Trying to help a MG owner, any tips?

[hermanmaire]

I am trying to help out a owner of a 1964 MG. I have zero experience with these models. The car just had quite a lot of work done by a garage that though they understood these early MG's .....

- new starter ring
-clutch and throw out bearing
-valves adjusted
-carburators rebuilt with kit from Moss. All new springs installed.
ect....

The car had a electronic unit installed in the distributor a year two ago. Engine was also rebuilt by a reputable garage a few years ago so engine condition should be very good. It has great oil pressure at all RPM.

The car currently starts ( not easily though) and idles but seems really down on power. The exhaust seems to be puffing black ( which would indicate a rich mixture, I think) .

If I floor it in 1st gear ...... the thing barely moves and will probably get a few back fires in the process. If I do the same in 2nd and 3rd its also quite slow to accelerate .

I was there when the garage tried adjusting the carburetors and the only adjustment that seems to have any effect seems to only raise or lower the idle.

The engine also shakes around quite a bit at idle ( dont know if its normal) .

Any tips on what I can check to maybe help out this MG owner.....

Thanks for looking

 

[DNK]

I don't know much but sounds like timing

 

[CZ_Dave]

I agree timing and do you have
a flow gauge to set the Dual Carbs?

That also could be the culprit.

But a garage that is unacostomed to rebuiling SU's
would crate a huge delima too.

Sounds like it could be rich too.

Running rich, carbs and timing out of adjustment.

 

[hermanmaire]

Thank you for the replys.

So theres no secret/magic adjuster.... it really comes down to timing and carbs.

I am going to call napa tomorrow and see if they have the flow gauge. I am also going to open up my Haynes manual for SU carbs.

Is the timing on this car set with a timing light and a marking on the crank pulley?

Thanks again

 

[hermanmaire]

Another question,

Is it ATF oil that is used with these carburetors?

 

[DrEntropy]

ATF will work fine.

The timing mark on the pulley and the pointers for BTDC are on the UNDERside of the pulley. Bit of a pain to see, but idle at 8°~10° BTDC should be close enuff to get that out of the way. The carbslikely need to have the jets set, check the procedure in the Haynes to get familiar with the treminology and we'll go from there.

And WELCOME to the forum!!! :thumbsup:.

 

[hermanmaire]

ATF will work fine.

The timing mark on the pulley and the pointers for BTDC are on the UNDERside of the pulley. Bit of a pain to see, but idle at 8°~10° BTDC should be close enuff to get that out of the way. The carbslikely need to have the jets set, check the procedure in the Haynes to get familiar with the treminology and we'll go from there.

And WELCOME to the forum!!! :thumbsup:.

Thanks. I am going to head over to the car now with my test light.

Is this just a normal mark the BTDC on the pulley with a paint pen and hook up the test light.

Thanks again

 

[DNK]

Check out this site first?
https://www.mgexperience.net/journal/B-racer/1818

 

[DrEntropy]

ATF will work fine.

The timing mark on the pulley and the pointers for BTDC are on the UNDERside of the pulley. Bit of a pain to see, but idle at 8°~10° BTDC should be close enuff to get that out of the way. The carbslikely need to have the jets set, check the procedure in the Haynes to get familiar with the treminology and we'll go from there.

And WELCOME to the forum!!! :thumbsup:.

Thanks. I am going to head over to the car now with my test light.

Is this just a normal mark the BTDC on the pulley with a paint pen and hook up the test light.

Thanks again

Any solution yet?

 

[hermanmaire]

Hello,

well, I finally had a chance to go over and help out...... something that I had planned to do in 1hr, turned in to over 5hrs !!!!

I first put some new spark plugs in, engine was running very rich so they were all very, very black.

The Other problem is that #4 cylinder spark plug is very wet with gasoline. I checked for spark and it has a good strong spark when testing with the spark plug sitting on the engine. Even with a brand new plug and testing another spark plug wire it still wont fire that cylinder. The spark plug is always soaked in gasoline, even with the carburetors very lean it still wont fire.

I dont get it.


I tried to set the timing. As far as I know, the cylinder closest to the radiator is #1. I hooked up my timing gun to that spark plug wire.

If I adjust the timing so that the timing mark on the pulley is in the middle of the 3 timing marks, the engine dies.

The closest I can get the timing mark on the pulley is about 1 inch away from the 3 timing mark ( I can mark a picture if that would make it more clear) .


So, then I moved to the carburetors. I adjusted the carburetors the best I could ..... I leaned them out and it now idles OK and the exhaust is not black now.

I go for a test drive. It still feels like its running on 3 cylinders and it still back fires.

This car needs a professional mechanic.

 

[Billm]

It is very much like your TR3A with the dual carbs. It really sounds (to me) like your rear carb is still rich and your front is (possibly) lean (if you are still getting backfiring).
The MG should have an electric fuel pump- the safest and easiest way to check that the float bowl levels are correct is to remove the dashpots from the carbs, turn on the fuel pump and see that the fuel is about 1/8" below running over the ridge. I will bet that the rear carb is running over and that the front is not.
You can set the float level by the book all that you want but if it is not 1/8" below the ridge then it is still not right.
BillM

 

[DrEntropy]

Another thought: Is the fuel pump an SU or a replacement? The carbs won't tolerate much over 3~4 PSI fuel pressure, more than that will cause 'em to flood.

 

[JPSmit]

one other thought - as I've read descriptions of dual carbs being revived, regularly they have mismatched needles and floats.

 

[tomkatb]

Seek professional help. An MG specialist.

My guess: The dizzy is worn out or damaged or filthy. Then someone messed with the carbs compounding a simple issue. Possibly the fuel pump is putting out too much fuel or the floats are in need of help. Is fuel running out the overflows on the floor? On this specific car, usually this is a symptom of fuel issues!

Anyone who has dealt with these specific issues could get it running in hours.

Step one while it is still running. Verify idle advance. Advance at 3000 rpm. Advance increase when you suck on the dizzy vacuum line. If all are correct (about 10,32,6) then verify the fuel pump as correct(2-3 psi). Float level correct. Needles not stuck.

Check timing again. Adjust as necessary.

 

[hermanmaire]

Thank you all for the replys.

I may go over to help a bit more.... not looking forward to it though.


The distributor has a electronic system installed in it. The vacuum advance is NOT EVEN CONNECTED.
Thats another thing I dont understand.

Does anybody know if the vacuum advance is needed even with the electronic point system??

There is so many things not right i dont even now where to start!!!!

 

[DNK]

Not if it's a mechanical advance dizzy.

 

[DrEntropy]

If it is the original unit, it has both a mechanical (weights and springs under the points plate) and a vacuum pot advance. The weights could be corroded on the pivot pins, the camshaft could be stuck on the inner shaft.

All that said, the fuel issue seems to me to be the bigger problem. SU carbs are about the same no matter which version they are. Too much fuel pressure, pin-holed float or one out of adjustment are all possibilities. A systematic hunt for what's outta whack is the only way to get 'em right.

I am trying to help out a owner of a 1964 MG. I have zero experience with these models. The car just had quite a lot of work done by a garage that though they understood these early MG's .....

- new starter ring
-clutch and throw out bearing
-valves adjusted
-carburators rebuilt with kit from Moss. All new springs installed.
ect....

The car had a electronic unit installed in the distributor a year two ago. Engine was also rebuilt by a reputable garage a few years ago so engine condition should be very good. It has great oil pressure at all RPM.

Has this engine run at all correctly after all that stuff was done?

 

[jessebogan]

I think I would start with a compression test, followed up by checking the valve adjustment. If the engine was "gone thru", and then never fettled after that, perhaps we have a tight valve or two, compounding the issues. However, no amount of tuning will correct anything if the basic mechanical condition is not correct. Last thing, be sure the firing order of the wires in the cap is correct, and correct for the rotation of the distributor.

 

[DrEntropy]

Yup.

That's why I asked if the thing had ever run well after all those things were done.

 

[jessebogan]

I Knew that, just thought I would "clarify", just in case....Great minds an all that.