Stromberg 150CD butterfly/throttle flap screws

[daver clasper]

Hi

Have bought new throttle spindles, though awaiting some new screws to secure the air flaps, as new spindles appear to have larger diameter thread holes for these.

Burlen (who I bought them off), advise thread lock and also peening the end of screw to the spindle to secure it.

If the new screws are like my originals (narrow slotted grub screw), then I was wondering if they would be hard to undo again in the future and also if the peen on the screw could muller the spindle thread when undoing.

Any tips on this would be great please.

Cheers, Dave

[RobPearce]

You obviously have to undo the peening before unscrewing them. A pair of pliers will straighten the ends out good enough to remove the screw without damage, if you're careful. These screws are single-use because once straightened you can't really re-peen them reliably.

[daver clasper]

Thanks Rob

The original screws were grub screws ,and fitted, the ends were a bit below the spindle face. don't know if they were peened in any way, but came out easily.

I assume your info is for the screw threads proud of spindle. What's the best way to peen, if my new ones are like this and also supporting the spindle/screw heads please?.

Cheers, Dave

[Pete Lewis]

dave    not too much force is needed  if the screws have a split end a small punch and tap with small hammer is all you need  just enough to stop a loose screw coming out and going into the engine.  just a small deformation is all you need , youre not riveting the titanic.

some thread locks dont like petrol   need to read the label.

the plates are shaped and chamfered to make a full closure , make sure there is no daylight thro the throat and all are nicely centred and pivot and close nicely before you finally tighten the screws

Pete

[daver clasper]

Thanks

The new screws have finally arrived. When fitted the ends are only slightly proud of spindle. They have a small round indentation in the ends, for a punch I guess (so once peened, not able to unspread the top of screw to undo without damage to spindle threads I guess?).

The heads of screws are a bit  proud of spindle when fitted, so I guess I need to support These to peen. I thought of some 1/4 plate, sized to accommodate both heads, held in a vice and some one to support the carb, or is there a more obvious way please.

Any help much needed please, as can't afford to knacker anything.

Cheers, Dave  

[Pete Lewis]

Ues anything in a vice you can steady the screw head onto and give the dimpled end of the thread a light tap to lightly bruise it  youre not riveting the screw , just enough deformation to stop a loose screw escaping into the engine,  amd if it did it would probably be pass through without any internal damage

a 5/16nut is a different piston wrecking option,  a small brass screw is lesser problem

you only need a light tap    youre not trying to repair the Titanic.

pete

[daver clasper]

Cheers Pete

They were steel screws with a wider head and larger diameter thread than the skinny grubs from the original spindle set up, so a bit more chunky.

Just used the top of a socket in the front of carb and corner of kitchen table to support screw heads (a bit bouncy) and tapped some crosses with into the top face with a filed to suit  old flat blade. which I thought would have spread the tops a bit.

Hope this will do?.

Thanks Dave

  

[Pete Lewis]

That sounds a good plan

I can nearly hear it running

pete

[daver clasper]

Cheers Pete

Running again and well (new jets and needles as well). I may have messed up ,as screwed the butterfly flap screws and peened them with the throttle stop plates and screws in place, so maybe the the butterfly's were not completely seated and a bit out of line. It is idling a bit high and I can't get it slower maybe due to this, and it ran on a bit when shut off.
Haven't finer tuned the mixture or played with the timing a bit yet.

As long as this doesn't wear the flaps or more importantly the carb body throats ? then will sort it in the future.

Cheers, Dave

          

[Pete Lewis]

I doubt you have the screws bludgened into riveting obscurity ,  if the discs are not central and dont seat nicely when closed undo the screws half a turn to release them and retighten with the idle screws backed off , throttles fully closed off re nip the two screws

all is not lost
pete

[daver clasper]

Cheers Pete

I properly got a bit over cautious about things. I  originally thought as these fixings as low stressed related, then a good nip up of screws would be ok.

Then you read out peening and thread lock on these (maybe too much info ?).

Thanks again, Dave