Spark Plug Issue

[steveg]

Recently my #3 plug fouled. I replaced all the plugs and this is what they look like after a couple hundred miles or less:

Left to right #6 to #1
I'm thinking it's an issue with the wires, which are copper with the Moss screw-on bakelite ends.
The plugs are BPR6ES
Cylinder #5 is 145psi; the others are 155 - 165.

Any comments or suggestions?

 

[steveg]

Recently my #3 plug fouled. I replaced all the plugs and this is what they look like after a couple hundred miles:

Left to right #6 to #1
I'm thinking it's an issue with the wires, which are copper with the Moss screw-on bakelite ends.
The plugs are BPR6ES
Cylinder #5 is 145psi; the others are 155 - 165.

Any comments or suggestions?

 

[steveg]

Apologies - am unable to delete the dupe posting - first post should be deleted.

 

[Bob_Spidell]

Hmmmmm ... even a Healey 'log' manifold does a better job of distributing mixture than that (four of the plugs look a little lean). My guess is weak spark to #2 and #3--maybe arcing in the distributor cap or cross-firing in the plug wires.

What do I win?

 

[andrea]

Very strange issue Steve-
clean the sparks (very well) and put the number 3 to 4 and 2 to 5 or better to 6-then cover aprox the same mileage -I am very interested on your next photo
My opinion -at this moment- are that your front carb must be controlled --but is better wait the results of this simple test
Problem is strange but not dramatic

 

[DerekJ]

If those Bakerlite caps are anything like the ones AH Spares used to sell already attached to 'bumblebee' wires, they are useless. I'd switch to NGK.

 

[steveg]

Forgot to mention they were factory-gapped to .033. Replaced cap, copper-core wires with metal ends, non-resistor BP6ES plugs gapped to .025":

 

[steveg]

I'm using a DMD manifold which separates the front carb from the rear except for a 3/8" balance tube.

 

[Keoke]

HI Steve

Try changing to Bosch WR7DP Plugs.

En get rid of screw on Bakelite ends-:highly_amused:

 

[steveg]

HI Steve

Try changing to Bosch WR7DP Plugs.

En get rid of screw on Bakelite ends-:highly_amused:

That's a resistor plug - same as the ones in the photos. I'm getting rid of the resistance in the plugs and bakelite caps.

 

[RAC68]

Hi Steve,

I experienced a similar condition back in May of 2010 and posted on the Forum:

In preparation for taking an initial vacuum profile inpreparation for the installation of an oil catch can and PCV, I was surprisedto find a vibrating needle with low readings (7” to 14”of Hg) at a 900RPMidle. When preparing to adjust thevalves, in concert with recommendations, I found cylinders 2 & 3 with blackplugs and a nice brown on all others. Following the valve adjustment and after exchanging black plugs theirlight brown counterparts, I took the car for an hour’s aggressive ride and thenreexamined all plugs. Expecting to findcylinders 2 & 3 turned black, I was surprised to that all plugs were a nicebrown. However, the vacuum gauge stilldisplayed a low reading with a vibrating needle.

Now phase 2. Earlythis morning, after an aggressive run (it is common for me to shift between 4K& 5K RPMs), I ran a compression test. The reading were as follows:

Cylinder	1​	2​	3​	4​	5​	6​
Dry	170​	162​	165​	171​	171​	172​
Wet	210​	200​	210​	183​	183​	183​

Although I did intend to run a leak down test, I never did and the condition disappeared. However, I did adjust the carburetors and reset timing but don't think that really did much to eliminate the problem. Although I don't feel the wet compression was done reliably, the dry test seems to indicate the problematic cylinders did have lower compression ...but still within the 10%. This seems to reflect what you have experiences as well.

Since you seem to find no loss in performance, I would just clean and move the plugs to see if anything changes.

Good luck,
Ray(64BJ8P1)

 

[steveg]

Ray,
That is interesting. I will check the valve adjustments and report back.

 

[steveg]

Checked my valve adjustment (int/exh, thousandths):
#1 - 18/24 ; 2 - 15/15 ; 3 - 18/18 ; 4 - 17/15 ; 5 - 16/14 ; 6 - 12/12
Reset all to 12/12
Doesn't seem too far off.

 

[RAC68]

Steve,

Since our similar issues on the same cylinders seem to have no obvious cause, maybe there is something unique about cylinder 2 and 3 that is not related to the other cylinders. Although our engines were manufactured years apart, they are basically the same. So, what components, constructions, or passages are unique to the area between cylinder 2 and 3? Since, cylinder 2 and 3 are fed by the same carburetor, If a fuel supply issue, why is cylinder 1 not even slightly affected?

Ray(64BJ8P1)

 

[steveg]

Steve,

Since our similar issues on the same cylinders seem to have no obvious cause, maybe there is something unique about cylinder 2 and 3 that is not related to the other cylinders. Although our engines were manufactured years apart, they are basically the same. So, what components, constructions, or passages are unique to the area between cylinder 2 and 3? Since, cylinder 2 and 3 are fed by the same carburetor, If a fuel supply issue, why is cylinder 1 not even slightly affected?

Ray(64BJ8P1)

Maybe we both have oil coming into the cylinders.

 

[vette]

Hi fellows, I just thought I would jump in here to add more fuel to the fire because my engine exhibits the same condition. I don't believe that it is oil in the cylinder as my plugs are more sooty than oily and the engine doesn't blow any blue smoke at all. I do believe that it is a carburation issue. Right now and all this summer my carbs have been running alittle lean as noted by the the piston lift method. But the front carb seems to be alittle richer than the rear. The leaness on the other 4 plugs is because the rear carb is deffinately lean and the No. 1 plug is leaner than 2 & 3 because it is further down the line or at the end of a longer runner than 2 & 3. Front carb being richer than the other but not by much. I believe if I get the carbs equalized and closer to the correct mixture then all cylinders will look much the same. Having said all that, since I put the carbs together after restoration, they are responding to my tuning efforts differently than they had in the past. Thats why they are alittle lean right now. When time permits I am still trying some things with them. Bye the way, My BJ7 has a BJ8 cam and HD8 Carbs.
The HD8 carbs are adjusted with the throttle plates completely closed and the idle speed it set with the slow run screw. the jet and mixture is set with a small screw which pushes a lever against a membrane damper which raises or lowers the jet. Previous to my restoration I had a membrane that was stiffened up and would not allow the jet to come up to it's at rest position. I didn't know that at the time and could not understand why I could not get the engine to idle much below about 900 rpms. since the restoration I decided to make the carburetors right, and that I would tune them with the slow run screws instead of the throttle plates. anyhow to make a story short, I have found that I can not get enough idle speed out of just the slow run screws alone, although I can have it running well at about 400 rpms that is not an ideal senario. So I am experimenting with cracking the throttle plates just a tesch and doing the slow speed adjustment with the slow run screws. In any case I believed that my experimenting with the adjustments of the carbs is what has been causing the difference in the spark plugs. Dave.

 

[RAC68]

Dave,

You bring up a number of issues I have experienced for quite a long time. Although my BJ8s have been rebuilt a number of times since the car was new and can't remember how fast the idle speed was when new, I have had always had difficulty getting my idle down to the 900 RPM vicinity and usually see 1,000 RPMs. As you have mentioned, I don't see any blue smoke and when installing an oil catch can in preparation to install a PCV, did not pull any oil into the container at all. As a result, I eliminated the catch can and postponed plans to install a PCV.

Yes, I do run a little rich on both carburetors and a little high on the idle, however, my performance is very good and pull strongly well past 5K. I don't know if it is the cam, the carbs, or the combination that causes most of us with a BJ8 setup to require a higher idle but I can tell you I would find achieving 400 RPM almost impossible and would like to hear more on how you achieved this idle.

All the best,
Ray (64BJ8P1)

 

[vette]

Hi Ray, I don't know if I would be hi-jacking this post talking about the HD8 carbs verses talking about the spark plug situation. So I will start another thread: "Adjusting HD8 Carbs". Dave.

 

[bob hughes]

Guys

I am experiencing similar problems on my BJ7 with HS 6 carbs this year, after 13 solid years of reasonable service, considering the state of my engine before I rebuilt it in 2013, my car suddenly developed a habit of dropping down to five cylinders. I replaced everything on the ignition side ( points, condenser, coil, but not the rotor arm or dizzy cap and leads) - admittedly a lot of it was 'used stock' and still the problem continued. In desperation I resorted to passing it to my Healey Guru, and he replaced all the ignition side with new parts including dizzy cap and leads, and after two attempts at bringing the car home from his work shop, the problem still existed. I did manage to get home on the second attempt and after checking the plugs I found that the front three were considerably fouled up with soot whilst the back 3 were lean-ish. A quick change of the front three plugs and the engine was running tickety boo again. We were unable to control the carbs judging by the spark plug colouring and I have now replaced the jets and needles on both carbs. Using colour tune again on cylinders 2 and 5 ( I have several) I am now able to control both carbs. It was interesting to see that the new needles appeared fatter at the shoulder than the old needles, but I am still at a lost as to why this problem occurred so abruptly. As I have not yet been able to take the car on a good run, I am not certain that the problem has yet been totally fixed but early indications are looking extremely promising, having carried out a few short but quick runs up my local test track ( the A3M, a dual carriage way to motor way standard runs fairly close to home)



Bob

 

[vette]

Thanks Bob, it is always good to keep each other informed. Let us know your ultimate results. Dave.