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The CHT's should be less at wide open throttle ( WOT) because of the cooling due to all that fuel exceeding the extra heat from all the power.

In my case, the climb CHT was higher with WOT. So, having a nice set of number drills, I opened out the jet just a tiny bit. This seemed to help a bit, but not that much, so I opened it out again with the next drill bit. It still doesn't run cooler at WOT and I am too chicken to do the opening trick again.

Any ideas?

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Has your fuel consumption increased? If it hasn't it would indicate that your efforts to increase cooling with extra fuel haven't worked. A fuel flow gauge should show this if you have one.

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Sometimes a wide open throttle will allow Laminar flow in the inlet manifold, sometimes the air/ fuel mixture will wall attach, either way you will have a ahot lean stream with a cool rich mixture. The heat from lean mixture is two fold owing to the flame front bring so much slower that your crank is not in the best position for absorption of the hot gas energy etc. Maybe put a small obstruction just after the carburettor to get good mixture.

 

Also use a carbon monoxide Meyer in the exhaust and time engine to a barely perceptible reading.

 

Impossible to tell without instrumentation.

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Annoying much younger days in the 70s I used to play with Holden V8 a 4.2 litre V8. If you put to bigger Holly on it the performance was less than if you put a smaller Holly on it. A lot to do with turbulence and mixing of the fuel and air.

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  • 2 weeks later...

Flightrite I am running Iridium plugs in a 2200.

I fitted them as I was changing to resistor plugs to tackle some interference and decided to use Iridium resistor plugs to counter possible harder starting due to extra resistance

 

They seem to be performing well with easy starts

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Not directly subject related but is anyone running iridium plugs in their Jab donks?

Yep. Someone on this forum bought a job lot for a bunch of us a few years back. I removed them for inspection last week, after years of good service, then put them back.

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Flightrite I am running Iridium plugs in a 2200.

I fitted them as I was changing to resistor plugs to tackle some interference and decided to use Iridium resistor plugs to counter possible harder starting due to extra resistance

 

They seem to be performing well with easy starts

Yeah the donk I have has the NGK Iridium's, I re gapped them at 0.25 thou, they where around 0.30, runs well.

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