Weber butterfly screws Peen ?? or

[Lyndon302]

I have rebuilt my Webers. Very happy with how they turned out. What is the contempary thinking on butterfly screws.
Locktite or peen them. I would rather not peen them if its not necessary.
I also don't want to drop one either.
Lyndon

[chrismorse]

A few years ago, I went through the 4 DCN 40s on my old 308. I believe the recommendation in the F car threads was to "Peen", so I used a slightly dull chisel to stake the screw. (upgraded to sealed ball bearings).
NOTE, it is important to solidly back up the head of the screw with a steel rod in a vise to take the force of the stake. You don't want to hit the unsupported screw and bend the shaft. Set the head of the screw up on the end of the rod to lift the throttle body clear of the vise, so no load transfers to the shaft/body.
Might be worth it to talk to Pierce Manifolds for the latest thinking on the point, (and any other questions you might have.

As a side note, I stumbled across a thread recommending two 4 cylinder mortorcycle manometers, hooked to the nipples below the throttle plates to facilitate syncing the throttles. Worked slick.

good luck,
chris

[Trackrash]

I have used a large dull center punch with success. As mentioned you need to solidly back up the head of the screw. You only need to lightly tap the punch. No need to totally peen the screw. Just enough to keep it from easily backing off.

[Lyndon302]

Peening it is.

[Quickstep192]

Really nice looking job on the carbs. Did you re-bush the shafts? If you did, I'd be curious to know more about how you did it, since I think mine are coming up due on that.

[Lyndon302]

Yep. I used brass shim. Traced and cut from the original Teflon ones. I was surprised how well it worked and went together. They are prefect.
New expensive screw driver.
File the butterfly screws to the shaft then crack. You only get one go. Done properly you will have a 100 percent success rate as long as no one has been there before.
I vapour blasted the carbs. Well worth it.
Lyndon

[KTL]

I personally would loctite them with low strength blue threadlocker. Just my preference and not implying others are wrong in recommending peening.

Great job on the carb restoration! How are the fitments of the secondary venturis in each slot of each carb throat? Reason I ask is because when these are a loose fit, it REALLY compromises the operation of the carbs at lower rpms.

A friend of mine pointed out to me how loose mine were and we took them off the car at the race track. He helped me shim them with some feeler gauge material. Wow what a difference. It was a massive improvement in low rpm power.

The weber carbs, and carbs in general were still rather new to me back then, as I was learning on the fly as I went through various issues with tuning up the race car. Made sense to me later on after looking at the carb cutaway diagrams why there was such an improvement. A loose fit of the secondary venturi compromises its ability via suction to draw fuel into the throat. This condition is even more pronounced at low rpms when air velocity is slower.