5200 Secondary Sputter

Rustang Racer

Well-known member
When the secondary opens on my Holley 5200, the car sputters and then takes off hard. I've tried everything I can think of to get rid of the sputter. I'm pretty sure there are no vacuum leaks. I've tried a huge range of secondary jets which made absolutely no difference at all and didn't change the plug color at all either. I put 90psi of air through the secondary fuel passage below the jet to make sure there are no clogs. When I look down the secondary and rev the secondary with the engine running, a mist of fuel sprays immediately and it looks adequate compared to the primary. My timing is right. The float level is high enough. I took the idle jet all the way out to try and get more fuel. (I put a screw back in its place just enough to plug the hole) That didn't make any difference. No matter how slow I open the secondary it still sputters so I think the opening rate is ok. The only time it sometimes doesn't sputter is when its reved up somewhere over 4000. Is this a problem that you other guys have been able to fix?

Also, if I floor it just off of idle (like I might do if I ever paniced) the car just stops completely for about a full second and then takes off. Is this normal for a mechanical secondary progressive carb?

I'm all out of ideas :x

Other than this problem, I really like the carb. Starts better, idles better, better low end torque, better gas mileage, and a lot more powerful than even my 300 YF.
8) it sounds like you need to richen up the accelerator pump circuit. if you dont have a flat spot when you accelerate normaly from a stop then try using a smaller pump shooter. this will give a finer but longer duration spray(this assumes the shooter can be changed in these carbs, i dont remember). a larger pump pump jet can also help here.
What do you mean when you say sputter. Is the car running out of fuel, of getting to much. Is it a hesitation or a getting the rpm up enough to use the fuel. The reason I ask this question is that the 5200 DOES NOT come with an accelerator pump on the secondary in stock form. It can be modified, but that leaves the shot volume to be sorted out by the builder.
Another thought, maybe the secondary is opening to soon. It is mechanical, and can be adjusted. The idle jet on the secondary side of the 5200 / weber progressive is only needed to keep the secondary main circuit wet, i.e., ready to flow when the secondary opens. However, to large a jet can induce a flooded condition until rpm's are high enough to use the fuel. I would guess that when you removed it the problem was imcreased. The 5200 is popular short track race carb and is fequently modified to support consistant high rpm running. Where do you get yours. It may need to be rebuilt back to stock. Parker Carburation (www.parkercarburetion.com) specializes in these carb and will rebuild one for $65. Hope this helps.

Wrong address on the suggested sight. Try this surpluselectron.com/aaron/holley.htm
How is your ignition system?

It sounds like you may have loose wiring, or old leads and plugs. If its carbeuretting well, and you say the timing is fine, then it may be caused by a faulty ignition component..
The sputter is a hesitation and the engine sounds like its not firing right. Its pretty brief. I have a site about modifying for a secondary accelerator pump but you should only do that if the primary and secondary open at the same time because the pump will spray in the secondary even if it isnt open. I don't think it is ignition because the car runs fine at all other times, plus its all pretty new (Duraspark II). When I took the idle jet out , the problem didn't change at all. That's why I'm so baffled. I was just hoping to see some kind of change, better or worse, but it ran exactly the same. The carburetor is freshly rebuilt by holley. When is the secondary supposed to open ? Right now it opens at about 3/4 throttle. This problem happens even when I open the secondary very slowly, only while driving though, not in nuetral. The car runs great at all times except for the initial opening of the secondary.
I'm with ya on this one !?!?

I assumed from your original post that you had a secondary accelleator pump. I suspected this was part of the problem. You are correct, the pump would put fuel into the secondary need it or not. I thought maybe your issue was flooding. I am not convinced that it isn't. Removing the secondary idle jet should have made it worse. Should also make the car idle ruffer. The beauty of the 5200 / Weber series is the tunability. The down side is the tunability. If you had a problem with one of the internal circuits it could be had to find. So, if it runs well on the primary, you can adjust idle mix and get a nice idle, your ignition is in good shape and set up correctly, then the hesitation is a sudden "to lean" (something clogged - which you have already looked into), or a sudden "too rich". Could be either, and it is clearly in the secondary main circuit.

Try replacing the secondary idel air bleed and idle jet with new / clean jets. These jets control the amount of fuel stored in and flowing to the main circuit. Use the size the carb came with. Go one step at a time, i.e., don't concern yourself with adjusting the jet size til the problem is solved.

Second possibility, at the bottom of the idle circuit there is a secondary transfer hole that is feed by the seconary idle circuit. It is exposed to the air flow in the throat of the secondary just after the throttle plate starts to open. If it is clogged it could contribute to the problem as it is the stand in for the secondary accellerator pump that the 5200 doesn't have. If it is over size (drilled or whayever - no jet) it could contribute to a sudden dump of raw fuel just as the secondary opens (you need to take the carb off the car to see this hole). I hope this makes sense. This is hard to do in print. A good carb manual may be a good investment.
That secondary transfer hole sounds like a good thing to check. It's all the way on the base of the carb, not in the air horn, right? I can't find that hole in any of the pictures I have of the carb but I'll probably find it when I take the carb off. This will be the fourth time taking it off :unsure:
Yes. In the base just above the secondary throttle plate. As the secondary opens the hole is uncvered, i.e., air is able to flow past through the venturi and into the manifold. Hope it hasn't been bored out by a prior owner thinking this would improve throttle response.
8) when i made my suggestion i knew the 5200 had the accel pump on the primary side only. i forgot about the transition slot though, if it is clogged it can cause the problem. enlarging the idle jet wont neccessarily cure the problem as the fuel has to be able to flow. if the idle air corrector jet is clogged it to can cause the problem by delaying fuel flow. and if the idle air jet is too large the mix can be too lean so you might drop it one size and see if that helps.
I decided to try the lazy man's aproach before pulling the carb off again. I took the secondary idle jet out with the engine running and sprayed carb cleaner in the hole while revving the secondary. When I did this with the engine off, I could see the carb cleaner coming out into the bore just below the secondary throttle. This helped quite a bit. I still had to use pretty big jets in the primary and secondary. 315 and 470 respectively. Is that a lot bigger than they should be? I'm planning on just leaving it this way. There is still a bog if I open the secondary at low RPMs, but no misfiring. Above 2500 the transition is fine. Thanks for your help.

When I first put this carb on, I said I would I would run the car with my G-tech and compare the time with my times with the 300 Carter YF. I tried but my rear main is leaking oil all over the clutch so it slips pretty bad. The shift light came on in third gear and that shouldn't happen til a little over 100mph. I never got over 70mph. So sorry I don't have any hard numbers but this carb is a lot stronger than the 300 YF and the YF was a lot stronger than the original Autolite 1100.
Rustang Racer
I still had to use pretty big jets in the primary and secondary. 315 and 470 respectively. Is that a lot bigger than they should be?

Sounds like you have it jetted to big? is the tip of your exchaust black? Does it blow black smoke when you rev it up? (have someone look!)
I just rejetted mine and am using 325 & 340 and it's still a little rich!
And it was tested on the dyno and 14 to 1 air ratio.

If your just running the 5200 to a regular log head 1.5 or 1.75 your probly too rich, the 5200 has two 1.5 ports feeding into the smaller log opening, I'd jet down to 225 & 225 or some where close and see whats up?

I'm running the Aussie 2V head now, but I first installed the 5200 on a regular log head and my jetting was 140 & 240 and I only had a little stumble when floored! Hope this helps?