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Looking for a little help reading these plugs. 1981 vette with a stock targetmaster 350. Motor sat in crate for 10+ years before I put it in this past spring. I swapped cam before installation to a XE262H. About 2000 miles on motor this summer and 500 on these plugs. Motor was still using computer and all electronics with the exception of smog pump. No CEL or codes stored.
This winter I will be removing computer, distributor, carb and changing heads to Summit 152123 heads.
Before I pull the heads, can you help read the plugs? I was planning on leaving motor in car but if rings are a concern, I'll have to pull the motor. Compression is 150-155 across all the cylinders.
Way too much oil in cylinders to read anything effectively but what I look for when I’m reading a plug that already has the correct heat range is …
1 ,the ground strap (the piece you bend to set gap) should be clean all the way down to where it attaches to the casing if the timing is set right
, not enough timing and the very tip will be clean while the rest of the strap is black or just be clean on the tip and black soot the rest of the way to the casing … to much timing and the ground strap will be clean all the way down along with down and around the plug casing .
2… for jetting you look at the color of the porcelain but NOT at the tip (like your picture) but way way down inside the bottom of the plug where we can’t see in your picture and the same reason NASCAR tuners use a magnifying glass with light is because they’re looking way down in there . When tuning two stroke motocrosser we actually cut the spark plug casing off so we can look at the porcelain better
Thanks for the reply. I need to find out why they are so oily. I am quite familiar with the 2 stroke world. I have cut plugs many times. I am learning and trying to understand reading 4 strokes. My default is to apply 2 stroke logic but that doesn't always apply in the 4 stroke world.
In a recent thread there is a description that sounds similar to what I was experiencing and it has me thinking about a possible internal intake gasket leak. I suspect that when I pull the intake, 2 & 5 will have signs of oil leaking in.
In a recent thread there is a description that sounds similar to what I was experiencing and it has me thinking about a possible internal intake gasket leak. I suspect that when I pull the intake, 2 & 5 will have signs of oil leaking in.
I second the intake gasket fault. Especially considering your compression test seem to indicate rings are fine.
They all look oily to me. With 5 and 2 having additional oil issue.
Look at the base of the plug. I would do a leak down test. How did you break in the engine?
They all look oily to me. With 5 and 2 having additional oil issue.
Look at the base of the plug. I would do a leak down test. How did you break in the engine?
Thanks. Where exactly would the "base" of the plug be?
I broke it in per the instructions from gm but with royal purple break in oil.
it appears to me that all the cylinders are having oil introduced at varying levels. A leak down test would give you more information to work with regarding ring seal.
factory break-in procedures often lead to poor ring seal. After 10 years of sitting…maybe more so?
it appears to me that all the cylinders are having oil introduced at varying levels. A leak down test would give you more information to work with regarding ring seal.
factory break-in procedures often lead to poor ring seal. After 10 years of sitting…maybe more so?
This was my fear. 10 years of sitting and the effect on the rings.
This was my fear. 10 years of sitting and the effect on the rings.
it could be. It could be an intake gasket. Or it could be a combination of things. Sitting 10 years without being "pickled" is not ideal for sure.
A leak down test is the way to test for ring seal.
Oil consumption, it could be intake gaskets leaking oil into the port , could be rings but more than likely being a Target master it had a cheap valve job and guide knurl when built, my bet the heads need sent out and redone , that would be a good time to have the machine shop machine the heads for some modern positive stop valve seals instead of the umbrella style . I have a 67K original 80 L82 that is getting ready for a valve job with spark plugs looking like yours due to oil consumption
I was thinking along the same line as ERIC P..... it being a targetmaster, sitting for 10 years, cheap rings, and likely some bore corrosion or pitting letting oil by, or the heads are letting some oil in through the guides or gaskets on the sealing surfaces.
Since your planning to replace the heads anyhow, I'd get a borescope and have a look at the cylinder walls and make sure they are OK...or just pull the heads and have a look.
You should consider some heads like these instead of those cast ones you quoted, the price is close and they are cast overseas, but assembled in the USA. https://www.summitracing.com/parts/flk-102-505
I'd look at the intake gaskets for sure. Target Masters came without intakes so someone had to install it. I put in many of them back in the day and they are not "cheaply" built. They are good basic engines...nothing fancy at all...but nothing wrong with them either. The heads came with the same valve seal arrangement SBC's always had and it definitely lacked. But if changing heads anyway, that will take care of it.
Just for fun...trace out which cylinders are connected on which intake plane and see if the oiling is matched in the worst cylinders.
I will do a leak down test over the next couple days. Something tells me it is all in the intake gaskets. I will carefully pull the intake and note which look worse than others. I bet #2 & #5 look pretty bad.
The heads currently on the target master are 624's. I already bought the heads I listed above durning the past summer and they have been sitting on the shelf. Since I am dumping all the computer stuff, funds have to go towards carb and distributor while using the heads I already have.
Do a compression test, don't worry about the oil on the plugs too much. Valve seals get hard and brittle when they sit and will leak. Those target masters were generally not bad motors, a cam and heads will really wake it up.
Do a compression test, don't worry about the oil on the plugs too much. Valve seals get hard and brittle when they sit and will leak. Those target masters were generally not bad motors, a cam and heads will really wake it up.
Cool you already have the heads, be sure to do a video or capture some pics along the way when you change them out.....the forum always likes to watch and read this stuff on cold winter days
Cheers
Get some nice thin head gaskets to kick up all the compression you can get.
2 and 5 are on the same intake runners and 4 and 6 are also as well as 8 and 3. Look at the similarities in the oil and overall burn to the matched pairs. Really points to gasket leaks. The bad ones are bad and the good ones are "sorta good".
JIM
Last edited by 427Hotrod; Nov 22, 2022 at 12:55 AM.
Leak down across all the cylinders ended up at 10-15% on a cold motor. Finally got around to pulling the intake and snapped some pictures. Enjoy! Let me know what you think......
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Help reading plugs. Stock targetmaster 350
