TR4/4A TR4A Spark Plugs

The Moss book says to use Champion L87Y spark plugs but when I went to change them the previous owner used Champion J12YC. Is one hotter than the other or better than the other? Thanks

Stinger, the J12YC (TR6)is not even close to the right one, too long for a start. The L87Y is right, gap .025 unless you have electric pick up then you can go .030 with no problem and .032 with a high performance coil.

Wayne

I think it's the other way around, my chart shows the J12YC as 3/8" reach, while L87Y is 1/2" reach. If the too-short plugs have been in there for very long, you'll probably want to chase the plug threads (using a special purpose tool that is readily available at Sears or any good auto parts store).

And, just my opinion, but I would stick with the stock plug gap. High performance coils are all well and fine, but high performance rotors and distributor caps are harder to come by. A bigger gap means more electrical stress on the rotor, and rotor failures seem to be common these days.

Personally, I've been running Bosch Platinum plugs, WR7BP, ever since Ken Gillanders reported finding another 5 hp on the dyno with them. Probably make no difference at all to my relatively stock TR3 motor, but they do seem to work well and be more resistant to fouling than conventional plugs.

Randall, not often I disagree with you, but the N12Y and all N series are 3/4 reach, which on a TR4 can cause clearance problems. Sorry, but just wanted to clear it up for other readers.

I do agree on the hot coil issue giving rotor blow ups and as has been noted heavy duty ones are available.

Wayne

trrdster2000 said:

Randall, not often I disagree with you, but the N12Y and all N series are 3/4 reach,

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One of us is missing something, Wayne.

I agree about the N12Y being 3/4" reach. But the plug mentioned above is a <span style="font-weight: bold">J</span>12YC, not N12Y..

At least everyone is in agreement..........>

All, I would like to blame it on these 69 year old eyes but I had my $3.98 best pair of glasses on and a real exaime next Wednesday might help. I wonder if they do brain transplants. Just trying to do too many things

Sorry, Wayne

Get NGKBP6HS....forget about the Champions...their 1/2 reach. NGK's are way better than the Champions that just arent what they used to be quality wise.

karls59tr said:

Get NGKBP6HS....forget about the Champions...their 1/2 reach. NGK's are way better than the Champions that just arent what they used to be quality wise.

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Maybe not, but they've been ok for me. On the other hand, I've a decent stash of NOS Champions...and a few NOS Lodge and KLG plugs. :wink: