'79 304 Edelbrock carb problems vs Holley carbs?

My '79 CJ-5 304 seems to have fuel related problems. It is difficult to start when the engine is cold; it turns over fine, but takes too long for the engine to start. Once running, it emits gassy fumes out of the exhaust side- pipes that make your clothes smell like gasoline while the top is off.

I had a carb specialist try to adjust the carb, but it didn't help. The carb is an Edelbrock 4-barrel mounted on an Edelbrock hi-rise manifold. The motor has a street cam and headers.

I was told that Edelbrock carbs do not work well with 304's, and to get a Holley Avenger truck carb with an electric choke. Before I drop the cash on a Holley, I would appreciate some advise to this problem.

Reply to
Skyjacker
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Without knowing what size carb, choke or no choke, and which manifold, it is hard to tell you what the problem could be. What I can tell you is that Edelbrock and Holley carbs are both set up from the factory with a general tune. This mean the carb may or may not need to be set up properly for your particular engine. In general, the Edelbrock carbs run too rich with the factory set up. Normally they will require a metering rod change, and maybe a jet change as well. You also don't specify the cam specs. When you say "street cam" that really doesn't tell anyone the specifics of your cam. The manifold cam also be a factor. Is it single or dual plane? Does it have the heat crossover to warm the engine properly?

The last thing is, I like some of the features of the Avenger truck carbs, but a 300 cubic inch engine doesn't need a 670CFM carb. If they make a smaller version now, it would be cool, but again, you're probably going to have to do some jet and power valve changes to get the engine running the way it should. Remember, they call these carbs universal for a reason.

Chris

Reply to
c

To start, you will 'always' have the gas smell in your clothes from side pipes, that is why they are not street legal in lots (most) of places. The gas smell comes with a whole bunch of carbon monoxide as well, which is deadly.

The exhaust pipes need to exit the body at the back corners on about a

30 to 45 degree angle to be safe and not as smelly.

As you have them, the exhaust vortexes under the wheel well which fills the cab up. Really dangerous if you have a top or doors on.

The cold start issues can simply be a matter of having the gas filter in upside down. The filter has 2 outlets. The center outlet goes to the carb and the 'top' outlet goes to the return line. If the return line outlet isn't at the top, then gas will syphon back to the tank creating a vapor lock as it sits.

The return lines primary purpose is to prevent vapor lock after a hot shutdown also.

A pinhole leak in the suction pipe from the pump to the tank can also cause cold start issues. It can just let air in when it sits. You can usually see a stain on the line (usually near a frame clip) or rubber hose where the leak is.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Any idea if the Edelbrock 600cfm 1405 Performer + Edelbrock 2131 manifold will require a metering or jet change on a stock 360 '91 Grand Wagoneer ?

Reply to
Dave Milne

Reply to
L.W.(Bill) Hughes III

I guess that means that any car that has a 426 Street Hemi in it isn't considered a musclecar.

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Just a "little" 276/284 split duration cam in those grandma engines that had

2 4 barrel carbs from the factory. Also the 340/440 6-pack engines if those rich old grannies couldn't afford the hemi in their new car back then. And to think my whole life I though most grandmas would have enough power with 425 HP rated engine that actually made closer to 500 HP when you wound them a little higher. Those darn grannies!!!

Chris

Reply to
c

Dave,

When the companies that make carb give them their initial settings from the factory, they take all kinds of compromised in to consideration. They don't know if the carb will be used on a large or small displacement engine, or if it will be used in hot or cold climate, high altitude, etc. They also don't know what other mods have been done to these engines. The baseline settings they give these carbs will allow them to run on most of the applications they will see, but they almost always require tuning to get them to be optimal. My guess would be that this carb would still be a little rich, but it is just a guess. I'm not saying it won't run, it will, and it will probably be pretty damn close to right.

The metering rod system that Carter/Edelbrock uses will "adjust" the mixture based on engine vacuum. The rods are controlled by a piston and spring, similar to many other carbs. When the engine vacuum is low, the metering rod spring will start to overtake the vacuum pulling the piston down. The rods are tapered, and when they move up in the bore they are in, a smaller diameter of the rod will still be inside the main jet, effectively increasing the total main jet area that fuel can pass thru. If the engine runs too rich at high vacuum conditions, but is ok at low vacuum or wide open throttle, then you simply change the metering rod to on the has a larger diameter on the part of the rod that is in the jet at high vacuum conditions. It really is a simple process, and normally will only require 1 or 2 sets of rods to get the carb where you need it to be.

Chris

Reply to
c

Need to correct myself here. I misread the cam specs. The duration was 276 in 1966-1967 and 284 after that.

Reply to
c

Thanks. Looks like perhaps I should have ordered the calibration kit in retrospect. Anyhow, after a 2 week wait, it has arrived so I'll fit at the weekend.

Quite looking forward to it - my carb experience has been mainly with multiple SU's (single barrel downdraft) and the odd side draft Weber - never done anything on a 4 barrel like Holley or Edelbrock before.

Reply to
Dave Milne

Reply to
L.W.(Bill) Hughes III

Reply to
L.W.(Bill) Hughes III

Dave, you shouldn't have a problem tuning the Carter/Edelbrock carb, and yes, they are basically the same carb inside. I believe the jets and rods interchange, but I'm not positive on that. I do know that the Edelbrock carb is heavily based on the Carter design. If you understand basic carb functioning, and what the rods and jets do for the mixture, it will be a simple process to get it dialed in. If you ruin in to problems, I'm sure we can get you going in the right direction. Also, there is a book available called Carter Carb Tuning. Most of it will apply to the Edelbrock as well. I had the book at one time, but loaned it out and never got it back. I do know that the book is very thorough.

Chris

Reply to
c

This one?

Super Tuning and Modifying Carter Carburetors for Performance, Street and Off-Road Applications, Dave Emanuel

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Reply to
Frank

Reply to
L.W.(Bill) Hughes III

Yup, that's the one.

Chris

Reply to
c

Our rule of thumb was to leave the carbs alone and fix the ignition system first. Then open up the exhaust with good headers and pipes at which point you could usually go a bit richer on the carbs without fouling plugs as much at low speed. Best to put on a good manifold as well. With a really good ignition, the plug fouling was usually not as big a problem, often with a bypass to go back to stock to make it easier to read the plugs for tuning the gas/air flow.

L.W.(Bill) Hughes III proclaimed:

Reply to
Lon

Reply to
L.W.(Bill) Hughes III

Chrysler's first generation electronic ignition was accurate to 9000+ rpm.

They came both with and without limiters. The models with limiters came in

2 or 3 settings

There was also an easy to install retrofit available from the parts department that was initially limited to the V-8 models.

Reply to
billy ray

Best ignition ever made used radar pulse transformers with local oscillators and a pickup wheel rather than points. Generated a pretty good burst of high voltage pulses that were width modulated by the pickup wheel. No point bounce, superheavy spark at low rpm, the voltage could be bumped at high rpm. Not too many sold commercially by the guy that invented it, but you could build your own if you were a radar tech. A bit noisy in the RF range since you were generating a pulse train rather than a single spark, and rather pricey unless you had access to something like a T-9 Radar. Then Delta and a few other folks made electronic ignitions that didn't suck as badly...

Dual points worked, dual plugs worked even better but dunno anyone using them since the old straight 8 Nash engines of the late 30's.

L.W.(Bill) Hughes III proclaimed:

Reply to
Lon

Alfa Romeo have been using "twin spark" engines as they call them, since the

60's (and still use them today). I had the 3.0 v6 hemi which was conventional - they only did them on the 4 cylinder models which ran up to 2 litres.

Dave Milne, Scotland

Reply to
Dave Milne

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