I have a 68 E-type with the 2 Stromberg set up. Recently #4 spark plug (#3 from the rear of the engine) has started occasionally carbon fouling. All the rest have the nice light brown color. I know this indicates a rich condition on #4 but seems like at least all 3 rear plugs fed by the rear carb would show similar deposits. Anyone know if this indicates the rear carb is not set right since #4 appears to be most in line with it or should I look elsewhere too for the problem ?

David Barnes
68 E-Type FHC

Submitted by NE23-54945 on Sun, 02/09/2014 - 19:28

Could be, make sure the double butterflies are also closing all the way in the secondary manifold.
The overall set up, is really not good.
My 70 went to triple su's 25 years ago.for a reason.
Back in the day people would cut out the butterflies, which would then dump unburnt gas into the cylinders, also the distributor is VACCUUM RETARD , NOT ADVANCE due to the set up.....
Your mild fouling is really not bad if its running okay. If not its all of the above, make sure once again the butterflies are in sync with closing or you will have leak downs.........
It REALLY was a bad setup.
GTJOEY1314

Submitted by DavidBarnes71@… on Sun, 02/09/2014 - 17:07

Today I pulled the tops off both carbs. The spring load on the rear carb metering needle to bias it toward the engine seems much weaker than it does on the front carb. Since the rear carb seems most in line with the #4 cyl anyone think this could be the source of a rich condition on that cyl ?

David Barnes
68 E-Type FHC

Submitted by DavidBarnes71@… on Sat, 02/08/2014 - 17:36

Joseph and Michael thanks very much. I put in new Champion N12YC plugs and just got back from a 15 minute drive around the neighborhood where I romped on it pretty good off the line a few times. Still dry black deposits on #4 so still seems like running rich there. If I let it idle in the garage it looks a little wet but turns dry when I run it on the road. I checked the breather screen about 6 months ago and it was clean but I will check it again along with the pipe and switch the #4 plug on the off chance the new one I put in is weak. Both carbs are springing back so the stops are resting on the idle adjustment screws. The car is running and idling great but if it keeps up the same recent trend it will load up #4 after awhile and start missing.

David Barnes
68 E-Type FHC

Submitted by NE23-54945 on Sat, 02/08/2014 - 12:39

Just a shot but also check that your front breather screen is clean and the return pipe for blow by is also clean and not blocked up.
They run heavy in the blow by and always need a good cleaning.
Also make sure in the filter holder its not gummy , after you replaced the floats, load up is common as well.
Just a shot, Ive driven mine 5,000 miles each year and they still load a little, kick up the revs and also check that your throttle shaft springs are returning ALL THE WAY. Good luck.
GTJOEY1314

Submitted by DavidBarnes71@… on Sun, 02/02/2014 - 13:07

Thanks very much George. I checked the compression and all 6 cyl are in the 120-125 range with the offending #4 being one of the higher ones. I guess this is a bit low on all of them but are the same values as when I bought the car in 2000. It idles smooth and runs strong for days until it fouls that plug. I swapped the plug wire with one of the good cyl and put in new Champion N12YC plugs in place of Bosch plugs that were in it. The spark looks strong on either type plug. Looks like a little oil on #4 too so may have a failing valve or guide but still think I may be running rich.

You say the front carb would have an effect on #4 from the front of the engine ? The front carb was the last one that had a leaking float. Perhaps I did not get things set properly when I put the front carb back together after replacing the float. If so I will check on that next if the new plugs do not make an improvement after I drive it a few days.

David Barnes
68 E-Type FHC

Submitted by SE98-32482CJ on Sat, 02/01/2014 - 09:00

David I would check compression and make sure that cylinder is not low. If not I would check the spark strength on that plug. You might then check the float level on the front carb as a slight flooding issue in the front could affect 4 more than 5 or 6 but I think that would be rare. Let us know.