Well, I've been working with this for a while.

Basically, the car (de-smogged 4-port 13B) suddenly started running horribly at part-throttle. Backfires, surging, .... I relocated my coolant temp sender in the water pump thermostat neck (it broke off in the block) and, since reassembling, this has happened. I'm running a Holley with vacuum secondaries. The car requires the AP to keep it alive if running on the primaries. I've taken the carb down and nothing out of the ordinary. The idle set screws were at 2.5 and 4.5 turns following the waterpump reassembly and are now at 2.0. The vacuum accessories are capped off for now. The choke adjustment doesn't have a heat riser attached and is set at full open. My floats are good and right at the weep holes. The brass fitting RB added on the primary side is capped off (not the OMP fitting - that one's hooked up). I've removed the intake manifold looking for vacuum leaks and put a tiny bit of silicone sealant to each side of a new Mazdatrix 4-port gasket and reassembled. Cap and rotor were replaced yesterday too, since there was a chance the old one was wet, but no improvement was evident.

I originally thought this was a vacuum leak problem, but it doesn't appear to be.

I'm supposed to be selling the car to another forum member (who's very understanding) but don't want to let her go like this. Under full throttle, she does just fine, it's strictly light-throttle that runs so poorly. If you have worked with this stuff, please give me a call at 678-467-0463 or IM me (Critteroso). I'm really under the gun and just don't know what else to do.

Here's my current progress
https://www.rx7club.com/1st-generation-specific-1979-1985-18/help-holley-vacuum-leak-330106/

And here's what I've been using for reference
https://www.rx7club.com/1st-generation-specific-1979-1985-18/alllllrighty-then-holley-thread-novel-285484/


Thanks.

Crit
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Did you remove the power valve in the carb and plug it? If not, your power valve is probally bad.
All it takes is one good backfire to blow it.

If you plugged it, you'll need to go up about 2 jet sizes on the primarys

 

This is the carb I've used the whole time. Power valve is replaced with a block-off piece, and main jets are 61s. The car ran great last weekend and suddenly will not run on primary idles circuits. It looks like either the no.1 primary isn't getting as much fuel as no.2 or it isn't atomizing. I've cleaned the metering block and passage into the carb VERY well and can't think why the two would be metering differently.

 

Here's what my atomization looks like in my primary barrels. Looks like the left is gettin it done and that the right isn't. Thoughts?

 

I've replaced the carb and manifold with the Dellorto I've been trying to sell, and the car runs great. I now have a Holley that suddenly runs like absolute *** and have no idea why. Can someone help me work though it?