What spark plugs are you using in your 915 heads?

[Geoff 2]

So WileE, if they [ spark plugs ] bring the engine back to its optimal operating hp, that would mean the engine is making more hp wouldn't it...not less. If you don't want to learn from the results of post #15, that is up to you.

My last comment? Do you mean ' Less misfires means the engine is making more hp'. You must know even less than you think you know....
A misfire caused by a rough idle due to excessive cam overlap is going to produce less hp than an engine with a smooth idling cam, all else being equal. This is reflected by an increase in idle rpm, the rpm increase due to the engine making more hp. What is typically seen is the inverse of this: a hot cam is fitted, engine fired up & idle speed has to be increased for the engine to keep running. Engine will stall if kept at the original idle speed because it is misfiring & not making enough HP to sustain itself.

Below is test by D. Vizard where a change of spark plugs caused a substantial loss of HP.

 

[Geoff 2]

Bob,
Only you can have expertise? And only if it accords with your view of the world? And what is the difference between an ' accurate comment' & a ' substantially accurate comment'?
Pathetic.

 

[Geoff 2]

Sinitro,
To answer your questions, I would say this: The better the ign system, the less a change of spark plug design would make a difference. Ign systems are far from perfect & the fact even in the twilight years of the petrol engine engineers are still experimenting with improving ign [ post #25 ] shows that some think 'outside the box'.

The test below had no misfires but HP increased with a larger plug gaps.

I have messed with ign systems my whole life. In the mid 60s, I was using an SCR, two resistors & a diode to switch coil current in points ign. Not my design, but it gave a smoother idle....which meant less misfires....& by definition more hp. On my 1970 Honda 750, using Champion R6 spark plugs would foul very quickly. The then new NGK plugs with a copper centre electrode did NOT foul.

 

[Geoff 2]

Sinitro,
Forgot to add: I tried Pulstar plugs about 8 yrs ago. Definite improvement in idle quality. My engine has a sizable cam with what I would describe as a medium idle: not smooth, not rough, but 'noticeable'.... Idle was definitely smoother with the Pulstars & that was all that was changed.

Prior to this about 20 yrs back, Bosch brought out the plugs with 4 grd electrodes. I tried them.... [ I had been using NGK BP5S plugs ]. I got surging at about 40-50 mph with the Bosch plugs, didn't know why. Refitted the NGKs, all good...
I cut off two of the grd straps on the Bosch...& no more surging....that I could feel anyway. I refitted the NGKs because I was worried that the Bosch plugs might have been misfiring....but I wasn't detecting it.

Unless you experiment, you will never know...

 

[WileE]

So WileE, if they [ spark plugs ] bring the engine back to its optimal operating hp, that would mean the engine is making more hp wouldn't it...not less. If you don't want to learn from the results of post #15, that is up to you.

My last comment? Do you mean ' Less misfires means the engine is making more hp'. You must know even less than you think you know....

Again, you make comical statements. ^ Where does a spark plug make MORE hp ? It's only reverting it back to it's actual power. It's not making more hp, it's only returning to what it's supposed to. I've learned my knowledge from formal education, not from a silly forum post. What is it that you don't understand. Your last comment, yeah, comparing an engine running on fouled plugs compared to new plugs. The engine is making the hp it was designed to do. Let me bring this down to an elementary level for you: a spark plug only ignites the fuel/air mixture... that is it. That's the only thing it does. It does not increase the power the engine was designed to do. It can't. A particular spark plug may enable the engine to reach it's optimal power capability, but it can't by itself add power.

 

[RJRENTON]

So WileE, if they [ spark plugs ] bring the engine back to its optimal operating hp, that would mean the engine is making more hp wouldn't it...not less. If you don't want to learn from the results of post #15, that is up to you.

My last comment? Do you mean ' Less misfires means the engine is making more hp'. You must know even less than you think you know....
A misfire caused by a rough idle due to excessive cam overlap is going to produce less hp than an engine with a smooth idling cam, all else being equal. This is reflected by an increase in idle rpm, the rpm increase due to the engine making more hp. What is typically seen is the inverse of this: a hot cam is fitted, engine fired up & idle speed has to be increased for the engine to keep running. Engine will stall if kept at the original idle speed because it is misfiring & not making enough HP to sustain itself.

Below is test by D. Vizard where a change of spark plugs caused a substantial loss of HP.

View attachment 1903748

Your # 41 expose is a example of some obscure opinon.....BOB RENTON