So I'm having problems with my 680 ss quick fuel carb. I'ts always been rich and I guess I never got it figured out. But since I rebuild my engine and broke it in I can't get it to idle down and I can't find a vacuum leak so with it pouring fuel down the cylinders I need another one to try. I've been looking at summit and they have the 750 holly I think it's a 4150 for a little over 300 bucks with a electric choke U think this would be to big? It's going on a small block 392 stroke engine 318 based block rhs heads xe 284 cam mp ignition edlebrock airgap four speed car. I am willing to go smaller also as I'm tired of fouling plugs.
Ditching a quick fuel carb.
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What is the ignition timing at idle?
dano
Evil Handy Man
I had a similar issues with a 625 Demon and it ended up not being the carb. I had weak spark from a bad coil and poor ground to the ignition box. You could also have a vacuum leak under the intake. Was the block decked? Are you running a vacuum advance distributor and if so is it plugged into the spark timing vacuum port? The choke be it manual or electric needs hooked up. If manual wire it open if electric make sure it is wired and working.
Yes it's a vacuum advance dist. It's plugged into the port on the passenger side of carb metering block per direction that came with carb. It's a mp igniton orange box I think it's grounded good I had this all running last fall but the carb has always been rich. I just broke in the cam but the engine screams as soon as you fire it up. I could'nt find a vacuum leak on manifold or under carb. I was thinking the choke was sticking but with the carb pouring fuel into the engine I just fouled out the new set of ngk uridiums I just put in. So I'm hoping to get another carb to try after I change plugs again and before I end up washing out the rings. The timing is around 32 degrees at 2500 rpms set the best I could trying to hold the choke plate down to keep it from screaming. And turning the distributor and trying to time it with a lite all at once.
Once the engine started I did'nt want to shut it off till after the cam was broke in. So I had to hold the choke plate on the carb almost closed and keep the rpms up where they needed to be for cam break in. I was thinking a choke or vacuum leak but can't find a vacuum leak yet and it's getting old changing plugs when they foul. If it's a vacuum leak I don't know that my timing is correct as I had to use the choke plate to keep it from screaming and to keep it from stalling If I closed it to far. But could'nt get it to just idle. And it is a new coil I have two just in case. When it first fired up it screamed but sound good but now it's missing and spuddering I pulled plugs and they are all fuel fouled as before when it would act like that.
Once the engine started I did'nt want to shut it off till after the cam was broke in. So I had to hold the choke plate on the carb almost closed and keep the rpms up where they needed to be for cam break in. I was thinking a choke or vacuum leak but can't find a vacuum leak yet and it's getting old changing plugs when they foul. If it's a vacuum leak I don't know that my timing is correct as I had to use the choke plate to keep it from screaming and to keep it from stalling If I closed it to far. But could'nt get it to just idle. And it is a new coil I have two just in case. When it first fired up it screamed but sound good but now it's missing and spuddering I pulled plugs and they are all fuel fouled as before when it would act like that.
I just want to rule out the carb for the high idle and mass amount of fuel it's pouring into the cylinders. At least if i put on a differant carb and it stops idleing up so high I can maybe get this thing to idle and set the timing where it need to be. As I can't find a vacuum leak with it running the way it is and me having to hold the choke plate to keep it running. The engine has'nt been decked.
JamesRR
Well-Known Member
What is your INITIAL timing? I had the same problem with a quick fuel. With the cam I have I needed like 20 degrees of initial timing so I could back off the idle speed screw and actually run off of the idle circuit. You are probably super rich at idle because youre idling off of the primary a bit. I down jetted 2 sizes in the front. went up 3 sizes in the idle air bleeds. I also put a bit of a smaller power valve in the front. I suspected the power valve was dumping fuel into my idle mixture because I only had like 8.5in of vacuum and a 6.5 power valve. Just my experience. If I had to do it again I would have gone with a 650 instead of a 750 and possibly bought a blueprinted carb. Good luck!
Yeah I can't get it to just idle on it's own it wants to rev up, so I can't get an initial on it. I was leaning towards just getting another carb because it would probably cost just as much to take it in to a shop and have it looked at. As I don't know much about carbs. I did down jet this carb last year hoping to have got it closer but it looks like it did'nt work. I put the smallest jets for primary I think 67 or 68 and I think 70 or 72 secondaries and adjusted the floats and backed off the fuel pressure. I do have a 6.5 power valve in the carb right now. Last fall when the car was running initial was around 20 on my car as well. It would run real well but the plugs would'nt last that long before fouling.
dano
Evil Handy Man
Does it have a provision to open the secondary's with a set screw on the base plate? You might have to remove the carb and look. Is the choke linkage all free? I had a issues once where it was bound.
I don't recall, but I am going to turn it over to the pros. I just called a shop here that does hot rods and they told me to bring it down there and they would fix it for me. I just have to have it towed there and they would'nt quote me a price.
Which is ok, I am willing to pay rather than me messing something up. I just hope I did'nt screw anything up yet.
dano
Evil Handy Man
Well, let us know what they find.
Like your other thread months ago, if you don't give the engine the initial timing that it wants, you will chase your tail for a long time thinking you have a carb issue.
Stop being sucked in by the total timing monster. It's the wrong way to set up a car that is street driven.
Everything in the carb needs to be set up correctly as well. Float level, primary/secondary plate openings. Take the carb off and see how much of the transition slot is exposed on the primary side. It should be roughly a square shape. If it's a rectangle being long going up into the bores, the primary throttle blades are too far open.
Stop being sucked in by the total timing monster. It's the wrong way to set up a car that is street driven.
Everything in the carb needs to be set up correctly as well. Float level, primary/secondary plate openings. Take the carb off and see how much of the transition slot is exposed on the primary side. It should be roughly a square shape. If it's a rectangle being long going up into the bores, the primary throttle blades are too far open.
Yes I've been messing with this thing for awhile but it's hard to get in the garage and work on my car during the winter. The weather just starting to get nice and I got the ambition to get it up and running again. I thought I had worked out the carb thing back in September just before I tore it all apart and redid it for the millionth time, but I guess not.
And not knowing much about carbs and the nice weather will go fast I guess it was a throw up between trying a different carb or putting that money toward letting someone who does this stuff for a living fix it for me. I will post the outcome when I get it back. Thanks guys for the input. I am officially throwing in the towel on this carb thing.
moparclown
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I was thinking the same thing
Its located on the passenger side secondary shaft(get yourself a small mirror and one of those pocket screwdrivers)and you won't even need to remove it.
Wow. Stop with the carb being bad talk until you get the other systems correct.
Loosen the distributor hold down and turn the housing counter-clockwise... how much does that cost. NOTHING!
If the engine picks up RPM, it wants the timing. Turn idle down and do it again.
If you don't know what the idle timing is, you are BLIND to tune the carb
I seriously doubt it's a carb issue at all. Borrow one that runs good on another car and see if you have the same problem. If you need to crank in a bunch of idle speed adjustment screw... it's not the carb!
Timing light and a vacuum gauge is about all you need to get this right. A xe284 cam? Minimum of 20* of initial timing, NO LESS! Might want as much as 24-26*
Loosen the distributor hold down and turn the housing counter-clockwise... how much does that cost. NOTHING!
If the engine picks up RPM, it wants the timing. Turn idle down and do it again.
If you don't know what the idle timing is, you are BLIND to tune the carb
I seriously doubt it's a carb issue at all. Borrow one that runs good on another car and see if you have the same problem. If you need to crank in a bunch of idle speed adjustment screw... it's not the carb!
Timing light and a vacuum gauge is about all you need to get this right. A xe284 cam? Minimum of 20* of initial timing, NO LESS! Might want as much as 24-26*
My carb guy used to work at Quick Fuel and showed me that they had numerous carbs go out that weren't machined correctly. Mine would look like it was leaking around the base gasket all the time. Not the one under the carb but the one between the throttle plates and the base plate. I believe the step on the ends of the main body where it fit over the base plate were to tall. You might look at that.
I took the carb off cleaned it up with carb cleaner, seems the choke was stuck. I got it running good enough to drive it down to the place where I had it tuned. I don't feel bad about not knowing how to tune a quick fuel carb or any carb for that matter. The guy there has been doing engines and tuning hot rods for years and he's still messing with it.
I went down there today to drive it home, I talked to the guy up front said it runs like a bat outta hell, first and second gear is just short of nasty. I drove it home, and checked it out. Yeah it's awesome.. But there is a slight sputter from just cruise to when I just start to ease into the peddle but after that it's all business. I drove it back to the shop and he said he would work on it a bit more but was taking tomorrow off and I probably wouldn't get it back till Wednesday. But very happy with my decision...
So what did he do? I'm curious.
TrailBeast
AKA Mopars4us on Youtube
SRT_DSTRHOLC
Well-Known Member
I got a two year old holly from BIGGS performance I am trying to sell. 450 plus shipping. 750 DP
No kidding!
From what I've worked on over the years, 90-95% of carb idle problems had nothing to do with the carb. 90% were initial timing issues and the other were vacuum leaks, etc.
I wonder what the total timing is now?
Plugged power valve off, rejetted it, plugged vacuum, turned the choke all the way down next to nothing or off I don't remember, and put the timing around 22 I believe. He left the floats and fuel pressure where they where set at.
I had to take it back a couple of times before he got it to stop fouling plugs, but it runs like a scalded dog. He says I may need to look into a different clutch, it's hard to find the sweet spot when I feather it out it chatters and churps the tires if I don't let it out just right. I may just need to get used to it and drive it a little more. It's a new mclead clutch and new mclead flywheel.
I don't know if what he did to get it to run right is the proper fix, but it works.
He took it over to a belt sander and cut them down.
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