Uni-Syn tuning

You probably had a leak at base of PV (or a bad diaphrgm)and the plug you put in does not leak. Only way a PV could affect idle mix.
Idle stuff: What spec did you set float at? What model is carb?
Idle air bleeds on metering bar...the actual holes are tiny and often do NOT open up just from soaking in cleaner. Idle jet size, but needles should trump those. I think even if vac is reaching the off-idle holes, idle jets are smaller.
There are kits available now with totally wrong float specs...and these carbs often like lower than stock floats, like the earliest 1939 specs.

 

I went through the Unisyn battle almost 40 years ago now. 1970s I don't know where it was made. It says foreign pat. pend.. I was setting up a Man-A-Fre for the street.

I don't know if this is still available but it is so easy compared to fighting the Unisyn. IMHO If you haven't bought one yet, try to find a Holley.

 

Bruce,
Thanks for the info.
I think it's time to go back through the carbs to see what I missed the first time around.
As all the pv's I have are new, never used, I would ***ume that they are good. I have a fixture somewhere to test pv's, time to find it.
I have wire drills, so I will look closely at all the air/fuel bleed holes, clean them out as needed.
Floats were set (from memory) parallel to the inverted carb body. I did lower them a little, thinking that the float level was contributing to my idle issue.
The kits were purchased through Vintage Speed. Would you suggest a different supplier?
Ken

 

I never had a problem with a Uni-Syn.....the whole deal is to not hook up any linkage till you get the carbs on the same page.

 

Try around 1/3/8--1 11/32 measured inverted from flange, not at seam on float...this is the early low setting. What model carb?? Later ones differ considerably. Problem with kits I referred to was the instructions...some have picked up a float setting from a 337 truck carb that is horrendouly wrong for 94 types.

 

Yes, all idle setup with linkage disengaged, when happy hook up linkage without disturbing throttle postions.

 

sounds like you have the idle sorted, but you NEED a PV on the street.
Figure out how to put in a PV so it does not affect idle.
Next, work on mains and steady state cruise.
Then tune pump shot, and PV to cover flat spots. Get the choke working and you should be done with fuel.
Don't expect spark to cover lean spots during transition.

Panic, I agree that you shouldn't use 14.7 as an absolute at idle. However as someone who used to do a bunch of smogs in CA, I know what many engines liked and what you could lean them down to.
A big cam and headers wants a richer mixture, but most stockers are pretty happy at 1-2% CO. Under 1% is pretty lean, over 3% is pretty rich, so it works out about the same. That's why I mentioned 12.5 since most engines do prefer a slightly rich idle mixture. If you have adjusted a lot of cars over the years, you can often feel the spot where it's happy, and that is usually a 1/16th of a turn out from the first hint of lean drop, before it starts shaking. Lean shakes, richs rolls. You can use a vacuum gauge or tach to develop the touch. Many non-feedback carb'ed cars p***ed smog at around an eighth to a 1/4 turn lean, provided they did not misfire. That is usually around 14.7 to 15. If the engine is in good con***ion and there are no other issues, it's better to run slightly lean, so it doesn't load up at idle.

BTW, blipping the throttle while adjusting will cause a rich situation.
When it's accelerated, the carb is lean, except for the acc pump shot, which is usually a bit rich to cover this lean transient point. End resu lt is rich, unless the pump is not set up r ight yet. Then you release the throttle, causing a rich condition (high vacuum signal, low air flow). More rich... This will take a few seconds to clear out. If you want to test this, adjust the idle to a slight lean misfire. Blip the throttle a few times, and see how long it takes to return to the lean misfire.

 

A little OT, but I would make sure the ignition is top shelf.....I messed around with 2 different 1 bbl. Holleys and finally found an equivalent NOS Carter to try and fix a rough idle situation.

I checked everything, valves, compression, vac leaks, and all the ignition components were new. Still idled rough.

I broke down and put in a Pertronix and a MSD Blaster coil with the proper resistor and even some NGK long reach spark-arcers. It fixed the SOB, finally. Runs as smooth as a gravy sandwich with mayo.

I don't trust new out-of-the-box points ignition stuff anymore. I just don't.

 

Both carbs are 8BA, Holley 94.
I can't check float settings until tomorrow evening. I started the car tonight, smooth idle, 12.5-12.9 AFR.
From what i have been reading, I probably shouldn't be expecting to go much leaner at idle. No signs of loading up.
Once I recheck the float settings, I'll get it out on the road and see what happens.
I agree that a pv would be advantageous, will work on getting one reinstalled.
As this is the first carb(s) I have worked with in over ten years, it's been a rapid re-learning curve into carb technology. It's also the first A engine I've worked on. Nothing like "on the job" training.
The feedback has been incredible, thanks again.
Ken