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Holley 850 Questions

Bruzilla

Bruzilla

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I just put a Holley 850 on my 440, and aside from issues with kickdown adjustment, there are no real issues, but I have a couple of questions as it's been about 25 years since I've messed with a double-feed and there's been some changes. :)

The first question regards the idle mixture screws for the rear bowl. This one doesn't have any as seen in the picture. There's a hole, but no screw. The car is idling fine, and mixture seems good, but should there be a screw there?

carb1_zpsztxtwj7l.jpg


The second question is what the heck is this pressure connection on the choke side for? I can't find any description for it.

carb2_zpswhvwo0js.jpg


Thanks!
 
Last edited:
The rear metering block is not finish machined for a screw. The fitting at the thermostat is for a hot air source to assist in choke opening. Chrysler did not use the hot air type choke so no provisions exist on stock engines. If you are so inclined 1/4" copper tubing can be clamped to the header or exhaust manifold to heat air for the thermostat. Some type of filter should be used on the open end of the tubing to keep crap out of the carb.
Mike
 
493 Mike said:
The rear metering block is not finish machined for a screw. The fitting at the thermostat is for a hot air source to assist in choke opening. Chrysler did not use the hot air type choke so no provisions exist on stock engines. If you are so inclined 1/4" copper tubing can be clamped to the header or exhaust manifold to heat air for the thermostat. Some type of filter should be used on the open end of the tubing to keep crap out of the carb.
Mike
Click to expand...
So just leave it be?
 
my guess is that's an 80531 list 850vs which is holleys modern version of the old 3418 list. shouldn't have or need mixture screws for the secondaries.
 
Bruzilla said:
So just leave it be?
Click to expand...
that choke needs a hot air source. usually the source would be a hole in the heat crossover in the intake. converting to an electric may be simpler to deal with.
 
Bru, you don't have a double pumper since you have a vacumn pot on the secondary side. Not sure what the port by the choke is, but the choke is an electric choke so not sure why it would have the port for manifold heat.
 
66Satellite47 said:
Bru, you don't have a double pumper since you have a vacumn pot on the secondary side. Not sure what the port by the choke is, but the choke is an electric choke so not sure why it would have the port for manifold heat.
Click to expand...
That's what I was trying to figure out. I was wondering if it was there for a manual choke and they just add the electric one without taking that fitting off.
 
It seemed like the secondaries weren't opening, and apparently the clamp holding the throttle cable came loose and when I floorded the pedal it wasn't moving the throttle arm very much. Readjusted the cable and now she's screaming! :)

Still having an issue with the kickdown. I need my son to come by so I can see where the WOT position is on the carb with the pedal all the way down.
 
Yes, the 850 is a double pumper carb. It looks like yours could be a 780, which has a vacuum sec opening, and the 3310 list number. That is also a great carburetor. Look on the front of the carb for the list number. It would be stamped in small numbers on the front of the housing that holds the choke butterfly. Post those numbers, and we can tell you exactly what carb you have. Then you can look up the stock specs such as jet size, etc. That always helps with tuning, and getting the mixture set just right.
 
The port for the choke is a vacuum operated heat riser assist and needs to be capped if not used. It is a Ford thing. I just cut a little round piece of gasket material and put it under the brass cap. Does look like an earlier 3310.
 
A 3310 is the only vac secondary Holley that I could consider using......all other Holley vac secondary carbs are mostly junk.
 
Garys1969RR said:
Yes, the 850 is a double pumper carb. It looks like yours could be a 780, which has a vacuum sec opening, and the 3310 list number. That is also a great carburetor. Look on the front of the carb for the list number. It would be stamped in small numbers on the front of the housing that holds the choke butterfly. Post those numbers, and we can tell you exactly what carb you have. Then you can look up the stock specs such as jet size, etc. That always helps with tuning, and getting the mixture set just right.
Click to expand...
all 850's have the short choke tower like the one pictured. there's several 850vs variants out there.
 
Bruzilla said:
It seemed like the secondaries weren't opening, and apparently the clamp holding the throttle cable came loose and when I floorded the pedal it wasn't moving the throttle arm very much. Readjusted the cable and now she's screaming! :)

Still having an issue with the kickdown. I need my son to come by so I can see where the WOT position is on the carb with the pedal all the way down.
Click to expand...
You mention the secondaries weren't working. This is something you can't just blip the throttle and see, they work off of vacuum (the motor being put under load). To test it's function put a paperclip on the vacuum rod against the bottom of the vacuum can. Take it out being sure to hold it to the floor for some good hard pulls then take a look at the paperclip location, if it's working the paperclip should be slid down away from the canister. You can play around with different springs to fine tune it but going really light for quicker acceleration on a heavy car can do the opposite.
 
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