New carb vs. old?

[JeffMcKC]

Re: New carb vs. old?

If you have not changed any thing on the car a lot of money went into making that one work to start with. I like Quadra Jets on Street cars!

[2bbl318]

Re: New carb vs. old?

[quote=mike343sharpstick ]

I could tune or rebuild them with my eyes shut. While getting 8 of these on my AMC would be cool, it would not be real practical :D

the cool factor would be through the roof!!! just do it 8) 8) 8)
just kidding. I'm really a "if it aint broke" kind of guy.

[yellomalibu]

Re: New carb vs. old?

Most Edelborcks come out the box without needing any tuning. Bolt it on, hook everything up, set your idle, and go. You might have to play with the air/fuel screws a little, but that's not hard. Overall a great replacement carb for a stock vehicle. And after a little research, I confirmed my earlier suspicion. You will need a new intake manifold if you replace the carb. The carb bolt pattern on the 2nd Generation AMC motor you have is different than todays carbs. And something else to consider, you'll probably need a new air cleaner. I don't think your stock air cleaner will fit.

The same is true for the new holleys, if you buy the right one for your application. Their website has a feature that helps you choose the right one for your application.

... with the holley, don't rely on the small filter on the inlet, be sure to have a good inline filter. If a piece of trash gets in the needle and seat, they can stick open, causing gas to flood... you could say it's a fire hazard among other detrimental things to your motor.

I, personally like the holleys... but I keep hearing that the edelbrocks and quadrajets get better gas mileage. The chevelle came (to me) with a Carter AFB (which is just like the edelbrocks), and until it started leaking fuel out the throttle shaft, it ran and drove great.

[SuperBuickGuy]

Re: New carb vs. old?

Are there differences? Yes, there are lots of differences. Most notably is the adjustable air bleeds, downleg boosters, and the variety of ways you could rejet the carb (adjustable jet block). Add to that the ability to run E85 with minor modifications, ease of tuning, ease of getting parts, and cost of those parts.

I have an Avenger.... and now I can't remember if it's a 670 or 780 (think 780). I liked it but removed it because I went to a DP with boost reference for my Buick. The avenger did work well especially if you tune it (it works okay straight out of the box, but tuning takes it to the next level).

[mike343sharpstick]

Re: New carb vs. old?

Sounds like 'just' a carb swap won't net much bennefit then. So I'm thinking I will hold off 'till I can get at minimum an ingake to go with it at a minimum.
I did notice something interesting related to fuel delivery. First of all, I have been driving the car a little ;D harder in an effort to see where grip ends and sliding begins.
When I throw the car HARD into corner and roll on the throttle it will almost always bog down pretty badly then wake up again. It 'feels' like the cornering forces are are doing something inside the carb to move the fuel away from where is should be. :-\
FYI, the motor is stock at the moment but the suspension, tires and brakes are NOT. The car corners far better than I expected. :o

[mlcraven]

Re: New carb vs. old?

What's the set up with the fuel pick-up in the tank? Full tank of gas when it does that? Under hard acceleration? Maybe transient fuel starvation instead of bog?

Just suggesting that it might NOT be the carb -- even the old Carter -- in that partic scenario.

MMM made a good point relative to the carb: if it ain't broke, don't fix it. Advice I should follow more often :-[

[Ron Ward]

Re: New carb vs. old?

The chevelle came (to me) with a Carter AFB (which is just like the edelbrocks), and until it started leaking fuel out the throttle shaft, it ran and drove great.

If an Edelbrock or Carter AFB type carb leaks fuel past the throttle shaft, then there is a problem with the float level or needle and seat assemblies. Due to the fact there are NO gaskets in one of these carbs BELOW the top of the float bowl, there is NO way for fuel to get to the throttle shafts on those carbs unless you have:

1) a bad float (seldom seen with the Carters as the AFB's used brass floats.

2) improperly set float level. This can be caused by serious off-roading without the spring-loaded needle and seat assembly to absorb the shock, or simply by banging the float on the carb body if you had the top of the carb off at any time to replace jets or suck crud out of the float bowls.

3) Bad needle & seat assembly. Use the brass needles and seats from either Edelbrock or Carter (Federal Mogul). I don't like what the alcohol in some of today's fuel does to Viton needles. Also, stay away from crap needle and seat assemblies like Tomco offers. ACK!

4) A chunk of debris stuck between the needle and seat. I have seen this many times. It can be something as simple as a thin sliver of rubber fuel line that found its way in there or, believe it or not, a hunk of foam from the charcoal canister in the emissions system.


Eddys and Carters are good, reliable carbs and although the Holleys undisputedly have a performance advantage over like-sized AFB clones, the Holleys, by their design, are prone to leaks as they have gaskets below the float level (think bowl gaskets and metering block gaskets, here).

Myself? I like the Thermoquads and the Quadrajets. When tuned properly (including the secondary opening rate) these carbs will perform incredibly, yet offer remarkably good fuel mileage and driveability. People are scared of TQ's due to their unique appearance and phenolic carb body, but I have NEVER had a problem with one, once I figured out how to work on them. I would set it and forget it. Plenty of NHRA Stock and Super Stock racers utilize TQ's and QJ's and are getting KILLER peformance out of them.

One more thing. Just because a mechanical secondary carb opens all four barrels upon demand, it does NOT mean the engine should have that much air. I have owned several Holley carbs as well as the others mentioned and my best luck on smaller displacement engines with mild cams and nearly stock heads came from a 3310-1. With drop leg boosters, a secondary metering block and vacuum secondaries, these things WORK! Just be prepared to tinker with them as the gaskets get old and worn.



Ron

[SpeedJunkee's Carbs]

Re: New carb vs. old?

[THERMOQUAD!!!!

I have a couple boxes full of these if you need them........... ;D

[Ron Ward]

Re: New carb vs. old?

I have a couple boxes full of these if you need them........... ;D

So do I!


Ron

[Eric68]

Re: New carb vs. old?

Since the engine is stock and it "runs fairly well now" I would leave it alone.

The truth is carb technology has changed very little in the last 40 years, and the only real advantage to a new carb on a stock engine would be a shiny new finish and some valuable tuning experience!

[Mr4Speed]

Re: New carb vs. old?

Sounds like 'just' a carb swap won't net much bennefit then. So I'm thinking I will hold off 'till I can get at minimum an ingake to go with it at a minimum.
I did notice something interesting related to fuel delivery. First of all, I have been driving the car a little ;D harder in an effort to see where grip ends and sliding begins.
When I throw the car HARD into corner and roll on the throttle it will almost always bog down pretty badly then wake up again. It 'feels' like the cornering forces are are doing something inside the carb to move the fuel away from where is should be. :-\
FYI, the motor is stock at the moment but the suspension, tires and brakes are NOT. The car corners far better than I expected. :o

It's tossing fuel out the vents. AFB's are great carbs but they don't like to turn corners real hard. You can try extending the vents up higher with some hose and see if it quits or gets better. Slide a couple pieces of hose over the vents and tie them to the air cleaner stud-try to get them cut off about 1/4" below the lid. The theory is to make it so the fuel has to slosh all the way up the vertical tube before it dumps into the venturi.

[milner351]

Re: New carb vs. old?

Kris -
Would there be any advantage to tying the two bowl vents together on a holley?

a friend of mine always puts a piece of fuel line between the two vents on his....

[SpiderGearsMan]

Re: New carb vs. old?

AFB likes 3 psi of fuel pressure

[Mr4Speed]

Re: New carb vs. old?

Kris -
Would there be any advantage to tying the two bowl vents together on a holley?

a friend of mine always puts a piece of fuel line between the two vents on his....

I've seen it done-one piece of hose connecting both vents with a hole in the hose on top. Holley's aren't near as prone to fuel sloshing as AFB's though.