# Fuel Injection for Judge



## nautoncall (Feb 14, 2017)

I searched on here but haven't heard of many fuel injection their 400's. The 69 Judge I just got has a Holly drag racing carb and a big cam. I will have to get the exact carb from the build sheet and give you guys specifics for more recomendations. With the new fuel injection set ups (FAST, Holly, etc) is it worth it or should I just get a more streetable carb? I like to drive my car in all year around. 

Right now we have it pretty dialed in. A friend of mine who knows how to tune carbs had it pretty dialed in but it is very cold natured. It does not have a choke. Once warmed up it fires right up and runs good, however, it has some hesitation under low rpm cruising and likes the rpms to be up to be "happy". It loves me hammering on it but the low rpm cruise it just acts like it wants to "go faster"...if that makes any sense. 

Thanks.


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## nautoncall (Feb 14, 2017)

I got more information. Its a Holly 4150 HP series. 72 fronts and 74 rears. Not sure CFM but at least 750.


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## PontiacJim (Dec 29, 2012)

Well, I am not a Holley guy, nor an expert, so I had to web check your carb. It seems the 4150 has mechanical secondaries which is not always the best for a street car unless you have some 3.90 - 4.33 gearing, high stall converter if automatic, or a desired close ratio 4-speed. Vacuum secondaries are much better for the street and offer a smoother transition when the secondaries do open as the engine demands more air/fuel. Mechanical secondaries just pop open immediately when you mash the gas and if the engine isn't pulling enough rev's/air flow through the intake, they open too quick and the engine can bog down or even back fire through the carb before it picks up again. This is why the need for the gearing or higher stall converter to help get the engine to rev faster more quickly.

Next issue could be the large cam - too big. Big cams are typically aimed at upper mid-to-high RPM's which sounds like what you have by your explanation. The cam profiles dictates your torque and RPM range where the power really turns on. For a street engine, you would be better off to select a cam for lower end-to-upper mid range RPM's. Not knowing any more about the engine or what is inside it, it would be hard to advise what to do.

The best carb/intake selection is exactly what the factory put on the engine, Quadrajet and matching intake. 750 CFM's, small primaries to cruise on, big vacuum secondaries to kick the power on. The small primaries can provide better gas mileage while pulling higher velocities of air/fuel creating a good transition for the vacuum secondaries to kick in.

So it may be you have the wrong carb for you application, the wrong cam for your application, or both. The first thing I would do is go with a vacuum secondary carb whether you stick with a Holley or go with a Q-jet/intake swap. The vacuum secondaries may help if the cam is a little too big.

Take my advice with a grain of salt and hopefully others will chime in, but that's my opinion on what may be going on with what you have. Fuel injection? No experience using any of the new systems. :thumbsup:


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## nautoncall (Feb 14, 2017)

Pontiac Jim, just the thing I was wanting. I think I just need to change the carb first. That may be the simplest.


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## nautoncall (Feb 14, 2017)

This is what was running before the went back to carb.


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## goat1964-2004 (Nov 14, 2005)

Agree on the carb and cam. A big cam isn't the greatest for a daily driver.


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## BearGFR (Aug 25, 2008)

I agree. If the root problem is "too much" cam, changing to EFI isn't going to solve that problem. However, if the problem is all carb then it could help a lot. The ability to properly tune a carburetor is a dying art. It can be done, but you have to know what you're doing and understand the principles involved. I'm one of the weirdo's who happen to enjoy that sort of thing, but not everyone does or wants to. For them, EFI is a good alternative. I have a friend in my Pontiac club who recently converted his T/A to EFI, and he loves it. Is there any way you could provide the details on the cam? Also.... which transmission, what's your rear gear ratio, etc...

Bear


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## nautoncall (Feb 14, 2017)

Bear, I know an old "hot rodder". He's built my Cobra. He drove the car and said it's 100% the carb. He said this carb is perfect for my car and he took it apart and said vanes were wrong, wrong jets (a friend of mine who supposedly knew carbs rebuilt it). He said it was way to lean and all the problems were carb related. He's going to rebuild it and install MSD also. 

I should've just take it to him to start with.

I'll keep you guys updated. Going to start a new thread on air conditioning because I want to add and it was not factory.


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## BearGFR (Aug 25, 2008)

nautoncall said:


> ..... (a friend of mine who supposedly knew carbs rebuilt it).....


Man, if I had a dollar for every time I've heard that. The most common problem cause with Quadrajets (or any carb) is usually the last "expert" who touched it.

Bear


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## geeteeohguy (Feb 2, 2008)

A LOT of guys over on the Corvette forum have tried out the various aftermarket fuel injection systems with very little success. Poor support, electrical gremlins, and very expensive. A properly tuned/calibrated Quadrajet will run as well as a fuel injected car without the problems. My '67 GTO has its original carb, and is as turn-key as any modern car. Very often, 'upgrades' made by non-experts lead many to believe that Quadrajets are a poor choice.....a bad mistake.


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## nautoncall (Feb 14, 2017)

These are my cam specs


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## nautoncall (Feb 14, 2017)

Just got the car back. Runs great. Here's what my mechanic said was the problem.

I found a big problem as I was pulling the carb is the dist. Has vacuum advance and needs vacuum under acceleration and the carb you have doesn't have ported advance and looses vacuum under acceleration. Also the dist is not indexed correctly either from the manufacture. I have a new msd ordered that should be exactly what she needs to vroom.


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## BearGFR (Aug 25, 2008)

Hold on there, Buckaroo ---- NO engine makes vacuum under heavy acceleration. Now, partial, very light -- not full throttle, maybe some vacuum but it'll still drop off quite a bit even then. But at full throttle? If your engine is making ANY detectable vacuum under those conditions, there's something wrong -- like maybe a carburetor that isn't big enough. If your mechanic believes that it's supposed to be making vacuum under load at full throttle, then it's time to find a new mechanic.

Bear


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## BearGFR (Aug 25, 2008)

nautoncall said:


> These are my cam specs
> 
> View attachment 88977



242/254 @ 0.050 lift - that's a pretty rowdy cam, especially in a flat tappet profile.

Bear


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## nautoncall (Feb 14, 2017)

It's hydraulic.


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## BearGFR (Aug 25, 2008)

nautoncall said:


> It's hydraulic.


Right, but still flat tappet ---- as opposed to roller.

There are flat tappet mechanical/solid lifters, flat tappet hydraulic lifters, roller mechanical/solid lifters, and roller hydraulic lifters.










Bear


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## nautoncall (Feb 14, 2017)




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