Topic: spark plug indexing

[Don R]

   Could apply to our motorcycles but I'm learning on a V8. Trying to aim the open side of the plug towards the intake valve. (My last engine had to be indexed to avoid closing the gap by contact with the piston)
  I've been frustrated with plug indexing on my race car for years, and couple years ago bought extra sets of plugs to swap them around until I liked the result. Now I'm left with the ones that weren't optimal.
  I decided to use my brain for a change, the plugs are 14mmx1.25 which is close to .050 thread per inch. By measuring my 3 color indexing washers it seems they are .048, .050 and .060. all frustratingly close to one full turn. No wonder.
  I went online and found some washers in smaller thicknesses that can actually change the index in fractions of turns. .019, .024, .034" so like 1/3 turn, 1/2 turn and 2/3 of a turn?
  I can imagine the seller of my many years old index washers having a good laugh at my expense.

[BenelliSEI]

Don….. I went through this for a race motor, years ago. Then decided there were better ways to spend my time!

[Tracksnblades1]

Has the spark plug indexing position changed??

The reason I asked was because “Smokey” taught on SBCs and BBCs
to position spark plug gap towards the exhaust valve.. in his power secrets..
on “How to build a SBC” which required in the text to read the “How to build a BBC”,
because he wrote a lot was the same..or visa versa…🤔

Justifying the position because the Air/fuel mixture by the exhaust valve is hotter and more apt
to auto ignite (detonate) by the radiated heat of an approaching (propagating) flame front.

And when burning very large amounts of fuel (think alcohol) the ground strap helps shield and keeps
 the gap dryer, instead being soaked wet by every incoming intake charge..

🤔

[Tracksnblades1]

Accel used to offer soft selective washers advertised as indexing spark plug washers.
Later they offered very soft copper washers for the R44TS tapered seat spark plugs.
That you could tighten until they indexed and then they work hardened and heat cycled hard..

[PeWe]

So the gap can face towards ex valve on a CB750?
I have faced them towards in valve.

When I did that I noticed more even throttle response, smoother. But could be something else too.

I ordered ca 7-8 boxes of Denso and NGK plugs to my CB750 from UK before Brexit. The cost was ca 1/3 of the cost here.
So far mark and test method. I  accepted the gap aiming ca +/- 20 degrees  towards  the in valve center.

So, ex side can be better?

I had to search on the Internet and found both in and ex valve directions
Avoid piston/valves another important reason.

Here one informative link.
https://www.enginelabs.com/engine-tech/discussing-spark-plug-indexing-methods-and-techniques-with-brisk-usa/

Maybe I have to test the ex valve direction on my K6 and have a ride

[Tracksnblades1]

PeWe,

I watched your video.
Didn’t recognize the speaker..
I understood what he was saying and what was written in the article.

Guessing their thought is there is more air/ fuel by the intake…?

I’ve never indexed plugs towards the intake valves…perhaps I’ll try that..
I don’t think I believe there is more air/fuel at the intake valve..
The intake valve has already shut prior to the compression/ignition stroke…

We were all formally taught proper quench/squish clearance on the compression stroke imparts high velocity turbulence into the chamber aiding in a more complete homogeneous mixture.. If turbulence is present through proper
squish clearance, I don’t see how one could theorize where the best air/fuel mixture is without testing or dyno comparisons.  I’m still having trouble with an 8,000 rpm intake charge just hanging out or stratifying by the intake valve...🤔.  😳

We all were also formally taught an ideal size fuel droplet generated by the carburetor would not vaporize into
a complete vapor until it was subjected to the heat of combustion. Further aiding the engine’s volumetric
effeicency by the fuel remaining in a droplet(liquid) instead of prematurely vaporizing and expanding(exponentially)
in the intake track.. (cold intake vs factory heated intakes).. And additionally what fuel did vaporize in the intake due to the pressure differential would help cool the intake air, through the latent heat of evaporation (heat absorption) of the liquid gasoline changing states to a vapor…. ....providing a denser intake charge..

I’m still thinking Ole Smokey and Zora had this right..🤔
They were responsible for the original angle plug cylinder head moving the spark plug closer to the exhaust valve from it’s original position….regardless of the gap’s orientation…🤔

A feature that’s still retained in modern OEM and aftermarket cylinder head offerings…

[PeWe]

I did not watch the video, only read the text.

Funny, I said to myself after my last ride "what to test now on my rides when carbs, charging voltage and shocks + forks are adjusted and working fine?"

Sparkplugs!
- Maybe equal orientation is one thing for an evenly running engine?
- Next the direction for power?

Towards EX valves next

[Don R]

 We solved the problem on jr. dragsters by running a surface gap plug. I knew the compression was high enough when I could read the pistons part number on the inside of the combustion chamber.
 I need to have a look at the chamber on my old spiderwebb cracked heads and think this through.
 While looking at a set of old plugs that were in those heads I'm seeing the red deposits caused by the coolant leaking. My engine guy was sure my crankcase moisture issue was caused by the vacuum pump relief valve being on a valve cover, my comeback was then why does Barrs leak cure it? I moved the relief valve to the pump about the same time the defective heads gave up.

[NitroHunter]

I knew the compression was high enough when I could read the pistons part number on the inside of the combustion chamber.

[simon#42]

i spent a day on the dyno trying to prove this works but failed . i liked the idea but on 6 different engines it made no measurable difference .

[willbird]

i spent a day on the dyno trying to prove this works but failed . i liked the idea but on 6 different engines it made no measurable difference .

I had heard this also from a guy who does a LOT of engine dyno work across a lot of different admittedly typically pushrod Detroit mfg v8. If it was worth even 3-5hp for say 350 cu inches everybody would do IMHO.



Bill

[Don R]

 So, the only good reason to do it is to miss the dome on the piston.
 My 383ci/684 hp SBC had such big domes it wanted 41* of advance. My engine builder said he thought it took a while for the flame front to travel around and over them. He lectured me about the unocal gas I brought, but it made 3 more hp than his VP.

[Tracksnblades1]

We solved the problem on jr. dragsters by running a surface gap plug. I knew the compression was high enough when I could read the pistons part number on the inside of the combustion chamber.
 I need to have a look at the chamber on my old spiderwebb cracked heads and think this through.
 While looking at a set of old plugs that were in those heads I'm seeing the red deposits caused by the coolant leaking. My engine guy was sure my crankcase moisture issue was caused by the vacuum pump relief valve being on a valve cover, my comeback was then why does Barrs leak cure it? I moved the relief valve to the pump about the same time the defective heads gave up.

Maximum squish/quench….😁

i spent a day on the dyno trying to prove this works but failed . i liked the idea but on 6 different engines it made no measurable difference .

 I always wondered.. the only thing I thought I noticed was a very good consistent idle and off idle slow throttle transition….with a long duration cam…

But thats well below what a dyno operator would do here…our local guy starts at 3000….It could’ve just been hopeful after spending a couple hours with the engine lifted up to get to them all..

[willbird]

So, the only good reason to do it is to miss the dome on the piston.
 My 383ci/684 hp SBC had such big domes it wanted 41* of advance. My engine builder said he thought it took a while for the flame front to travel around and over them. He lectured me about the unocal gas I brought, but it made 3 more hp than his VP.

Kind of odd that we were able to get 14:1 on sprint car engines without anything like that going on ?? The longer the stroke the smaller the dome needs to be ?? The guy I helped race started with iron heads but quickly went to Brodix spread port. Circa 1980. Best dry slick 3/8 mile engine the guy ever had was a 327 with aluminum rods. He swapped mags and put a cast iron distro gear on a billet cam and munched the gear hot lapping, broke one rod and it made a window in the block. he sold the 7 rods and pistons to a guy who ran stock body cars, guy bought one rod and piston and ran them for years. Drag race guy built that engine and it's cam started to come alive about 7500rpm :-).



Bill

[Don R]

 I think our piston vs spark plug situation was a miss match between the Brodix Track 1 plug location and the particular piston we had. We also ran race gas. My engine guy was a Super Stock racer who could make a small block run. Back then, people didn't believe our 383 really made 684 hp but we had a stack of 8.0 at 165 mph time slips to back it up.
 I took in the used roller cam when we built the engine, he didn't think it was a good idea but after he checked it, he didn't want to tell me the specs. I think it became his house grind. 

[Tracksnblades1]

So, the only good reason to do it is to miss the dome on the piston.
 My 383ci/684 hp SBC had such big domes it wanted 41* of advance. My engine builder said he thought it took a while for the flame front to travel around and over them. He lectured me about the unocal gas I brought, but it made 3 more hp than his VP.

Kind of odd that we were able to get 14:1 on sprint car engines without anything like that going on ?? The longer the stroke the smaller the dome needs to be ?? The guy I helped race started with iron heads but quickly went to Brodix spread port. Circa 1980. Best dry slick 3/8 mile engine the guy ever had was a 327 with aluminum rods. He swapped mags and put a cast iron distro gear on a billet cam and munched the gear hot lapping, broke one rod and it made a window in the block. he sold the 7 rods and pistons to a guy who ran stock body cars, guy bought one rod and piston and ran them for years. Drag race guy built that engine and it's cam started to come alive about 7500rpm :-).



Bill

Those old small journal 327s could wind to high heaven without much cam..😇

A stock flat top piston 400sbc wearing a set of 283 power pack heads with a 0.038 total squish/quench
was as close to 12:1 that all factory production OEM parts could go.. Not sure about 265sbc heads. Never experimented with those..
Had to have a oil tube intake and a lifter valley crankcase vent for those valve covers..

[Don R]

 We turned the 383 to shift at 9,300 once when I accidentally shifted on time, not rpm and the rev limiter had a bad chip in it. It didn't seem to mind. What killed it was the over-tightened tapered pipe plugs in the valley return holes. The crack went from plug to plug zigzagging side to side to back etc. then down the main web and through the main cap.
 It was running but slowed a tenth and a half.

[willbird]

We turned the 383 to shift at 9,300 once when I accidentally shifted on time, not rpm and the rev limiter had a bad chip in it. It didn't seem to mind. What killed it was the over-tightened tapered pipe plugs in the valley return holes. The crack went from plug to plug zigzagging side to side to back etc. then down the main web and through the main cap.
 It was running but slowed a tenth and a half.

There were a few folks who advocated back in the late 1980's for putting short pipe nipples in those valley drains up the middle to reduce windage on the crank and connecting rods. Your deal there is kinda crazy, with a good sealant the pipe plugs could have just been hand tight and sealed up fine. Most loctite products would have done the job :-).

Bill

[MRieck]

We solved the problem on jr. dragsters by running a surface gap plug. I knew the compression was high enough when I could read the pistons part number on the inside of the combustion chamber.
 I need to have a look at the chamber on my old spiderwebb cracked heads and think this through.
 While looking at a set of old plugs that were in those heads I'm seeing the red deposits caused by the coolant leaking. My engine guy was sure my crankcase moisture issue was caused by the vacuum pump relief valve being on a valve cover, my comeback was then why does Barrs leak cure it? I moved the relief valve to the pump about the same time the defective heads gave up.

I saw that with the R6 road race engines I built...squish was about .025 or so with Carrillo's. Some people ran it tighter than that but I'm not a fan of building bombs rather than engines. Those things were shifting at 15,500 or so too.
I tried the indexing thing and have .020, .030 and .040 washers (if memory serves correct). It looked cool when looking at the chambers but that was about it. I think shortening the electrode had more of an effect but never tested it on a chassis dyno and that was before Iridium plugs.
 I've heard/read ...as have other fellas on here I'm sure....about different port finishes.... rough, super rough, dimpled, chiseled and others I've forgotten about being the greatest thing since ice cream. If one finish was absolutely proven to give that 1 or 2% extra everybody would copy it and do it.....hard to keep secrets.
 Attention to detail and using proven parts/ideas is the key to success IMO.

[Don R]

  The dragster gets NGK's with the ground strap that ends at the middle of the center electrode. The engine came with -10's in it but we had a hard time getting it warmed up. I went to -9's and it warms up clean now. I put new plugs in it just because the old ones had two short seasons on them. I'll keep indexing just because it makes me pay attention to things a little more. I'm thinking the .050 shims are just designed to pull the plug's threads back out of the chamber.

[willbird]

 I've heard/read ...as have other fellas on here I'm sure....about different port finishes.... rough, super rough, dimpled, chiseled and others I've forgotten about being the greatest thing since ice cream. If one finish was absolutely proven to give that 1 or 2% extra everybody would copy it and do it.....hard to keep secrets.
 Attention to detail and using proven parts/ideas is the key to success IMO.

The Smokey Yunick trick of painting the ports with lacquer and then wet sanding them to get a smooth port without modifying the cylinder head might be worth a try LOL, if a glassy smooth port was what a guy was seeking.

Bill

[Tracksnblades1]

We solved the problem on jr. dragsters by running a surface gap plug. I knew the compression was high enough when I could read the pistons part number on the inside of the combustion chamber.
 I need to have a look at the chamber on my old spiderwebb cracked heads and think this through.
 While looking at a set of old plugs that were in those heads I'm seeing the red deposits caused by the coolant leaking. My engine guy was sure my crankcase moisture issue was caused by the vacuum pump relief valve being on a valve cover, my comeback was then why does Barrs leak cure it? I moved the relief valve to the pump about the same time the defective heads gave up.

I saw that with the R6 road race engines I built...squish was about .025 or so with Carrillo's. Some people ran it tighter than that but I'm not a fan of building bombs rather than engines. Those things were shifting at 15,500 or so too.
I tried the indexing thing and have .020, .030 and .040 washers (if memory serves correct). It looked cool when looking at the chambers but that was about it. I think shortening the electrode had more of an effect but never tested it on a chassis dyno and that was before Iridium plugs.
 I've heard/read ...as have other fellas on here I'm sure....about different port finishes.... rough, super rough, dimpled, chiseled and others I've forgotten about being the greatest thing since ice cream. If one finish was absolutely proven to give that 1 or 2% extra everybody would copy it and do it.....hard to keep secrets.
 Attention to detail and using proven parts/ideas is the key to success IMO.

There’s been a lot of old research on the sbc and bbc squish/quench. They used to agree that the best performance was achieved, when at operating temperature, the piston could not build up any carbon in the squish zones..however. If the pistons tops were being polished, lightly touching the head, the rod bearings would fail becoming the bomb you indicated…No clearance near TDC can place loads greater than the oil film protecting the bearing can support..Its been explained like a die-cast’s break over center locking device..When the pistons near TDC and aren’t  traveling up very much, even the mixture in the squish zones can be similar to a mini hydra-lock because it can’t get out quick enough…But the rod at TDC will break over center easily anyway..

And Will that’s sounds like old Smokey was just being old Smokey, doing what wasn’t written in the rule book…
But, that said, he was right when he said. “ it’s best if you don’t go over 12.5:1 and don’t turn it over 8500, it’ll live 500 miles like that”. “But if you don’t go 14+:1 and turn as hard as it’ll go”, “ someone else WILL and you WILL lose”..😁🤔

It’s interesting you mentioned Carrillo rods. They recommend 0.002 clearance for their rods.. It seems they’re not keeping up with the latest pro stock clearances for the low viscosity oil gains some are enjoying..?🤔

[Don R]

 I actually did print the piston part number on a head, it was a billet head we made for a Briggs and Stratton flathead jr. Dragster motor, it was an accident. I didn't allow for the aluminum rod I guess. Another mistake I made was when the head bolts bottomed in the bolt holes distorting the bores. The bores went from .174 over to .195 in short order, when we realized what happened we sleeved it back to +.174 and started over. The head gaskets leaked a lot too. lol.

[Tracksnblades1]

I actually did print the piston part number on a head, it was a billet head we made for a Briggs and Stratton flathead jr. Dragster motor, it was an accident. I didn't allow for the aluminum rod I guess. Another mistake I made was when the head bolts bottomed in the bolt holes distorting the bores. The bores went from .174 over to .195 in short order, when we realized what happened we sleeved it back to +.174 and started over. The head gaskets leaked a lot too. lol.

Did your top ring land close up on the initial part number stamping on the head…?

[Don R]

 It's crazy but I couldn't find any marks on the piston, it had a little dome just the reverse number stamped in the head. A thicker head gasket would have solved a couple issues.
 
 

[Don R]

 What was previously a frustrating effort was easy as pie with the correct thickness washers. I color coded the washers, the thinnest with black marker, middle blue marker and thickest no marker. Approx 1/3 turn, 1/2 turn, and 2/3 of a turn.