www.lj10.com

Thank you, redsnodog, that was interesting.

hmm, the lj10 plugs are supposed to be a NGK b7hz but the parts house said all they could supply me with was a b7hs. I looked at a chart to see what the letters and numbers mean in the designation. the z has a 1mm wider diameter center electrode than the s does so then theoretically does that make the b7hs hotter than the b7hz, or do they compensate for that in the resistance? after what Redsnodog said I think its hotter and thats why I brought it up, so we can discuss it. maybe this topic is somewhere else here, I dunno.

Hi Jimny,in regards to your question,Neither of those plugs will be hotter or cooler than the other.I 'm sure that version plug[hz] would be thought of as a longer life plug.The spark is said to jump from one sharpest edge to the other.Since the hz plug has a larger diameter center electrode,the "spark area" or circumference would be increased some.This is also the reason why the other plug variations like the "V" groove plug,the split fire plug etc were offered.They offered more spark area and so ,in theory at least,they could operate efficiently longer.As the electrodes wear to a more round shape the electrical requirement/load to jump the gap goes up and up until the plug starts to misfire. misfires.The spark starts to erode away the sharp edge and travels down the electrodes looking for the next sharpest and shortest distance.It's amazing the whole thing works as well as it does

Thanks for the info redsnodog, but I don't think I asked a question, maybe it was someone else.

Oops,right you are, it was Idahopaul

...and I was too lazy to look through the other posts to see who it was.

Idahopaul wrote:hmm, the lj10 plugs are supposed to be a NGK b7hz but the parts house said all they could supply me with was a b7hs. I looked at a chart to see what the letters and numbers mean in the designation. the z has a 1mm wider diameter center electrode than the s does so then theoretically does that make the b7hs hotter than the b7hz, or do they compensate for that in the resistance? after what Redsnodog said I think its hotter and thats why I brought it up, so we can discuss it. maybe this topic is somewhere else here, I dunno.

Paul,

B7HS is the proper spark plug. I've never heard of B7HZ; must be a typo in one of your manuals!

Great info Redsnodog! I worked in auto parts a long time ago, and a lot of people who I worked with couldn't understand why certain vehicles seemed to run better on Autolite plugs, some worked better on NGK's, and some better on Champion. I tried to explain to them that "cross-reference" is a relative term in spark plugs, given the different specs that different mannufacturers use for their heat ranges, but you explain it much better than I think I ever did!

and some better on Champion

Never heard of such a thing! LOL Just kidding.

When we rebuilt two 1959 Cadillacs I rebuilt both engines and was trying to start the first one and it wouldn't start, so I thought I had the distributor 180 degrees off, so I re-stabbed it and still would not start so I re-stabbed the dist again and still nothing and my dad said "you know, I had problems with Champion plugs before", so I went to the parts store and got AC plugs and it started right up. They were the 'cross referenced' plugs that was supposed to be for that car but they just didn't want to fire right.

It wasn't long after that I went to a seminar at a local parts store about Spark Plugs and all the in's and out's, it was very interesting and I learned a lot, I didn't think there was that much into plugs but there is, just like what redsnodog has posted.

I got the spark plug info from the lj10 service manual on this forum, maybe when it was scanned the computer misprinted it? http://www.lj10.com/lj10service/6.htm" onclick="window.open(this.href);return false;
interesting....

One of the many typos that can be found in LJ manuals. I guess that's what happens when the proofreader doesn't speak English!

stevec wrote:One of the many typos that can be found in LJ manuals. I guess that's what happens when the proofreader doesn't speak English!

Couldn't be Jr., he's too young.

Here is something all should read, it's very interesting.



http://www.ngksparkplugs.com/tech_suppo ... p?mode=nml" onclick="window.open(this.href);return false;

Great info there jimny.

Just a quick thought in reference to the foul plugs or burn holes in pistons comment has anyone had a head done on one of these? I have a couple spares and plan to have one done asap. By looking at mine I can tell you the combustion chamber is huge and way to deep and piston to head clearance is huge as well, these things lead to a long mediocre life of low compression, no power, fouling plugs and will be prone to detonation if you do attempt to make power. Getting the squish down around 40 thousands and resizing the chamber would make this motor better in every aspect but one. It will have higher compression which would put more stress on the bottom ends, although these have very stout cranks from what I am told. Remember this is sixties tech, two strokes have come a long ways since then esp in the head and porting department. Not to mention the expansion chamber and carb. Basically this motor has the potential to reliably make over double its stock power. Sorry for being so long winded.