Thread: white exhaust valves

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Just pulled a Holden 6 cylinder 202 out of the sons Torana.The engine had just been rebuilt and a Yella Terra 9 port head was installed with the required mods.Engine seem to be good at first but started to have heating problems and was'nt idling nicely at times.
Typical teenager saw an engine on ebay and the next thing I new he had ordered another one.( Engine that was )
Pulled the old engine out today and found the head gasket looked good but the 2 rear cylinders looked as if they had been running lean and the exhaust valves with light grey come white and the plugs also looked like they had been running lean.The front 4 cylinders looked fairly rich.The car has 3 new su carby's installed and the engine has a reasonable cam installed.
Any idea's guys

Originally Posted by roadster

Just pulled a Holden 6 cylinder 202 out of the sons Torana.The engine had just been rebuilt and a Yella Terra 9 port head was installed with the required mods.Engine seem to be good at first but started to have heating problems and was'nt idling nicely at times.
Typical teenager saw an engine on ebay and the next thing I new he had ordered another one.( Engine that was )
Pulled the old engine out today and found the head gasket looked good but the 2 rear cylinders looked as if they had been running lean and the exhaust valves with light grey come white and the plugs also looked like they had been running lean.The front 4 cylinders looked fairly rich.The car has 3 new su carby's installed and the engine has a reasonable cam installed.
Any idea's guys

Vacuum leak(s) on the rear?

Tight valves, not adjusted correctly?

Carbs not sync'd?

What was the compression like? High, low, uneven?

Originally Posted by John Palmer

Vacuum leak(s) on the rear?

Tight valves, not adjusted correctly?

Carbs not sync'd?

What was the compression like? High, low, uneven?

The compression was good and even thoughout the cylinders.
The vacuum connection for the master cylinder was on the section at the rear of the manifold maybe it's been takeing vacuum away from the rear 2 cylinders

Originally Posted by roadster

The compression was good and even thoughout the cylinders.
The vacuum connection for the master cylinder was on the section at the rear of the manifold maybe it's been takeing vacuum away from the rear 2 cylinders

That's a possible solution, is the power brake booster diaphram good?

Originally Posted by John Palmer

That's a possible solution, is the power brake booster diaphram good?

yeh checked that a while ago.Will check it again but it should be all right

What is your intake configuration? Do the three carbs feed a common plenum with lots of mixing, or is it more stratified flow? Also, is your center carb the one with idle/secondary function with the outers only having secondary like a "traditional" 3 carb setup? Teenagers like to "tune" - any chance the back carb got "tuned shut" at idle, making it run lean in back at WOT (probably at WOT a lot with a young driver...)?

Originally Posted by rspears

What is your intake configuration? Do the three carbs feed a common plenum with lots of mixing, or is it more stratified flow? Also, is your center carb the one with idle/secondary function with the outers only having secondary like a "traditional" 3 carb setup? Teenagers like to "tune" - any chance the back carb got "tuned shut" at idle, making it run lean in back at WOT (probably at WOT a lot with a young driver...)?

No the mechanic balanced them with a flow meter and it's 1 carby to 2 intake ports and then there's a straight runner that joins all three carby connections together but the power booster is connected to the rear carby ( where cylinders 6 & 6 are )