Hard deposits on spark plugs, pre ignition?

[Therealdusky]

Hi guys!


Changing headers on my Chevy SBC and desided to do a comp test while at it. ( all 8 cylinders at 200 psi, so happy me)
Anyway, found some hard deposits on some spark plugs. And I wonder what it could be. I do run a lead additive so might have overdosed on that ? I also changed the distributor , running 36 degrees all in at 2500 rpm.
Those are the only changes I made between putting these new plugs in and now.

Running NGK BP6FS plugs.
The old plugs didnt have this problem ( AC DELCO RT45) .
I know that the plugs look very very black here, but that's 99% sure because I just ran the engine for 40 seconds to drive it up the ramps on choke. ( dont think its oil burning, no smoke and no oil consumption)

Happy to hear your thoughts. I was thinking it might be overheating the plugs or pinking ( wouldn't hear it in this car, it's too [censored] loud) .

 

[Therealdusky]

 

[MolaKule]

Originally Posted by Therealdusky
Hi guys!


...Changing headers on my Chevy SBC and desided to do a comp test while at it. ( all 8 cylinders at 200 psi, so happy me)
Anyway, found some hard deposits on some spark plugs. And I wonder what it could be.
Those are the only changes I made between putting these new plugs in and now. ..



Octane Booster deposits.

Is the fuel of such low octane that you need a booster? Are you racing this engine?

Your oil is probably loaded with the Octane Booster.

 

[Lyman]

I used to run octane booster in a Harley I built with higher compression. I always had those deposits when I changed plugs. Never had the deposits before the additive.

 

[Therealdusky]

Originally Posted by MolaKule
Originally Posted by Therealdusky
Hi guys!


...Changing headers on my Chevy SBC and desided to do a comp test while at it. ( all 8 cylinders at 200 psi, so happy me)
Anyway, found some hard deposits on some spark plugs. And I wonder what it could be.
Those are the only changes I made between putting these new plugs in and now. ..



Octane Booster deposits.

Is the fuel of such low octane that you need a booster? Are you racing this engine?

Your oil is probably loaded with the Octane Booster.



Interesting!
The lead replacement is Castrol valve master plus, wich indeed is an octane booster too. I just use this to be on the safe side because I'm running a high ignition advance (afaik) and it buys me some safe zone when I let the car sit for longer periods of time.
Now that you mention it, I did only recently start using this brand. Maybe better to use a different one?

 

[2004tdigls]

that looks like overfueling a "wet" plug

https://www.championparts.ca/Parts-...maintenance/how-to-read-spark-plugs.html

also could be caused by a really large cam with overlap

 

[sloinker]

Too rich. You say your old plugs didn't do this so I would go back to them and check to see if the problem mitigates by using them. Hard to believe a plug heat range could cause this much rich fouling.

 

[Therealdusky]

Originally Posted by sloinker
Too rich. You say your old plugs didn't do this so I would go back to them and check to see if the problem mitigates by using them. Hard to believe a plug heat range could cause this much rich fouling.

Just From the choke I think. Engine hadn't run for 5 weeks and then just ran 30 seconds to get it up the ramps.

 

[Amkeer]

Too rich and under torqued plugs. I would ditch the additive, put new plugs in.

 

[ARCOgraphite]

You don't even TRY to read plugs after idling a car up on ramps wit the choke on.

Fully warmed a couple WOT runs , key off engine at end of third WOT run in third gear.

Let cool, then read plugs. You should know which too cylinders are the lean and rich running - just pull those.

Now, What carb, how is the carb jetted what powervalve ( Holley)

Tell us more about the engine. Cam, heads, static compression, distributor ( hope it's a DELCO HEI )

I see you have later vortec heads with peanuts - is this a 90's Caprice by any chance?

If it's high comp you should'nt need 36 deg all-in at 2500 rpm! More like 34 all in at 3200-3500, esp on the vortec.

Ar you running vacuum ported vacuum advance and how much?

And ditch those NGK and run Champion or ND or standard copper Bosch.

 

[dnastrau]

Originally Posted by Therealdusky
Hi guys!


Changing headers on my Chevy SBC and desided to do a comp test while at it. ( all 8 cylinders at 200 psi, so happy me)
Anyway, found some hard deposits on some spark plugs. And I wonder what it could be. I do run a lead additive so might have overdosed on that ?... .


You are running a lead additive? What year is your small block Chevy? For the 1971 model year, all GM passenger car and light truck engines in the US (and probably Canada) started using induction hardened exhaust valve seats and compression ratios of no more than 9.0:1 to accomodate the new 91 RON (marked as 87 R+M/2 in the US and Canada since the mid '70s) low-lead and unleaded fuels. No lead additive is needed on those engines. If the engine is a '71 or newer and is stock, you probably don't need any octane booster either. Isn't gasoline is Belgium either 95 or 98 RON (roughly the same as current 91 or 93 R+M/2 fuel in the US and Canada)?

Andrew S.

 

[Therealdusky]

Originally Posted by Amkeer
Too rich and under torqued plugs. I would ditch the additive, put new plugs in.

Why under torqued?


Originally Posted by ARCOgraphite
You don't even TRY to read plugs after idling a car up on ramps wit the choke on.

Fully warmed a couple WOT runs , key off engine at end of third WOT run in third gear.

Let cool, then read plugs. You should know which too cylinders are the lean and rich running - just pull those.

Now, What carb, how is the carb jetted what powervalve ( Holley)

Tell us more about the engine. Cam, heads, static compression, distributor ( hope it's a DELCO HEI )

I see you have later vortec heads with peanuts - is this a 90's Caprice by any chance?

If it's high comp you should'nt need 36 deg all-in at 2500 rpm! More like 34 all in at 3200-3500, esp on the vortec.

Ar you running vacuum ported vacuum advance and how much?

And ditch those NGK and run Champion or ND or standard copper Bosch.



I was not trying to read the plugs, just took them out for a compression test because it's so much easier to remove them with the headers removed.

The base of the engine is a 4 bolt goodwrench, with ported 416 heads on. Cam the lunati equivalent of the comp 268.
I run vac advance, IIRC its manifold vacuum, 8 degrees. Compression is 10.5:1
Running a MSD HEI.

 

[Therealdusky]

Originally Posted by dnastrau
Originally Posted by Therealdusky
Hi guys!


Changing headers on my Chevy SBC and desided to do a comp test while at it. ( all 8 cylinders at 200 psi, so happy me)
Anyway, found some hard deposits on some spark plugs. And I wonder what it could be. I do run a lead additive so might have overdosed on that ?... .


You are running a lead additive? What year is your small block Chevy? For the 1971 model year, all GM passenger car and light truck engines in the US (and probably Canada) started using induction hardened exhaust valve seats and compression ratios of no more than 9.0:1 to accomodate the new 91 RON (marked as 87 R+M/2 in the US and Canada since the mid '70s) low-lead and unleaded fuels. No lead additive is needed on those engines. If the engine is a '71 or newer and is stock, you probably don't need any octane booster either. Isn't gasoline is Belgium either 95 or 98 RON (roughly the same as current 91 or 93 R+M/2 fuel in the US and Canada)?

Andrew S.


Thing is, I dont know how old these 416 heads are. Mind, they had valve work done so 99% sure they have unleaded seats.
Indeed, Only use 98 ron from Shell ( which has no ethanol in it - for now).
Cheers

 

[dnastrau]

Originally Posted by Therealdusky
Originally Posted by dnastrau
Originally Posted by Therealdusky
Hi guys!


Changing headers on my Chevy SBC and desided to do a comp test while at it. ( all 8 cylinders at 200 psi, so happy me)
Anyway, found some hard deposits on some spark plugs. And I wonder what it could be. I do run a lead additive so might have overdosed on that ?... .


You are running a lead additive? What year is your small block Chevy? For the 1971 model year, all GM passenger car and light truck engines in the US (and probably Canada) started using induction hardened exhaust valve seats and compression ratios of no more than 9.0:1 to accomodate the new 91 RON (marked as 87 R+M/2 in the US and Canada since the mid '70s) low-lead and unleaded fuels. No lead additive is needed on those engines. If the engine is a '71 or newer and is stock, you probably don't need any octane booster either. Isn't gasoline is Belgium either 95 or 98 RON (roughly the same as current 91 or 93 R+M/2 fuel in the US and Canada)?

Andrew S.


Thing is, I dont know how old these 416 heads are. Mind, they had valve work done so 99% sure they have unleaded seats.
Indeed, Only use 98 ron from Shell ( which has no ethanol in it - for now).
Cheers


Aren't "416" heads originally found on the 305 HO engines from the 1980s? They should already have induction hardened exhaust valve seats from the factory. No lead additive needed - you should be fine.

Andrew S.

 

[ARCOgraphite]

Originally Posted by Therealdusky
Originally Posted by Amkeer
Too rich and under torqued plugs. I would ditch the additive, put new plugs in.

Why under torqued?


Originally Posted by ARCOgraphite
You don't even TRY to read plugs after idling a car up on ramps wit the choke on.

Fully warmed a couple WOT runs , key off engine at end of third WOT run in third gear.

Let cool, then read plugs. You should know which too cylinders are the lean and rich running - just pull those.

Now, What carb, how is the carb jetted what powervalve ( Holley)

Tell us more about the engine. Cam, heads, static compression, distributor ( hope it's a DELCO HEI )

I see you have later vortec heads with peanuts - is this a 90's Caprice by any chance?

If it's high comp you should'nt need 36 deg all-in at 2500 rpm! More like 34 all in at 3200-3500, esp on the vortec.

Ar you running vacuum ported vacuum advance and how much?

And ditch those NGK and run Champion or ND or standard copper Bosch.



I was not trying to read the plugs, just took them out for a compression test because it's so much easier to remove them with the headers removed.

The base of the engine is a 4 bolt goodwrench, with ported 416 heads on. Cam the lunati equivalent of the comp 268.
I run vac advance, IIRC its manifold vacuum, 8 degrees. Compression is 10.5:1
Running a MSD HEI.


Decent combo, never run 305 smog heads, small chambers can shroud the intake but give good tumble.

I like the only 8 deg vacuum advance, make sure you arent running too much initial mechanical - and you said you were.
Thats and engine killer under wot bc you dont loose mechanical advance. Let the vacuum can take care of light throttle cruise.

Take a look at your metering if you are running a carb. You have steady vacuum at a 650rpm idle?
You may want a stiffer metering spring if you are running a Carter or a fatter rod.

The Soot may just be a coincidence of taking time to get the car on ramps with choke. I'd would let it warm first before ramping it.

But taking the headers off I understand "the get er up and get er done".

And get rid of those NGK! Dare you try Autolite on a Chebby? They are a decent copper plug

 

[Therealdusky]

What I have been wondering about, is an ac delco 4 heat range the same as NGK 6?
Or 5? I've been getting conflicting answers about that topic. Wondering if my NGK 6 plugs are just one step too cold.