Holleys Very Rich ??
 

I am running 2X4 holleys 4160 on a stock intake with a 501 lift CP cam in my 427. The motor runs rich (burn your eyes rich) the adjustment all the way out or all the way in no difference. The engine builder said replace the power pumps but Summit would not sell them to me because: First if they are bad it would lean the motor out and Second newer carb are built to prevent damage to the power pump from back fire.
I don't have access to a dyno with an oxygen sensor to test on.

Who is right? What should I do?:JEKYLHYDE

"power pump" are you referring to the power valves?
Take a manifold vacuum reading before buying new ones, they are rated for different vacuum levels.

Nantucket,

when you say "runs rich " , do you mean idle?, acceleration?, mid RPM's?....

If you are rich at idle and the screws make no difference the odds are you have a blown or incorrectly sized power valve ( I have personally been through this with a similar setup)

what carbs are you running?

are they new?

KK

What is the number on the PV?? I run 2.5 on everything, there isn't any need for enrichment above that number.....if you're vacuum is higher than that you're not at WOT, and that is the only time you need the PV...if the PV isn't working you will run lean, not rich, PV has to be working to run richer. Check your timing, put in lower PV's, then start lowering your jets sizes until your idle screws start to work...

Jack,

I must respectfully disagree,ruined powervalves are notorious for dumping fuel at idle.

KK

Vacuum signal keeps a power valve closed, when that vacuum signal goes away, the spring overcomes the diaphram and they dump fuel. Torn diaphram will result in the power valve being open the whole time.

Nantucket,

Do what Mr. Fixit says. Hook a vacuum gauge up and measure your vacuum at idle. The power valve should be rated 1-2 inches lower than the measured vacuum. The carbs I've seen come with 6.5 inch power valves. If you're measured vacuum is lower than that at idle, your car will run very rich and you'll find that adjusting the idle mixture screws does little to nothing. I speak from experience. Swapped my power valve out for 4.5 and it made a huge difference.

Chris

Nantucket,

Try this; start your engine , and slowly turn in your idle screws , do not bottom them out hard or you could dammage the seats, if your engine is still trying to run with the idle screws turned in all the way , you most likely need to change your power valves.

Good luck

KK

You also have to remember that if you don't get any change with mixture screws you may have the idle screw open too far just to get it to idle. When you do that, the throttle blade is open too far causing fuel to be drawn in from the main circuit. Check positioning od the secondary throttle blade and make sure that the blade is just barely uncovering the transfer slot. The adjustment for that is reachable from the underside. If you run to radical of a cam you may need to drill small holes in the blades to get the engine to idle without having to open the throttle blade too far. I have tuned many Holley's and this is the best way I have found to allow an idle mixture adjustment. Remember, the wider open the throttle, the greater the pressure differential, which changes the "signal" the carb circuits respond to. Good luck. Also what everyone else said about power valves is true. Drop to 2.5"s and make sure you are using the right gasket (as they made 2 different ones). That should allow you to get some adjustment

Make sure the power valve gasket is seated correctly, if not, it will run rich. Len

Thank you all for your imput. I am going to re-check the throttle bades but I am sure they are closing all the way. The power valves seem to be the starting point. I will have to test the vacume to get the right valve. They are 65s in the carbs now.
The carbs are Holley 4160s Back one #80457-2 date code 0508 and the front one #1850-5 date code 2280. Can anyone de-Code the date code for me? Are they new with the power valve protection built in ?

My carb is an 1850-5 1609. Holley said that it was built the 160th day of 1989. So I would surmise yours is 228th day of 1990. The 80457 I would guess was made the 50th day of 1988.

I'm sure you are already aware that the 80457 is an electric choke, the 1850 a manual choke, and both have the vacuum secondaries.

I'd be interested in sharing info as I'm running my carb now and can't get the engine to idle below 3500 rpm. I'm about to go into it to check out the power valves to see if they're blown. It has no response to the idle screws. Mine has the power valve protection, but I won't be surprised if they're blown. I don't think the "protection" is a guarantee...

zipzip,

If the lowest you can get your motor to idle is 3500, there is some serious airflow getting in. Either the front and or rear throttle blades are not closing all the way, or you have a monster vacuum leak.

Sometimes it is hard to see the forest for the trees. Remember...no air = no rpm. Mr fixit is right, big air coming from somewhere. There is a Holley book that is really good if you haven't messed with them very much. I believe you should be able to get one at Barnes and Noble, but if you can't find one I may have an extra one I could send you. I have gotten so much information from everyone on this site, we should have a "pass around library" of printed information that could be sent from person to person as needed. I teach automotive technology at a community college an have tons of info on just about everything. Subject matter is all I need and it's everyones for the asking.

John

I'm with mr. fixit. your throttle blades are not closing far enough. Take the carbs off. Turn them over. The small flat headed screw controls the secondary throttle blade. Back the screw off until the blades close almost completely. Give it 1/3 to 1/2 turn (clockwise) Put the carbs back on. Try that.

If that isn't it some older 4160 carbs used a reverse mixture screw. tightening the screw actually opens the idle mixture. You may have those BUT 3500 rpm isn't an idle circut problem. You are running on the main circut. (I suspect the secondaries are open due to the throttle position see above)

RE: the poster above with the 3500 RPM idle, when I installed my dual quad setup I had a similar problem but my idle was around 1600 RPM with both idle speed screws backed completely out. I am running a pair of #8007 390 cfm carbs. After several attempts at removing and adjusting the carbs I found that on one carb the primary throttle plates were installed upside down which prevented proper seating in the throttle bores. FLipping the plates over solved the problem. You must remember that the edges of the throttle plates are beveled to provide a proper seat and seal against the bores. If you can hold the carb up to a light source and look up from the underside of the carb and see light around the throttle plates you need adjustment. A vacuum leak from areas other than the carb usually produce erratic idle, poor throttle response and a lower than normal manifold vacuum reading.

RE: Power Valves - help me out here. My vacuum gauge reads 17-18 at idle. The power valves are 6.5s. Should I swap for different valves or leave well enough alone?

RE: Power Valve Protection - this is fairly easy to determine if you have a power valve protector installed. Look at the underside of the baseplate between and in front of the primary bores. If you see a hole with what looks like a tiny steel ball in the hole then you have a power valve protector installed. If not, several manufacturers make a retrofit kit which is a snap to install.

John S. Peterson
 

What is the Name of the Book ? I would like to have one for reference.

On a street engine, idle vacuum is often much higher than steady throttle cruise vacuum, for this reason idle vacuum should not be used to determine the correct power valve. To select the correct PV, check vacuum at various steady throttle cruise speeds.

Using idle vacuum is the correct way to select the PV for race engines since they don't experience steady throttle cruise.

Scott

Thank you all for your replies
 

Some additional Questions: What is the useful life of a carb? How many times can you re-build them? I found alot of slop in the secondaries, will the re-build help to reduce some of the play?
If I were to buy new; What should I replace them with ?

Nantucket:

I don't mean to step on your thread, but I have an update on the items I mentioned. Just tell me to get the hell out if you want.

BTW: I have a Haynes book on the Holley's and a book by Mike Urich titled "Holley Carburetor Handbook 4150 & 4160, Selection, Tuning and Repair" It was only about 12 bucks on Amazon. I prefer the Urich book - it does a good job at explaining the functions of each circuit. I don't know if that's the one John was describing, but I'd recommend it anyway.

My update: you guys are da bomb! Right on for the secondaries! I took the carb off and found the throttle plates were open about 1/16". Duh. Oh, and during the removal, I found that one mounting ear was busted off. This carb was an ebay item, and the deadbeat that sold it to me packaged it in what amounted to a plastic bag. This mounting foot was damaged in shipment and must have had a hairline crack that I didn't see when I put it on. So I'm off to buy a better mousetrap. I think I'll try a Demon carb - you guys seem to love them and they seem to come highly regarded elsewhere. I don't even want to mess with this Holley anymore - I can't get the secondaries to close and who knows what else got damaged. Plus, from what I've read, I'll be able to use it as a parts carb for the Demon (jets, PV).

My thoughts on the rebuild: I would guess that the parts that truly "wear" (floats leak, needles wear, gaskets harden, etc) are in the rebuild kit. I wouldn't expect the other mechanical items to really wear. Plus, you can get just about any part for the darn things... Hey! I've got a parts carb... :)