Calling the Holley carb experts

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Matt69olds

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**** can the Holley, Q-Jet swap it!!!

Assuming the float is set correctly, you don’t have too much fuel pressure, the timing is correct, and no vacuum leaks, I would think a engine with a camshaft mild enough to idle at 15inches of vacuum shouldn’t need the secondaries opened up. And since it’s a brand new carb, I certainly wouldn’t go drilling holes in anything before asking some serious questions.


What air cleaner are you using? Hood clearance on a truck probably isn’t a concern, but if the air cleaner is too close to the top of the carb the float bowl and air bleeds can’t vent correctly, causing all kinds of calibration issues.

Main jetting will have almost zero influence on idle mixture. Holley calibrated the carbs a little on the rich side as a safe alternative. It’s easier to set the carb a little rich for a customer using the carb on a big block. If they set the carb to be ideal for a small engine, they will have plenty of complaints from people using it on a big engine. My point? You shouldn’t need to change keys more than a couple sizes either way from the factory setting. If you need a bigger change, either something is screwed up it’s the carb, or you have the wrong carb for the application.

This is my suggestions: make absolutely sure the timing is correct, the vacuum advance is on manifold vacuum and functional. Make sure the float is set correctly, make sure the fuel pressure isn’t too high. Does your fuel pump have a return line? Is it restricted? Engines equipped with A/C usually use a fuel pump with a small return line. That return line had a small orifice inside the pump. The idea is the small orifice provides a small calibrated leak, fuel is constantly circulating thru the pump, keeping the fuel and pump cooler. If the return line is capped off or restricted, the pressure will be too high. Not saying that’s your issue, but I have experienced it enough times that it’s a suspect problem.

If you have messed around with the idle screw on the secondary side, put it back they way it was. Ensure the choke opens completely. Spray a bunch of carb cleaner into the air bleeds. Lightly seat each idle mixture screw, then back then out evenly 3 turns (unless Holley has a different spec). That should be close enough to drive. Take the truck out for a few full throttle runs. Make sure the truck is fully warmed up, drive it long and hard enough that it burns off all the carbon from the plugs snd combustion chamber. Once that’s done, set the idle to around 650-700rpm. Connect a vacuum gauge to manifold vacuum, pick a idle mixture screw, and slowly back out the screw a 1/2 turn. Does the idle or vacuum go up? If so, go to the other screw and turn it out a 1/2 turn. Keep going back and forth until you get the highest idle speed/vacuum reading. Reset the idle speed.

If you have done all that and it still runs pig rich, I’d suggest calling Holley and explaining the issue. Did the engine run like crap with the other carb? Who knows, just because it’s brand new doesn’t mean it was machined correctly.
 

Ricko1966

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In that screen shot I put up from a Holley forumn it states that you may need to open the secondaries so you can close the primaries to get out of the transition circuit. Holley even has a video about it.If I were the O.P. if he has not yet I would watch all the Holley videos pertaining to this.
 

Ricko1966

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I typed drilling holes in primary carburetor butterflies into my search engine. The first thing that popped up was muscle car DIY calibrate Holley idle and transition circuits. Tried to copy and paste the link here but couldn't I'll try again later but you should see if you can find it and see if it or the Holley videos help you.

I typed the same thing again got multiple results the second time. Second time my autofill jumped to Holley throttle plates on its own instead of carburetor throttle plates as I had typed before. Anyway type that, read some stuff, not being a smartass it's just interesting. Anyway second try I was able to copy and paste the link
www.musclecardiy.com/performance/holley
 
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Dman1049

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**** can the Holley, Q-Jet swap it!!!

Assuming the float is set correctly, you don’t have too much fuel pressure, the timing is correct, and no vacuum leaks, I would think a engine with a camshaft mild enough to idle at 15inches of vacuum shouldn’t need the secondaries opened up. And since it’s a brand new carb, I certainly wouldn’t go drilling holes in anything before asking some serious questions.


What air cleaner are you using? Hood clearance on a truck probably isn’t a concern, but if the air cleaner is too close to the top of the carb the float bowl and air bleeds can’t vent correctly, causing all kinds of calibration issues.

Main jetting will have almost zero influence on idle mixture. Holley calibrated the carbs a little on the rich side as a safe alternative. It’s easier to set the carb a little rich for a customer using the carb on a big block. If they set the carb to be ideal for a small engine, they will have plenty of complaints from people using it on a big engine. My point? You shouldn’t need to change keys more than a couple sizes either way from the factory setting. If you need a bigger change, either something is screwed up it’s the carb, or you have the wrong carb for the application.

This is my suggestions: make absolutely sure the timing is correct, the vacuum advance is on manifold vacuum and functional. Make sure the float is set correctly, make sure the fuel pressure isn’t too high. Does your fuel pump have a return line? Is it restricted? Engines equipped with A/C usually use a fuel pump with a small return line. That return line had a small orifice inside the pump. The idea is the small orifice provides a small calibrated leak, fuel is constantly circulating thru the pump, keeping the fuel and pump cooler. If the return line is capped off or restricted, the pressure will be too high. Not saying that’s your issue, but I have experienced it enough times that it’s a suspect problem.

If you have messed around with the idle screw on the secondary side, put it back they way it was. Ensure the choke opens completely. Spray a bunch of carb cleaner into the air bleeds. Lightly seat each idle mixture screw, then back then out evenly 3 turns (unless Holley has a different spec). That should be close enough to drive. Take the truck out for a few full throttle runs. Make sure the truck is fully warmed up, drive it long and hard enough that it burns off all the carbon from the plugs snd combustion chamber. Once that’s done, set the idle to around 650-700rpm. Connect a vacuum gauge to manifold vacuum, pick a idle mixture screw, and slowly back out the screw a 1/2 turn. Does the idle or vacuum go up? If so, go to the other screw and turn it out a 1/2 turn. Keep going back and forth until you get the highest idle speed/vacuum reading. Reset the idle speed.

If you have done all that and it still runs pig rich, I’d suggest calling Holley and explaining the issue. Did the engine run like crap with the other carb? Who knows, just because it’s brand new doesn’t mean it was machined correctly.
Started with a Qjet... Couldn't keep a tune and got tired of rebuilding it. I have a regulated return system. Ive had the carb apart. Sprayed out jets and inspected for any debris. Had a 600 cfm Edelbrock and that was fine on road. Any bump off road or downhill or uphill off road and the carb would flood and die. Frustrating when wheeling. All Holley wanted me to do was send the carb back... Already waited 3 months for this one to show up. Truck can't be down that long again.
 

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What are the chances you have a plugged pcv valve?
 

Ricko1966

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Put in a pcv valve temporarily,I bet your carb is calibrated for one. The pcv valve is going to allow more air.
 

hirschdalechevy

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Put in a pcv valve temporarily,I bet your carb is calibrated for one. The pcv valve is going to allow more air.

That is a great way to introduce more air at idle.

The other thing guys do if you are still rich at idle is use a thin strand of wire in the idle feed restrictor in the metering block bent at a 90 degree's and the gasket will hold it in place..

I dont want to be the guy with bad news but I have been messing with holley's on my new sp350 gm motor I just put in my blazer. That being said I researched the truck avenger carbs. and they are not really meant for the street,(nothing to do with your idle problem), but they have no high speed air bleeds in the main body.

Look down the top of your carb. you will see two idle air bleeds, (outside the booster feed), but the high speed bleeds, (inside the booster feed, by the pump nozzle) are sealed off, no air for emulsion for higher speed, street driving. The way I see it the truck avenger is for rock crawling and hill climbs and such, not the street really. You can call holley and talk to them about that, (even though holley tech kind of sucks).

Another thing I found out is that the 670 cfm is really a marketing hype by holley. The 670 use's the same size base plate as the 1850 holley 600 cfm and basically the same main body as well, as well as the same straight leg boosters. So the 670 is really just a hyped up 600 cfm holley.

That being said, I went with an 1850 holley street warrior 600 cfm, it has spring loaded, side hung floats, (good for off road), has the high speed air bleeds of a normal holley carb. and I put on the holley secondary metering block conversion kit, (#34-6s) to get rid of the metering plate. I also put on the quick change vacuum secondary cover kit,(#20-59) as well. So the only thing that the street warrior doesn't have is the cross over vent tubes like the truck avenger. So I just extended them up higher for off road.

The street warrior works great off road set up like this and it has great tuneability and great street manners as well.

Also on a side note really make sure your timing is right for what your motor wants. I am at 5,000 feet elevation and my new motor wants a lot of initial timing,(20 degrees + 6 degrees from a limited vacuum can) and a total of 34 degrees all in by 3,000 rpm, (limited the total in the h.e.i.). I have vortec heads and they dont need a ton of total advance, and my cam is, 215 @ .050 / 223 @ .050 , .473 lift , 108 lsa. hydraulic roller. My fuel pressure is at 5 1/2 psi.

Sorry for the long post I just thought I would share some the stuff that I went through, Hope this helps you out.
 

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