TT5.9mag
Two atmospheres are better than one
Mine usually gets a few taps with the Holley all encompassing adjustment tool and it frees up.
Manifold Vacuum Experiment
- Thread starter RustyRatRod
- Start date
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LOL What would be the effects of just removing the check valve? I've seen people talk about it. Easy to see why it's there. To keep fuel from running back down so there will still be fuel right at the nozzle. That's why I've not removed it.
I also forgot to add that when I mash down on the pump arm and spring giving the pump some "help" that it pumps really good and the stumble disapears. So I think if the pump was working correctly, it would be ok.
Are the primary and secondary pumps the same? Could you swap them and see if the bog goes away?
Well, that's my plan. And no, they aren't exactly the same. Same color, yeah but the rear pump has three holes where the front cam only has two. I find that strange.
Charrlie_S
Well-Known Member
The check valve (weight) helps to prevent the air flow through the carb from pulling fuel from the accelerator pump nozzels due to venturi action.
TT5.9mag
Two atmospheres are better than one
Charlie_S beat me to it. It will drastically fatten up the fuel curve.
I would sswap the pump cam from the back onto the front. If you turn the 3 hole cam upside down, it will have a very close profile to what the blue cam does. You may have to slightly bend the pump lever. This has cured off idle stumbles for me several times. I can't remember which hole you use when putting it in upside down, but it will be obvious. Yes I am THAT cheap, but every buck counts.
Nothin wrong with cheap, but I was unaware they could be flipped like that, because their profile is not flat on the back side. I sure will look at it though. Thanks.
I think I am beginning to think this may be what's happening. I just went out and removed both pump arms and cams. I was wrong about the pump cams. They are both exactly the same pink cams with three holes. Same profiles and all. I don't know why I thought one only had two holes. Stupidity, I guess. Anyway, I did slightly adjust the primary pump arm a little flatter. Once I readjusted the pump sprAng, that seemed to solve it. But then, it started the stumble again. I looked and nothing was coming out of the primary pump squirter. Then it just arbitrarily started working again. So I think clearly this is an issue with the pump check valve. I'm tired of workin on it for today. I'll pull the carburetor back off maybe tomorrow and work the edges of the check valve with a file and see if there are any high spots. I bet there are.
Thanks man! That kinda tells alot about the pink cam. I may try the blue cam as well as deburring the primary pump check valve.
I've changed out the diaphragm. Send me a new 800 AVS and I'll slap it right on.
I wonder if I could replace the check valve with a check ball? That way, there'd be no edge to hang up on anything.
I replaced it already. I've inspected it since and it's good.
What I may do is get the check valve out and round the square end off. That will give it no edge to hang up on.
Aight den. Yall know good and dang well I caint leave well enough alone. I yanked the carburetor back off. I think I need wing nuts to hold it on now. lol I took the check valve out and inspected it with my magnifying glass. It had a VERY, VERY sharp square edge on one side. So, I took it and shortened it about 1/8" or so on the grinder and then took a file and put a really good bevel on it all the way around. I shortened it because I've read in some instances, the nozzle screw limits the check valve's travel. In any event, I believe I struck gold. Now it has zero stumble. I mean zero. We'll drive it tomorrow and I'll be able to tell more long term then. Thanks for all the ideas. They definitely helped point me in the right direction. All that said, this carburetor has had this issue since new. So much for real quality these days. lol
if it was fine before why do you think changing cams will fix it
Id pull the the acel pump check for crud and the gasket theres and adustment there as well
all of a sudden you shoudnt need the blue cam if she was running perfect on the pink
You're not reading the whole thread. It's never been "fine". It's always had a stumble off and on. Read post #146.
stumble off idle if you mat the throttle and it stumbles blows a lil black then goes after the mains start you need a bigger squirter you start with that not the cams.Sorry ive not read it all sounded like it was not squirting like the rear and that would be a delivery issue ill go read it
It was the primary pump check valve. Read 146 and you'll see my fix.
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