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Reverend

It Ain't Running Right!

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What are you using for the carb insulators between manifold and carb?

I cannot tell for sure by the photo.

Are you by chance using the o-ring type insulator?

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set of 3 40 SK/OER racing carbs, yes i have Gunson Carbalancer wich i used to syncronize. If they were out of sync at idle, should they be above that as well? Because they are not, thats the weird thing. Ive spent crapload of carbcleaner, of course i have not injected that among the fuel.

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I've located a small inlet manifold leak from cylinder Nr5. If i spray starter fluid at it, i can hear idle rising for a second. There is no visible hole or crack or anything. This could be the problem after all?

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I bet it does. I switched to bigger idle jets (55F9) but i STILL have to dial mixture open for 1.5 turns, just like with the smaller jets (50F9). But i have noticed some difference, idle is a tad smoother (even with the inlet leak).

 

One strange thing was that i drove on the freeway about 20 miles, after coasting to normal speed, i could hear faint "pop" from the exhaust occasionally, like it was burning excess fuel there. SO basically i have mixture on the verge of being too lean, but it still pops in the exhaust`??

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If your rpms are high and you take foot off gas to coast, the pistons are sucking hardest but the throttle plate is closed. This causes a huge vacuum in the manifold that sucks fuel from the idle enrichment circuit. If your idle is set to rich then too much fuel will be drawn through and it will build up in the exhaust and ignite making the popping sound.

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Sounds like lean-popping to me, due to some/all cylinders partially misfiring during coast-down. Proper idle jets will get rid of that.

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