2&3 too lean (?)

Post by **newagetraveller** » Wed Mar 29, 2006 11:18 am

The two inner cylinders ( 2 & 3 ) usually run hotter than the two outer ones ( 1 & 4 ) . It is something to do with the cooling of the A series cylinder head.
Thus it is much more usual for the exhaust valves on cylinders 2 and 3 to burn out than those on cylinders 1 and 4.

Post by **Cam** » Wed Mar 29, 2006 4:22 pm

Yes but usually the plugs are more or less uniformly coloured. In this case 2 & 3 were white (very lean) and 1 & 4 were black (very rich) which indicates an air leak somewhere for cylinders 2 & 3

Post by **bmcecosse** » Wed Mar 29, 2006 8:06 pm

That's because 2 and 3 exhaust share the same port ! Best to get the stainless jubilee clips- they last for ever and look better too.

Post by **bigginger** » Wed Mar 29, 2006 9:27 pm

Oh. I reckon the ones I put on will be OK, thank you. Even I had made the connection between 2 and 3 showing the same symptoms and the fact that they share a port, BTW.

The engine started today, and once I'd sorted out the huge over reving caused by the choke cable being stuck, not the best idea when there's a brand new head on the engine, I noticed the tappety noise so check the tappets again tomorrow - one of them sounds a bit queer now. Ah well, it's a relief that it runs

MOT postponed till Friday - this is going down to the wire...

Post by **Dominic** » Wed Mar 29, 2006 11:18 pm

Bet the over-revving wasn't as alarming as when I fitted an unleaded head and forgot the throttle return spring.........

Post by **minor_hickup** » Wed Mar 29, 2006 11:23 pm

heh heh i've done that when messing about with exhaust and crank case covers

Post by **bigginger** » Wed Mar 29, 2006 11:25 pm

Dominic wrote:Bet the over-revving wasn't as alarming as when I fitted an unleaded head and forgot the throttle return spring.........

I'd actually fitted a BRAND NEW SHINY spring - first time in my life that I've bought one, not just found something and used it

Post by **Cam** » Thu Mar 30, 2006 12:21 am

Yes, I've done that and I KNOW Ray has!

Actually, once I had to reverse Relfy's car back a yard or so without the exhaust & spring in place so I had to time it right for the revs to increase then let the clutch out to move it back then turn it off before it shot away too far backwards.

The fun we can have with a mog in bits.

Post by **Packedup** » Thu Mar 30, 2006 1:45 am

I don't know how anyone can possibly pass up on the fun of spending 12 hours or more under a car getting it working, till well past dark with only a small torch (if that) for lighting, knowing if they don't get it fixed they have no means of driving anywhere to buy groceries.

It's one of the highlights of DIY mechanics in my opinion... (there's no laced with sarcasm I hate my cars smiley, so imagine one here!)

Post by **Dominic** » Thu Mar 30, 2006 7:20 am

I have since fitted a brand new shiney, (sparkling even!) spring..... and..... wait for it chaps..... a bracket to hook the spring to instead of holding onto the exhaust pipe / manifold clamp! How's that for swish!

Post by **bigginger** » Thu Mar 30, 2006 10:03 am

Ooooh - so what does it attach to? The bracket, I mean - I know the spring attaches to that

Post by **paulk** » Thu Mar 30, 2006 10:16 am

On the 1 1/2" SU on my desk there is a bracket that goes between the carb and inlet manifold that the spring connects too Also holds the throttle cable sheath.

The Spring to exhaust bracket setup strikes me as a Friday afternoon bodge just to get the engine running before the weekend. I know this has then ended up on the production line but I can't believe this was actually 'designed'

Post by **bigginger** » Thu Mar 30, 2006 10:59 am

And it makes putting the clamp on even MORE awkward

Post by **Dominic** » Thu Mar 30, 2006 6:44 pm

bigginger wrote:Ooooh - so what does it attach to? The bracket, I mean - I know the spring attaches to that

I attached the bracket to one of the exhaust clamp bolts, it then needed to be bent outwards to line up comfortably with the spring. It may be an afterthought, but it works!

Post by **bigginger** » Thu Mar 30, 2006 8:12 pm

Oh - isn't that where it's meant to be? My ones seem to.

Post by **bmcecosse** » Thu Mar 30, 2006 8:44 pm

The newer HIF carbs have return spring built in. And they don't cut out/splash petrol about when throwing the car round tight bends and roundys!

Post by **bigginger** » Thu Mar 30, 2006 8:59 pm

The spring can (and does) still break though.

Post by **Dominic** » Thu Mar 30, 2006 9:19 pm

And they don't cut out/splash petrol about when throwing the car round tight bends and roundys!

I seem to remember that the RR Merlin engines had SU carbs that would cut out when going inverted, which was the reason why fighters of WW2 era powered by these engines had to "peel off" keeping positive G, rather than just push the nose over into a dive, thus suffering negative G. The injected Daimler Benz powered Messerschmitds had the upper edge in this particular manouevre!

Post by **grahamt7** » Thu Mar 30, 2006 11:14 pm

The injected Daimler Benz powered Messerschmitds had the upper edge in this particular manouevre!

Didn't do them a lot of good though!

Grahamt7, Flt Lt RAFVR(T)

Post by **Cam** » Fri Mar 31, 2006 2:25 am

Dominic wrote:
And they don't cut out/splash petrol about when throwing the car round tight bends and roundys!
I seem to remember that the RR Merlin engines had SU carbs that would cut out when going inverted, which was the reason why fighters of WW2 era powered by these engines had to "peel off" keeping positive G, rather than just push the nose over into a dive, thus suffering negative G. The injected Daimler Benz powered Messerschmitds had the upper edge in this particular manouevre!

Yes, I remeber being told about that but wasn't there an advantage that we had using the system that the injected engines didn't? I'm sure there was, but I can't remember now.