Idle Air Mixture Screws little or no effect

[bnorris_74]

Carb is a 17057274.

Installed new idle tubes @ .038. Idle mixture holes behind screws are .090.
Idle down changes are .052.

74 Pri Jets and 44 Rods. Bought from Cliff.
New rebuild kit from Cliff.

I added .070 idle bypass holes in the base plate.

Cars idles fine. Adjustable and stable at any RPM with the idle stop screw.

I can't get the driver's side idle air screw to make any difference in carb idle screwed all the way in.
The passenger side screw will cause a slight stumble fully closed but not of any consequence.

Performance wise it runs great on the primaries. Secondaries seem rich with a noticeable miss under hard WOT acceleration. DB secondary rods from Cliff. Secondary feed tubes are now .036
Secondary flap at 5/8 turn tension and choke pull off at around 2 seconds.

I have a 7044262 that I normally run and it performs fine. I built up the 17057274 for a performance upgrade.

Any ideas what causes this?

[bnorris_74]

Well I think I found what I thought was the secondary miss. Tore the carb apart today and I somehow managed to mangle one of my brand new primary rods.

I also noticed that I can move the one secondary bushing located in the main body back and forth a little bit. Is that ok?

I think I also failed to enlarge the lower air bleeds. These are located in the main body too correct?

[bnorris_74]

OK, I couldn't wait on you guys forever.

I took the carb apart and opened up the lower idle air holes per recipe two. Straightened up the bent primary rod and I now have control of the idle mixture via the screws. Cranked all the way in, either screw will cause the engine to stall out.

I still have the miss at a WOT start from a dead stop. I'm going to work on the secondary flaps to see if I can cure that.

One last question. The recipe calls for opening up the secondary POE restriction. I've searched and could not find out where this is. I opened up the secondary tubes and the well restrictions. Just don't have a clue on the others.

[Cliff Ruggles]

Same carburetor number I use on my own engine.

The rich condition may be pulling fuel from the vent on top of the airhorn.  Plug the long vent where the screen is used behind the choke flap with epoxy and see if anything improves before tuning the flap spring tension, or opening up anything associated with the POE system.....Cliff

PS:  Went on vacation for a few days, or I would have responded sooner....

[bnorris_74]

Thanks Cliff.
When we talked on the phone last week you mentioned you might be going away.

So this vent is actually the screen part by the air cleaner stud? Do I just seal up the screen?

Thanks

Brian

[bnorris_74]

I sealed the screen-vent area and still have the sputter from a WOT start.

The sputter is not present from WOT at higher RPM's. I have adjusted the secondary tension from 1/2 to 3/4 turns and have the pull off set at 2 seconds.

Any ideas?

[bnorris_74]

I'm about to give up.

Worked on the carb the last two days and still cannot eliminate the sputter from a WOT start from a dead stop.
No sputter anywhere from 2K RPM up.

I'm ready to put it in a box and send it to you Cliff.

[Schurkey]

Accelerator pump shoots gas even if you don't "whack" the throttle open?

[bnorris_74]

Yes, pumps shoots through the entire range of travel.

I changed the primary rods to a 45L yesterday thinking it needed leaned out but it still does it the same thing.

It gives me the impression of running rich during these episodes and then finally blows itself clear and runs great once it cleans out.

I'm running a lot of things thru my mind trying to figure this out. One thing I thought is that maybe with the stock converter I'm not coming out at a high enough RPM for this recipe. Thoughts?

[bnorris_74]

Yesterday I did a couple of quick 3/4 throttle openings by hand and noticed that there was drops of fuel coming up past the upper secondary flaps. Seems like that is where the sputtering could be coming from.
I adjusted the pull off to around 1.5 and 1 seconds and 3/8 turn on the tensioning spring but still have the sputter at WOT starts.
Again, it runs great from a higher RPM.

[Cliff Ruggles]

I'd try different hanger heights, to see if raising or lower the metering rods helps any.  Just gently bend the hanger, no need to buy an assorment of them.  To keep yourself in check you can measure the distance down to the metering rods from the top of the choke tower.  Measure the distance to establish a baseline, then bend the hange slightly and do some testing......Cliff

[CadilaChris]

You should check for grounding wires around the vacume advance in the dizy.  Something might be touching at that one particular point.
Chris