Correct Spark Plugs for Bristol

[prototypefan]

What are the correct plugs for a D2 Bristol engine?
   
   Lodge 2HL10  with short thread and exposed electrode
   NGK  C6HSA   with short thread and exposed electrode
   Lodge  10RL49 with long thread and non exposed electrode
   
   Thanks in advance!

[AC Ace Bristol]

Fred
   
   Welcome to the ACOC Forum
   
   
   I run my 100D2 on   NGK C7HSA plugs,  no problems over the past 10 /11 years.  Compression approx 10.2
   
   Used in UK and Europe, can pink on steep inclines on poor quality petrol hence use of additive.
   
   Hopefully  info of use.
   
   What's the 100D2 in ..  Ace Bristol BEX???
   
   
   Keith..[]

[prototypefan]

Thanks for the welcome Keith,
   
   Two different Bristol 100D2 engines, one in BEX1210, the other in a Tojeiro TAD 2/55.
   
   Both of these were running the shorter reach plugs but BEX1210 had some used long reach Lodge 10RL49's in the spares.
   
   Did the factory spec the long reach originally? The cylinder head sure could use the longer reach plug.
   
   Cheers,  Fred

[AC Ace Bristol]

Fred
   
   Nice pair of Cars, the ExM Gessler Ace BEX1210 and the 2/55 Tojeiro-Turner  which has a fasinating full history, reference  Toj..... John Tojeiro and his cars.. ( page  75 )
   
   Getting Back to:- PLUGS.
   
   The NGK  C7HSA has a 12 mm reach same as  CR7HIX ( Iradium upgrade -resisted plug)
   
   C7E   has a 19mm reach and the CR7EIX (Iradium upgrade)
   
   A thread on the subject of Plugs of various reach was on this Forum some time ago, might be worth scrolling back into the Forum Archives.
   
   Your 6s are softer than the 7s I use and therefore have a higher heat rating.
   
   
   Extract/s from NGK  Catalogue 2009.
   
   NGK'S Heart of COPPER
   
   Copper wire used in place of the Iron core in conventional plugs is the secret of NGKs Wide Heat Range.  Coppers superior heat conductivity dissipates heat quiker.  It cools the electrode tip and insulator which prevents hot spots that could cause pre-ignition.
   
   HEAT RANGE & HEAT DISSIPATION
   
   Spark plugs do not produce heat in the combustionchamber.
   One of the functions of the spark plug is to dissipate some of the heat produced during combustion. This is mostly transferred into the cylinder head.  The "Heat Range" indicates the measure of the spark plugs ability to do this. A "hot" spark plug is designed to maintain a sufficientl high temperature at the insulator nose to burn off carbon and oil deposits.
   A "cold" spark plug is designed to allow a faster transfer of heat to the cylinder head thus preventing overheating and premature fialure.
   
   Firing end Temperature
   
   FOULING AREA.   ..  Idle Temp....  150 /250 degrees C
   Carbon accumulates on the insulator nose forming a leakage path to earth.  Engine misfires, bad starting and poor acceleration.
   
   OPTIMUM TEMP AREA.  ..   450/ 870 degrees C
   The insulator is brown or light grey.
   
   
   OVER HEATING AREA.  ..    870 degrees C and above.
   The insulator is white and sometimes blistered. If insulator is over 870C pre ignition may occur. Engine power reduced and piston may be damaged.
   
   Keith.