Dellorto carb housing stripped?

[ketchup]

Behold my calamities! 
 

I'm trying to determine the thread pitch and diameter of the accelerator pump jet cover of a pre-emissions Dellorto dhla 40 side draft. 
 

I recently rebuilt a matching set. They are pretty fab except these housing threads are stripped and the brass cover won't grab.

 

Obviously I don't want to trash the whole thing, so wondering about helicoil/timesert – not sure if there's enough meat to work with – which is why timesert would be better. But I can't figure out the threads?

 

If I can't fix it, I'll be going to a lynx manifold to make use of the other side draft. (LMK if you have one if dem:)

[SydneyTii]

If you ran a correct size tap down it it may help, if not is the a good quality outfit near you that could refurb the thread, im with you those walls are quite thin from new.

[TobyB]

Gerf.  That's a jet holder, huh? How does it seal?  as in, what does the jet it holds look like?

 

Fixing aluminum isn't easy.  A helicoil might do it... but you'd have to be precise.

To get the thread pitch, just use a thread pitch gauge!  

(or some bolts you know the thread pitch of)

It could be whacka- doodle- doo, as things made of brass can be made easily in 

all sorts of thread pitch and size combinations.

 

heresy- glue it on with something like Loctite sleeve retainer.

When you need to get it undone, just heat it to 500f and it'll pop right off.

 

t

hates that sort of thing, too.

[ketchup]

22 minutes ago, TobyB said:

Gerf.  That's a jet holder, huh? How does it seal?  as in, what does the jet it holds look like?

 

Fixing aluminum isn't easy.  A helicoil might do it... but you'd have to be precise.

To get the thread pitch, just use a thread pitch gauge!  

(or some bolts you know the thread pitch of)

It could be whacka- doodle- doo, as things made of brass can be made easily in 

all sorts of thread pitch and size combinations.

 

heresy- glue it on with something like Loctite sleeve retainer.

When you need to get it undone, just heat it to 500f and it'll pop right off.

 

t

hates that sort of thing, too.

Thanks! I'm leaning on first bringing it to a machinist and hoping they are in a good mood and not offended by my "foreign" non-GM car parts. If they laugh me out, I may research this intriguing "Loctite sleeve retainer" you speak of. But I DO think there is a chance the existing threads can be chased out...

[Son of Marty]

Kinda thinking along Toby's line you might consider sticking a ball of blue tape down the hole then taking some paraffin wax and coat the threads completely and coating the hole with jb weld and after everything has set up you can screw the jet holder out remove the tape and thread the holder into place.

Edited August 14, 2023 by Son of Marty

[ketchup]

Just now, Son of Marty said:

Kinda thinking along Toby's line you might consider sticking a ball of blue tape down the hole then taking some paraffin wax and coat the threads completely and coating the hole with jb weld and afer everything has set up you can screw the jet holder out remove the tape and thread the holder into place.

Yeah – I read a similar approach on a motorbike forum. The wax acts a releasing agent and then you just hope the whole thing holds up for awhile in the presence of gasoline 👍 nonetheless, it's good to have a serious of options, each reflecting an escalating level of desperation!

[Son of Marty]

Gas won't dissolve epoxy at least so far. 

[cda951]

Looks like M10x1.5 or so, but this can be measured. The DHLA accelerator pump jet holder uses a fiber washer, so it doesn't need a lot of torque to provide sealing. You could try to carefully run a tap through the bore and see if that works, but of course taps work by removing material, so that could make it worse.

 

There is not enough material to install a Time-sert, and probably not enough for a heli-coil. 

 

I think the other suggestions here are as good as it might get, try to make the threads a bit better, and use epoxy to keep the thing in place. Paint a witness mark to tell if it is backing out.

 

Our '74 Jensen-Healey roadster has a Lotus 907 engine with Dellorto DHLA 45s. One of the idle mixture adjustment screws was seized, but I was able to drill it out dead-center, and had to buy a special fine-thread tap (M7x0.5 I think) and was able to save it. I hope you have the same luck!

 

If you need Dellorto parts, CB Performance in central CA still has a decent amount, but Eurocarb in the UK has everything.

 

CB Performance offers a wide selection of hard to find Dellorto Carb Replacement parts. Use our handy Parts Locator diagrams to find the right parts for your Dellorto Carburetor.

WWW.CBPERFORMANCE.COM

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CB Performance offers a wide selection of hard to find Dellorto Carb Replacement parts. Use our handy Parts Locator diagrams to find the right parts for your Dellorto Carburetor.

 

DHLA parts Archives - Eurocarb

WWW.DELLORTO.CO.UK

 

Edited August 14, 2023 by cda951

[Hans]

Try a thread chaser/cleaner rather than a cutting tap. Check amazon. I got Lang set.

[ketchup]

Just wanted to provide an update/resolution: chasing out the threads seems to have worked. I think there is still damage there, as the jet cover required much persuasion to screw down, but it held, and it's not something that needs to be removed very often. Thanks to everyone for your contributions, as always 👍

[TobyB]

Good to hear!  

When threads like that bind, use lube.  

It mostly washes out, but any little bit left

in there will help prevent galling when you

next remove it.

 

t