Edelbrock 600cfm carb
01-06-2008, 10:42 PM
#1
2nd Gear Member
Thread Starter
Join Date: Jun 2005
Location: Arizona
Posts: 419
Edelbrock 600cfm carb
What is your opinion of the carb? I am having a few problems with my car (which I suspect to be related) and I am thinking that it could be the carb... I have had the carb for about a year and have tinkered (idle mixture screws, jets, and metering rods)with it here and there but it doesn't seem to help.
http://store.summitracing.com/partde...p;autoview=sku
this is the same as the one on my car.
http://store.summitracing.com/partde...p;autoview=sku
this is the same as the one on my car.
01-06-2008, 11:08 PM
#2
5th Gear Member
Join Date: Sep 2006
Location: Australia
Posts: 2,266
RE: Edelbrock 600cfm carb
kbunny, remind us what your engine is and state of modification?
you bought it new?
they are supposed to be just as goodas the equivalent Holley - you'll get plenty of arguments over which carb is best, but I doubt the carb is the root cause of your problems unless maybe it was a usedebay special.
you bought it new?
they are supposed to be just as goodas the equivalent Holley - you'll get plenty of arguments over which carb is best, but I doubt the carb is the root cause of your problems unless maybe it was a usedebay special.
01-07-2008, 03:36 PM
#5
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Thread Starter
Join Date: Jun 2005
Location: Arizona
Posts: 419
RE: Edelbrock 600cfm carb
Well its a 302 that I recently rebuilt, it has E7 heads and a crane cam 266 dur and 469 lift (advertised) with matching valve springs,Mallory Unilight disywith a Mallory matching Coil, Edelbrockperformer intake,edi600cfm carb, and long tubed headers with duel all the way out and no H or X cross over.
Edit: I got the carb used from a friend, but he said he bought it new put it on his engine didn't like how it sat on the engine (liked how the holly had the fuel inlet on the other side) and sold it to me for cheep. But he did run the carb for a few weeks. :End of Edit
The problems are a uneven (rough) idle (its not the cam because its not the same king of "rough idle"). I have played with the idle mixture screws with no success.
Hesitation out of the hole, seems like when it is changing from the cruse circuit to the power circuit, as if it hits a spot where no fuel (or to much) is pumped in to the engine and the engine power/rpm drops allot...
Cloud of smoke when I shift/high rpm's, smells like oil but it cant be because I replaced the rings, seals, gaskets, and everything else I couldwhen I did the rebuild, unless they didn't seat because I only honed the cylinders but I am sure that its not the rings... I am thinking its running really rich.
Very seldom I will try and punch it out of the hole to get in front of traffic and it will bog down and not recover until I let off the throttle and let it idle for a few seconds... but most of the time when I punch it it just takes off.
While I am just cruising down the road the steering wheel will start to vibrate off and on in a consistent pattern like the rough idle... and its not suspension/steering because its not aconsistent problem.
Is that enough info?
God Bless,
Brian
Edit: I got the carb used from a friend, but he said he bought it new put it on his engine didn't like how it sat on the engine (liked how the holly had the fuel inlet on the other side) and sold it to me for cheep. But he did run the carb for a few weeks. :End of Edit
The problems are a uneven (rough) idle (its not the cam because its not the same king of "rough idle"). I have played with the idle mixture screws with no success.
Hesitation out of the hole, seems like when it is changing from the cruse circuit to the power circuit, as if it hits a spot where no fuel (or to much) is pumped in to the engine and the engine power/rpm drops allot...
Cloud of smoke when I shift/high rpm's, smells like oil but it cant be because I replaced the rings, seals, gaskets, and everything else I couldwhen I did the rebuild, unless they didn't seat because I only honed the cylinders but I am sure that its not the rings... I am thinking its running really rich.
Very seldom I will try and punch it out of the hole to get in front of traffic and it will bog down and not recover until I let off the throttle and let it idle for a few seconds... but most of the time when I punch it it just takes off.
While I am just cruising down the road the steering wheel will start to vibrate off and on in a consistent pattern like the rough idle... and its not suspension/steering because its not aconsistent problem.
Is that enough info?
God Bless,
Brian
01-07-2008, 05:03 PM
#6
5th Gear Member
Join Date: Sep 2006
Location: Australia
Posts: 2,266
RE: Edelbrock 600cfm carb
fwiw, i think you may have 2 issues and one sounds like balance.
if it were me i would take it to a reputable dyno tuner who works with carbs and get that side of it sorted first. Then have a look at the possible balance issue.
good luck
if it were me i would take it to a reputable dyno tuner who works with carbs and get that side of it sorted first. Then have a look at the possible balance issue.
good luck
01-07-2008, 06:35 PM
#7
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Join Date: Aug 2007
Location: Elk Grove, CA
Posts: 5,896
RE: Edelbrock 600cfm carb
You should be able to get the carb tuned without a dyno. Takes some time and effort, but it's perfectly doable. Definitely does sound like there's a balance issue though, causing the cruising vibration. Tires, driveshaft, or possibly bad u-joints or even engine balance.
First off, check both your initial timing and mechanical advance curves. If either is off, the engine will never run properly and you'll never get the carb tuned right. Same goes for the rest of the ignition system; if you have bad plugs, wires, cap, or rotor, you'll never be able to get the carb tuned.
The rough idle could be any of several things. A vacuum leak is the first thing that comes to mind. Spray around the carb base and intake gaskets with some brakleen and listen for the rpm's to increase. If they do, you've found your leak.
Edelbrocks have a slight issue with cams that produce low idle vacuum in that the low vacuum isn't enough to overcome the stepup spring tension at idle. This results in a large amount of fuel being dumped into the intake at idle. If you can hear a tapping noise coming from the carb, this is likely what's happening. The solution is to replace the stepup spring with a much lighter one. I've got a 3"Hg spring in mine. Stock is usually 5" or 7".
To set the idle mixture, lightly seat both idle screws and back them out 2-1/2 turns. Fire the engine up and set the idle speed. Turn one screw in inhalf turn increments until the rpm's drop, back it out half a turn, then repeat for the other screw. Go back to the first screw and do the same thing except in quarter turn increments, then repeat again for the other screw. This should get you pretty close. If you can completely seat one or both screws with the engine still running, you've got a vacuum leak somewhere.
The flat spots during acceleration and smoky exhaust sound like tuning issues; rods, jets, springs,and accelerator pump. I'd try to lean out the power mode (and/or secondary circuit)and see what happens to the smoky exhaust.Lighter springs may help the transition from cruise to power mode. You may also move the accelerator pump linkage rod to the outside hole and see if that helps as well.
First off, check both your initial timing and mechanical advance curves. If either is off, the engine will never run properly and you'll never get the carb tuned right. Same goes for the rest of the ignition system; if you have bad plugs, wires, cap, or rotor, you'll never be able to get the carb tuned.
The rough idle could be any of several things. A vacuum leak is the first thing that comes to mind. Spray around the carb base and intake gaskets with some brakleen and listen for the rpm's to increase. If they do, you've found your leak.
Edelbrocks have a slight issue with cams that produce low idle vacuum in that the low vacuum isn't enough to overcome the stepup spring tension at idle. This results in a large amount of fuel being dumped into the intake at idle. If you can hear a tapping noise coming from the carb, this is likely what's happening. The solution is to replace the stepup spring with a much lighter one. I've got a 3"Hg spring in mine. Stock is usually 5" or 7".
To set the idle mixture, lightly seat both idle screws and back them out 2-1/2 turns. Fire the engine up and set the idle speed. Turn one screw in inhalf turn increments until the rpm's drop, back it out half a turn, then repeat for the other screw. Go back to the first screw and do the same thing except in quarter turn increments, then repeat again for the other screw. This should get you pretty close. If you can completely seat one or both screws with the engine still running, you've got a vacuum leak somewhere.
The flat spots during acceleration and smoky exhaust sound like tuning issues; rods, jets, springs,and accelerator pump. I'd try to lean out the power mode (and/or secondary circuit)and see what happens to the smoky exhaust.Lighter springs may help the transition from cruise to power mode. You may also move the accelerator pump linkage rod to the outside hole and see if that helps as well.
01-07-2008, 08:53 PM
#10
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Join Date: Aug 2007
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Posts: 572
RE: Edelbrock 600cfm carb
sounds like a vacuum leak, that cam should pull plenty of vacuum, the first thing I thought is "is it a used carb"? You want to make sure everything is to stock specs, jets, metering rods, check float levels etc.....I would even buy a rebuild kit and take it apart and blow out every orafice wtih compressed air and carb cleaner and I mean everything, those carbs are simple but run great. A little rust in passages or stickingneedle and seat it will run and idle like crap.
Put it back together and start there, look at your plugs as well that will tell you how its running.
Edelbrock carbs even though holley guys say they are crap are one of the best street carbs, throttle response is excellent as well as fuel economy and when tuned right the power is right up there with a holley. The older models werent that great out of the box but the new ones are very close in A/F ratio out of the box. I'm not an edelbrock carb guy either, I think demon carbs rock but edelbrocks are great street carbs in most situations.
Put it back together and start there, look at your plugs as well that will tell you how its running.
Edelbrock carbs even though holley guys say they are crap are one of the best street carbs, throttle response is excellent as well as fuel economy and when tuned right the power is right up there with a holley. The older models werent that great out of the box but the new ones are very close in A/F ratio out of the box. I'm not an edelbrock carb guy either, I think demon carbs rock but edelbrocks are great street carbs in most situations.