Who would have thought changing the air filter would cause so much grief.

[Steam]

This started out quite innocently as a change from a "Performance" air filter (or should that be less performance) to a standard filter in a factory housing.
I expected to have some tuning to do after the change but the huge can of worms I opened was unexpected.
Close to 3 months and we have finally got to the bottom and sorted out the A series engine.
I will chronicle all the hassles here as time permits so hopefully others may benefit from it.

[Steam]

Having got a filter housing from HP, first up was to make a couple of bolts for it



The top one is the original and the bottom 2  are the newly made ones.
Then we fitted the elbow and the filter to the engine.
Just a bit of history the car has not been used regularly for a couple of years but as son no1 now has Ls and is into cars we have decided to get it running properly. It is on club plates.
We fired it up as it was to see what was what before doing any retuning, it started but was a bit lumpy and there was a distinct miss and lack of response from the throttle.

[Steam]

I use and EGA for mixture settings on SU's so we warmed up the engine. gave it the obligatory 20 second blast to clear things out then checked Exhaust gas. It was a little high at 5% CO which was to be expected and 1 flat was all it required to bring it down to 3.8% which is my goto level.
 We checked where it was on the jet nut by turning up to stop and counting flats then back down and a recheck of CO gave us 2 turns which is about spot on.
 but there was still a slight hunt and the throttle response was still a bit sluggish. but we decided on a test run to what was revealed on the road. but that would have to wait for the next weekend.

[Halfpint]

Hi,
Those screws are getting hard to find now.
Hunting may be a leak, like a manifold gasket.
Finicky thing setting the mixture.
HP

[Steam]

Yeah Tony, I have actually fixed the faults but I am relating this in a series of posts as it actually happened.
I am up to December.
We took it for a run and it pulled  reasonably through all gears up tp 100 and would cruise ok but was bogging down when trying to accelerate from 90 ish. It was also stalling when slowing to a stop at junctions etc.
Back home we srarted rechecking the mixture when Jack (No 1 son) noticed a fuel leak from the tank to pipe hose.
Didnt have enougjh hose to replace it so we drained the tank and tried to shorten it but a split was in the wrong place meaning we would have to wait and get some fuel inj hose & clamps before continuing.

[Steam]

So having replaced the fuel hose we went for nother run but nothing had changed.
We had thought air in the fuel line may have been playing with us but not so. A recheck of the mixture showed that it was till at 3.8% CO so we decided to pull the carbie dashpot to make sure all was clean and to check the needle.
There was a small amount of fuel varnish middle of the needle and we changed the needle to one out of our selection which would match the engine. This made things worse so we cleaned the original needle (a standard for stage one tune) and reassembled the carb.
 The heat was rising in the shed so we d3 ided to continue when the weather cooled some.

[Steam]

The folllowing weekend was cooler so back to the shed. We did a quick check on the timing which was fine both idle and max advance were correct.
 Out for another test run but the misfire was worse and seemed to be at all revs, pulling the choke did not improve things, in fact it was slightly worse.
 Back in fhe shed and the miss was worse. The engine was hard to start after switching off, finally got it running and pulling leads 2 & 3 made no difference but 1 or 4 stalled it. The leads were new silicone stainless spiral and we had a spark on all 4 leads.  The plugs in 2 & 3 had failed despite looking fine. These were only 2000ks old as I had this problem before. The plugs are ngk resistor. We put some good second hand ones in and started the engine fine. But we had noticed that the spark was not super strong and was bluey orange. The spark from the coil lead was slightly stronger but still blue orange.
The dissy is a 65dm4 A+ converted to a series. We removed the cap and rotor to check and found signs of wear on the cap poles. These are alloy poles which are not as good as brass. We cleaned the rotor arm and put another used cap on which was better then the original. The engine ran ok but we neece new plugs and I wanted to see if a cap with brass poles was available.

[Steam]

Well if you learn something new the day has not been wasted.
While researching caps for the 65dm4 dissy I found out that a specific coil was needed. The current coil is a gt40 which is not correct. I did not know the coil needed was a particular unit. The gt40 has been in use for 6 or so years.
 There were 3  brands available, an original AustinRover, an Intermotor and a Lucas. The AR is no longer available and I ordered a new Lucas unit from the UK. This was the week before Christmas so it would be after new year before it arrived.
 Project on hold.

[FNQ]

Thanks for documenting this situation. Chasing fuel/air/spark concerns can be a hassle - and often the time gaps in getting a chance to trial different settings makes things worse. 


Can i also suggest checking the dizzy has a good spot to earth. Some electronic dizzies and others have an earth wire to connect to ground, but others use the interface between their base and the dizzy drive hole to get to earth. Often newly painted engines have a nice film of paint on both the block and the dizzy clamp/collar. (just scratch down to bare metal on the seating ring and the underside of the clamp- no one will see it)


And i realise you are documenting this after the fact, so please ignore all of the above info if it is now redundant. Cheers Darryl

[Steam]

Thanks for documenting this situation. Chasing fuel/air/spark concerns can be a hassle - and often the time gaps in getting a chance to trial different settings makes things worse. 


Can i also suggest checking the dizzy has a good spot to earth. Some electronic dizzies and others have an earth wire to connect to ground, but others use the interface between their base and the dizzy drive hole to get to earth. Often newly painted engines have a nice film of paint on both the block and the dizzy clamp/collar. (just scratch down to bare metal on the seating ring and the underside of the clamp- no one will see it)

And i realise you are documenting this after the fact, so please ignore all of the above info if it is now redundant. Cheers Darryl

Thanks Darryl as you say documenti g these things may help others.
The fact that I refuse to work in the shed when it is like an oven in ther also means jobs in the summer take longer.
Your suggestions are valid and correct despite not being relevent to my sittuation. The distributor has an earth connection but some do not. The more we relate our knowledge the more others may benefit.

[Steam]

The new coil arrived middle Jan but with the hot weather, conditions in the shed were not condusive to clear thought or productive work.
 We finally got back to it at the end of january.
We fitted a new set of spark plugs and then turned our attention to the new coil. We orintated it the same way as the old o e regarding the bracket then we sw itched over the wiring, finally bolting in to place.
 We checked the spark from the plug leads and while it did appear a little stronger it was still bluey orange in colour. We spent quite a while checking different plugs and leads including coil leads as well.
 Wondering if we were just chasing shadows we started the engine and allowed it to come up to temp. A check of the mixture with EGA showed it still at 3.8% CO. There was very little change. The throttle response was still sluggish albeit a little better.
 I am still not sure why but I looked at the coil wiring thinking something did not seem right, then Jack asked about the polarity of coils.
 We checked the wiring and found that the coil was reversed, we had simply changed the coil keeping the wiring the same but it was definately reversed. The wiring through the coil connections to the distributor was correct.
 Double and triple checking to confirm we were correct then we changed it around. We now had a really strong blue white spark from the leads.
We had trouble starting the engine  and needed about half choke initially,  but it ran with no choke albeit with a distinct misfire.
 What we found next really surprised  me, the EGA showed that the mixture was way lean. 0.8%CO. I have always known that the ignition will affect the mixture but i was surprised how low it was.
 Two flats rich on the jet nut brought us back to 3.8%CO. And the change was unbelievable, instant throttle response and on the road it was like a different engine, no flat spots and rapid acceleration at all revs.