FJ40 Mark/Downey Header

[wngrog]

Can you tell me more about this?
How does a leaky flange gasket kill the O2 sensor?
Thanks!

Not sure how exactly but it will.

 

[PabloCruise]

Not sure how exactly but it will.

That was my reaction as well, how does that happen?

 

[gonzopancho]

Can you tell me more about this?
How does a leaky flange gasket kill the O2 sensor?
Thanks!

Should ambient air find its way into the exhaust stream, the amount of oxygen present in the sensor's active environment is artificially increased.

If this occurs, the sensor will essentially signal a lean condition that isn’t occurring, and the ECU will add fuel, causing a rich condition.

I don’t know that the excess air will ruin an O2 sensor. (The introduction of water certainly will, and excess fuel will.) (edited)

What definitely will occur is that a “self-learning” EFI system will corrupt its own fuel maps trying to compensate for the “lean” condition.

The other thing that could happen: some techs or shade tree mechanics will try to salvage a leaking flange gasket with sealer of some kind.

Doing this risks having the sealer ooze in-ward, contaminating or clogging, and thus ruining the sensor.

 

[Downey]

Same here.. I'd be super interested. That is, as long as they fit a 60?

As I recall, the Downey Header required you put a small dent into the FJ60 firewall for clearance. I never owned an FJ60, so only passing along info FJ60 owners gave me.

 

[brian]

As I recall, the Downey Header required you put a small dent into the FJ60 firewall for clearance. I never owned an FJ60, so only passing along info FJ60 owners gave me.

I do not recall having to do this.

 

[Downey]

I do not recall having to do this.

Possibly different equipment on the firewall on different year models ???

 

[Godwin]

As I recall, the Downey Header required you put a small dent into the FJ60 firewall for clearance. I never owned an FJ60, so only passing along info FJ60 owners gave me.

I installed one on an '85 and had no clearance issues. The drive to the muffler shop with an open header was fun for about 5 seconds.

 

[matubrembrem]

@gonzopancho please add me to the pre-order list. I would love to throw one of these bad boys on my soon to be reassembled 2f. Thanks!

 

[PabloCruise]

Should ambient air find its way into the exhaust stream, the amount of oxygen present in the sensor's active environment is artificially increased.

If this occurs, the sensor will essentially signal a lean condition that isn’t occurring, and the ECU will add fuel, causing a rich condition.

I don’t know that the excess air or fuel will ruin an O2 sensor. (The introduction of water certainly will.)

What definitely will occur is that a “self-learning” EFI system will corrupt its own fuel maps trying to compensate for the “lean” condition.

The other thing that could happen: some techs or shade tree mechanics will try to salvage a leaking flange gasket with sealer of some kind.

Doing this risks having the sealer ooze in-ward, contaminating or clogging, and thus ruining the sensor.

I can see where a sealer would contaminate the sensor.

As for a leak letting ambient air into the exhaust stream, I am thinking about that. Wouldn’t the positive pressure from the exhaust be escaping through the leak, not letting air that is at atmospheric pressure in?

 

[wngrog]

I know I lost 2 O2 sensors when I had a header to exhaust gasket go bad and I just kept driving.

The O2 was upstream from the blown gasket.

Either way, they location is not recommended by Holley in their manual.

 

[gonzopancho]

The O2 was upstream from the blown gasket.

In a word: atmospheric reversion.

If you have any exhaust leaks between the combustion chamber and 18-24” after the sensor you are going to have problems.

 

[PabloCruise]

In a word: atmospheric reversion.

If you have any exhaust leaks between the combustion chamber and 18-24” after the sensor you are going to have problems.

2 words?

 

[PabloCruise]

@gonzopancho please add me to the pre-order list. I would love to throw one of these bad boys on my soon to be reassembled 2f. Thanks!

Awesome to see the interest in the new header!!!

 

[Mile2885]

Any updates on these? Shopping for options! Thanks!

 

[PabloCruise]

We are working things on our end trying to build some prototypes!

Stay tuned for more…

 

[GA Architect]

We are working things on our end trying to build some prototypes!

Stay tuned for more…

any updates by chance?

 

[Advrider639]

@GA Architect keyed me into this today...

Put me on the list!

 

[johnmac]

Put me on the list as well, please.

 

[Camotubebender]

Put me on the list.
Thanks

 

[PabloCruise]

any updates by chance?

Unfortunately, we hit another delay on the tooling.

Still waiting...