Erratic Tickover

[Britishbest]

Hi Guys,

 

My 4A is nearly on the road after a lengthy re-commissioning. Can you advise a few things please -

 

On tickover my engine revs and drops on its own accord, I've yet to fix the rev cable so cant say what rpm but it goes quite high. I was advised by a very helpful forum member (thank you) at Basingstoke Car show to change the springs in the distributor.

 

I ordered an 'advance/retard spring kit' from Rimmers, there are 5 springs in the kit, the 2 smallest I can see go on the distributor weights, where do the other 3 slightly larger springs go??

 

The Stromberg carbs have been rebuilt but I've just bought new diaphragms, stronger piston springs and tappet cover breather diaphragm.

 

I also need to adjust the float level which I've never done. Is there a guide anywhere?

 

I was also advised to retighten the lower manifold studs.

 

Hopefully one of these is the culprit, anything else I need to check?

 

Thanks

 

Colt

Edited May 13, 2016 by Britishbest

[MRG1965]

HI, Colt, you 've been advised to replace the bob weight springs (as pictured), might also be worth looking at the distributor in general if you have wear on the cam lobes (assuming you still have points), main shaft bushes. You mentioned the manifold bolts being retightened, air leaks and wear in the throttle spindle bushes could also be an influence, but you say you've had these rebuilt, but to what level? Breather system can also cause changes in idle speed if there are leaks in the blow back valve or split leaking hoses, if it is a closed system.

In truth there is fair bit and until its been run for a few miles and tuned, could be almost any or all of the above plus a fair few more things at play.

Mark

[boxofbits]

Hi Colt

 

Does sound like carburation or air leak. It also sounds like your carbs are not in balance. You will need to back off all choke adjustments/ fast idle etc and slacken connecting linkage so effectively they can be adjusted separately. You will need an airflow meter ideally to balance the throttles, but I use a piece of heater hose connected to a good old fashioned ear. Listen to the airflow and balance both the same. Why did you change damper springs? You also need to adjust mixture on both 'til you get smooth tickover and check for air leaks, Do you have a servo fitted. Retighten linkage to equal settings on both carbs. Good luck

[RobH]

It is difficult to understand why you were advised to change the distributor springs as they have no function at tickover speeds. The distributor springs alter shape of the advance curve as you go up the rev range and you only need two of them - you should use one weak one and one strong one but it should be the right types. The 5 spring kit you have bought is a general-purpose one which might or might not have the right weight springs and it will be a matter of experimentation which ones will work best. Far better to talk to the Distributor Doctor and get a pair of the correct ones if the originals are not working.

 

Rob

[Britishbest]

Some good advice thank you.

 

I swapped the 2 springs and turned the engine over and Disaster! One of the weights flew loose, jammed the distributor and it spun through 90 degrees ripping off the diaphragm and snapping a peg that the spring wraps around. Now I need a refurbished or new distributor. I might swap to electronic are there any decent ones for fair price? A 25D rebuilds is £190 plus vat.

 

Hopefully no internal engine damage, cant see any. Nightmare, bad day.

Edited May 13, 2016 by Britishbest

[sadman]

If the engine is 'hunting' (engine revs increasing/decreasing) try manifold gasket for leaks aswell, it's happened to me.

Doug

[stillp]

My inlet manifold had been shotblasted, which had uncovered a pinhole in the casting! Found it using a piece of plastic tube in my ear, while trying to balance the

carbs.

 

Pete

[RogerH]

Hi Colt,

the replacement distributors on ebay work well for general use and as a spare. £40 is worth a punt.

http://www.ebay.co.uk/itm/Points-25D-25D4-distributor-with-top-entry-distributor-cap-replaces-Lucas-25D4-/120649139341?fits=Car+Make%3ATriumph%7CModel%3ATR+4A&hash=item1c173fc48d:g:Wy0AAOSw3v5XI0zM

 

 

Roger

Edited May 13, 2016 by RogerH

[stillp]

Hi Colt,

the replacement distributors on ebay work well for general use and as a spare. £40 is worth a punt.

http://www.ebay.co.uk/itm/Points-25D-25D4-distributor-with-top-entry-distributor-cap-replaces-Lucas-25D4-/120649139341?fits=Car+Make%3ATriumph%7CModel%3ATR+4A&hash=item1c173fc48d:g:Wy0AAOSw3v5XI0zM

 

 

Roger

Interesting, but is it just me or do others think they look wrong with the top entry cap?

 

Pete

[AndyR100]

I don't think there is anything preventing you from using your existing cap/leads with these replacements

 

....... Andy

[peejay4A]

There isn't. I've used both.

[Britishbest]

Thanks guys, replacement distributor ordered until I can sort out my old unit.

 

I will closely look at the manifold gasket tomorrow. Hadn't really thought you could hear the air escaping from there.