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MG MGB Technical - Parade driving fouls plugs

I have a 1965 or 1964 MGB motor and drive train in a 1955 mgtf. I have owned it about a year. I have been working out the bugs for the year. I have been really happy with the way it runs, but over the 4th of July I participated in a parade. The parade was about 2-3 miles long and progressed very slow, there was marchers involved. The weather was 100 degrees and my engine got very hot, but short of boiling. By the time(about an hour) I got to the end of the parade I was having trouble keeping the engine running. Very rough running and seemed to be missing very bad. I took the spark plugs out and two were fouled. I washed the plugs with ether and burned them off. When I reinstalled the plugs it started right up and ran pretty good. I think they were fouled with fuel. On my way home I think the performance was lessor than before. Any ideas as to why this would happen? If I drive it normally, it does real good. The parade was so slow the clutch had to be depressed most of the time. thanks, Don Baker, Burleson, Texas
d.g. baker

Don. One hundred degree heat means less dense air than is found at sea level, barometer of 29.92 and 20 deg C temperatures. This latter is the definition of average air. Thus, with the increase in temperature, you have less dense air resulting in a richer mixture. The result is plug fouling, particularly when driving at low engine rpms and not being able to burn off the fouling. This is why the cars seem to perform better on a cool, slightly moist day--the engine is, truly, running better. Unless it has been tuned to run in very hot weather. In that case, it would run lean under the more "proper" conditions.

I would install a set of new NGB BP6ES plugs, gapped to about .035" and take the car out for a long test drive. Should help to clean out any carbon build up in the combustion chambers from your parade drive.

Les
Les Bengtson

Don,
I was in the USN color guard in 1975, and I marched in a parade in Ennis, for 2-3 miles, during the July holidays. It was hot, and I was in a foul mood, too, by the end of the parade.
Fred Doyen

thanks Les, I had wondered if I needed hotter plugs. Don Baker
d.g. baker

It may also be the fuel overheating in the float bowls causing the floats to sink and thus flooding fuel into the engine and out of the overflow, Do you have a good heat shield and an engine driven fan?

Carl
Carl B

Carl, thanks for responding. The engine does have a heat shield in place and I never smelled raw gasoline during the parade. I beleive there would have been a gasoline smell if the bowls overflowed. Don Baker, Burleson, Texas
d.g. baker

Carl, Sorry I forgot to mention I have installed an engine driven flexfan. When I bought the car it had one half (one blade) of the MGTF fan which was not sufficient. In installing the flex fan (12 inch) I had to move the bottom of the radiator forward 1/2 inch to get enough clearance. In temperatures not so hot the engine will idle for an hour and the temp never goes above 180 degrees. thanks, Don Baker
d.g. baker

I agree with Carl but I don't believe the floats sink, I think the increase in underhood temp causes the fuel to expand and flood the motor. Unfortunately the fuel will run out of the jets and into the motor before it gets high enough to run out the overflow tubes. There is nothing worse for a car then a parade.
John H

Don't do parades...It's not good for our MG's....I turn down requests all the time....
Pete

Mine used to foul it's plugs in traffic queues but presntly is fine after sorted out the mixture and ignition. I also resolved the overheating by fitting the moss shroud on the fan, however I would still not enter a walking speed parade in the car. When we went up to Longbridge in 2005 for the protest parade we split off after the motorway and went past on our own, as we came back the only other MGB in the queue was clearly very unhappy!
Stan Best

Les suggested I put NGB BP6ES plugs. I have NGK BP6ES. I can't find NGB BP6ES listed anywhere. Was this a typo and should have been NGK BP6ES? Also would a hotter plug be what I need? thanks, Don Baker Burleson, Texas
d.g. baker

I too entered a July 4th local parade. The temps were pushing the 90-F range. To help the cooling process, several cars including mine, staggered the parade line to get cooler air into the grille. One needs to realize also, the temperatures are even hotter than ambient due to the line of cars and the extra heat generated by the cars in front of you. I was behind a 77 Corvette and I noticed my temp guage was climbing. When I staggered the parade line, the temp gauge began to drop as I also held the idle around 1500 RPM to increase circulation of coolant.

After the parade, my MGB also was a bit "fussy" but an ice cream run ten miles away cured that.

cheers
Gary :>{D
79mgb
gnhansen

Any prevaling air flow will also make a noticeable difference. At the end of one run while waiting in a line to be interviewed by a commentator we all had a slight tail wind and several people were getting twitchy about their temp gauges. They had to let a bunch of cars through so people weren't waiting as long.
Paul Hunt

I did hear that once (before the abolition of customs posts here) a thermo syphon cooled car was waiting to go through the green channel with predictable consequences for water temp. It was driven up to the deserted red channle and admitted back to England on the basis of nothing to declare except my car is about to boil its water :-)
Stan Best

This thread was discussed between 15/07/2008 and 18/07/2008

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