JamesC

iTrader: (5)

Not a carb guy, so any assistance is very much appreciated.

Until a day or so ago, the car ran fine. Now, the carb only goes to around a 1000 RPM on high idle (used to be higher). When the choke comes off, the idle is so low that the motor bogs (but runs). Seems to accelerate as normal. A lot of black smoke fouling the rear bumper.

Any suggestions on where to start?

JamesC

sofakingdom

iTrader: (1)

Fuel level, followed if unsuccessful by a quick rebuild.

Jonathan Dyer

iTrader: (5)

Have you worked on the car recently? I've had similar problems after introducing dust/debris into the fuel bowl such that the needle and seat assembly needs a cleaning.

Also, once had the misfortune of somehow installing a power valve with 2 o-rings. At that point though so much fuel was pouring into the intake the car wasn't driveable.

Jon

bestracing

First check to make sure your timing hasn't changed then check what has been said above. Sounds like you are running really rich with all that black smoke

redneckjoe

this might be a longshot, but i saw very similar conditions on a holley once. the guy had a leaking aircleaner & sucked up dirt/dust into the airbleeds. some compressed air and a blow-tip had it fixed like new in 2 minutes.

JamesC

iTrader: (5)

Actually, the Holley book and several net sources recommend that. I've already shot the bleeds this morning with carb cleaner and may do it again before I start the car. We'll see what happens.

JamesC

JamesC

iTrader: (5)

The above failed to work. I'll remove the carb in the next few days and go through it. Maybe time for the DP I've always yearned for.

JamesC

JamesC

iTrader: (5)

I managed to yank the carb this afternoon but have done nothing more than give it a visual. Note the nasty-looking accelerator pump cover. I assume the diaphragm is the culprit. Does replacement require arm adjustment?

Also, is the 4160 supposed to have a fuel filter screen (mine doesn't)?

JamesC

paulo57509

The accellerator pump appears to be leaking, but I don't think that's the cause of your sudden poor idle. You shouldn't have to mess with the arm adjustment if it was running well before the idle issues.

Since you have the carb off already, I'd remove the bowl and check the power valve that's screwed into the metering block. If the valve is punctured it would cause a rich running condition.

five7kid

iTrader: (14)

No, the accelerator pump can't cause idle problems.

However, the gunk all around it may indicate you've got gunk buildup in internal idle passages.

JamesC

iTrader: (5)

I disassembled today, cleaned passages thoroughly with carb cleaner, and blew compressed air through them. I've installed new gaskets and a power valve (55). I'll complete the assembly tomorrow and mount the carb. Hopefully all will work. If not, maybe the DP will be an option.

JamesC

JamesC

iTrader: (5)

There are some clutch head screws securing the secondary body metering plate. I can't find info about how tight they should be--they weren't terribly tight when removed. I finger tightened them snugly with a clutch head bit in a socket. Should I be good to go?

JamesC

five7kid

iTrader: (14)

Snug is fine. You're more likely to cause damage by over tightening than problems by under tightening.

JamesC

iTrader: (5)

I did hand tighten them a bit more (hey, I'm obsessive), but not overly so. I reassembled everything this morning and at the moment of truth all went well. Actually, the Holley wasn't as complicated as I'd led myself to believe. The experience was a good one. Thanks to all who offered advice.

JamesC

paulo57509

True this. I've seen warped carb bodies from over tightened bowl screws.

redneckjoe

glad to hear you got it fixed. 4160s arent bad carbs. did you end up changing the accelerator pump diaphram? if your looking for more power, the 50cc reo kit is usually a good upgrade. one part i bought that i really like is the quick fuel technology, adjustable vacuum secondary. no more spring changes on the secondaries. you can get these carbs to respond like fuel injection if you get them dialed in.

JamesC

iTrader: (5)

Yes.

I ordered the adjustable once upon a time but returned it. Instead I installed a quick change spring kit, which probably leaves something to be desired, but I'm satisfied for the moment.

JamesC