What do these Carb hoses do?

[Davea Lux]

Should I screw around with adjustments on the carb or just leave them alone?

Your choke is fully closed so leave that much alone. Have you checked your heat riser yet? 10-12 mpg is about normal mileage for the de-tuned 400 in 1972. As noted in the previous posts, this Holley was not one of their better efforts, you appear to have some fuel on the top of the carb, check the floats for proper heights, the gaskets and the needle valves for leakage. Given the long period of time you car was sitting, the fuel system may have a bunch of accumulated crud in it that could be lodged in the carb.

Dave

 

[Jon O.]

Your choke is fully closed so leave that much alone. Have you checked your heat riser yet? 10-12 mpg is about normal mileage for the de-tuned 400 in 1972. As noted in the previous posts, this Holley was not one of their better efforts, you appear to have some fuel on the top of the carb, check the floats for proper heights, the gaskets and the needle valves for leakage. Given the long period of time you car was sitting, the fuel system may have a bunch of accumulated crud in it that could be lodged in the carb.

Dave

as much as I am trying to take your advice, I am young and don't know too much yet. I know how to check the float and gaskets. Thats about it. Where is the heat riser? how do I check it?

 

[Davea Lux]

as much as I am trying to take your advice, I am young and don't know too much yet. I know how to check the float and gaskets. Thats about it. Where is the heat riser? how do I check it?

Heat riser should be on the passenger side exhaust manifold just above the connector
for the exhaust pipe. There will be a round or rectangular weight on a shaft that sticks out of the manifold. Grab the weight and attempt to turn it, it should move freely.

Dave

 

[david hill]

Should I screw around with adjustments on the carb or just leave them alone?[/QUO

Should I screw around with adjustments on the carb or just leave them alone?[/Q

Should I screw around with adjustments on the carb or just leave them alone?

Leave everything alone see what happens. If it is better call it a fix. If not, PM me or post the results.

Jon start it up and note what happens. If you have problems either PM me or post results.

 

[Big_John]

This may help. Download a service manual here: MyMopar - Mopar Forums & Information - Service Manuals

 

[Jon O.]

This may help. Download a service manual here: MyMopar - Mopar Forums & Information - Service Manuals

Oh my goodness thank you, I was about to buy one.

 

[CBODY67]

If that Holley 2bbl has horrible gas mileage, it's probably due to the air horn being warped, as I mentioned earlier. So it probably needs the Bridge Kit. The carb might need to be cleaned up internally, but I also suspect that if you did that, not much improvement.

From having TWO of those carbs, I can truthfully say they were great carbs, for what they are. Fuel metering and throttle response are crisper than the older Carters and Strombergs, by observation. The first highway trip I made in the '66 Newport at 55mph, the car got right at 20mpg on the highway. That trip was after the national speed limit dropped to 55mph in the 1973 era.

I suspect the ONLY way to decrease any "hot soak fuel heat issues" might be to add an electric pusher fan with a timer to run the fan after the engine shuts off, in hot weather. GM had those issues, too, otherwise there would not have been factory Chevrolet "heat shields" to go under the QuadraJet 4bbls. Even when we had better fuel formulations in the earlier 1970s.

CBODY67

 

[saforwardlook]

I have said it before, Holley's usually always ran better than the Carter carburetors when new, better more crisp throttle response and better mileage. The problem was that they just didn't stay that way for very long before warping from hot/cold cycles. The original Holley 4160 4 bbl on my avatar car (1970 Chrysler 300) was warped and messed up at 31K miles. I replaced it with a Carter AVS but it never felt as good. And a 360 with that Holley 2 bbl was a sweet running vehicle - if you didn't know better, you would think it was a 4 bbl - until the airhorns warped on them (the air cleaner hold down rod screwed into the airhorn, not the base of the carburetor - a big mistake, because when owners tightened their air cleaners normally snug, then the heat - cold cycles plus the upward force on the air horn warped them and caused them to leak air and run rich depending on what load range you were in). Holley's were more expensive to build (and much heavier) than the Carter carbs, so in order to be cost competitive with the Carters so Chrysler would buy them, they ended up using cheap casting material that didn't hold up well. Too bad.

 

[tbm3fan]

Wish I could have experienced a good Holley on my 360. Tried two and both had issues when trying to tune at idle. Put a light on the timing marks and timing would bounce around 4-5 degrees while watching it. Could never get it stable for tuning. Got fed up and put another well known reliable 2 bbl on it and voila timing steady as a rock.

 

[saforwardlook]

I have found that the rebuilt Holley carburetors from Autoline are done right to fix the warpage. They press the air horns to flatten them and then plane them to be perfectly flat. Just don't tighten down the air cleaner any more than needed to hold it in place. They are available from Rock Auto.