@jalexquijanoSitting here sipping my PineSol and Quinine I seem to remember previous trouble with one of those center plugs that I thought you cleared up with a new quality (Bosch?) cap and rotor. You already had new wires and plugs. Is this the same problem cylinder and problem that has come back or is it ongoing?

Thanks for the idea Mark. I'm having trouble sleeping these past few weeks so I decided to mix up a warm nightcap of Pine sol topped off with some whipped oven cleaner. Having a hard time finishing this post, getting very slee

14 hours ago, Mark Maras said:

@jalexquijanoSitting here sipping my PineSol and Quinine I seem to remember previous trouble with one of those center plugs that I thought you cleared up with a new quality (Bosch?) cap and rotor. You already had new wires and plugs. Is this the same problem cylinder and problem that has come back or is it ongoing?

I have new wires, new rotor, new cap. I just replaced all those plugs with new ones and do experience change in idle in plug 4. I had this problem previously and with some hard acceleration i could clean that plug to make it go away. 

Edited May 8, 20204 yr by jalexquijano

 Interesting. How many miles do you drive before a new plug in #4 starts to crap out when accelerating? "Back in the day" if we had one cylinder that loaded up a plug more than the others we would use a hotter plug. In your case you'd use a BPR5ES in that cylinder, but the problem with #4 is most likely an electrical or a problem that would show up in a compression test..

 

12 hours ago, Mark Maras said:

 Interesting. How many miles do you drive before a new plug in #4 starts to crap out when accelerating? "Back in the day" if we had one cylinder that loaded up a plug more than the others we would use a hotter plug. In your case you'd use a BPR5ES in that cylinder, but the problem with #4 is most likely an electrical or a problem that would show up in a compression test..

 

Last compression test results

 Those numbers are excellent. I remember going down this road in the past. Deja Vu all over again. I can't think of any other reason for the dark #4 plug than electrical and it has to be somewhere in the cap, rotor (unlikely), or the wire. As I recall you replaced the cap and rotor with a good brand along with many sets of plugs. The wires were fairly new and of good quality but I'd start looking at #4 wire connections, both ends and measure the resistance in all the wires to see if #4 is going bad before the others. Meanwhile how is your float project going?

How about a bad valve seal?  And, the oil rings scrape oil, the compression rings create pressure.  You can have a bad oil ring with good compression rings.  A possibility.

This is an old California Datsun engine, maybe Datsun Parts LLC.  Quality was suspected from the start.  I'd put that hotter plug in and just drive it.

1 hour ago, Zed Head said:

This is an old California Datsun engine, maybe Datsun Parts LLC.  Quality was suspected from the start. 

Bingo!

@jalexquijano If you're going to try the hotter plug in #4, I'd use a BP5ES not a BP5RES. The rest of your plugs are BP6ES. No need to throw a resister plug into the mix.

31 minutes ago, Mark Maras said:

@jalexquijano If you're going to try the hotter plug in #4, I'd use a BP5ES not a BP5RES. The rest of your plugs are BP6ES. No need to throw a resister plug into the mix.

I.have a new set of bp5es. What will i achieve with that? Wouldnt using such plug value damage the engine?

 Heck, you're all set. No damage to the engine. The hotter plug extends into the combustion chamber a bit farther is all.

Learned something new. Thanks Mark!

Is it the porcelain tip part or the overall length of the plug? Gap stays the same?