that it is exposed with the slightest movement of the throttle.

If setting up for an unknown condition engine I will expose a bit of the port to make sure they will run on first start up then close them up for desired idle RPM.
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Grapes of Wrath $200 Engine Rebuild
Official Dual Carb Thread
Cylinder Head Quick Reference Sheet

[virusdoc]

[tommiebsmith]

I had a set of 40IDFs brand new have 2 of the mixture seats fall out.. they were causing issues to begin with then we found that issue of them being lose and they fell out.. the CB "replacement" ones .. were way to big to actually fix the issue.. I mixed up some JB weld.. and lightly touched the original seat to it on the side and pushed it back in.. very very little.. but it was enough to hold the seat back in place.. I let it set up for a day or so.. before messing with it..
been like 4 or 5 years and still working fine.

just my .02 on the scenario.. best of luck

[virusdoc]

[modok]

Pre-set half a hole or bottom edge of the hole?....good question.
Whichever way works better, I don't think I have a preference.

In either case the idea is to set the throttle position on both... to be equal relationship to the progression ports, as a baseline setting.
Then from there you can "COUNT TURNS" as needed, and make equal adjustments to both once on the engine.
Remembering whichever way you DID pre-set them... is handy in that, then you can know generally what the relationship is to the progression ports IS at idle, without having to take them off again and physically look.

If one side is significantly different than the other on the engine then that can be fixed with the bypass screws. Assuming the difference is the carbs and not the engine.
At one time, the bypass screws were pre-set at the Weber factory...... but that was long ago. Maybe the same fantasy past in which the "instructions" were written.


How far the throttles can fully close is not a concern on the engine IMO as long as they close far enough to get the idle speed you want.
Backing off the idle speed screws so the throttles touch the bore does not have any useful purpose, other than to check the fit of the throttle plates in the bores. (I would be doing that before putting them on the engine)
When it's running the throttle is not supposed to touch the bore.
Some carburetors are designed so the throttle closes literally all the way.....but turns out that can cause a lot of problems in the long run, because it wears out. I bet you could have guessed that. And yet the engineers didnt

Good job gluing the idle thingy back in place. I've discussed loctite VS epoxy many, many times... and I don't know why it "doesn't stick".
Loctite is the right tool for this job. Even if you used the right kind of epoxy I don't think it would work any better.
It does not hurt to make the surfaces as clean as possible but actually equally or more important is to freshly scuff non-reactive surfaces.
Excess can be blown away with compressed air.... and flushed with a quick shot of carb juice (smog in a can).

[virusdoc]

I'd appreciate feedback on how my engine sounds here. All four cylinders are tuned to LBI to the best of my ability, and they all now are participating in idle. Carbs are all sync'd at idle at 5kg on the snail gauge.

When I rev the engine up, around 3000-4000 rpm (not sure exact rpm) there is a loud raspy sputtering/roaring note that starts. At first I thought it was an exhaust leak, or a rattling tin. Confirmed it is not either of these. It's quite loud in person, although the iPhone noise suppression dampens it a bit in the video. I try to hold the engine at that rpm several times so you can hear the new harmonic.

https://share.icloud.com/photos/00CsLMJG4VTZPDEFp3QxaCb3Q

Thanks!
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1976 Convertible Super Beetle, "June Bug".
FI-->34PICT3 carb conversion-->now dual 40 IDFs
Self-rebuilt 1904 (after totally botching a 1641 rebuild, cussing a lot, and throwing lots of cash in the fire)

[74 Thing]

How come your velocity stacks are not bolted on (don't they hold the air cleaner base to the carb and the linkage in tact as well as provide a seal for your unisynch?).

That rumble sounds like the fan/pulley or exhaust. To eliminate the fan/pulley just take off the belt and fire it up quickly up to those rpms and see if the sound is still there. If it is gone check the crankshaft pulley bolt for it coming loose, the alt pulley to crank pulley alignment, and then pull the fan and check the hub as well as a crack on the fan or any rubbing and mark the fan before removal and maybe flip it on your mounting hub to see if the noise goes away.

I think it is fan related.

[virusdoc]

[virusdoc]