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Car Forum / Jeep / September 2006'79 304 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. 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 > 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 [quoted text clipped - 13 lines] > on a > Holley, I would appreciate some advise to this problem. 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 ? Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ > 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 [quoted text clipped - 3 lines] > 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. You need a cam of at least 270 degrees, like AMC use in the sixties to be able to use a four barrel: http://www.compcams.com/technical/Catalogs/106-07/16-19.pdf Stock muscle cars used 300 degrees of duration. God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > 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 ? > > Dave Milne, Scotland > '91 Grand Wagoneer, '99 TJ I guess that means that any car that has a 426 Street Hemi in it isn't considered a musclecar. http://www.426-hemi.com/hemi/info/tech/426/specs.htm 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 > You need a cam of at least 270 degrees, like AMC use in the sixties > to be able to use a four barrel: [quoted text clipped - 8 lines] >> Dave Milne, Scotland >> '91 Grand Wagoneer, '99 TJ Need to correct myself here. I misread the cam specs. The duration was 276 in 1966-1967 and 284 after that. >I guess that means that any car that has a 426 Street Hemi in it isn't >considered a musclecar. [quoted text clipped - 24 lines] >>> Dave Milne, Scotland >>> '91 Grand Wagoneer, '99 TJ The whole idea of a hemispherical chapped dome is to fit bigger valves. Maybe they thought that was adequate for a street engine. And keep their customers from sucking valves. I ran 330 degrees with an ISky Roller: http://www.billhughes.com/IskyRR1000.jpg In my Seven: http://billhughes.com/thunderb.htm What do you run? God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com > Need to correct myself here. I misread the cam specs. The duration was 276 > in 1966-1967 and 284 after that. 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 > 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 ? [quoted text clipped - 12 lines] > maybe >> a jet change as well. You also don't specify the cam specs. 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. Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ > Dave, > [quoted text clipped - 40 lines] > > maybe > >> a jet change as well. You also don't specify the cam specs. 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 > 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 [quoted text clipped - 65 lines] >> > maybe >> >> a jet change as well. You also don't specify the cam specs. This one? Super Tuning and Modifying Carter Carburetors for Performance, Street and Off-Road Applications, Dave Emanuel http://www.amazon.com/o/ASIN/0931472113/ > Dave, you shouldn't have a problem tuning the Carter/Edelbrock > carb, and yes, they are basically the same carb inside. I [quoted text clipped - 112 lines] >>> >> a jet change as well. You also don't specify the cam >>> >> specs. Yup, that's the one. Chris > This one? > [quoted text clipped - 97 lines] >>>> > maybe >>>> >> a jet change as well. You also don't specify the cam specs. AFB: http://www.carburetorfactory.com/expvw04.html God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > 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 [quoted text clipped - 8 lines] > > Chris Sounds like a good purchase - will order and wait 3 weeks for it to arrive (!). Got it fitted at the weekend, relatively painlessly. Well, I mean that metaphorically actually, as I cut the hell out of my thumb as I was putting on the valley pan gasket with blood going everywhere and trying to keep it off the RTV. So now the nastier bits of the emissions control are disconnected (the EGR and the air injection stuff). As it is now not really an emssions controlled vehicle, I attached it to the non-timed part of the carb per the instructions, but that gave me 34 degrees BTDC, so plugged it into the timed-port and got a more sensible 10 degrees BTDC. Gas analyser was playing up a bit, so I'll do the tuning next weekend, but even on the default settings, it is pulling way more strongly than it ever did before - can't be far off. Oh, Edelbrock's instructions in the 2131 manifold state that the Performer 1405 requires a Square bore to Spread bore adapter. Except that both carb and manifold are square bore already, and I hadn't ordered one. Doesn't seem to mention the need for it anywhere else - will drop them a line to check that it is a mistake on their part. Certainly seems to run fine without it. Dave Milne, Scotland > 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 [quoted text clipped - 78 lines] > >> > maybe > >> >> a jet change as well. You also don't specify the cam specs. Dave, It would be a shame to install less restrictive intake components, without similar changes to the exhaust. Earle > Sounds like a good purchase - will order and wait 3 weeks for it to arrive > (!). [quoted text clipped - 118 lines] > > >> > maybe > > >> >> a jet change as well. You also don't specify the cam specs. Indeed. This was a tactical fix - my LPG system broke (the guys who installed it were clearly idiots, and with the partially disconnected emissions system, the Ford Motorcraft 2bl carb wasn't running right). So, I went back to basics with a simple choke. How it is running, I guess the next thing is to look at what headers and exhaust are available. Might look at changing the camshaft since I'm about it. Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ > Dave, > > It would be a shame to install less restrictive intake components, without > similar changes to the exhaust. > > Earle It sounds like their instructions are generic. The reason I say this is that many of the Performer series manifolds have the spreadbore carb opening, but they have both bolt patterns. Some of the square bore carb flanges will not seal on this type of manifold, hence the reason for the adapter. If your carb and manifold are both square flange, then you definitely don't need the adapter. Glad to hear it is running good for you though. Chris > Sounds like a good purchase - will order and wait 3 weeks for it to arrive > (!). [quoted text clipped - 127 lines] >> >> > maybe >> >> >> a jet change as well. You also don't specify the cam specs. yes, their email technical support confirmed it wasn't necessary. Pretty impressively fast response actually - couple of hours. So next weekend, I'll put the gas tester on it. I had a shot at it, but it was late and the start reading in clean air didn't match the end reading in clean air, so I discounted the readings I took. Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ > It sounds like their instructions are generic. The reason I say this is that > many of the Performer series manifolds have the spreadbore carb opening, but [quoted text clipped - 4 lines] > > Chris The rule of thumb was during the muscle car era, was any carburetor that came form the factory needed to be jetted by about ten percent, of course that was too rich for the street and fouled plugs, but it was that little edge I had on everyone. God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > Dave, > [quoted text clipped - 23 lines] > > Chris 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: > The rule of thumb was during the muscle car era, was any carburetor > that came form the factory needed to be jetted by about ten percent, of [quoted text clipped - 30 lines] >> >>Chris Mallory dual point, total 38 degrees on the crank. first transistor ignitions were junk along with all factory stock ignition that limited at five grand. God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > 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 [quoted text clipped - 3 lines] > 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. 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. > Mallory dual point, total 38 degrees on the crank. first transistor > ignitions were junk along with all factory stock ignition that limited [quoted text clipped - 9 lines] >> 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. 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: > Mallory dual point, total 38 degrees on the crank. first transistor > ignitions were junk along with all factory stock ignition that limited [quoted text clipped - 9 lines] >>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. 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 > 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. Don't foerget the Mazda Wankel rotary: http://www.rotaryengineillustrated.com/animations.php > Alfa Romeo have been using "twin spark" engines as they call them, since > the [quoted text clipped - 6 lines] >> 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. A 1934 Nash with dual plugs, the other eight are on the carburetor side: http://www.vapinc.com/1934nashrestoration/July%202002/PIC00004.jpg And of course Top Fuel use two: http://www.billhughes.com/temp/DickLaHaie.jpg God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com > 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 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 in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > 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 [quoted text clipped - 8 lines] > Holley Avenger truck carb with an electric choke. Before I drop the cash on a > Holley, I would appreciate some advise to this problem. |
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