Most folks know to remove sharp edges from the combustion chambers to prevent pre-ignition and knock-retard that results in overall engine power loss.

There's one place that many overlook. Can you guess what it is ? think a minute, then scroll down.

























A: exposed spark plug threads. Smoothen those babies, that's a hot portion of the chamber and very sharp if left un-touched.

 

Ok at the risk of sounding foolish how do you know how many to threads are exposed in the head? I understand you would file or grind them off but you could also cause a problem getting them to tread in properly afterwards especially into aluminum. I guess if you knew how far the tread was going into the combustion area you could use additional washers to prevent the plug from going as deep. Dose it really make that big of a difference? I doubt it.

Most of the cars here are driven on the street, this is way over thinking things.

 

I don't know, but sounds like a disastourous recipe for cross threading a cylinder.

 

 

I never heard for this but the only way for this to be done is to do it while the heads are out. I would not take a chance on "guessing".

...and we are back at the airfoil BS, how many ponies is this going to give you?

 

That's why this work should only be attempted by an "over-thinking" and skilled craftsman.

And of course, with the heads on the bench, not on the motor.


Overlooking such seemingly-minor details is a common power-robbing error. Why anyone would smoothen other chamber features but neglect the sharp exposed threads, can only be attributed to negligent oversight, or ignorance.

Add up the effects of this one detail, with about a half dozen others that are commonly overlooked, and guess what you get ?

 

Hey I think I will spend this nice sunny afternoon indexing the plugs so the gaps are all placed the same..

 

Absolutely nothing......except comprimised threads in the head due to deforming the spark plugs.

I think this more likely falls into the "under-thinking" catagory......

 

I'd measure the contact to electrode tip resistance also, to make sure they're substantially the same, hopefully around 15k. Some plugs out there have significant variances in resistance among a set of eight, which can lead to premature failure of solid-state ignition parts, as well as delivering a spark of different intensities to different cylinders.

I'd also smoothen the sharp edge on the insulator side of the plug's threaded tip. More likely than not though, these details won't do much to prevent timing retard and torque loss if you haven't already paid attention and remedied sharps present in other areas of the chamber. )

 

I don't think any reasonable person would disagree with my proposition - it has nothing to do with threads that the plug engages with, rather, the sharp exposed edges of the unused threads at the end of the bore.

Your conclusion doesn't follow from the facts. You all are free to do or not do whatever you want.

Next time, I'll keep my mouth shut, which is why I haven't published my article on this forum.

For an under-thinker, I sure did retire at an early age !! Later.

 

OK power robbing provide a Dyno graph before & after. This is dangerous advise and if done wrong and could lead to serious troubles
Where is the advantage for a under thinking craftsman
So you are also advocating head removal to change plugs

 

I don't need to provide you with anything !! You're far too argumentative, to a guy who was just sharing a tip. Walking down the stairs, if done wrong, could be dangerous also. I don't expect everyone who reads what I write to comprehend, but some do. Others argue. Its the same anywhere you go. Management at one of my client companies provided stiff resistance to one of my ideas which, through my persistence resulted in creation of a new division that netted $ 40MM its first year. It was "not invented here" syndrome. People always resist change, which is why you have to give them only a little bit at a time. I thought spark plug thread sharp edges in the chamber was small enough of a change that it wouldn't raise a stink, but admittedly, I was in error.

You've read it wrong in yet another way. I never said I advocate removing the heads to change plugs, as everyone who reads the foregoing can readily see.

For the benefit of others, and not you, I'm working a set of heads which are presently on the bench, all my vehicles still running just fine and all bearing a different set of heads.

Sheesh. I suggest you read more closely and not read things into messages that aren't there.

 

First I read very closely where did you first say the heads needed to be removed and on a bench to remove threads NOWHERE read your first post it was about pre- innition & spark knock
Second I have no pre-ignition and knock-retard that results in overall engine power loss and untill you can prove other wise your post fails. This is not a place to come on spouting things you can not back up sorry if you don't understand that
Like I stated if I was going to alter plug depth in a head I would add washers to the plug base rather then remove threads

 

It's the way you present your idea that bothers me. Your post makes it sound as though exposed threads has been proven to rob power. Some poor newbie reads your advice, and runs out to the garage and starts grinding off the first few threads of his spark plugs thinking he will get some enormous, or even modest HP gains.

Not to mention the "expense vs. benefits".This mod may look good on paper, but that is as far as it should ever go.

 

You're still off. I never mentioned altering plug depth in head, only removing sharp edges IN THE CHAMBER, as anyone with even the most rudimentary skill in the motor arts recognizes as being a source of pre-ignition. Good luck in your endeavors.

 

This is my point also
People read things on here and trust they are fact
It's not always the case

 

How many people on here do you thingk have there heads removed from there car?
And are worried about the exposed threads I have a guess for you ZERO
Do every one a favor post real facts or have a nice day

 

Exposed threads are proven to rob power, Mike C4. Any hot spots in the chamber which can result in pre-ignition, on knock-retard system equipped vehicles, a single knock in a single cylinder causes timing retard to all cylinders, robbing power. One find many articles written on this, some over 50 years old.

Anyone who went out and ground the threads out of their spark plug holes based on what I wrote, shouldn't have a drivers license in the first place. I disagree with your implied proposition that what I write is dangerous in any way. Of course, matches are dangerous in the hands of idiots too. Shall we lobby Congress to ban matches ?

 

Ok here is the deal post results stock motor
with threads
without threads
walks truth talks

 

My guess is that at some point, most people on this forum will have heads off their engine. So the answer is - nearly everyone.

I don't give a ratsass what people worry about - I was looking for constructive thoughts, yet you chose only to throw rocks and argue.

Do yourself a favor and don't worry about what I write - which is opinion, not fact as you wrongfully assert. You see, opinions by definition are neither right nor wrong, they're just opinions, not facts.
Your attitude and that of others here, in reply to a simple writing concerning sharp edges everyone recognizes as problematic, guarantees that I'll never share any data I generate on this forum.