4 replies to this topic

[DClarke1954]

Hi folks,  It's me ...again with another newbie question.

 

I have been struggling with the mini on the carburetion and tuning front from day 1.   It's a bitsa Mini with a transplanted MG Metro 1275 in it.

 

It has been on a rolling road and "tuned" by an expert but while it went like a bat out of hell it was turning the plugs black & sooty inside a few miles.

I took the custom needle out (hacked/filed a bit crudely IMHO as i can see/feel huge nicks/gashes in the needle) and put a brand new standard BDL needle in.

 

I have tuned it myself in accordance with the SU workshop manual for the HIF44 as guidance, and it runs really well but it still isn't quite right and something is going on that I don't understand (to be honest, there's an awful lot I don't understand....  Women, betting odds, football to name just a few).

 

I just pulled the plugs and they are as shown below L-R plugs 1 - 4.  Plugs 1 & 4 are what I would call "perfect", but 2 is a bit mucky and 3 is positively "WET".

I'm not burning any oil and performance is more than adequate.  Now 3 looks like it isn't firing full-stop, but it doesn't feel like that when driving; it isn't "lumpy" at all.

I have given the plug connectors for all plugs a little squeeze and they "click" on to the plug tops nicely.  The plugs (BP6ES), leads, dizzy, coil etc. are all brand new.

 

Just as a test I have now swapped plugs 1 & 4 with plugs 2 & 3 and I will pull them again after a few runs to see what they look like then.

 

Is it "normal" (whatever that is) to have such a disparity with outer plugs running better than the inner plugs?  I would not have thought so, but what do I know?

 

Many thanks in advance for any hints/tips/guidance.

 

Dan.

 

 

 

 

 

[KTS]

personally; i'd start with a compression test and see if that shows anything unusual

[mab01uk]

Is it "normal" (whatever that is) to have such a disparity with outer plugs running better than the inner plugs?  I would not have thought so, but what do I know?

 

Many thanks in advance for any hints/tips/guidance.

 

Dan.

 

Often with BMC A-series engines which have siamesed inlet ports (ie. 5-port cylinder head) the inner spark plugs may exhibit a different color to the outer spark plugs due to the way the fuel and air mixture is distributed. This is because of uneven fuel distribution with one pair of cylinders receiving a richer or leaner mixture than the other pair. Aftermarket intake manifolds, etc are often designed to improve fuel distribution as much as possible but the ulitimate (but expensive) solution for high performance A-Series engines used in competition is an eight port head...as was used by the later BMC Works Minis!

 

CYLINDER HEAD 8 PORT :-

https://www.minispar...-c-ajj4064-kit/

Edited by mab01uk, Today, 04:56 PM.

[KTS]

 

Is it "normal" (whatever that is) to have such a disparity with outer plugs running better than the inner plugs?  I would not have thought so, but what do I know?

 

Many thanks in advance for any hints/tips/guidance.

 

Dan.

 

Often with BMC A-series engines which have siamesed inlet ports (ie. 5-port cylinder head) the inner spark plugs may exhibit a different color to the outer spark plugs due to the way the fuel and air mixture is distributed. This is because of uneven fuel distribution with one pair of cylinders receiving a richer or leaner mixture than the other pair. Aftermarket intake manifolds, etc are often designed to improve fuel distribution as much as possible but the ulitimate (but expensive) solution for high performance A-Series engines used in competition is an eight port head...as was used by the later BMC Works Minis!

 

CYLINDER HEAD 8 PORT :-

https://www.minispar...-c-ajj4064-kit/

 

 

in short, and to be clear; yes, it's common to see a colour disparity between the inner and outer plugs for the reasons above, but not to the degree your plugs are showing

[Earwax]

I would do some swaps on leads as well ( don't assume new equals good)