SU carburetor overhaul - screw types BA?

[martinclan56]

I am overhauling my twin HS4 SU's. Does anyone know the scew types that were used. BA perhaps?
You can get all the screws from the SUcarb website but blowed if I am paying 0.90 for a single screw!

Cheers, Robin

[chris_cussen]

Re: SU carburetor overhaul - screw types BA?

Well if you took the carb apart you could try to match the thread to the BA spec, can be found here.. https://en.wikipedia.org/wiki/Britis..._screw_threads then eBay for a supplier
Alternatively you could visit a fastener supplier and they should be able to match the thread.
But either way you may spend more than 90p
Good luck

[greyV8pete]

Re: SU carburetor overhaul - screw types BA?

I am overhauling my twin HS4 SU's. Does anyone know the scew types that were used. BA perhaps?
You can get all the screws from the SUcarb website but blowed if I am paying 0.90 for a single screw!

Cheers, Robin

According to the link below the thread is 3/16th Whitworth. Carbs metal is usually fairly brittle so expect a coarse thread in these applications. Peter.
http://www.retrominisltd.co.uk/index...roducts_id=187

[stevejgreen]

Re: SU carburetor overhaul - screw types BA?

A good source of screws and fixings for me was here or there

[marlinmick]

Re: SU carburetor overhaul - screw types BA?

Hi All

1.8 TC Marina Engine (Twin HS4 Carbs.)

I have just refurbished my twin SU's and I got my new screws and washers from ebay (off seller wem19520 (3817) and they were £5.90p for 12 screws and washers, good quality as well, sorry I tried copying link but it didn't work. I also brought service kits and new jets from SU, my original gland rubbers where the flexi pipes enter the float bowls had disintegrated. I also fitted new needle jets which led onto concerns with my float heights.
During the mixture setting and synchronising of the refurbished carbs I could not stop the engine from running-on when the ignition was turned off. I had used a Colortune to get the mixtures right and a tube to balance to the intake hiss. I read all the information in the SU Carb Manual but it omits any mention of adjusting the float levels on later model (plastic float equipped) carbs apart from stating that they are non adjustable.
I eventually found the correct information in the Haynes Marina Workshop Manual whereby you have to run the prewarmed engine, carry out any adjustments required, blip the throttle and allow the engine to settle back to an even idle of about 800 rpm then turn it off. Then remove the dashpots and piston/needle assemblies and check the fuel level in the jets, it should be 1/16" of an inch below the top of the jets. If it deviates from this measurement remove the top of the float bowls and either add or remove washers from under the needle jet or add extra gaskets to the float bowls. In my case the fuel level was very low so I removed the washer from under the needle jets and this cured my running on problems however the fuel level in the jets was still low so I am investigating methods of bringing the fuel levels up to their correct levels. I don't know if different needle valves are available to adjust the fuel level in the jets? I will look into it further once I get the car back on the road when I have completed its refurbishment. Hope this information helps.

Regards

Mick.

[martinclan56]

Re: SU carburetor overhaul - screw types BA?

Thanks Mick useful info.
I am surprised the float level is that critical.
I never got on with colortune I found the mixture always too weak in practice.
Running on seems to be a problem with the B series. In later models that fitted an anti run on valve to mitigate the problem.
Cheers Robin.

[stevejgreen]

Re: SU carburetor overhaul - screw types BA?

Thanks Mick useful info.
I am surprised the float level is that critical.
I never got on with colortune I found the mixture always too weak in practice.
Running on seems to be a problem with the B series. In later models that fitted an anti run on valve to mitigate the problem.
Cheers Robin.

The anti run on valve was essentially a US model development for emission controls, it’s not necessary on UK cars.

[Ye Ol Ripper]

Re: SU carburetor overhaul - screw types BA?

"I have just refurbished my twin SU's and I got my new screws and washers from ebay (off seller wem19520 (3817) and they were £5.90p for 12 screws and washers, good quality as well, sorry I tried copying link but it didn't work"

Hi Mick
I believe this is the listing that you refer to for the screws that you had difficulty copying.

https://www.ebay.co.uk/itm/12-off-SU...oAAMXQVOhRFrK3


With regard to your running on issue , what have you set your ignition timing to, as too much advance can cause this ?

Provided the mixtures are not set too weak at idle and the ignition timing is set correctly and there are no air leaks , then the engine wont run on assuming your idle speed is also 8-900 rpm, but it will do above 1000rpm.

There were a few different distributors used on that engine , the serial number is stamped on its aluminium body .

The early type was a 25D and the latter a 45D type.

Your next step is to refer to the supplementary section in the Marina Haynes manual that you have and try setting the ignition timing to match your engine spec and also the distributor number.

[martinclan56]

Re: SU carburetor overhaul - screw types BA?

Hi All

1.8 TC Marina Engine (Twin HS4 Carbs.)

I have just refurbished my twin SU's and I got my new screws and washers from ebay (off seller wem19520 (3817) and they were £5.90p for 12 screws and washers, good quality as well, sorry I tried copying link but it didn't work. I also brought service kits and new jets from SU, my original gland rubbers where the flexi pipes enter the float bowls had disintegrated. I also fitted new needle jets which led onto concerns with my float heights.
During the mixture setting and synchronising of the refurbished carbs I could not stop the engine from running-on when the ignition was turned off. I had used a Colortune to get the mixtures right and a tube to balance to the intake hiss. I read all the information in the SU Carb Manual but it omits any mention of adjusting the float levels on later model (plastic float equipped) carbs apart from stating that they are non adjustable.
I eventually found the correct information in the Haynes Marina Workshop Manual whereby you have to run the prewarmed engine, carry out any adjustments required, blip the throttle and allow the engine to settle back to an even idle of about 800 rpm then turn it off. Then remove the dashpots and piston/needle assemblies and check the fuel level in the jets, it should be 1/16" of an inch below the top of the jets. If it deviates from this measurement remove the top of the float bowls and either add or remove washers from under the needle jet or add extra gaskets to the float bowls. In my case the fuel level was very low so I removed the washer from under the needle jets and this cured my running on problems however the fuel level in the jets was still low so I am investigating methods of bringing the fuel levels up to their correct levels. I don't know if different needle valves are available to adjust the fuel level in the jets? I will look into it further once I get the car back on the road when I have completed its refurbishment. Hope this information helps.

Regards

Mick.

Out of interest what air filters are you using? Mine had some of those horrible pancake filters from the 80's. About as much use as a chocolate teapot...

Cheers, Robin

[marlinmick]

Re: SU carburetor overhaul - screw types BA?

Hi Robin I am running with Twin Pancake Filters because that all I can fit in, but like you say they're only just better than nothing. I've just changed the filter on my Cabrio I've fitted a K&N in place of the Pancake filter that was on it when I brought it and I can confirm that it does run better.

Regards

Mick.