Carburetor popping
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Joined: Mar 2014
Posts: 60
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From: Palm Bay florida
Carburetor popping
So I have this street demon 625 carb on this engine, adjusted the idle mixture screws with a vacuum gauge, set the vacuum secondary adjustment to come on at just the right time. The car runs extremely well until you drive it for a while and occasionally it will feel like a pop out of the exhaust briefly when accelerating hard, like a weird backfire and then disappear. I noticed the plugs are smutty like the carb is running rich, does anyone know how to tune this carb to correct the problem? If it makes any sense, the carburetor was delivering too much fuel causing a bog initially until I adjusted the spring rate on the secondary's and set the accelerator pump shot to deliver fuel in a slower rate which these carbs allow you to do pretty easily
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Joined: Mar 2014
Posts: 60
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From: Palm Bay florida
Everything is modified. 355 10:1 compression, msd distributer and box, 18 degrees in distributer the rest in the crank, trickflow aluminum heads with roller rockers, lunati flat tappet cam 1500-5500 rpm power range, edelbrock performer rpm intake, with a street demon 625 carb timing is set at 36 degrees total connected to a 2004r with a 2000-2500 stall converter with 3:73 gearing in the rear.........It was originally a 1981 corvette standard
Race Director
Joined: May 2006
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did you read the section in the instruction manual concerning step up springs and vacuum with long duration cams? What is the idle vacuum reading?
http://documents.holley.com/lit701rev10.pdf
http://documents.holley.com/lit701rev10.pdf
Thread Starter
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Joined: Mar 2014
Posts: 60
Likes: 1
From: Palm Bay florida
did you read the section in the instruction manual concerning step up springs and vacuum with long duration cams? What is the idle vacuum reading?
http://documents.holley.com/lit701rev10.pdf
http://documents.holley.com/lit701rev10.pdf
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From: Thunder Bay
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From: Palm Bay florida
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
It may be cheaper to open it up and see what jets are in there now and buying some that are smaller. At least on the primary side.
On the secondary side I don't see individual jets for sale.
I'm not really familiar with the carb, just googled it and it looks like there are primary and secondary jets both.
If you do some research you might find that jets from another carb that fit the street demon too.
The kit is kind of expensive and doesn't have a large range of jets in it, although it does include rods. It sounds like the rods work very much like the q-jet rods. The kit may be all the more you need.
I did find this article during my search. It might give you some idea's
http://www.chevyhardcore.com/tech-st...on-carburetor/
Reading the article the secondary jets are the same as in the traditional Holley carbs.
On the secondary side I don't see individual jets for sale.
I'm not really familiar with the carb, just googled it and it looks like there are primary and secondary jets both.
If you do some research you might find that jets from another carb that fit the street demon too.
The kit is kind of expensive and doesn't have a large range of jets in it, although it does include rods. It sounds like the rods work very much like the q-jet rods. The kit may be all the more you need.
I did find this article during my search. It might give you some idea's
http://www.chevyhardcore.com/tech-st...on-carburetor/
Reading the article the secondary jets are the same as in the traditional Holley carbs.
Last edited by REELAV8R; Apr 15, 2017 at 12:01 AM.
Thread Starter
Advanced
Joined: Mar 2014
Posts: 60
Likes: 1
From: Palm Bay florida
It may be cheaper to open it up and see what jets are in there now and buying some that are smaller. At least on the primary side.
On the secondary side I don't see individual jets for sale.
I'm not really familiar with the carb, just googled it and it looks like there are primary and secondary jets both.
If you do some research you might find that jets from another carb that fit the street demon too.
The kit is kind of expensive and doesn't have a large range of jets in it, although it does include rods. It sounds like the rods work very much like the q-jet rods. The kit may be all the more you need.
I did find this article during my search. It might give you some idea's
http://www.chevyhardcore.com/tech-st...on-carburetor/
Reading the article the secondary jets are the same as in the traditional Holley carbs.
On the secondary side I don't see individual jets for sale.
I'm not really familiar with the carb, just googled it and it looks like there are primary and secondary jets both.
If you do some research you might find that jets from another carb that fit the street demon too.
The kit is kind of expensive and doesn't have a large range of jets in it, although it does include rods. It sounds like the rods work very much like the q-jet rods. The kit may be all the more you need.
I did find this article during my search. It might give you some idea's
http://www.chevyhardcore.com/tech-st...on-carburetor/
Reading the article the secondary jets are the same as in the traditional Holley carbs.
help
Thread Starter
Advanced
Joined: Mar 2014
Posts: 60
Likes: 1
From: Palm Bay florida
It may be cheaper to open it up and see what jets are in there now and buying some that are smaller. At least on the primary side.
On the secondary side I don't see individual jets for sale.
I'm not really familiar with the carb, just googled it and it looks like there are primary and secondary jets both.
If you do some research you might find that jets from another carb that fit the street demon too.
The kit is kind of expensive and doesn't have a large range of jets in it, although it does include rods. It sounds like the rods work very much like the q-jet rods. The kit may be all the more you need.
I did find this article during my search. It might give you some idea's
http://www.chevyhardcore.com/tech-st...on-carburetor/
Reading the article the secondary jets are the same as in the traditional Holley carbs.
On the secondary side I don't see individual jets for sale.
I'm not really familiar with the carb, just googled it and it looks like there are primary and secondary jets both.
If you do some research you might find that jets from another carb that fit the street demon too.
The kit is kind of expensive and doesn't have a large range of jets in it, although it does include rods. It sounds like the rods work very much like the q-jet rods. The kit may be all the more you need.
I did find this article during my search. It might give you some idea's
http://www.chevyhardcore.com/tech-st...on-carburetor/
Reading the article the secondary jets are the same as in the traditional Holley carbs.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
live and learn. Good job figuring it out.