ROG100

I keep being asked for replacement screws for the butterfly valve to flappy shaft.

Has anyone been there and done that and can share the size please?

worf928

Damn. I was going to ask you.

Last time I needed to replace them I found a reasonable substitute at the local True Value. But, the head wasn't quite right.

IIRC, it's a machine-head screw but an odd size.

If no one has the answer, I'll measure the remainder pictured here:

soontobered84

Roger, I swear I have seen that posted somewhere, but since I've become afflicted with CRS, I can't remember where I saw it. Somebody will know this and post it.

ROG100

Bump

Rob Edwards

I have an intake on the shelf and could measure one- is there something non-standard about the thread pitch?

soontobered84

Rob, I think it was something about the abnormally short length and the head(oval head machine screws)

Bigfoot928

It also have a divot in the end that you are supposed to tap with a chisel so it won't back out.

karl ruiter

I lost one when I did my flappy a couple of weekends ago so had to go hunting. Its M4. I think I started with 10mm (might have been 15) and ground 75% off one side down to the point it stuck out of the pivot shaft. Then, when I inserted it I could bend the remaining 25% over to lock it. I did not want to try re-punching the divot as I was worried I might bend the pivot shaft. The head on the one I bought at home depot was wrong (too big) , so I ground that down as well. Of course the 'lost' part showed up as soon as I had the manifold assembly bolted back in the car.

karl ruiter

The home depot part was a flat head, probably similar to mcmaster 97613A523, which has an 8mm dia head, their oval head part, 90258A214 , has a 7.5mm dia head. That is closer, but I don't think its enough. I think you need something more like a 7mm head. The actual part is a slotted, oval head. I can send you one when I send the MAF core if you like.

GregBBRD

Roger:

I got a whole box of these screws from when I was machining and changing the butterflies in 3.2 liter Carreras. I think I got them from the guy that made the oversize butterflies for me (who rebuilds and replaces worn butterflies in 911 mechanical injection throttles.)

That's been a couple of days ago....

Let me see if I can find that box.

dr bob

Roger- foggy memory says they are oval head machine screws. Thy MUST be staked after tightening. I'm not ready to trust threadlocker alone. In carburetors I always used brass screws, FWIW, so if one did manage to come out it might get beat up and do a minimum amount of collateral damage on the way through.

karl ruiter

Per Dawyne's thread it seems like the '87 did not have staked screws. At least he did not mention grinding them out, and he was not exactly brief.

928Myles

My 1990 S4 butterfly screws were loctited in, no flange on the end. The same applied to the butterfly in the spate TB I have.

I managed to damage the head on one getting it out.
Myles

worf928

M4 x 8mm 0.7 pitch; 6mm head (machine head); slotted. (Edit: 6mm head seems a bit small; hard to measure the shard.)

About, maybe a bit less, than 50% of the time I can unscrew these. The rest of the time, drill and dremel.

Going back in, I heat the spindle with a heat gun and turn the screws in cold with red loctite. (That needs 500°F to loosen.)

Now for the next question: are they the same screws as for the throttle plate? (I forgot to measure when I was just out in the garage with the shards pictured above.)

worf928

I would have to assume that the original part is brass. Else it wouldn't be so easy strip the head with a hand tool and you wouldn't be able to punch the divot in the bottom.

Even so, supporting the spindle would be necessary.