Rebuild the Holley or Replace the Holley

[ThePsychologist]

My daily driver is a 1974 Challenger with a 1969 Plymouth 383 / 727 / 3.55 gears.In 1982 I replaced the Thermoquad with a Holley 750 cfm 4160 3310-2 and an Edelbrock DP4B intake.The engine is stock except for the Mopar electronic ignition,Schumacher headers and a DC cam ( a bit larger than stock) My question is should I rebuild the Holley using some of these upgrades I see in catalogs or get a new carburetor?

[Duster Don]

I had a 70 Challenger with a Holley and it needed rebuilt, I had it done and it worked great. I have a 73 440 Duster drag car now with a 850 Holley and it was acting up, so I took it to my carb guy and all he did was bitch about the Holley 850's, he had one and he called Holley about it and they told him that was the worst carb they ever made. I ask him if I should buy a new carb. and he kept on bitching but he told me to bring it over and he would see what he could with it, Well to make a long story short It works like a champ, I stage hit the rev limitor at 3000 and let go off the button and hang on no supter no hesatation it just goes. What I guess I'm trying to say is take it to somebody that knows what they are doing and they can make it work. It only cost 125 bucks and thats a lot cheaper than a new carb.

[ThePsychologist]

Hey Don~You are right.My problem is that I don't know much about tuning,modifying and rebuilding carburetors. I look in these catalogs and see dozens of upgrades,springs,spacers,trick kits,power valve savers,and 4150 t0 4160 conversion kits and I have no idea if any of these would give me better performance.I think I'll order a Holley Guide Book and start reading.

[Jims451]

If the throttle shafts are worn or the carb body/metering plate/base are warped then get a new carb.

If those parts are OK, then rebuild the carb.
Usually all you need are the bowl and metering plate gaskets, the power valve(s), neadle and seat (with the "o" rings and gaskets), and maybe the vacuum diaphram for the secondarys and a few cans of carb cleaner. A rebuild kit should have all the gaskets you need and most of the parts, but may not include the vacuum diaphram.

[ThePsychologist]

Hey Jim~ Good point.I just bought two books by Mike Urich and Dave Emanuel which are all about tuning and repairing Holley carburetors.They have good diagrams and show step by step procedures.The Jegs catalogue has several rebuild kits so I figure I can do the job.Interestingly, both books say that the 750 cfm is too big for my tiny 383 motor yet the original Thermoquad was even bigger.Go figure.

[Belvedere65]

Go for it! Holleys are great to work on. If someone is bitching, usually they don't know what's going on in a carb. I had an 850 DP for years and had no trouble with it. Freshened it up many times. Your big problem would be if the throttle shafts or linkage shafts were worn as said in a past post about the carb. Have a carb shop do it if that's the case. Rebush etc. Am running a Carb Shop holley Dominator that flows 990 cfm., which I've redone a couple of times and have a 1050 Dominator that i have been into. Swap between the two from time to time.

[ThePsychologist]

I have been in the garage with the Holley for an hour or so. I took my new books with me. The bowl fuel levels are perfect and the mechanical choke works fine. There are no apparent leaks. The accelerator pump is squirting fine.I cannot tell if the shafts are loose but when I operate the throttle by hand things seem good and tight. The two small adjusting screw (idle mixtures) have no effect on the idle at all. I attached a vacuum guage to the upper port and have 4 Hg at idle in neutral and 9 Hg at 1500 rpm.It seems that I have every tool necessary to complete a rebuild but I don't know which kit to buy.Do I need a 50 cc pump? What power valve do I need? How do I know if my seat size is .097 or .150? I added up the costs of the potential parts I may need and they equal a new Carter AFB.

[Jims451]

The upper port is ported vacuum, not manifold vacuum. Since the idle adjustment screws have no effect, and there is vacuum at the ported vacuum port, I think the throttle is too far open.

Either the engine has very low engine vacuum (like when using a big cam) or the carb needs to be cleaned/rebuilt.
If you remove the carb and look at the position of the throttle plates at the idle setting, they probbably show you are uncovering the idle transition slots, which basically makes the idle circuit un-adjustable.
I think cleaning and rebuilding the carb will fix this.

Usually the Holley carbs come with a 6.5" Power valve. If your engine has low vacuum at idle (in gear) you may have to use a lower value power valve.
If you plan to change jets in the carburator often, you may want to buy the Holley Quick Change fuel bowls which allow you to change the jets with out removing the fuel bowl(s).

The parts should not cost more than a new carb?

[Crank]

do you have any idea what the carb came off of or what was changed on it the first thing i would do is get the blue gaskets then see what size jets and squirters are on the carb if the jets and squirters are to big their will be no adjustments on the screws.then get the vacume readind in gear if it's 14 then cut the reading in half and get a 7.0 power valve.

[ThePsychologist]

You guys are better than having the Holley books. I bought the carb off the shelf at Harry's Hot Rod Shop in Grand Prairie,TX. I did not know that the ported upper port pulled zero vacuum at idle so that could be causing some problem with my vacuum advance on my distributor.The carb is dirty so cleaning is a must. Summit sells the Adjust-A-Jet kit for $79.95 , the Fuel bowl gaskets(2) are $4.95 ,Spectre's Power Valve Saver is $7.95 ,Holley Uiversal Trick Kit is $76.95 and Barry Grant's Standard Rebuild Kit is $25.00. Plus there are Jet Assortment Packs for $37.95 and Accelerator Pump Tuning Kits for $98.95. But I really want Holley's Titanium Needle-and-Seat Assembly for $19.95.LOL
Maybe I'll just buy a Holley Quick Kit for $19.95.

[goldduster]

Its a Vaccum Secondary, Right?

I would buy:

Quick Change Secondary Spring Housing
Secondary Spring Assortment
Holley Quick Kit

and if you feel the need to adjust your secondary jetting, buy the 4160-4150 conversion kit.

Really, the cost of all of these parts is less than $110, and without the 4160-4150 conversion kit, its only $35

[ThePsychologist]

Hey Goldduster, I think you're right about the Quick Kit and the Secondary Spring Kit. Plus I want an assortment of jets to experiment with. I've always felt that the jets I've been running were too rich.Have you ever used the 50 cc pump?Also some racers recommend a phenolic spacer between the carb and intake to reduce fuel temperatures.What about this Power Valve Saver that Spectre sells? Some guys on another thread were talking about fuel pressure regulators so naturally I am now considering one of those. I have Summit , Jegs and a P.A.W catalog and am almost ready to place my order

[Jims451]

Unless you have a really over cammed engine you don't need the 50cc accelerator pump.

Look for the Holley jet assortment sold under the Mopar Performance name, it was cheaper to buy it that way, but I think the Jet sizes go from 69 To 99, so if you need smaller jet sizes you have to buy them individually.

I think the power valve saver is a check ball that you have to drill the carb base plate to install.
I have never used one of the savers, so I don't know if it's worth it?

I usually use the thick (maybe 1/4") Holley gasket between the carb and intake with the longer carb studs to help keep the carb a bit cooler. I haven't used the taller phenolic spacers because of cost and hood clearance, and linkage alignment problems.

With a Mechanical fuel you shouldn't need a pressure regulator unles it is a high pressure race pump. A bypass system (you can just use one of the fuel filters with the vapor return ports) works good to reduce the possability of vapor lock, but you need a 1/4" line back to the fuel tank for the by-pass.