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#1
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the old holley hesitation
hi guys. im sure most of you have run into this from time to time when dealing with a holley carb. i have a 70 challenger with a 72 400 engine in it. i really dont know the specs on the cam but i was told by the previous owner that it was pretty lumpy, which it is. i replaced the converter to a 24 to 2700 stall. i have a new holly 750 cfm performance carb and edelbrock performer intake installed. the problem im running into is when i take off from idle( not flooring it just a regular push of the gas pedal) the engine seems to either stumble, bog a bit and sometimes spits out the carb then picks up and goes. a few times it has stalled.the only thing i have changed at this time is the power valve to a lower no. because of the lumpy cam. still no improvment. i have it idleing at about 1400 rpms because if i go any lower than that and put it in gear it will stall.im not a lumpy cam guy but im really not in the position now to start changing cams. any suggestions on this guys? somebody throw me a bone please! its cruising time! thanks.
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#2
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first thing i would check is your accelerator shot, sounds like its too weak (could be too strong)
next, do you have a vacuum advance? if so, hook it to the other port (no vac at idle) hten, i would lean more towards a distribiter problem than a holley problem. oh, if you get the chance, grab a edelbrock 750, you'll be amazed! |
#3
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old holley
dodgetboys right check your vacuum first you could have slow valve timing also once you know the timing is right you well also know how much vacuum your motor has at idle if you know that then you can tell what power vavle you need but i would also say its your accelerartor shot it may just need adjusted or they maybe to small are they 30s or 5o cc need more infor ?
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#4
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Yep, you'll be amazed that EB is able to sell that piece of crap. The EB carb tends to be a hit or miss (more often miss) carb.
A Demon or a TQ would have been a better choice than the Holley. As you have already spent the money on a new Holley that is close to the size that you need, let's just talk about that carb, instead of saying you should have bought this and you should have bought that. First things first. Make sure that you have properly setup the carb... Adjust the fuel level in the bowls. It should just begin to trickle out of the site hole. If you are using clear sight plugs, then it should be just at the bottom. Adjust the accelerator pump linkage. With the throttle at idle, the accelerator pump linkage should have no play in it. When at WOT, the linkage should have just a little movement left in it. If it doesn't, you will kill the accelerator pump. Make sure that fuel actually sprays out of the accelerator pump nozzles. Make sure that the vacuum advance unit (if you are using one) is connected to metered/ported vacuum and not to full time vacuum. At 1400 RPM, odds are you are no longer in the idle circuit. That is not a good thing either. With the car and distributor properly tuned, that cam should be able to idle in gear at closer to 1,000 RPM. If you are not odleing on the idle circuit, you need to close the butterflies to the point that you are in the idle circuit. Then you will need to drill a couple of holes in the primary butterflies. This will give the engine the extra air at idle and keep the carb in the idle circuit. BG thought about that with the Demon carb. They now come with the Idle-EZ baseplate. There is a screw that you adjust to allow more air without getting out of the idle circuit. If you aren't sure about being open too far for the idle circuit, just turn the idle jet settings all the way in. If the engine stalls, you are in the idle circuit. If the engine keeps running, you are in the primary metering circuit. Unless the metering body has been modified with a PV check valve (from the factory they aren't) odds are you blew out the PV when it puked through the carb. |
#5
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[QUOTE=ehostler]Yep, you'll be amazed that EB is able to sell that piece of crap. The EB carb tends to be a hit or miss (more often miss) carb.QUOTE]
well, i could start counting all the ones i have ran, and installed, and tuned for other people, who have had years now of trouble free carburation. i have three that go alll summer, never a carb problem. my machine guy? we biult two 750's for his 502 blown chevelle, never a lick o trouble, and perfect mixture (he's VERY happy)(oh, yeah, 900 HP) my racetruck has had a edelrock, works flawlessly, no trouble, no flooding, good aceleration. we used edels on our tuff truck, they bounce better than anything else with the off road mods, mud trucks? edels are perfect, they run at an angle, and get good fuel economy. so, if you are having trouble with your edelbrock E, send it to me, with a summary of what your engine is, and the plugs out of the four corners, i would be happy to build it for you |
#6
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well so far i went to the holley web site and did get some info on my problem and i will change the discharge nozzle first. according to my paperwork i got with the carb it comes with a .25 nozzle which is the smallest one you can get. im going to jump it up 3 sizes to a .28 and see what happens. im just a little confused on how to change it. there diagram on there website is very vague and iv looked at the top of the carb and scratching my head on how to do it but it looks like i will have to remove to carb from the engine and check things out. keep the info coming and thanks for the info on the edlebrock carbs, good and bad.
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#7
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A stumble off idle is usually caused by a lean idle mixture. If you can't get it rich enough at idle with the mixture screws do like Ed said and drill the butterflies to allow them to close further and activate the idle circuit.
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#8
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6pakman, EZ stuff, its the only philips screw you see inside the choke tower. Keep the carb on. Put a rag under the shooter so you dont drop it down the throat. Remove the screw and the shooter will come off with a little help as there is a gasket under it that usually keeps it in place. put on the new shooter with the gasket under it and replace the screw. Done deal. You can fine tune the shot with the colored plastic cam that is attached to the throttle arm too.
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#9
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I ended up with a pretty standard tune on those 3310 750 vacuum secondary Holleys when using them on 383's and 440's. I would replace the stock white accelerator pump cam with the green one installed in the #1 screw hole and then at least a #28 accelerator pump shooter. That got rid of the carb-related stumble for those size engines. Some cars wanted a #31 shooter and some did just fine with the #28 shooter, but NONE of them liked the #25 shooter that usually comes standard. And the green pump cam hits the pump harder at first then tapers off and that seems to be what they want.
The shooter determines how long a period of time that the pump shot is spread out over. The pump cam determines how much pressure the pump delivers and when in the cycle. Also make sure the pump lever is adjusted corectly or you could be losing pump shot. Regarding the symptom of dying when it goes into gear, could be a distributor tuning issue. If you have too light of springs then thay may be letting the advance kick in above 1000rpm, so when the engine is at 1400rpm the ignition is already advancing making for a strong idle. When it goes into gear the rpms drop a little and sometimes this can let the springs pull the weights back in and you lose timing and the strong idle goes away. Lumpy cams need about 1000 to 1100 rpm for idling, so you don't want the weights to start until after that or the idle will go up and down as the weights bounce around. |
#10
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Quote:
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#11
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old holley
darn DCW cant belive you would say that about a holley lol but you are right about one thing and that is before he starts drill and holes or changing squirter he needs to pull it off and check his butterflys to see if theres about .25 opening most people dont even know the slot is there then he needs the see which cc pumps are on the carb 30cc or 50 cc then check the pump stoker to see if it set right you what no slack in it but at wide open you still want movement left i'm not saying the .25 squiters may not be too small for a big block we run a 850 holley on are 318 dirt car and its got .30 squiter on it but if your not getting the gas to them it dont matter how big they are as for the power vavle that depend on your vacuume at ilde i know you said you changed it what size did you put in ? holley are one on the easies carb to work on i thing that why alot of classes wont allow them
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#12
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[QUOTE=dodgetkboy78]next, do you have a vacuum advance? if so, hook it to the other port (no vac at idle)
hten, i would lean more towards a distribiter problem than a holley problem.QUOTE] he needs to check the distributer and timing before going hog wild with a drill and such too, or, at least, thats what i'd do |
#13
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old holley
you are right there also dodgetboy i really think he need to give alittle more inform about what hes got !
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