[OLD 9]

I'm rebuilding a 4165 Holley spredbore double pump carb (list 6497). On Holleys website it states Turning the screws clockwise will "lean" the idle system. Turning the screws counter-clockwise will "richen" the idle system.
This is opposite of how I've been doing it for years. I have had a LOT of 4165 & 4175 carbs in the past. The only square Holley I've ever owned is an 870 SA on by 402 72 C10. (hate it, replacing with 6211)
I've also read that the spredbore carbs DO adjust opposite of the square Holleys. Counter clockwise leans the air/fuel mixture and clockwise enriches the mixture. Well, now I'm a little confused and unsure of myself. Any help with this?

P.S. Does anyone know where I can get a choke housing for the hot air choke OR of an elect or manual choke kit that I can adapt to work on this carb?

 

[Dave Ray]

Thee are two different types of idle screw circuits used in our Holley carbs.

The regular type we are aware of, are FUEL screws, in leans out, out richens. These screws have the same outer diameter their entire length.

The "reverse" type is an AIR screw, in richens, out leans, to a point. These screws have an enlarged head with serrations at the outer end of the screw, and are usually covered by a plastic limiter cap over the end of the screw.

The amount of change is low, versus the regular type circuit, and the reverse setup has a set lean fuel meter for fuel, that is why turning the air screw all the way in richens, to a point of controlled leanness. The reverse idle system is designed as an emissions certified idle system, part of an emissions certified replacement carb, usually for Q-Jet change over, and always used on Spread Bore vacuum secs carbs.

Single feed double pumper spread bore carbs use reverse idle circuits.

All dual feed, double pumper spread bore carbs are deemed as "emissions performance", and can have either style idle circuit, but mostly the regular type circuit.

Look at the screws in the metering block, straight all the way, regular FUEL idle circuit. Tapered large serrated head, reverse AIR idle circuit.

A reverse idle circuit carb should not be used on a non-emissions engine, as getting them to even a reasonable idle richness takes drilling the idle restriction jet inserts in the metering block, and that take a hand held set if miniature drills, and going slowly to attain good mix control. Then, you would also want to change the two stage power valve of the emissions carb, to a single stage, like the performance carbs, and swap the close limit main jets for regular ones. Then, there are transition air bleeds that would need to be adjusted smaller, and a host of other issues to make the emissions carb even work on a stock non-emissions engine. And, it goes on.

 

[OLD 9]

Thanks, Dave
Trying to get my head around this info. The 4165 will be going on my CJ5 with 360 AMC and Preformer intake. It will replace an Edelbrock 650 and I'm trying to get some more MPG and a little more preformance. (11 mpg around town)
I checked the screws on my 800 dp 6212 (said 6211 earlier) and they are the regular type so out lean, in rich, correct?
On the 4165 going on my Jeep, the screw heads are larger and are knurled so out rich, in lean, correct? I'm putting a Holley renew kit in it with single stage power valves. I also want to try something I read about here. I'm going to block the sec PV and increase the jet sizes by about 6 while decreasing the fronts by 2 sizes (4000+ ft altitude) Any thoughts or comments?

 

[Tom Mobley]

>>> "On the 4165 going on my Jeep, the screw heads are larger and are knurled so out rich, in lean, correct?"

Nope, backwards. On that 4165 turning the screws in richens the mix. It's not actually adjusting fuel flow, it's adjusting air bleed into the idle circuit. turning the screw in cuts off the air bleeding into the circuit, richening the mix.

re-read what Dave said to get the whole picture.

 

[OLD 9]

Thanks Dave and Tom. That clears things up a little. Any thoughts on blocking the secondary PV?

 

[Tom Mobley]

Yeah, don't waste your time. On a regular Holley its known that plugging the PV will require increasing the sec main jet 8 or 10 sizes.

On that 4165, who knows. As long as the PV is good leave it there. You have nothing to gain by screwing around with it.

 

[OLD 9]

Yeah, don't waste your time. On a regular Holley its known that plugging the PV will require increasing the sec main jet 8 or 10 sizes.

On that 4165, who knows. As long as the PV is good leave it there. You have nothing to gain by screwing around with it.

Thanks, Tom. I'll take your advice but what would be the advantage of doing a PV block off, if any.

 

[Dave Ray]

The main reason for a secondary PV is to help handle severe fuel stack on braking. Used mostly in road racing, the Secs PV was used as a second set of man jets, so the actual fuel level in the bowl could be lowered, so the level wouldn't stack so high up the rear metering block, that it carried forward into the secs booster ventirii, loading the engine up.

Done right, a secs PV works on a street engine, but, NOT the emissions 2 stage ones, only the performance single stage ones.