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Hi Z community. My 75 Z has idled roughly since I got it running again and plugs oil-fouled despite doing many different items. Stock EFI. Here's a few important items I've done worth noting --
1. Head was rebuilt with new medium cam, springs and rocker arms. New oil seals installed by head shop. New head gasket and valve cover gasket. New header.
2. Gas tank professionally redone and all gas hoses and fuel filter replaced
3. Replaced fuel injectors and fuel rail (aftermarket aluminum) and new aftermarket adjustable fuel pressure regulator. Removed the cold start valve when new fuel rail installed as I thought it maybe the culprit.
4. New timing chain and guides and sprocket
5. I've done 3 valve adjustments
6. Performed all tests via 'fuel injection bible' and everything in line
7. Water temperature sensor replaced
8. Tried the guitar volume pot on the water temp sensor to attempt to make it run less rich..
9. Replaced plugs with NGK twice at different stages of the above and each time they get oil fouled pretty quick
10. Have also replaced the alternator and thoroughly cleaned all wire connections in engine bay and replaced the fusable links.
11. Spark plug wires replaced along with new rotor and dist cap.
12. Have done compression test three times and here's the avg readings --
Cyl 1 - 155
Cyl 2 - 154
Cyl 3 - 152
Cyl 4 - 152
Cyl 5 - 155
Cyl 6 - 158
Have not done - The block was not rebuilt and I'm guessing it's running original rings stock dished pistons. The piston tops were badly coated with sludge. Cylinder 5 and 2 were the worst. Cleaned off all sludge with rebuilt head going back on. Have not touched the distributor other than pulling and reinstalling with head rebuild.

Attached pics of plugs 1 through 6 from left to right...these prob have less than 200 miles on them. Cyl 4 hole has oil outside of it... I've been avoiding pulling whole engine and having block redone but may have to now? Overall timing maybe off as well?. New oil seals may not have been properly installed?

I realize this is a lot of into but would love to hear any thoughts or Q&A welcome please!! Thank you so much!
 

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Do the fouled plugs correspond to the cylinders that where sludged? If so you might have stuck oil scraper rings on the pistons. If they are fuel fouled then you might try fuel pressure and checking for leaking injectors.
 

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Id run some BG44K or use spray seafoam and put an entire can of seafoam in the tank. And do an italian tuneup. And follow up with berryman B12, its a great mop up cleaner, do another italian tune up and see if that helps. That should A remove gunk, B unstick rings. Fingers crossed.
 

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Discussion Starter #4
Do the fouled plugs correspond to the cylinders that where sludged? If so you might have stuck oil scraper rings on the pistons. If they are fuel fouled then you might try fuel pressure and checking for leaking injectors.
Thank you. No they pretty much are all fouled with oil gunk
 

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Id run some BG44K or use spray seafoam and put an entire can of seafoam in the tank. And do an italian tuneup. And follow up with berryman B12, its a great mop up cleaner, do another italian tune up and see if that helps. That should A remove gunk, B unstick rings. Fingers crossed.
Thanks I actually have a couple of cans of the high mileage seafoam. How much did you put in the intake?
 

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Hi Z community. My 75 Z has idled roughly since I got it running again and plugs oil-fouled despite doing many different items. Stock EFI. Here's a few important items I've done worth noting --
1. Head was rebuilt with new medium cam, springs and rocker arms. New oil seals installed by head shop. New head gasket and valve cover gasket. New header.
2. Gas tank professionally redone and all gas hoses and fuel filter replaced
3. Replaced fuel injectors and fuel rail (aftermarket aluminum) and new aftermarket adjustable fuel pressure regulator. Removed the cold start valve when new fuel rail installed as I thought it maybe the culprit.
4. New timing chain and guides and sprocket
5. I've done 3 valve adjustments
6. Performed all tests via 'fuel injection bible' and everything in line
7. Water temperature sensor replaced
8. Tried the guitar volume pot on the water temp sensor to attempt to make it run less rich..
9. Replaced plugs with NGK twice at different stages of the above and each time they get oil fouled pretty quick
10. Have also replaced the alternator and thoroughly cleaned all wire connections in engine bay and replaced the fusable links.
11. Spark plug wires replaced along with new rotor and dist cap.
12. Have done compression test three times and here's the avg readings --
Cyl 1 - 155
Cyl 2 - 154
Cyl 3 - 152
Cyl 4 - 152
Cyl 5 - 155
Cyl 6 - 158
Have not done - The block was not rebuilt and I'm guessing it's running original rings stock dished pistons. The piston tops were badly coated with sludge. Cylinder 5 and 2 were the worst. Cleaned off all sludge with rebuilt head going back on. Have not touched the distributor other than pulling and reinstalling with head rebuild.

Attached pics of plugs 1 through 6 from left to right...these prob have less than 200 miles on them. Cyl 4 hole has oil outside of it... I've been avoiding pulling whole engine and having block redone but may have to now? Overall timing maybe off as well?. New oil seals may not have been properly installed?

I realize this is a lot of into but would love to hear any thoughts or Q&A welcome please!! Thank you so much!

I have found that the oil control rings can become frozen in the ring grooves. The best way to find out if the problem is frozen rings or worn out rings is to dissolve the deposits around the rings. I like to use a product called Motor Flush. It comes in a one quart can and is mostly kerosene and detergents. Think parts washer if you are/were a mechanic. I put half a can in the oil and run the car at idle for 30 min. Do not drive, do not race the engine. After a half hour, stop the engine, pull the spark plugs and pour the remaining half quart of motor flush evenly between the six cylinders, through the spark plug holes. A small funnel is useful, or you can use an old style oil can and pump the fluid into each cylinder. Allow the fluid to set for at least one hour, but longer is better. Once the hot set is finished, crank the engine with the spark plugs out. This will force any remaining fluid back out through the spark plug holes. If you don't get rid of the fluid, the engine could become hydro locked, which is bad. Once the fluid is out, install the spark plugs (clean them while they are out). Then start the engine and allow to run for 15 minutes. Stop the engine and change the oil. Then you can drive the car again. The process is fast acting and if done correctly, will free up stuck rings. You can smell the exhaust for a burning oil smell or possibly see smoke. Some times it takes significant driving to burn off the oil in the exhaust, be patient. You can look at the spark plugs again. If the problem is solved, the plugs will look good after driving 20 miles. If the problem persists and you want to drive it anyway, you can use a product called anti-foulers or non-foulers. these are little bushings that can be screwed into the spark plug hole before the spark plugs. They pull the spark plug away from the chamber and help the spark plugs burn clean. You will however be consuming oil, so you must check your oil frequently to prevent running out of oil, which would be bad.

You may have run the compression test incorrectly. You should count the strokes and allow 3-5 strokes per cylinder. Some people allow too many strokes, which will give a false high reading. I am always suspicious of a car that burns oil with good compression. BTW, if you see a puff of smoke behind the car when you let off the throttle, it is caused by valve stem seals, not rings. Also, beware of flooding carburetors. That can foul the plugs as well.
 

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Discussion Starter #7
I have found that the oil control rings can become frozen in the ring grooves. The best way to find out if the problem is frozen rings or worn out rings is to dissolve the deposits around the rings. I like to use a product called Motor Flush. It comes in a one quart can and is mostly kerosene and detergents. Think parts washer if you are/were a mechanic. I put half a can in the oil and run the car at idle for 30 min. Do not drive, do not race the engine. After a half hour, stop the engine, pull the spark plugs and pour the remaining half quart of motor flush evenly between the six cylinders, through the spark plug holes. A small funnel is useful, or you can use an old style oil can and pump the fluid into each cylinder. Allow the fluid to set for at least one hour, but longer is better. Once the hot set is finished, crank the engine with the spark plugs out. This will force any remaining fluid back out through the spark plug holes. If you don't get rid of the fluid, the engine could become hydro locked, which is bad. Once the fluid is out, install the spark plugs (clean them while they are out). Then start the engine and allow to run for 15 minutes. Stop the engine and change the oil. Then you can drive the car again. The process is fast acting and if done correctly, will free up stuck rings. You can smell the exhaust for a burning oil smell or possibly see smoke. Some times it takes significant driving to burn off the oil in the exhaust, be patient. You can look at the spark plugs again. If the problem is solved, the plugs will look good after driving 20 miles. If the problem persists and you want to drive it anyway, you can use a product called anti-foulers or non-foulers. these are little bushings that can be screwed into the spark plug hole before the spark plugs. They pull the spark plug away from the chamber and help the spark plugs burn clean. You will however be consuming oil, so you must check your oil frequently to prevent running out of oil, which would be bad.

You may have run the compression test incorrectly. You should count the strokes and allow 3-5 strokes per cylinder. Some people allow too many strokes, which will give a false high reading. I am always suspicious of a car that burns oil with good compression. BTW, if you see a puff of smoke behind the car when you let off the throttle, it is caused by valve stem seals, not rings. Also, beware of flooding carburetors. That can foul the plugs as well.
Wow, thank you so much Richard for this level of detail and instruction. Much appreciated! I will do all of this. FYI, I actually did 10 strokes per cylinder will redo the compression test again.
 

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Thanks I actually have a couple of cans of the high mileage seafoam. How much did you put in the intake?
Id meter a half can in the intake put the other half in the tank. For normal seafoaming upper cylinder. You may want to do more in the intake in your case.
I came upon this on bob is the oil guy, Auto RX. Might want to look into that.
 
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