Rebuild Carb Advice

joestram · September 28, 2014, 09:27:02 AM

Hi All,

I was finally given some time alone with the car yesterday (30 mins is better than nothing) and I have pulled my carbs off ready to have them rebuilt.

I am just wondering, how/what do I buy to rebuild them?

I have been told the dellorto 40's that I have were rejetted to 52mm so do I buy a 52mm rebuild kit or a 40mm rebuild kit?

I am so confused!! I would like to attempt to rebuild them myself because I am sure once I have the parts it will be a fairly straight forward process, it's just getting the right parts that I am confused by.

Where would you guys get the rebuild kits from? eBay or locally?

Thanks guys

Joe

john m · September 28, 2014, 09:41:46 AM

I"ve bought rebuild kits and jets form this firm in the UK. Was happy with service.

http://www.dellorto.co.uk/

joestram · September 28, 2014, 07:35:12 PM

Thanks for that John. With a rebuild, is it only the gaskets and o rings that get changed? Are you supposed to replace the jets as well?
The reason why I think I need a rebuild is because there is petrol leaking under the carb when the motor is running or the fuel pump is on.
Thanks
Joe

joestram · September 28, 2014, 07:37:01 PM

joestram · September 28, 2014, 07:37:53 PM

Can someone please tell me what the screw is called that is lying across the carb as the top was snapped (lucky I was able to remove it)

brook308 · September 28, 2014, 09:24:37 PM

Quote from: joestram on September 28, 2014, 07:37:53 PM
Can someone please tell me what the screw is called that is lying across the carb as the top was snapped (lucky I was able to remove it)

That screw is used to adjust the air flow between chokes on each carbie.

Normally the screw is all the way in till it seats, you only need to adjust this screw if you have measured different air flow readings between each choke of your carbie.

joestram · September 29, 2014, 04:59:31 PM

Thanks for that explanation brook308. Bought a new one today but it is a different shape at the tip so I will just use the old one.

Also - Can someone please recommend a method on removing the gasket of the float assembly. Struggling there - everything else has been changed

Thanks

Joe

joestram · September 29, 2014, 05:06:55 PM

BTW - Just bought the carb rebuild kit from thornbury carbs for $67 for the twin kit which I thought was good value. Just a heads up for anyone else looking for the kit.

Joe

colcol · September 29, 2014, 08:51:34 PM

Thornbury carbs know their.....carbs, been around a long time, hardly any carby joints left anymore, Muller and Jacka used to be on every corner.
Angelo must be getting on now, i think his son is running it now, Angelo had a Lancia that he used to display at the Grand Prix, nice bloke, always up for a chat about Italian cars, Colin.

john m · September 29, 2014, 11:19:39 PM

So what did Thornbury Carbs advise on your carbs. Are they 40mm or 52mm?

Some tips I've picked on rebuilding carbs up over the years-
Don't use steel wool for cleaning as it can leave particles in side the bodies, use SPAM scourer instead.
Use the correct size screw drivers, if screws or caps are seized, an impact driver will do the job. Best to place the carb on a folded towel on your lap and tap on the impact driver. An egg carton is usefull for storing jets, screws and caps until assembly. Do one carb first as you can use the other to guide you on assembly. Never over tighten screws on carbs. CRC carb cleaner also works magic, but wear gloves and brush it around the insides, try not to breathe the stuff though. Remember to regrease the shaft bearings.

joestram · September 30, 2014, 06:46:45 AM

Thanks Colin and John.

Some useful tips there.

How did you go about removing the float assembly gasket? I can't seem to remove it. It looks like the float mechanism needs to be removed but I can't seem to see how I can remove the pin to do so.

Thanks

Joe

joestram · September 30, 2014, 08:12:06 AM

Hi John - just in relation to your question about the 40 or 52mm.

Peter wasn't avail. so his wife served me.

She mentioned that the carb didn't look bored out but the jets would have been changed.

The main jet is 210 top and 145 bottom so not sure what that means.

Maybe the guy I bought it from was pulling my leg but he mentioned that the car has PACE street cams and they needed to deliver more fuel so they had to rejet.

Apparently Lloyd from Sirius Motorsport in Adelaide (a club member) did the work but when I called him he didn't quite remember.

Ettore from Il Bolide Rosso said the chokes looked standard.

This is a response from the seller when I asking about more info on the engine:
#1
the engine was built at Italservice which was built to standard bottom end specs then the camshafts and carbies were installed and modified at Sirus in Adelaide who happens to be a Alfa car club member here in Adelaide
his name from memory is Lloyd Clonon not sure on his surname spelling he is the one that rebuilt the diff and gearbox as well.
when he first tuned the car he had to give it more fuel so the carbys have been taken out to 52mm as for the cam is they are P.A.C.E. camshafts which to my understanding
are the biggest you can go with that engine with out starting to do machine work on the heads for clearance if you need the specs of this cams best to speak to Lloyd as he arranged them
straight from p.a.c.e

I'm still confused

Joe

LukeC · September 30, 2014, 10:14:33 AM

Forget this 52mm misinformation.... If the carbs say DHLA 40, that most probably have had nothing done to them.

145 Mains (bottom jet at the emulsion tube) and 210 Air corrector is standard from memory. Hopefully no cretin has drilled/reamed the jets.

Choke will be 32 mm if it is standard. Performance (street) engines this should be enlarged to 34, but a dyno session would be advisable if this is done.

Be VERY careful removing the float pin from the top cover to replace the top gasket and needle and seats. This casting is NLA, and are getting harder to find (ham fisted people breaking the float poats). I drive the pin out from the side with the split using very small screwdriver. It only takes hand pressure. *DO NOT* try to pry the post apart at the split or you will be posting that you need a replacement top cover! Gentle pressure is all that is needed.

Setting the float height is a precise business, and should be done according to the weight of the float. To get it absolutely correct, the engine should be run, and then the fuel height checked in the carb with a vernier. For most purposed, off car is good enough if done correctly. If you are not sure, take the tops, gaskets and needles and seats to your carb shop.

I have never regreased the bearing on the shafts in 100s of dellorto/weber carb overhauls. If there is any roughness (bearings need work), best leave messing with this area to the experts.

brook308 · September 30, 2014, 06:20:12 PM

52mm probably refers to .52mm idle jets.
So your idle jets may have been changed or drilled out to a larger size.
.52mm idle jets may have been needed to get a smooth idle from an engine fitted with performance camshafts.

You can buy carburettor drill sets on ebay or you can get good sets of drills from Jaycar.
You can use the shaft of the drills to check if your jets have been drilled out.

Idle jets have a number on them, ie 45 is .45mm.
Main jets have a number on them, ie 140 is 1.40mm
Air Correction is the part on the top of the main jets ie 110 is 1.10 mm.

joestram · October 04, 2014, 06:56:31 PM

Hi All,

Just want to thank you all for all your advice and assistance over the last couple weeks!

I have installed the carbs and fired her up and there is no leaking fuel and she seems to be running ok so far.

I will need to give her a little tune but at least I can safely driver her now!

Here is a little video of her just after installing the carbs :

http://youtu.be/WAm9JqTxIdI

Also, I checked the idle jets and they are 55

Thanks again for all your help everyone

Joe