Hi All,
I have a '72 B20 engine that I bought and I've put in a 544. This motor has had a cam,head work done by the precious owner. I put a electronic ignition, and a street header on it. It also has the SU's and they have been reworked. I'm getting to the point where I will be trying to start it for the first time soon. Has anyone done anything close to these mods that can recommend a good plug for this set-up?
Thanks
Mike

I'd just like to add a note to the responses that have already been made. There is a question regarding resistor or non-resister type plugs. Remember, when these motors were new they came with copper core ignition wires and a screw on resistor (brown bakelite housing--or the later type with a metal shield as on early B21/23 motors). If you have resistor wires or plugs you don't need the screw-on type as well-- or -- conversely -- if you have non-resistor plugs--you'll need a screw-on resistors or resistor type wires. Personally I prefer NGK plugs after working at Honda where the method to set carb float height is to use the external adjustment to flood the engine then back off a set amount. Even after flooding, the motors restarted without problems. -- Dave

Start with the resistor version (consideration for other drivers nearby, in case you have no radio) of the stock heat range in Bosch, Beru, Autolite or NGK plain copper type. Many have the opinion to avoid Champion brand. After some running, pull the plugs and examine the colour of the tips;
-> Light to medium tan or beige is perfect.
-> Very clean, recheck a few hundred miles later.
-> If too clean, or there is any signs of blistering, then move one heat range colder.
-> If dark brown or any shade of black... a heat range hotter.

Euro & Japanese brands: higher number is colder
US brands: higher number is hotter

The final answer will depend not so much on your "specs", but on carburetion, timing advance curve, the fuel and also your driving style.

Depends on cranking compression & how much HP your engine makes. I like NGK plugs & always use BP7HS. If your engine runs OK on low octane, then the colder BP6HS would be better.

A BP6xx is HOTTER, not colder, than BP7xx. Only American (Autolite, Motorcraft, Champion, AC) mfgrs use higher number = higher heat range. Japan and European is opposite.

Correct, I typed hotter instead of colder.

I got the plugs the right way around, 7 for high compression and/or high output, 6 for low compression engines.

Hello,

As Walrus and Matt already stated, both NGK BP6HS and Bosch Supers work very well. I've used both and had absolutely zero problems with either. I tried iridium plugs, and while iridiums made a huge difference in my old Nissan Sentra, I noticed no improvement when installed on the B20. I've heard many, many bad things about "crossfire" type spark plugs.

I have put NGK BP6HS spark plugs in my 122S that has a B20 engine.. The engine came from a 1972 1800 that was fuel injected but now has a Weber carb.. The plugs seem to have a white ash on them now.. The car runs great and now starts great.. The old plugs had a brownish color to them so I would assume the air mixture is set right.. I thought I would try the NGK BP6HS plugs to see if it would improve the starting which it did.... I don`t see any blisters or glace , just white ash... Is this white ash normal ??

You might possibly be running a bit weak overall but modern fuels don't burn the same way they did when those plug check photos were taken years ago. Example, the plug pictures in the Haynes manuals. NGK BP6HS is a good commonly used plug in our engines for average road use. If you are running the downdraught Weber kit, they aren't the easiest to jet properly.

This 122S is nicely tuned !! https://www.youtube.com/watch?v=pjg50f0-8ag&ab_channel=TARGATasmania

Thanks for the reply !! The car runs and starts great.. The old plugs had the tan color so the mixture setting etc. must have been alright.. The NGK BP6HS plugs must just run hotter,, I just don`t want to do any harm to the engine.. I do have the weber carb as well.. I may try to set the air mixture to a little richer and just see what the plugs look then..

Your statement--"set the mixture a little richer" leads me to think you don not realize what must be done to change the mixture. The screw at the base of the Weber controls fuel at idle--and that's it. You need to change jets to change running mixture. - Dave

IPD has long recommended NGK BP6HS. I have used them and been happy with them.
They are also reasonable in price.
--
George Downs, Bartlesville, Heart of the USA!

Hey, George,

you are recommending a non-resistor plug? Not the BPR6Es?

I already have some engine static/noise on my AM radio scale. Won't the non-resistor plug worsen this?

How are you going to pay attention to the hearty throb when those dual carbs
open wide (Tom Demarest) with the RADIO on??
Frankly, with valve noise, exhaust and such I have rarely used a radio in a
B20 powered car. It has been interesting enough without it.
--
George Downs, Bartlesville, Heart of the USA!

of course.... every backyard hack mechanic has their opinions on spark plugs.. myself included. I like Bosch Supers for B20s. Nothing special... no platinum nothing. Just plain old copper core Bosch Supers.

I've had bad luck with *way* premature fouling with Nippendenso plugs. I won't buy them again.

At the end of the day though.. for a fresh engine like you have.. it probably really doesn't matter. I'm sure you'll hear good things about NKG, and they too would be fine I'm sure.

--
-Matt I ♥ my ♂