Hey guys, new to the forum here. I have a GM Performance crate 350/290hp engine in my 57 chevy truck and I have had nothing but problems with it. Right now the problem is that it is running really rich all over the rpm range and at idle. I've adjusted the idle mixture set screws to get max vacuum and had it idling well before, but right now it is just not idling unless I keep it at 800rpm or higher with the gas pedal (I can't even adjust the curb idle screw high enough. It's running crazy rich and sputtering a lot and then sorta leans out over 1500 rpm. then the worst part. when I shut the engine off fuel is leaking all over the intake manifold from all around the base of the carburetor . It started out of the blue one morning and have been at a loss of words and directions since trying again to adjust idle mixture and idle speed. I have a non adjustable float style holley 600 cfm on top of a edlebrock performer rpm manifold and this is the first time fuel has been leaking out of the bottom of the carb or leaking fuel of any kind! please help because this is my pride and joy and I love driving every chance I get!!! Summer in VT is short and I don't have much left. Many thanks in advance!
Sounds like you have a piece of gunk stuck in your float needle , you have to take the bowl off and clean it out.
The bowl gaskets, jet plate gaskets or accelerator pump might be leaking. Get the LIST number off the air horn on the carburetor and get a rebuild kit for it. Internal leaks on the jet plate gasket might cause the rich condition. A failed power valve could also cause the idle problem. The alcohol in gas causes problems and the gaskets can fail if the gas evaporates and the gaskets dry out.
This carburetor was bought new from Summit in 2008. Could it already need a full rebuild even though it didn't leak at all a week ago, and now it's leaking on all sides of the base plate?
Although it seems your base plate or a fuel bowl gasket is gone, check the fuel pressure anyway. My 4160 was dead rich for months as I chased down power vales, needle & seat, float level, etc. My stock, replacement, mechanical pump was putting out 10 pounds of pressure once it got hot. Once I put a regulator in, problem solved.
Did you have a backfire recently??? That can blow out power valve and cause some gasket leaks....... LW
If your carb was working a week ago it must be a minor problem. A Holley rebuilt 5 years ago might have a stuck float needle. Buy a new one and fit it. No need to remove the fuel bowl. It comes out from the top. Set the float level by removing the brass plug on the side of the bowl and adjusting the needle up or down so fuel is just level with the bottom or the thread. I'm surprised nobody gave you this advice earlier!
midroad, unfortunately it's a 4160 carb with non adjustable floats. and LWEL I haven't had any backfires in the last month or so. as I said in the OP I have been trying to adjust the carb to run right since I installed it, has been running rich the whole time. I'm going to look at the needle and try and clean it to see if that fixes the fuel leaking problem and then get a regulator to help the rich condition. Then if it's still running rich I'm going to try and take the jets down 2 sizes.
You may need to replace the needle and seats in both bowls... And check the fuel pressure... No more than 5 psi for that carb!!!... I don't think that those style needle and seats could handle more than that... If it were me, I'd just change those bowls out for the ones with adjustable floats...
I've never seen a modern era holley that didn't have externally adjustable floats, it'll also have a check valve for powervalve blowout. Have you run the motor without the air cleaner? It sounds like there is trash in the neede & seat - have you had the air cleaner off it while running? According to your description I'd expect to see raw fuel running out of the front or rear bowl vent into the engine and when the engine is shut off the overly filled bowl will continue to run raw fuel into the engine thru the boosters until the fuel level is too low to flow. I might be misunderstanding the carb, a 4160 is a vacuum secondary 4bbl holley..is that what it is?
I think for 40 dollars i would get a kit comes with needle and seat and all gaskets face it 5 year old carb, this junk fuel at the pumps you might save your self alot of aggervation go the extra mile. Good luck my friend!!!!
Still throw a regulator on that then any more than 7 psi can push fuel out places you did not know you had!!!
Nobody here added the need for a filter , Holleys are great at the smallest particle sticking the needle open , over pressure will mimic this too. as for getting dirt in needle / seat from running without an air cleaner , that is just not possible, we have run without air cleaners on dirt track for years , got mud in venturies before ,but dirty air cannot backtrack into fuel bowl. put in new needle/ seat , new gaskets , and filter , filter, filter , and 5psi at carb, is plenty
Sounds to me you must have a sticking float, or bad float valve needle seat, or bowl gasket. If your Holley has the screw out sight plugs on the bowls, you shouldn't see fuel coming out the plug holes when idling. Fuel pressure could be to high as well if something went wrong with an in-line electric fuel pump regulator (been there, done that). --- Steve ---
So the plan is to spend money!!! I am going to get a fuel pressure regulator set up. and while I'm at it I'm going to get new lines to run from the pump to the carb to make it look the way I want too. I'm also going to take the carb apart and possibly replace the float/needle/seat as needed. Probably going to add an inline fuel filter as well. updates and photos to come in the next few weeks...work takes up a lot of time these days.
yes that is what it is...it is a mechanical choke, vacuum secondary, 600cfm carb. this version does not come with adjustable floats and it is still a readily available carb through summit or jegs or anywhere else.
The great thing about Holley is, you can pull the needle and seat out with out pulling the float bowls.... That should tell the story... On that engine, I would plug the power valve and run 72 square myself. Read the plugs as you go to do final adjustments over time I like a crisp throttle and plugging the P/V does just that, it also eliminates the variable..... I guess that's why Holley sells the plug
If it ran good for a week and then started running too rich and leaking fuel there is something wrong with needle/seat or possibly the power valve. High ethanol content in your fuel could be causing this problem as well as dirt or too much fuel pressure.
I've never heard of a non-adjustable float on a 4160. Some of the early ones you have to remove the float bowl. They are adjustable, just not externally.
http://www.summitracing.com/parts/hly-0-1850s/overview/ Here is just one example of the 4160 model carbs with non adjustable floats. If this is adjustable internally please let me know, but I don't believe it is...
I had a Holley, that was on a recall list. They would not tell you, unless you called them to complain. I had taken the bowls off, to find that the inside of bowls were flaking off. This would hold the needle up. What it would do, was to flood, untill all of the pressure bleed off. A very hard restart. At times it would idle perfect, then WTF. . Noticed you bought it in 08, about the time of the recall Google link below https://www.google.com/webhp?hl=en&...cp.r_qf.&fp=2ca993b8caa4843b&biw=1600&bih=645
holy cow, I'm glad that you brought that up because that is pretty much exactly how my engine runs...I'm still probably going to spend the money and get the fuel pressure regulator since it has been running rich from the start, but I'm going to take the carb off and look at the inside of the float bowl and give Holley Tech Support a call! thanks for the great info!
I think Summit is mis-labeling these carbs. They are adjustable, they are preset by Holley so they theoretically don't need it. From the Holley carb description: <LI class=feature>“Next Gen” needle & seat design eliminates the need for external float level adjustment. They can be adjusted internally.
The carb in the pic clearly has externally adjustable floats. Loosen the Big screw by the fuel inlet, and turn the nut under it it uses a 5/8 wrench..... or.... loosen the big screw, then unscrew the nut to pull out the needle and seat.....But hey, what do I know......
Not sure who told you the 4160 doesn't have adjustable floats, but that's wrong. They don't have externally adjustable floats, but you can most certainly adjust them by pulling the bowls and setting the float level by bending the tab like many Edelbrock, carter, Qjet carbs. I just had the same issue of flooding on a 4160, and it's less than a year old. Crud can get into the needle, or seat, so in my case I pulled the bowl, blew out the seat with air through the feed tube, while working the float up and down. Put it back on and no more flooding. If you can buy a couple float needle valves while it's apart, replac them while it's apart, and all should be great. I also run a pressure regulator and gauge on all my hotrods, regardless of having mechanical or electric fuel pumps because I've had flooding from pressure issues before. Even mechanical pumps can put out over 6 lbs. pressure, and most carbs can have flooding issues when it gets over 6 lbs. I keep all mine set at 5 lbs. and that helps the float needles work and not seep past to flood.
BB427, I don't technically consider "bending" the float to be an adjustable float...I can remove leafs from a spring to lower the ride height but that doesn't make them adjustable height springs, it's a modification not an adjustment...I plan on running a regulator when I get time and money, but for now I am going to take the bowl off and clean out the needle/seat, and I had received info that the 4160's went through a recall around the time that I purchased mine for the coating on the inside of the float bowls flaking off and causing the needle to stick so I'm going to check that out while I'm at it and give Holley a call and see if they are willing to help me out. And I appreciate everyone's help, but we should all know at this point that a picture on a parts suppliers web site are not always of the exact part, but sometimes just a similar item...it clearly says non adjustable float and the Holley manual that came with it also says the floats are not adjustable. Again thanks to everyone for the help and updates to follow.
If not mentioned, with engine OFF pull one lower screw from each float bowl and drain empty. Restart and try. If it works I'll explain what happened (too much typing). It's fast, easy, and may work
The Jalopy Journal
