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MG MGB Technical - carb and general advice?

Hi!

I have a standard MG motor, with twin SU HS2's (I think, although they could be HS4's... what is the material difference). Anyway, I read through the excellent resources on that MG Experience page, and balanced my carbs last night... and have some questions:

1. what is the best way, if I should be doing this at all, of cleaning inside the dashpots? There is no "sticking" when I swivel the piston when it is up in the dashpot, but when it is at its resting position at the base, it seems a bit "gritty"... will this affect the piston's travel?

2. each fuel reservoir is attached to a bar, with a little hole in it, next to the bottom of the jet. The arm off the reservior is held on with a steel then rubber washer on top, and the same on the bottom, with a nut underneath (by "rubber" I mean nylon, or something else black and hard?) These are both dripping fuel. I took both apart then reassembled and tightened, this only helped a little. Is fixing this as simple as replacing the rubber components (they LOOK unworn, but I don't have access to any pictures of the original parts)... are they hard to get hold of?

3. I hope you aren't offended, but I am not a MG driver! My rebuilt engine is inside a Riley 1.5. Given the different engine capacity but same carb. setup, does this mean I should be using a standard needle? This leads to the next question... what air filter setup is standard on MGB's? My two carbs are attached to a single inlet manifold and Riley oil-bath filter. Is this choking the intake of air compared to your setups? Also, the interior of the inlet manifold is rough... if there is a way to polish this, does it make any difference?

4. It can get quite hot in the car... will wrapping the exhaust make any difference, to either heat or horsepower?

[5. not an MG specific question: what do you all do for car radio, if anything? I like the look of my original AM PYE radio, and was wondering if it were feasible to get this converted to a modern setup which is amplified, has FM, and allows other things to be plugged into it. A waste of money? Any tips if I tried to hide a modern head unit in my car (otherwise the fluoro green flashing display might detract from the walnut veneer).]


Thank you for any advice and tips. Sorry for the long message, and the fact that a non-MG owner is hijacking your page... but it is so informative. It's great to see all the friendly and expert advice!

Cheers,
Tom.
Thomas

Hi Tom.

It should be possible to get new seal washers without probs.

If you are looking for power, you basically need to have the shortest, widest, smoothest route possible between the outside air and the cylinders.
David Vizard's 'tuning the A series engine' explains the principles well.

Oil bath air filters usually have a centrifugal effect, which (I guess) does reduce airflow.

The filter will affect the required needle size.

Wrapping the exhaust is a little controvertial, check the archives.

It is impractical to modify the radio in the way you describe.
Have you considered a hidden modern radio with a remote control ?.

Don
Don

Welcome!

I expect you replaced the 1.5 in your Riley with a 1.8 from a MGB?

If so, and you got the carbs that came with it, then you will have SU HS4 carbs (1" + 4/8" bore, a HS2 has 1" + 2/8" bore, HS8 has 1" + 8/8" bore).

If you used the original carbs they are most likely HS2.

Full rebuild kits are available from Burlen Fuel Systems and likely other suppliers much closer to your home. ALL the "perishable" bits are available.

1) Spritz the carbs real well with a decent cleaner like Simple Green and rinse. Once cry, remove the intake tubing and air filter. Remove the three cheese-head screws holding the "dome" on the carb body. Stick your finger in the carb throat and lift the piston as you lift the "dome." Once it is clear of the carb body, hold the piston up and lift straight up so as to not injure the needle. Lay it all down on a large rag as the oil in the dashpot will spill out. Extract the piston and polish with a soft cloth. If the deposits are unruly a little kerosene (parafin) is OK. Assembly is the reverse of dis-assembly, careful of the needle and don't forget to re-fill the dashpots with oil!
DON'T use any abrasives!

2) A rebuild kit will have all the necessary parts and nice instructions. The various glands, unions, washers, o-rings and seals need refreshing. Who knows which one is faulty? It could also be a cracked head-piece ont he jet assembly (also in the rebuild kit).

3) Polishing the intake upstream of the jet is a bonus to flow, however the oil bath air cleaner is a real drag on the system. Fit paper cartridge filters or K&N cartridges if you can. As mentioned above, The proper needle will reflect your induction system (weaker for oil bath or other restrictive intake, richer for paper element).

4) Wrapping the exhaust will help a little. You are also contending with radiator heat and general engine heat. Insulating the cockpit will help more. Insulating the exhaust tends to lead to accelerated corrosion and erosion of the pipe/header.

5) Either fit a "small-head" receiver in the stock location or put a modern unit in the glove-box (or under the seat or in the trunk with a remote-control).

Mike!
mike!

Tom - Regarding the radio, it is possible to get the innards of the radio converted to modern AM/FM capabilities, however I don't know where to direct you to get it done. I saw something recently in one of the BBS about someone who makes these modifications. It was fairly recently that I saw it, so you might want to paruse the Magnette, MGA and MGB General sites as well as this one for the thread. The one thing to take into account in doing this conversion, most if not all modern radio innards are negative ground only, so if your car is positive ground, you will need to convert it to negative ground. Good luck - Dave
David DuBois

Tom - Back to the radio, the thread I saw is on the MGA BBS under the thread "Original Look' Radios". Scroll down to the third posting on the thread. Cheers - Dave
David DuBois

This thread was discussed between 09/08/2004 and 10/08/2004

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This thread is from the archive. The Live MG MGB Technical BBS is active now.