air filter position

Post by **tonym911** » Fri Jun 19, 2009 11:33 am

Sorry to be asking this but what is the correct orientation of the air filter housing? The big inlet pipe on my one is pointing towards the back of the car, and thereby ends up being quite close to the exhaust manifold. Logically I would have expected it to face forwards for a decent supply of cool air. Just trying to find out why the car (1970 model) runs so poorly, and then conks completely, after just a short run. Have already replaced distributor cap and coil. Plugs are OK and there is no condensor as the car has electronic ignition.
The engine compartment does have extra soundproofing felt which is not that well attached to the bonnet. As I close the bonnet I note the felt is already close to the engine and filter. Am wondering if, as heat builds, the felt is dropping further onto the filter and starving the engine of air. Symptoms are of running rich, eventually conking out entirely. Leave it for a while and it recovers, temporarily. I'm planning to cut the felt out entirely as my next step but all thoughts on this and the air filter question would be gratefully received, as ever.
PS The chap I was with when I put the new coil on was curious about the fact that one of the two leads from the coil went to earth just below the fuse box (the other one obviously going to the distributor).

Post by **pfgiz** » Fri Jun 19, 2009 11:53 am

It's moveable, the idea being that in the summer you point the intake towards the front of the car to get the cool air and in the winter you point it nearer the exhaust to get warm air.

Post by **tonym911** » Fri Jun 19, 2009 12:01 pm

Thanks Peter, I'll switch it round while I'm hacking the felt off!

Post by **Peetee** » Fri Jun 19, 2009 12:56 pm

Perhaps the increased temperature under the bonnet is leading to fuel vaporisation problems?

Post by **tonym911** » Fri Jun 19, 2009 2:22 pm

Hmmm, do you think? Just picked the car up from its last resting place and turned the filter round to its 'summer' position as per Peter's advice, that seemed to improve matters in that I was able to keep driving for longer (about fifteen mins as opposed to less than ten before) but it started misfiring again as I got home, getting worse when low-speed manoeuvring (ie when hotter under the bonnet). There is double-thickness felt under the bonnet. Think I will just remove all of that and see what happens next. Not massively optimistic, seems a bit too simplistic, but at least it will be one more thing eliminated. Very keen to get this sorted before the Rally!

Post by **bmcecosse** » Fri Jun 19, 2009 2:25 pm

The coil lead should obviously NOT go to earth on a standard system! Edit - However - see later comments re some electronic systems - this must be such a system! Since the engine runs -it must be ok! Remove the air filter element - maybe choked with oil fume - try it without. And - is the choke mechanism maybe stuck on - ok when cold but hopeless as the engine heats up.

Post by **tonym911** » Fri Jun 19, 2009 2:29 pm

Sorry Roy, a bit confused by your first two lines there. Are you saying the coil lead should or shouldn't go to earth? And would fume contamination alter the air filter's appearance (ie make it black?) It looks practically new.

Post by **bmcecosse** » Fri Jun 19, 2009 2:34 pm

Coil is connected normally only to 12V supply - and the other side to the dizzy - no 'earth' involved! Electronic ignition of course may make a difference - perhaps - but I doubt it! If the filter looks new - it should be ok - but only seconds effort to remove it - and try a run without just to eliminate from the equation. Also check the piston in the carb is free to rise and falls with a clunk - and 3in1 oil in the dashpot.

Post by **tonym911** » Fri Jun 19, 2009 2:48 pm

OK thanks. Just restarted it after letting it rest for 15 mins. Pickup from idle is very 'shuddery', ie it hesitates badly at low rpm before 'clearing'. Pressing the throttle again while there are still some revs on (ie before it reverts to idle) gets a much cleaner response. I'm wondering if the elec ignition is flaking out in some way.

Post by **dalebrignall** » Fri Jun 19, 2009 3:03 pm

it sounds like the dash pot in the carb has the wrong kind of oil.if its too thick the piston cant go up and down.take the dash pot off the carb and drain out the oil,and put some 3in1 in the dashpot or dashpot oil.

Post by **tonym911** » Fri Jun 19, 2009 3:08 pm

I'll do that right now. Wonder why it would just start to happen though? And why it would manifest itself more after 10-15 mins running? Whatever, I'll gi' it a go as they say in bmcecosse-land.

Post by **tonym911** » Fri Jun 19, 2009 3:19 pm

Is there a specific drain tap or do I just soak up the oil by dipping a rag into it?

Post by **millerman** » Fri Jun 19, 2009 3:29 pm

Check the petrol pump

Post by **tonym911** » Fri Jun 19, 2009 3:36 pm

I think that's OK. Have just unscrewed the dashpot doo-dah and it certainly does not fall back with a clunk, in fact there's quite strong resistance starting almost from when you put the piston back in. The oil feels much heavier than 3 in 1. To drain that out, do I remove the whole suction chamber and then just tip it upside down? Or will that result in tiny bits flying all over the place? Looking at the Haynes diagram it seems like it might be safe even for an idiot like me but I'd rather have some reassurance from the real experts, ie you guys. Odd that, if wrong oil is the problem, this should only have manifested itself recently.

Post by **tonym911** » Fri Jun 19, 2009 3:37 pm

The piston movement feels a bit 'scratchy' too.

Post by **tonym911** » Fri Jun 19, 2009 3:46 pm

I've got the piston here now. Is it correct that the brass sleeve and washer between the bottom and top 'stops' have free play to move independently, both along the length of the piston rod and laterally? That movement is what causes the 'scratchiness' I was on about earlier.

Post by **alex_holden** » Fri Jun 19, 2009 3:48 pm

I would undo the three screws that hold the aluminium dome on and lift it off, then carefully lift out the piston, empty out the old oil, and wash it out with some white sprit and a bit of rag wrapped around a thin screwdriver. While you've got the top off, you can check the piston slides up and down smoothly inside it.

Post by **tonym911** » Fri Jun 19, 2009 3:50 pm

How much oil do you put in? Sorry to be such a pest.

Post by **bmcecosse** » Fri Jun 19, 2009 4:04 pm

Yes - the little cylinder has free play - there used to be variations on that - to adjust the initial 'jump' of the piston before the damping effect took over. Just add 3 in 1 oil - to about an inch from the top - excess will just flow over into the carb so don't worry.

Post by **bmcecosse** » Fri Jun 19, 2009 4:07 pm

The 'piston' is the large round thing you see inside the mouth of the carb. It must rise and fall easily.
But if i were you - I would throw the electronic ignition (at least temporarily) and revert to good old points which I can trust!