Valve job needed - Page 2 - Toyota 4Runner Forum

gamefreakgc · 06-02-2023, 01:14 PM

Quote:

Originally Posted by brillo_76

How many miles on the engjne? Was the valves adjusted between 250 to 300k?

Just curious if the exhaust valves not being adjusted has anything to do with the Tim Sean's head project. As I suspecting the exhaust valves being too tight caused this?

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It is hard to say. Some say it's because it's an iron block and aluminum heads and they heat and expand at different rates (see 22-RE and 3VZ-E head gasket failures and the 3rd gen head gasket recall). Others say it's a weak point in the Toyota design which leads to cracks.

In my book, any engine that makes it beyond 200,000 miles without any major repairs is a win. If it can make 300,000 miles before the first major repair, that's entering legendary status.

brillo_76 · 06-02-2023, 01:36 PM

Quote:

Originally Posted by gamefreakgc

It is hard to say. Some say it's because it's an iron block and aluminum heads and they heat and expand at different rates (see 22-RE and 3VZ-E head gasket failures and the 3rd gen head gasket recall). Others say it's a weak point in the Toyota design which leads to cracks.

In my book, any engine that makes it beyond 200,000 miles without any major repairs is a win. If it can make 300,000 miles before the first major repair, that's entering legendary status.

Valid point. I was wondering if the valves adjustment eliminates this issue.

As Toyota had aluminum heads and cast iron blocks si n ce the 1970s. There 20R 22R engines stayed relatively the same since the early 1980s till 1995. Rust used to kill mine before the power trains had issues

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diverscale · 06-02-2023, 05:58 PM

Quote:

Originally Posted by brillo_76

Valid point. I was wondering if the valves adjustment eliminates this issue.

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wondering too. I mean, since there are so many of these V6 that hit 300K miles and over without any major problem....... beside tight valves and some reason causing a lean condition a WOT, why would a valve fail/crack?

19963.4lsr5 · 06-02-2023, 06:18 PM

Quote:

Originally Posted by diverscale

wondering too. I mean, since there are so many of these V6 that hit 300K miles and over without any major problem....... beside tight valves and some reason causing a lean condition a WOT, why would a valve fail/crack?

I think it has to do with a cylinder leaning out. The detonation and much higher combustion temps.

Leaner is meaner until you melt a hole in your piston……

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brillo_76 · 06-02-2023, 07:08 PM

Quote:

Originally Posted by 19963.4lsr5

I think it has to do with a cylinder leaning out. The detonation and much higher combustion temps.

Leaner is meaner until you melt a hole in your piston……

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The higher heat damages the valve, valve seat, and stresses the aluminum. Thus cracks start.. makes sense...

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19963.4lsr5 · 06-02-2023, 07:58 PM

Quote:

Originally Posted by brillo_76

The higher heat damages the valve, valve seat, and stresses the aluminum. Thus cracks start.. makes sense...

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I think cracks are from detonation or bad casting. All aluminum heads crack between the valves.

With our engine only having one bank and one pre-cat O2 sensor any cylinder with a poor flowing injector will cause the fuel system to add fuel. Sadly it’s adding fuel to the other cylinders to make up for the poor flowing injector. Richening up all the other cylinders in hopes of increasing flow to the one that’s not flowing well.

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gamefreakgc · 06-02-2023, 08:56 PM

Quote:

Originally Posted by 19963.4lsr5

I think cracks are from detonation or bad casting. All aluminum heads crack between the valves.

With our engine only having one bank and one pre-cat O2 sensor any cylinder with a poor flowing injector will cause the fuel system to add fuel. Sadly it’s adding fuel to the other cylinders to make up for the poor flowing injector. Richening up all the other cylinders in hopes of increasing flow to the one that’s not flowing well.

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Yes, many other engines of the same era have a bank one and bank two O2 sensor for a bit more fine tuned fuel injection. I get why they only have one to lower costs but it may come at a price. Thankfully Toyota over engineers almost everything so that if there is problem the engine and drivetrain can take it.

brillo_76 · 06-02-2023, 09:53 PM

I guess the rust hits before around here before the power train failures. As I only had 1 transmission fail all these years. [ years ago no filter change nor fluid change clutch scattered ] with 1 engine seize [2002 toyota Camry 4 cylinder had the engine low tension rings that burned oil like crazy suddly at 200k which I didn't catch fast enough. Internal engine sludge from low oil plugged journals and seized the crankshaft.

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