So this is not the time I wanted to be facing a setback..... but of course no time ever is.

I was running rich erratically, and getting awful gas mileage, and my engine actually idled better with the idle mix screws cranked all the way in (should be closed, engine off). I changed the power valve to one of the same strength (65), put everything right back together with new good gaskets, tried to start it, and got nothing but a veeeery sloppy run. Just to keep it alive I had to push the pedal way down.

It seems like it's flooding. All 4 header tubes coming off the lower plenum are barely warm, and all 4 off the upper are hot like they should be. All 4 of the lower plenum plugs are also gas fouled every time I check. I change them out for dry ones though, and they just foul again.....

I remembered the gasket behind the power valve.

The carb is a Holley 4160 elec choke vac secondary by the way. I have 66 jets in the front right now. It was running rich on those, because of the power valve, but running well. I was thinking that maybe the engine was just too lean to run now with a good PV and those small jets, but with the lower plenum showing every sign of flooding, that doesn't seem right.....

What do you guys suggest?

AleX

 

Also, I pulled off the front fuel bowl, and for the first time ever, it was empty...... very weird.

 

maybe im dumb...but what do you mean by upper and lower plenum and the headers being hot vs. warm?

The only time you should touch idle mixture screws is with the engine at operating temperature which = 200 or so-ish degrees F. which i think would make both headers F**^$%^ hot.

Maybe im missing something?


Or maybe you need to start over with a carb you haven't messed with...it is easier to run something not perfectly fine tuned...

 

Plenum means plane. It is the upper and lower plane of a dual plane intake manifold.

I did word it a little confusingly you're right, I was in a hurry.

What I meant was, all the cylinders that are fed by the upper plane of the intake manifold are firing, and all those fed by the lower plane are not. You can tell this by licking your finger and touching each individual header tube one by one and feeling which ones are hot.

You're correct about the idle mixture screw adjustment, you should only adjust them for tuning when the engine is fully warmed up, and in gear, but I'm talking about a completely different type of test. On this carb, when you crank the idle screws all the way in, as long as your idle is set conservatively, the engine should shut off. There should be zero gas running to it. When I cranked mine all the way in, my engine actually ran better, meaning that aLOT of gas is getting in from somewhere that it shouldn't be.

That whole test also was done when my engine was running very well, just getting awwwful gas mileage.

 

How do you know which ones are fed by what? is it as simple as looking at the intake and tracing?

 

Check your float bowl levels especially since you removed the front one. Those bowls can be turned one way or the other slighltly when putting them on changing your float level. Mine did the same thing as yours. If that doesnt work yiou maybe got a piece of dirt in there somewhere even when you think you didnt. I been there also it sucks.

 

LongTravel, no, it's not that simple at all unfortunately haha. But there are plenty of diagrams out there on the computer, and those, combined with forums like this, and technical write ups, can give you a pretty good idea of what's going on.

And PA yaaaa I've already been through the mill with floats, over the winter, so I'm always careful now, it's not that as far as I can tell. And a little speck of dirt or gasket is all that's been going through my mind too, but I'm always sooo careful, I vacuum all the surfaces right before everything goes back on.

I'll keep plugging away I guess, was just wondering if this was some common obvious problem.

 

I say double check your acc pump clearance too onec again because your bowl has been off. If its not that i say its dirt. It only takes the smallest piece of crap to cause a headache. I take it yours has the fuel tube on the side that gets sealed with an o ring at each end? I had one of them disolving on me too. Mine would only run good at like 2k on up anything below it sounded terribly flooded running on only a few cylinders.

You maybe in for a good soaking and gasket set again. I have basically the same carb as you just with mech choke. I'm up to #70 jets now. Mine had 66's in it and it was way way to lean. Seems pretty good now.

 

Wait wait, tell me more about that fuel tube O ring? Those are always a major pain to seat right as I'm sure you know, and with all the rejetting and all I've done recently, I'd put that high up on the list of things that could be wrong, and your symptoms sound the same....

Why would that make me run rich?

 

Well ours were not in the best of shape when we had it apart the last time. Between some othe the O ring missing and also another thing to check is the little gasket washers on your fuel bowl. The o ring pieces will end up directly in your carb since they would be past any filter you may have. Same goes for the washers. if they are falling apart at all everytime you push the bowl bolt in you could push a piece of garbage into your carb. It was one of those 2 things that was getting me since the rest of my system is clean and filtered.

My carb acted like it was just dumping fuel into the motor. Happened 3 times on different occassions till I got it figured out. When it did it it would just be all the sudden and not get better till soaked and blown out with compressed air.

 

Well my bowls are off and before I read this I figured I knew exactly what you meant. The rear O ring has apparently been getting munched every time I pop a bowl off, and when I blew into the fuel inlet of the rear bowl with the float up, air was still getting past the needle valve! A little piece of rubber must be in there, just like you said. That, and on closer inspection, my secondaries have a little play in them, and can open even when idling. This is probably exactly what the problem's been!

I'll be back, but thanks for the suggestion, I think you put me in just the right place!

 

No problem I'm full of useless information

When you do decide to put it back together for good make sure you lube the o rings so you dont butcher anymore.

 

Hmmmmm, well I fixed the secondary thing, adjusted the choke a little, changed power valves, cleaned both bowls (and made sure that valve was seating), and let the engine dry out allll opened up for a few hours while I did it all, and it runs EXACTLY the same......

This is really frustrating.

I have a brand new in the box 670 Street Avenger that I've been tryyyyying to avoid using, so I could sell it (it's a little big for my purposes anyway), but I may just plop it on. Nobodie's bought it in 2 months anyway. Agh.

 

You will have to soak everything and blow it out with compressed air. Trust me I been there. Going over each hole in the main body with carb and choke cleaner is not the same. It needs to be cleaned right at this point.

 

AGHHHHHH! This has just been quite the afternoon..... I just had this whole reply all set to go with a whole play by play and then the internet quit, GAH!

SO, here are the highlights: You're totally right PA, I tinkered with it a little more, but it ended up burping and catching my whole engine bay on fire. Luckily it was just gasoline, n the extinguisher put it right out, but now everything is COVERED with that white stuff, gahhhhhhhhhhhh.

Thank God though nothing was damaged, including my house......

So, after that, I was just fed up, and threw on the 670. It ran like a dream without so much as an idle adjustment, or a change of the old fouled spark plugs. That confirms everything you've been saying, that that old 600 probably just had problems all around. It has been through the mill.....

So, I caved, but the 670 will pay for itself in just a couple days of work, and I missed 4 this week....... And now I have time to reeeeeally take the 600 apart right, soak it LONG, and then build it to be PERFECT for my engine. For 400$ down the drain by not selling that 670, it's actually a pretty big relief to have time, and a darn car again.

Thanks for all the advice, should have just followed it in the first place..... as usual.

But at least she's back to life! AleX