Holley Jets and PV help please....

[Macgyver]

Ok Im almost there!!! I got it running much better but its still running rich no matter what. Ive turned the idle mixture screws all the way in and it wont die out. Any change in the idle speed screw and it runs like crap. So my question is what size power valve and jets should I be using on my mainly stock 81. I have the Holley4150 list 3777 sitting on a stock 350 w/ Performer Intake, 14x3 open air element, true duals no cats, soon to be 1 5/8 longheaders to 3in side pipes, and no computer. The person I got the Holley from rejetted it to run on a 400 Pontiac.

In the haynes manual it says that the 71' which came w/ the 4150 was OE w/ #70 pirmaries and #78 secondaries. I dont know what size engine it had though but Im sure it made more than my 190 horsies. I would like jets that would give me some fuel economy though (dont laugh). I forgot to do the finger in the front vent tube test that GerryLP noted to test the power valve but the carb has backfired probably 25times so Im sure its blown. What size can it be changed to to prevent this?

One more problem though the reason why Im real reluctant to take the Holley off again is that the threads in the intake might be stripped now! I was tightening it and suddenly it kinda went limp and just stayed w/ the same amount of tension no matter how much more I tried tightening it. Does that make sense? How much should I tighten these screws, cause I never had a problem when messing w/ the Qjet? Can I put some water sealing thread tape on it to improve that or am I going to have to throw the intake away and get a new one. Im not taking it off to have it machined or anything cause then that would just be a horrible product by edelbrock which has been my experience so far.

This thread was supposed to be a real simple question but I just keep rambling, sorry? Thanks guys.

 

[JohnZ]

Start with #68 primaries and #76 secondaries, and a #65 power valve and see how that works out. While you have it apart, install a Holley #125-500 power valve protection kit in the baseplate - that's the only way to protect the power valve (the protection isn't built into the power valve, it's a check-ball setup in the baseplate).

The intake should have studs in it with nuts to secure the carb, not bolts through the carb baseplate into the intake; heli-coil the hole that's stripped (permanent repair, better than the original threads), install a stud kit, and use nuts on the carb side. Don't tighten the nuts to more than 15-18 ft-lbs. or you can crack the baseplate ($100.00).

 

[Macgyver]

Well there are double sided bolts I guess. They have threads and then theyre smooth in the center and then threads again w/ no head. I threaded them into the intake and then thread the nut once I had the carb on. Its the bolt kit that autozone had for the Holley so... I saw the heli coil kit in summit but Im not understanding what that is or how its done. Can you explain a little. But the 68 and 76, thank you.

 

[72Mako]

Mac, I'm runing a Holley List 4777 650 Double pumper on mine. Double pumpers are basically race carburators and are tuned to run a little on the rich side. When I installed mine, it also was running rich, like way too rich. My idle screws were unresponsive. What I discovered was that too much of the idle transfer slots were exposed and were dumping excess fuel at idle. I could not spend more than a few minutes in the garage before my eyes started watering. I adjusted the idle transfer slot so that about only .040-.060 were exposed. After doing this, the idle screws became responsive and I was able to get it to idle correctly and no more burning eyes. Not saying this is your problem, just something to check. Charles

 

[JohnZ]

You need a Heli-coil kit for 5/16"-18 threads; you drill out the existing threads, then use the Heli-coil tap to cut new threads, then install the Heli-coil insert with the provided tool and snap off the tang on the insert. Stuff a rag in the holes in the carb pad so no shavings get into the intake, and be careful to drill absolutely perpendicular to the carb pad surface.

Your studs should be 5/16"-24 (fine thread) on the exposed end, with fine-thread nuts to secure the carb, and 5/16"-18 (coarse thread) on the other end that screws into the manifold.

 

[Macgyver]

Dang it I didnt bring my little red book w/me so Im not sure where this is at.

Theres one thing that I did forget to mention though. This might be what you are talking about but, the throttle lever adjustment thing thats supposed to be .15 inches when at WOT, will that cause a rich condition at idle or a bog when accelerating? Its the thing on front on the accel pump that is adjusted w/ a nut and bolt that tighten on a spring on the drivers side front of the carb. I messed w/ it thinking it was the idle adjustment a long time ago becasue I thought it was similar to a Qjet.

 

[Macgyver]

Well John my buddy here was telling me I would have to drill the holes out and tap them but knowing me I would end up not drilling straight and render it useless. So how hard is it to do? Or can I pick up a kit for that at Lowes or something?

 

[norvalwilhelm]

Richness in holleys rarely come from the jets. Power valves also do not cause problems unless the motor has no vacuum and the power valve value is really bad.
To start with the idle circuit is usually too rich and .015 wire bent in little L's installed in the idle circuit really help the idle mixture screws. Those screws should be out 1 1/2 turns or the carb is really off.
The throttle plates must be almost closed or at least any with idle circuitry. I assume this is not a double pumper so the primaries should be closed to close of the transfer slots. Open the secondaries to admit more air to lean out the idle.
Primary jetting only comes into play a cruiseing speeds not idleing.
Choose fairly LEAN jetting and have the power valve only a few points higher then the idle vacuum with the car in gear.
You start off of the idle circuit and the transfer slots and they never quit pumping gas into the engine, the jets start to add fuel also while cruiseing and the power valve should be set so that when you come to a hill it kicks in, passing a car it kicks in but right back out when cruising.
99% of holleys are too rich out of the box and need help.
The wires in the idle circuit are right out of the holley book as is drilling the primary throttles.
Good luck

 

[Macgyver]

what do you suggest then for the rich idling? the screws are unresponsive. Is that becasue a blown powervalve constantly letting in that extra fuel or not?

 

[GerryLP]

Macgyver,

The plugging of the vent tube is a good check, but I think that it was JohnZ or Jack who posted it.

Locate the list number on your 4150 carb choke tower horn near the left-front side. Now compare this number to the one in the attachment to see how your carb left the Holley factory. Let me know if you cannot make out the numbers, and I'll e-mail you the larger image.

This list will tell you if you have the correct metering blocks, boosters, pump shooters, jets and other details.

Another power valve protection can be found here:

http://www.powervalveshield.com/

I currently use this type of power valve protection and it works great. They come with a plug-shot to plug the hole that normally connects the base of the carburator to where the power valve is. The Holley power valve protection is a bit more work and its not that difficult, but most places don't carry it. I think that Moroso also makes one. The Centek one you'll have to order. I carry an extra one with me just in case.

I agree with JohnZ. You should repair the intake. The loose studs could be causing a leak and contribute to the idle-adjustment problem. Auto Zone and others sell a heli-coil kit that comes with the die and the heli-coil, and coil inserter. They're not cheap, but work like a champ. It beats replacing the manifold.

By the way, the carburator base nuts get tightened snug in criss-cross pattern to avoid warping the base. Also, you can install an heat insulator to help avoid perculation of fuel while the engine is hot, so you may want to install longer studs to acomodate this. Just remember that if get a too-thick insulator, then this will raise the carb and fitting under the hood could be tight; however, a 1/2 insulator should be easy to accomodate under the L81 hood ( I use a 1" phenolic insulator with a 3" X 14" air filter and drop-down base, and it all fits fine under the hood).

The 0.015" clerance you're talking about is for the acceleration pump lever, and this clearance is just there to prevent bending the lever arm while at WOT (fluid pressures are stronger that the metal used for the lever arm). Having said that, if you had a stumble or popping when going from idle towards part throttle, then I would suggest looking at the accelerator pump cam profile to see if it is not "timing" well with the throttle use.

I am guessing that an air leak is present maybe caused by the studs thread being bad. Get your carb to basics IAW the list, and then remember to use a vacume gauge when attempting to set the idle. I think that the List 4777 carb is a double-pumper. A Vac-sec is list 0-80783C.

One more thing, the power valve value for the idle portion should be slightly below the lowest vacume at idle. You need a vacume gauge that is not dampened (the needle will jump or fluctuate easily) otherwise you may not see how low the vacume gets during momentary fluxing of pressures (such as in a mild tempered cammed engine). For example, lets pretend that your engine has a 268 or 274 hydraulic tappet cam, and your engine is idle'ing with a lowest vacume of 6 InHg, then in this situation, you do not want to use the stock 6.5 InHg. What you should use is a 5.5 InHg valued power valve:HOWEVER, this will not be true if at WOT your vacume gets as low as 6 InHg. In this case, you would then have to settle for a 6.5. Otherwise the power valve will close too early and the engine could lean-out which could damage the pistons.

 

[norvalwilhelm]

what do you suggest then for the rich idling? the screws are unresponsive. Is that becasue a blown powervalve constantly letting in that extra fuel or not?

Sure the screws are unreponsive. If the throttle plates are open too much to allow air into the motor the transfer slots are uncovered and poring fuel into the motor, the motor is idleing on the transfer slots, not the idle circuit so the throttle plates must be closed but then the motor idles too low. 1/8th holes in the primary butterfies allows more air in the motor so the plates can be closed. If the secondary has NO idle circuit the carb can be turned upside down and the throttle plates on the secondary can be opened more to allow air into the motor.
That takes care of the transfer slots, now for the idle circuit. The float bowl on the primaries need to be remove, the metering block removed , the large gasket removed and .015 roughly diameter wire needs to be inserted into the idle circuit to lean it out and the gasket reinstalled.

I will try to find a link to how to do this and post it here.

 

[norvalwilhelm]

Check out this link


http://www.chevyhiperformance.com/howto/71498/index.html

 

[motorman]

i can not find a LIST # 3777 are you sure that is correct?

 

[Macgyver]

Norval thats perfect thank you. ill look over that better later at work and see if i have questions which i probalby will.


Motorman Street

[font=Arial, Helvetica]P/N 0-4777C 650 CFM Four Barrel, Model 4150 (shiny/classic) - Street/Strip .....youre right my mistake.[/font]
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[Macgyver]

WOW!!! This Holley is a Piece of ****!!!!!!!!1

The vette runs aweful. Not even remotely interested in taking it apart to replace power valves, jets or mess w/ worthless idle circuits.

i just bought a 1405 Edelbrock Performer carb to go w/ the intake, air cleaner and the valve covers. I hope that this is the answer to my prayers. Wish me luck!

 

[Robin7TFour]

Mac, i too switched from a holley to an Edelbrock. i am very pleased with how mine worked out. i may try different secondary needles and springs. it's cheap and easy swap so i want to at least try. curious about what the changes may do!
let me know what you think.BTW i am watching for a swap meet Q-jet just for giggles i'd like to see also what that does for the motor

Robin

 

[Macgyver]

Hey Robin I got your swap meet Q-jet right here! No seriously, I have one if you want it but its fully functional and ECM so proly not. I imagine you want no elect and something cheap to rebuild.

Its all hooked up and lookin DAMN good!!! But these playoffs (NBA) got me on the couch and not inthe garaje. That triple OT and the kings game have really sidetracked me. I just need to turn the key and tune but hopefully not the later. Then its Friday night cruise time baby.

 

[FLATOUT427]

Send Your Piece Of Cr__ Holley My Way. It's Not The Carb, It's Knowing How To Tune Them. Buy The Holley Book. It's Great.

 

[pws69]

Send Your Piece Of Cr__ Holley My Way. It's Not The Carb, It's Knowing How To Tune Them. Buy The Holley Book. It's Great.

Which "Holley Book" are you referring to??

 

[Macgyver]

I bought the little red book Holley 415/4160 Manual. Its all going to be on ebay in a few days.