I have a Holley 4160 that is driving me crazy. At least I can say WHAT the problem is, so that is something.

The "off idle circuit" on one side, doesn't work. It idles fine mostly, but as soon as you crack the throttle w/a load, it drops 4 cylinders and turns into a V4; it only runs on the 4 cylinders fed by one plane of the dual plane intake.

While it's doing this, if you manually manipulate the accelerator pump, the 4 dead cylinders jump to life -proof that they're starving for fuel just off idle. Open the throttle more, and as soon as the main circuit comes on line, it runs normally.

This started a couple years ago, and I took the carb apart, cleaned/shot air/shot brake cleaner through all the orifices in the metering block, and put it back together...same problem. Took it in to work (shop) and several mechanics played w/it, poking wire through orifices, etc, and after that, it ran much better, for one summer. Now...it's back to the same thing. Took it apart tonight, and I'm telling you...the thing is CLEAN inside. No residue, no varnish, it's clean. I started blowing though every orifice again, paying close attention to the ones that feed air and fuel to the idle and off idle ports. Found no restrictions or debris.

Any ideas?


One other thing that is odd to me, is that in the throttle body, there are two holes, forward of the primary bores. One has a TINY orifice in it that connects to the left side idle circuit. I can fit one strand of a coper wire through it, barely. The other side is blocked off. I can't get shop air or a wire through it. Thing is, when mounted on the engine both those ports are covered/blocked off by the base gasket. Any thoughts on these?

 

Similar problem with my former Holley.Took it apart a couple of times,replaced gaskets seals metering block.Still wouldn't run right.Said screw it bought a new Summit 600cfm carb for less than 300.00.Used a four hole carb gasket and closed up the cut down divider on the air gap manifold...Throttle response improved along with better MPG's...Summit carb has been perfect since install.
http://forums.corvetteforum.com/c3-t...or-review.html

 

Ive seen cases where the holes werent machined all the way through

Wish I could be of more help sounds like youve narrowed the problem down now just figuring out how to tackle it.

 

Well blew air and brake clean through every orifice in the primary side I could shoot stuff through. Then stuck wire in any hole that I thought wire-sticking might help.

Put it together this am, fired it up, no diff. I DON'T "GET IT". How can passageways that move air and fuel, stop working or "wear out"?? Grrr. Apparently, metering blocks for '06 and earlier 4160's have been discontinued too, which is BS. I'm pissed. I don't like Holleys, I don't "get" why in the world this thing won't deliver fuel off idle, I don't like Edelbrock carbs either so what do I do now? I want to understand why this thing won't work.

 

I sure wish I could help. I have a 4160 also and really enjoyed working on it.

The initial good news is that you know the carb was working correctly at one point. Then you have determined that one half of the primary circuit cuts out during the transition from idle to cruise. That is great troubleshooting sir.

The part about the discontinued metering blocks is interesting. What about the aftermarket ones like Quickfuel?

I had been thinking about one of these for a while but haven't done so.
http://www.summitracing.com/parts/qft-34-8/overview/

You may also check craigslist if there is a listing in your area for 4160 parts. You may be able to pick up a parts carb for $10-$15. Swapping in another metering block would test your hypothesis. Seems like the odds of the same circuit on the same side of a different block failing would be slim. It would at least give you a second set of parts to dabble with.

Good luck, keep us posted.

 

Just a thought... Are you using a real Holley carb kit to make sure you are getting the correct gaskets and seals? An aftermarket set may not be 100% correct for some reason.

 

Thanks for the replies. Replacing the metering block w/the QFT one is a great idea. I am waiting a return call from Holley tech, but I may go that route.

As for gaskets, I'm using "Holley" gaskets, but the problem started w/no changing of any gaskets, in the first place.

 

I got this sage advice from, of all things, an air-cooled engine dealership. He told me every single customer carb problem stemmed from our current crap gasoline. And it usually was letting the gas sit in the carb over winter. The volatiles evaporate and leave a sort of varnish in the tiny passageways. Those tiny holes are so small that capillary action prevents any kind of carb cleaner from dissolving it.

As a last resort I would try sticking a proper sized wire from an acetylene torch tip cleaner into the suspect passageway. They are not smooth or soft like a copper wire.

 

I can't get a wire of any stiffness though many of the passages due to bends, "Y's", etc. I think I may take it apart again and throw it in the dish washer...

 

Hey Tom,

Be careful with the aluminum in the dishwasher. I found out that hot soapy water will react and discolor the piece at the least.

John

 

10-4. Here is what it looked like when I took it apart.







I'll let you know how the dishwasher experiment turns out....I don't have high hopes, but maybe hot water, high pressure, soap...we'll see.

 

Did you try letting it soak in the Carb cleaner overnight (the stuff they sell in gallon jugs)
I second the ethanol messing things up.... fuel stabilizer helps. I pulled my edelbrock Carb off my vette last spring and it looked like it was filled with clear jelly. Same issue with my motorcycle .
I had dual dellarto carbs on a VW kit car that drove me nuts till I found two plugged passages I could not free up...ended up buying another set of "parts carbs" and swapping everything to them which resolved my issues. The ethanol also effects the rubber fuel lines I've been told.

 

Well....the dishwasher worked! I ran the main body, the metering block, and the TB in the dishwasher for 2 hours, with two detergent pellets, and about 3 cups of vinegar. When it came out, I re-shot every orifice with brake cleaner and air, put it together, and fired it up tonight.

Ran smooth as glass.

 

Killer!

Tom, would you be able to post an after pic of how things look after the dishwasher? I love the idea and would like to see how things turned out.

 

Af%#&ing amazing! The current Holley gaskets are blue and don't stick. From the photo your gaskets seem to have stocked and torn apart.
Great fix!

Pete

 

I can take some pics when I take it back apart...but basically, all the parts LOOKED like new. Unfortunately, you can't see the parts that matter; little passages, air bleeds etc.


Unfortunately, I spoke too soon. Ran absolutely flawlessly for about two hours....then went right back to doing the same BFS that it was before; hard staring, rough idle, wants to stall, and no off idle circuit feed at all. Odd thing is, if I run it under a good load for "a while" (5+ minutes?) then it idles smooth again, and comes up off idle OK. Shut it off and restart though, and forget it. Garbage.



Yes, good observation. I got the blue gaskets. Going to try the Harbor freight, ultrasonic parts cleaner w/carb cleaner next.

 

Tough problem! Sorry it came back. For me, at a certain point, especially with a carb, that you're just better off buying a new one. I always factor in how much time I spent working on it and then bounce that time, against what I make an hour at work. If it's waaay out of line, like you've spent 40 hours pulling, cleaning, adjusting and working on this carb, then (for me, at least), I'll just spring for the new carb.

As an example, Holley sells the Street Avenger series and we installed a 670 cfm on a client's classic Chevy short and wide, pickup at the shop, that had a terrible carb, that the customer picked (drag racing carb!) . The Street Avenger ran flawlessly out of the box! The misbehaving truck, that surged, with a rough idle and misbehaved in general, was suddenly a sweet, but potent little truck. The carbs are individually flow tested, wet at Holley and are very easy to deal with. Even the vacuum secondary springs, are right there at the top and it takes less than two minutes to even change one out. Smooth idle and very crisp response.

Of course, this is just a suggestion, if you want to continue, you might just defeat it. Just might...

 

I hear you. I feel that there HAS to be some little bit of something, plugging a tiny bleed or passage in the metering block. I'm going to try to clean it once more...then if it doesn't come around I'll buy a QFT carb.

I have <5 hours in it so far. Probably about 3.

 

It almost sounds like you have some obstruction caught in one of the orfices or tubes and you managed to knock it loose in the dishwasher, but it didn't come out. It reminds me of a piece of sand I had caught in my power washer, I could clean it and blow it out and it would work great for a short time and them plug up again. Ends up being a small piece of rusted metal that never did come out of the line, it just moved around.

What about something like trimmer line, it's flexible, just may not be small enough? Or large fishing line?

 

100%. The problem is, those passages make abrupt changes in direction (drilled from different angles). so you push something in there, not knowing which way a passage turns or jogs, and the "poking device" stops. There are tiny "freeze" plugs pressed into the top of the metering block -obviously plugging a drilled passage. /i may try to remove those so that I can actually SEE down into the passages in the metering block. Can't hurt at this point...I figure the metering block is junk at this point.