ive been doing some plug cuts, today i did a few jsut to see what my current combo is doing (it runs pretty good now) and im having trouble deciding if im a little too lean, at 3500 rpm, the plug is clean, the shrouded side just has some brownish (like crayon brown, light ) tint on the tip of the insulator, the ground electrode and firing side are just slightly grey
the exposed side of the insulator is way way clean. Very very light with just a very very slight hint of greying

it runs great at 3500 rpm
i then did another at 4500 where i feel i have a small flat spot. It seems a little bit leaner but pretty much the same as before only one difference and that is some small dark specs on the insulator.. what does this mean? Does this signify knocking?

i pulled again at 5500 rpm and it looks very much like 3500 rpm maybe not as much grey on the ground electrode and a little bit shiney like if you hold it in the light it looks almost anodized, not that extreme but the same coloring amongst the greyness.. its very very light and you have to look close. Whats that mean? otherwise it looks pretty much the same as 3500 rpm


i need some help because the car most certainly doesnt feel perfect, i think im dealing with a mixture distribution problem where the rear plugs are getting slightly wetfouled before they reach their optimal temperature (the front plugs are perfect looking but the rears are black)

just wondering what you guys think, ill be doing something about the mixture distribution shortly hopefully it is just a case of wet fouling

BTW, the original plugs were r43's and i stepped up to r45s, would a too hot plug read like the car was lean?

 

Super hard to say via wire,, but you described them well enough that I'll take a stab at it. The 3500 description sounds about right, although the "greying" could mean it's getting a little hot, the 4500 description (black specs) sounds like it could be preignition, 5500 sounds like it could be a little hotter than at 3500. Could be a one or a combination of , lean mixture, too much advance, insufficient cooling,, and last but not least,, heat range too high. And yes for sure you can install too hot a plug for the engine and have trouble getting any color to show on the plug. What did the 43's look like?

 

Pablo,

Asking for "expert advice" around here is like saying to a group of off-duty cops at the bowling alley..."hey, have any of you guys got any extra .44 automag loads layin' around"?

You'll get a response, but only with disclaimers...so here's mine......

Expert? Nope. BTDT a whole lot? Yup.

Ditto exactly to BADSS.... especially on the "specs" you've been seeing. That indicates detonation. Also, I'm thinking you've gone a tad hot on the plugs and a tad lean.

Keep experimenting - but I would richen it right away to get out of the "spec" arena... it's a bad place to be...those "specs" are most likely melted aluminum, and it came right from those high-buck pistons you're running.

Also, read plugs from two baselines -

1)After a 20-minute sustained cruise RPM, preferably at 70 mph or wherever you like to cruise at.
2)At the end of a 1/4 mile WFO blast - kill the motor as you drive thru the lights at full throttle, pull off the track into the grass on the return road, and pull a few of those nice, HOT, mothers outta' there with your tender little fingers screamin' OUCH, OUCH, OHMYGODTHATSHOT, STOP THAT YOU FOOL !!!!

The above 2 readings are the biggies, get them right and the rest is superfine tuning.

Good luck man.

BOR

 

lol i know all to well about the hot "Son of a $$%#^* JEE 5$*#^#)O Yeowch!" plugs hehehe

thanks for the knowledge guys! Very helpful
another quick Q is it possible to differentiate between aluminum melting and just carbon getting knocked off the chamber on the plug? i think i heard somewhere that if you really look close you can see that the aluminum would be grey amongst black specs..

i too believe that i should go back to the r43s but im sorta using the r45s as a bandaid to a situation i believe is occuring because of a design flaw of the two barrel tbi and the adapter plate im using
since the fuel is pretty much spraying at throttle blades (ive done my best to get the spray out to the edges of the blades) there is still a considerable amount hitting the blades and since they are angled so that rearward is lower the fuel drips down off the back of the blade into the manifold and of course this makes the rear cyls much richer

so right now for instance if the car is dead cold and i go for a spin, get the oil to operating temperature, and hit it, i get a flat spot in the 4000 rpm range big time and it sorta clears up but not to much. The egt that i have on the # 7 cyl drops like a rock too so ive determined that i think the rear cylinders are missfiring because of the bad fuel distribution wetting the rear plugs, ( i wish i had an egt on a front cyl too) and of course, as i open up the blades the distribution problem goes away and also heats up the plug tip since there is obviously gonna be more pressure in the cyl and a few wot runs clears the problem right up.. does this sound plausible? if i compare the #3 plug to the # 7 (the easiest to reach) after some extended low speed operation the results are disgustingly night and day, the 7 plug looks like its at about 12:1 while the # 3 looks like its at 15:1... i dont see how a carb avoids this same fate being that hte idle circuit is on the primary side closest to the front cyls right? am i missing something?

BadSS, the 43s were removed before i got it to this state of tune it was running way way rich before so its not really comparable im just scared to switch back thinking it might compound my little cold miss

Thanks again BadSS and BOR

Pablo

[This message has been edited by Pablo (edited October 14, 2000).]

 

hmm now that i think about it, the carb idle circuit does a better job of introducing fuel since none of it is dripping off the back of throttle blades (which im sure isnt conducive to atomization) whereas the primary circuit on a carb is doing a decent job at atomization at idle and low speed


im definately not sticking with 2bbl tbi for my next motor itll either be 4bbl tbi or a multiport single plane conversion so idont have to worry about this crap

 

Pablo,
Yes, you can differentiate carbon from aluminum, just as you suspected. Carbon will be dark (as you indicate), and piston material will be light.

Another way to help you read these plugs is to look WHERE the specs are appearing. Piston material (metal,light-colored specs) will usually occur on the insulator portion, and most likely will be found close to the electrode. Carbon, and rich deposits are often found way down toward the base of the insulator, deep in the plug.

I've actually got a picture of Smoky Yunick with a jeweler's loop and a maglite peering down into a plug - the cat was looking to see what his 9-second 327 Vega motor was doing on the big end thru the traps.

It sounds like you've correctly identified a fuel distribution problem. The dark specs are probably carbon that is accumulating during mid-throttle running. At WOT, turbulance/pullthrough in the area at the mouth of the runners will tend to pull fuel past the throttle blades, helping the spray pattern avoid puddling. The accumulation is blasted away, with the by-product being carbon specs.

So, it sounds like poor distribution at part throttle operation. Hummmmm.............

Without looking (bro; if you've got a digital camera, e-mail some pics at oldvette@bellsouth.net, looking straight down the air path, as it flows past the blades), I'm going to guess that part-throttle operation is causing fuel to accumulate in the floor of the manifold on some cylinders, and also causing fuel to almost completely miss being sucked into other cylinders. That is to say, at part throttle, some lucky cylinders are being fed a rich diet of fuel, and others are getting mostly air and darned little fuel.

In my carbed motors, I've always used a single-plane manifold with "turtles" super-glued to the floor of the manifold, just under the middle of the carb.

Edelbrock diagnosed fuel distribution problems that many single-plane guys were experiencing years ago - and many were running THEIR manifolds. Fuel would be pulled into a plenum at speed and would puddle on the plenum floor. Then, without proper atomization, it would introduce itself to the backside of an intake valve as RAW FUEL. That is why manifold manufacturers do not recommend fully polishing manifolds. It kills atomization.

The turtles look like an octopus laying on the sea floor - they are about the size of a quarter, round,high in the middle, with several little "legs" extending out from the center.

When fuel hits the turtle, it is broken up, kind of like directing a garden hose spray at a fan blade - it scatters in all directions.

Possible cure - have you looked to see if die-grinding two semi-circular notches in the throttle blades might be possible?

You can see my thinking here - if the fuel spray pattern misses the blades and hits the turtles (which would be centrally located), it may give each cylinder a better shot at it's 12.5% of the total fuel available.

Most all big-block Chevrolets suffer uneven distribution in the rear cylinders(for a different reason though), and a cure was found many years ago -

Run a different rocker ratio on the intake valves in the rear cylinders. It helps a ton.

Anyway, 'nuff said. Pics would help.

And....I think you've already figured out a better plan for your next intake setup. Good luck.

BOR

 

wow i really need to pick your brain BOR i have tons of questions.. if you have icq you can reach me at 11291690

lemme ask a few and clarify some of the things you brought up

Another way to help you read these plugs is to look WHERE the specs are appearing. Piston material
(metal,light-colored specs) will usually occur on the insulator portion, and most likely will be found close to the
electrode.


Yep thats exactly where im seeing very very very tiny specs of black. .like right on the edge of the insulator on the corner of where it ends. Should the plug NEVER have any tiny black specs? because these are very very small hard to discern looks almost like tiny little dust particles on there.


Carbon, and rich deposits are often found way down toward the base of the insulator, deep in the
plug.

Hmm ive noticed deep down in the insualtor if i look down i see it gets black towards the bottom and it obviously has carbon down there but the exposed part which is mainly what ive been looking at will be perfectly clean.. What can one decipher from looking deep down into the plug?


t sounds like you've correctly identified a fuel distribution problem. The dark specs are probably carbon that is
accumulating during mid-throttle running. At WOT, turbulance/pullthrough in the area at the mouth of the
runners will tend to pull fuel past the throttle blades, helping the spray pattern avoid puddling. The accumulation
is blasted away, with the by-product being carbon specs.


hmm whats happening can best be compared to a carb, that has all of the fuel always introduced from the boost venturi even at idle so picture how the primary blades are angled, alot of that fuel is gonna hit the blades and slide off the rear of the blade toward the rear cylinders. Ive done some research on this and from what I understand, this fuel dripping off the throttle blades doesnt atomize or burn worth a $%(t and the best i can figure is that since it is falling closer to the rear cyls its getting pulled into them just as a stream in addition to the fuel that is making it past the rear edge of the throttle blade in spray form which is why my rear cyls at idle show black plugs and the front cyls show clean plugs. The plug ive been pulling is the #3 so its one of the ones that stays clean.. i was thinking the little black specs were just one level short of piston melting detonation.. more mild, just knocking off the carbon imbedded in the chamber roof and piston surface (thats what i hope anyways)


Without looking (bro; if you've got a digital camera, e-mail some pics at oldvette@bellsouth.net, looking straight
down the air path, as it flows past the blades), I'm going to guess that part-throttle operation is causing fuel to
accumulate in the floor of the manifold on some cylinders, and also causing fuel to almost completely miss
being sucked into other cylinders. That is to say, at part throttle, some lucky cylinders are being fed a rich diet
of fuel, and others are getting mostly air and darned little fuel.


man i wish i had a digital camera id be briging it with me to document all these plugs and stuff. The flow path through the TB is pretty much like a carb that only gets fuel from the boost venturi, there are two big injectors standing over two throttle blades and the fuel is sprayed in a cone shape out to the edges of these throttle blades, but since the cone isnt PERFECT some of that fuel invariably hits the blades and slides off the back. Course at WOT its not a problem


In my carbed motors, I've always used a single-plane manifold with "turtles" super-glued to the floor of the
manifold, just under the middle of the carb.

Edelbrock diagnosed fuel distribution problems that many single-plane guys were experiencing years ago - and
many were running THEIR manifolds. Fuel would be pulled into a plenum at speed and would puddle on the
plenum floor. Then, without proper atomization, it would introduce itself to the backside of an intake valve as
RAW FUEL. That is why manifold manufacturers do not recommend fully polishing manifolds. It kills
atomization.

The turtles look like an octopus laying on the sea floor - they are about the size of a quarter, round,high in the
middle, with several little "legs" extending out from the center.

When fuel hits the turtle, it is broken up, kind of like directing a garden hose spray at a fan blade - it scatters in
all directions.


i like the turtles idea... in addition to another idea im probably gonna try but first lemme ask, would i use two turtles? I was thinking maybe yes, and heres another thought, would the best thing be to center the turtles directly below the rear of the throttle blades? so that say at part throttle while im having this problem because of fuel falling off the rear of the blades it would hit the turtle and split evenly front to rear?

The funny thing is that the problem im having is like the opposite of what carbs have when they have this problem which is at WOT the fuel slams into the floor like what you were saying, at WOT my injectors are so high up and they spread the fuel out in such a wide cone that they actually do an excellent job of atomizing, i just think that part throttle operation is crap and its ruining my WOT because its slightly fouling the rear plugs and causing a missfire until the plugs clean themselves off after a few WOT blasts

the other fix i was gonna mention is that im getting a bigger throttle body which ill need an adapter for. Holley sells an adapter which is obviously engineered with what ive found in mind because they put the throttle body to the front of the mounting flange, and then the holes are drilled rearward at an angle which is sort of hard to explain i guess their goal was to get the atomized fuel to make a turn toward the center of the manifold, while the non atomized fuel dripping off the blades will just fall straight down which ends up being the center of the manifold aswell. Im also gonna try tweaking the injector spray cone to get it out to the edges of the blades as best i can with different pressures etc so hopefully in addition all see about adding some turtles to really have the problem cornered from every angle

 

oh and two more questions i forgot to ask

would i have to make these "turtles" does someone sell them allready? Id probably want to make them myself but i wanna see what they look like to kind of get an idea.. and would i just epoxy them to the bottom of the plenum?


second question, what would an ideal wot plug look like? would it be like a light brown all the way around? (im assuming the exposed side of the insulator would be lighter than the shrouded side) and would it have no specs whatsoever?

 

Pablo,
Edelbrock still makes them, and PAW in California still carries them. They are dirt cheap, so you might as well buy them instead of fabricating them.

A "perfect" plug to me is a custom, parents-know-it-well, color I like to call "babyschizz brown".

And they have a nice, even color throughout the insulator, even down low. I've been thinking about your problem (and watching the Talledega race, sorry it took so long to get back) and have a few ideas.

You mentioned earlier that you're using a "plate" with your 2BBL setup - and it sounds as if the plate is suspect in the fuel distribution problems. This is not only possible, it's likely.

You know those 1" spacer plates that everybody sells, that "add 20 HP" ?

In frustration one nite at the track, I REMOVED a 1" spacer from my buddies' 350 with Edelbrock RPM manifold and guess what.....

It immediately ran .2 quicker in the 1/8 mile. Uh, this is equivalent to .35 in the 1/4 mile. THAT'S 35 HP in round numbers.

Any adaptor/spacer you run must be designed to operate with YOUR current parts. These "universal" hotrod/adaptor setups many times slow cars down. Have you seen the screens they sell for you to install in your intake runners? They improve gas mileage by 10% !!!!!

Well, they probably do....but only because they help atomize fuel, WHILE THEY RESTRICT FLOW BY 50%.

Here's the point (unfortunately, I'm still in the stone age, and don't have an ICBM, or whatever that communications tool is, so I cannot see what is going on).

You may want to go back to square one - looking at any and every part you have modified - because one of them, or a combination of them is causing fuel probs.

Also, I would go to 8*-10* initial advance on a cooler plug, and let the plugs read for you.

They will tell you a lot more if you start from a "conservative" baseline on timing, plug heat range, and rich/lean adjustments in Fuel Pressure.

I'll bet at least half the plugs will read good. This will put you in the ballpark, and then you can look to individual cylinders.

Maybe that adapter does not line up too well....or maybe it raises the TB so far as to screw the aim of the fuel cone. See where I'm going? Back to square one.

Now, back to plugs (and guys, I'll be the first to admit it, plug reading is almost an art-form, and, well, I'm a Crayola type guy).
Light brown by the electrode AND dark down deep on the same plug tells you that the fuel is not burning along an even, well-distributed flame front. The combination of too rich AND too much initial advance will do this.

OBTW - thanks to all you tree huggers out there who gave us Reformulated gas. RFG makes reading plugs almost impossible - like, uh, whats up with this PINK color?

So, Pab, try timing and cooler plugs. If this makes some cylinders really fuel foul, then look toward the adapter/spacer. Somewhere in there is a geometry problem, where the amount and direction of the gasoline needs to be corrected.

Man, I talk too much. Good luck.

BOR