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MG MGB GT V8 Factory Originals Technical - What sparkplugs for a 1988 rover 3.5l

I was looking at Summit Racing at spark plugs and saw something that puzzles me.

If you look up the engine as a Rover 3.5l V8, you get plugs that have a reach of 3/4".
[http://store.summitracing.com/egnsearch.asp?SearchType=....90853+115+4294842813]

If you look up the Buick 215, you get plugs that have a .380 or a .500 reach.
[http://store.summitracing.com/egnsearch.asp?SearchType=....90854+115+4294842813]

I thought that the heads were the same. I have a Rover (88 Range Rover) 3.5l but I think I asked for plugs for the Buick at NAPA.

Do I have the wrong plugs in my engine? (It has 10.25:1 cr pistons)

I will pull a plug tomorrow and get the type and number as well as the reach. Right now, I can't remember if they were long or short reach.

Does anyone have a head off a 88 Rover to measure the proper reach?

Richard



Richard Morris

Richard,
I have several years of Champion Spark plug catalogues and they do not clear up the confusion.
1971 lists UL-15Y for a Buick/Olds/Pontiac (4V - high compr), UL-12Y for(2V-low compr) and an L-87Y for Rover.
1975 lists RL-12Y for BOP and L-92Y for Rover.
1980 lists RL-87Y for BOP and L-87Y for (1971) and L-92Y ('72 - '75)Rover.
1986 lists L-87YC for BOP and RN-11YC for Rover.
I can rationalize changes in heat range, electrode or nose design or the addition of resistor feature but to go from a 14mm 1/2" reach (L) to 14mm 3/4" (N)reach, without a head/piston redesign, requires some investigation.
For the record, I ran RL-87YC plugs in my 10.25:1 CR Olds.
Graham Creswick

Richard
The reach depends on the cylinder heads used. I am sorry that I don't have my books to hand but from memory the 137BHP engines in the landrover and MG took short reach plugs - the 150+ BHP engines took long reach.

Some clown had put long reach into my MG - it didn't seem to make any difference.

Roger
RMW

Pre ’76 heads used the ½" plugs, post ‘76 has larger valves and ¾" plugs. An ’88 head will definitely use the longer plug.

Geoff
Geoff King

Richard,

Most recommended plug NGK BPR6ES which is for the later heads. If you are using electronic ignition the gap from memory should be 40Thou.

Kevin.
Kevin Jackson

This thread was discussed on 16/11/2006

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