H/W 5200 w/ PCV is rich, w/o is OK; Holley 2300 w/ PCV is OK

[Williboy]

This post probably should go under the H/W Jet STICKY, but I didn't want to get it buried and has different elements to it.

Well I finally got my jets and holder and hooked up my H/W 5200 with my AEM Wideband O2 and things got interesting.

According to my O2 sensor gauge, my 5200 was running way rich at idle. 10:1 or lower, the AEM only goes to 10. At first I wondered if it was a bad sensor or gauge so I pulled off my PCV and it instantly leans out to around 14:1 and idle kicks up, etc. I started out with basic jetting and was hoping to fine tune from there.
P/S:
Main: 160/160
Air: 185/175
Idle: 70/60
Pump: 50

I was think that it could be a bad PCV valve, but then I decide to install my Holley 2300 350 to see what happens.
With the PCV installed its 14-15:1. Close to the mark. I can even adjust the idle mixtures and bring it closer to 14.7. I took it for a test drive and cruising on the freeway I'm around 13:1, a bit rich but I'll rejet later. The mixture reading doesn't sit still, it jumps around a lot, but that is maybe normal or ???? That's were I ended last night. I sure would of thought that the 5200 would be lean and the 2300 rich.

I Looked on SEARCH and found some interesting post about 5200, PCV, and leaks but they were mostly running lean until the PCV or leak was fixed. There was one post regarding cracked piston rings which sounded frighteningly similiar, but why would the 2300 act different??

I'm getting ready to start investigating some more this morning, but was wondering if anyone had any ideas or suggestions. I know I could just run w/ the 2300 but I wouldn't be able to sleep not knowing why.

 

[grocery getter]

chose your battles

the a/f is good with the 2300, how does it feel? if the power is good , go with it.

 

[BIGREDRASA]

One suspect when your're rich all the time would be the power valve. When, where, how, and by whom was the carb rebuilt?

OTH, I'm going to have to put the Wideband O2 sensor on my wishlist for Anniversary (5/19), B'day (6/1), & Father's Day (6/15). I can tell the wife she can combine all. So, Brand Name, Source & Price?

 

[l3n]

I'm pretty sure it's a jetting issue, not your pcv.

 

[grocery getter]

One suspect when your're rich all the time would be the power valve. When, where, how, and by whom was the carb rebuilt?

OTH, I'm going to have to put the Wideband O2 sensor on my wishlist for Anniversary (5/19), B'day (6/1), & Father's Day (6/15). I can tell the wife she can combine all. So, Brand Name, Source & Price?

Tony, I bought an innovate lc-1 meter with gauge for about $200.00.
i'm going dual outs. i'll put two bungs in with plugs . i'll just plug in either bank for a reading.

I hope you get your wish

 

[Williboy]

I wasn't able to do as much as I wanted to do today( forgot I had plans w/ the wife).
Did do a quick compression test; 5@145, 1@140, so no major problems there..

The 5200 carb came new from Stovebolt a few years ago, I ran it until I got bored and put a Holley 2300 on just to see what happened. Didn't see any major differences in between the two. I drained the 5200 and boxed it until a month or so ago. I have it now where I can switch the two out in minutes.

The 5200 always seemed to run good, has an electric choke vs manual, and warmed up quicker. Now that I know it's rich at idle, that make more sense.

Bad power valve??? at idle???. Maybe it is just jetting but I'm running 70/60 idles, a little high but I didn't think too much to start. This week after work, I will hopefully put the 5200 back on and and run on the freeway and see what the A/F numbers are.

I got an AEM Wideband on Ebay for $200. There were a couple guys selling at that price. Very easy to install. Had the bung welded for $20, one harness plug the sensor to the gauge, then supply 12v and a ground to the other harness. I figure after I'm done I'll let my friends use it and then maybe sell it.

 

[JackFish]

Remember that the "Autolite" 5200 was used on cars with EGR.
So the gas would be diluted under certain conditions. And when the EGR was out of the loop, there were vacuum controls to adjust timing.
So I'm not surprised we find they're pretty rich now that some guys here are getting hooked up to the wideband.
If/when I get mine on I'll use it with EGR, since I'm already set up with it on the 1946.

 

[jamyers]

Stupid question, but you *have* adjusted the 5200's idle mix screw, yes?
From my playing around with my 5200 and wideband, I can get whatever AFR I want at idle with the idle mixture screw, with idle jets ranging from 55 to 80. Smaller idle jets just mean the screw comes out more.

If yours is stuck idling at 10 or richer and the idle mix screw isn't affecting it, something's wrong somewhere - throttle plates too far open, trash in a passage, something.

What are you AFR's at slow cruise, fast cruise, and wot?

For a reference, check out the AFR's in the 5200 jetting table that BIGREDRASA compiled, I agree that most people's 5200 are jetted rich (and about the only difference I can tell is in mileage).

Oh yeah, my AFR jumps around as well, I'm blaming it on the crappy log head intake with it's dismal distribution.

 

[Williboy]

I double checked the Holley 2300 for leaks and none found.
Installed the 5200 and still 10:1 at idle, went for test drive and got 11 -13,
pulled off the PCV and adjusted the idle mix screw way out to 15, test drove and was 15 -17, lean.

Idle mix screw doesn't seem to do anything w/ PCV , w/o PCV , very lean until I have to back it almost all the way out.

Then I lost my left strut rod bushing and I am done for the night.

 

[BIGREDRASA]

Jim (jamyers) is getting 15.5-16.5 @ cruise, so you have come very close to what he has with your "15-17." What's stoichiometric, 14.7:1? My only concern with running lean is that you're getting an average of the cylinders, I imagine. In that case, #s 1 & 6 would be much leaner than that, and could be trouble. Maybe we'll hear from the engineering types?

 

[Bort62]

Maybe we'll hear from the engineering types?

None of those here

 

[Bort62]

Alright, I just read the thread...

If you are going rich w/ the PVC connected, My first guess would be the PV. Idle vacuum will be slightly lower with the PCV on (it's a vacuum leak, remember) And that may cause the powervalve to crack open.

However, there are some things about that theory that don't make sense. It's also possible that, with the PCV connected, the carb is not idling on the idle circuit but instead on the main. That woudl explain why your idle adjustment screw doesn't do crap. This is also an extrmeley common problem w/ carburetors.

What is your idle vacuum? and what is your idle RPM? PCV on/off ?

Check to make sure you aren't on the main w/ PCV on. Infact, if the idle screw doesn't do anything, then you almost Have to be on the main (or PV) by definition.

Check to make sure PV isn't blown...

Also, is the PCV sucking oil? Oil vapor in the exhaust will cause the WB to read mega-rich. Ask me how I know...

 

[Bort62]

When you say pulled the PCV off and instantly leans out... what did you pull off from where?

 

[jamyers]

Good question, Bort - hopefully it's still sucking through the pcv valve when he unhooks it.

...Idle mix screw doesn't seem to do anything w/ PCV , w/o PCV , very lean until I have to back it almost all the way out.

I'm thinking that your throttle is too far opened so that either the progression slot(s) are exposed or maybe it's getting into the main jetting.

I'd back the idle speed screw out until the throttle plates are completely closed, then turn it in 1 turn, set the idle mix screw to 3 turns out and see what it'll do (pcv hooked up). Might have to bump up the idle speed screw a half a turn more, but I wouldn't go much more than that without pulling the carb to verify the actual throttle plate location.

Could also be your pcv valve isn't right for the 5200 carb. I had one with a 90-degree elbow on it that looked just like the correct one for my '68 engine, but it had my AFR's way off from where the correct one was. I'd have never thought they would be that different without seeing it for myself on the wideband.

 

[Bort62]

It really is a common problem to be idling on the mains.

That should be checklist item #1 when checking out a carburetor. Make sure it is idling on the idle circuit!

If it is on the mains, then it can mask all sorts of problems as well as cause all sorts of others.

It will appear to be running fine, but over all performance will be screwy.

It took me a while to figure this out. At first, I thought "If it idles, then it's good!"

Yeah right... Often the difference between a car that runs like a cantankerous old jalopy (hard to start, stalling at stoplights, smells like gas, backfires, etc) and a car that runs like it did when Ford delivered it starts with the proper function of the idle circuit.

 

[Williboy]

It seems that the 5200 is idling off of the mains. Looked down the throat and there is a lot off fuel pouring in the primary. Tried backing off the idle and adj the mix screw like Jamyers suggested but no change. Did remove the Primary idle jet, no difference unless I also removed the idle jet holder which helped a little but obviously that was adding air to lean it out.

As for the PCV it only makes a difference if the PCV is removed from the circuit, pulling the hose at the carb or PCV. Just pulling the PCV out of the valve cover doesn't help. It still pulls a good suction and I checked with NAPA and it's the correct PCV for a '68 ( motor year). Didn't get a chance to check vacuum yet.

So what differentiates the idle circuit from the main circuit?? Vacuum??
Bad Power Valve?? How do you check it??



I have the 5200 book on order. Hopefully it will come soon.

Thanks for everyones help on this.

 

[Bort62]

mmmm'kay.

It does sound like you are idling off the mains. The reason you are rich @ idle is because the primary circuit delivers way too much fuel. The reason you go lean & idle kicks up when you pull the PCV valve off is because you are creating a fairly large vacuum leak. That leans out your "idle" A/F mixture and also increases the idle. It's the equivilent of opening the throttle plate more. (without the increase vacuum signal pulling more fuel)

I am not intimately familiar w/ the 5200 - but somewhere around the throttle plate there is going to be a small slot/hole. Air flowing past this hole into the engine creates a vacuum via venturi effect.

That vacuum sucks fuel out of the bowl through the idle jet, and dumps it into the motor.

If this hole is plugged or one of the passages is plugged, this system does not work. Also, if the throttle plate is misaligned or open too far the hole will not be exposed to the airstream properly and no vacuum will be created.

Either way, your idle circuit will not function, which will force you to idle on the mains. Hence all of your other problems...

So, the question @ this point is... What's up w/ your hole ?

 

[Bort62]

The idle circuit is described above.

The main, or primary (in a multi bbl carb) functions by a similar fashion.

Air flowing past a "hole" creates a vacuum due to venturi effect. This vacuum sucks fuel out of the bowl.

However, there is a calibrated leak called an air bleed that essentially controls @ what point the main circuit starts flowing fuel.

Increasing the size of the air bleed will increase the amount of air flow past the reference point necessary to start sucking fuel out of the mains, and vice versa.

So the airbleed is what keeps the main circuit from engaging @ idle. With this in mind, it is also possible that your air bleed is plugged.

If you want to understand how a carburetor works, it is imperative that you understand the venturi effect. All the math is not important - but the fundamental concept that a fluid flowing past a small hole creates a low pressure zone is. Carburetors wouldn't work without it.

http://en.wikipedia.org/wiki/Venturi_effect

 

[jamyers]

I'm with Bort, there's something plugging up your idle passage (it doesn't take much at all, really).

On the 5200's the idle air bleed is fixed. iirc, it's just a drilled hole in the top of the carb body.

I'd strip the carb down, then shoot some carb cleaner backwards through the idle passages, starting with the idle mixture screw hole. then put the mixture screw back in all the way, and shoot into the progression / transition slot or holes. Then put the idle jet back in, and do it again. Then take it apart and flush it backwards another time, followed by some compressed air for good measure.

Then reset the idle speed and idle mix screws as above, and see how it runs. The basic idea with a 5200 is to get it to idle as well as you can with as little throttle opening as you can, since the idle mix screw adds not only fuel but air as well. (I can get mine to idle with the throttle (idle speed screw) nearly completely closed - something like 350-400 rpm, but it's pretty stable)

 

[Bort62]

I think it's just as likely that he has the throttle cracked open too far @ idle and is overcoming the air bleed.

What is your idle speed? What is your timing ?

Retarded timing + throttle open too far can give the appearance of idling correctly, but in reality be idling on the mains.