Quick Fuel metering blocks for a Holley 4150

[Steve26]

Has anyone tried the Quick fuel adjustable metering blocks for a Holley type 4150 carb? I'm running a 650 Speed Demon and I can't get it lean enough at idle no matter what I do. I would think adjusting the idle feed restrictions will solve this problem but wonder if anyone has gone down this road already? Thanks for your input.

Steve

 

[DaveM]

I ditched my Holley for a QF 750 mechanical. Great adjustability. I would think just the QF metering blocks would get you the idle adjustment you want by changing the idle feed restriction. You could try the old piano wire trick in the Holley feed restriction, but it's not as precise as the QF block.

 

[Andrew Robertson]

Has anyone tried the Quick fuel adjustable metering blocks for a Holley type 4150 carb? I'm running a 650 Speed Demon and I can't get it lean enough at idle no matter what I do. I would think adjusting the idle feed restrictions will solve this problem but wonder if anyone has gone down this road already? Thanks for your input.

Steve

Steve, I used the QF metering blocks on a 950DP that i was blowing through on a turbocharged 461BBC and they are a good thing. I have however also used fuse wire fed into the non-adjustable IFRs to lean down off-idle and light cruise mixture, so if that's the only issue there's a cheap way to do it.

However, the symptoms you describe point to other issues. You should be able to stall the car on the idle screws. It makes me think you have the primary throttle blades open too wide and are uncovering enough of the transition slots to start the transition circuit at idle. Once that happens the idle screws lose much of their control. The fix is to set the primary and secondary throttle blades by eye so that you can see only a small amount of the transition slot from underneath (so that the part you can see of the transition slot looks "square"), make sure you have no slack in the pump shot actuating levers, and then arrange for enough air to bypass the throttle blades at that position (along with adjustment of the idle screws) to acheive the desired idle by drilling progressively larger holes in the blades. There are several good and detailed write-ups on the net on exactly how to do this.

Hope this helps.

Cheers, Andrew

 

[Jim Rosenthal]

QF also make ProForm's carburetors. I have one on my Cobra (302 SBF) Easy to adjust and all parameters are adjustable. It might be easier to just change out the entire carb v. the metering block. Also, doesn't Holley now make a billet metering block for the 4150?

 

[Steve26]

Thank you all for your replies, always great help here.

Andrew, I have done all the things you describe with no success which is why I wanted to try the adjustable metering blocks. I have the throttle plates at .020 (measured) I have the float levels adjusted, timing checked and rechecked. I have drilled holes starting small in the throttle plates and have even tried the V bent piano wire in the idle restriction with no success. I have not had the balls to open up the idle air bleeds as I would have to drill them since they are not adjustable and it's a one way trip. VERY pissed at this point to be sure. I was going to buy a new Holley Ultra HP or Quick Fuel HR so as to have all the adjustment but thought I would try the adjustable metering blocks first for cost reasons. The Speed Demon works great in all other repsects but I'm tired of smelling like a 16 year old kid running a holley 850DP on a stock 307 Chev. Thank you again for your thoughts.

Steve

 

[Andrew Robertson]

Andrew, I have done all the things you describe with no success....
Steve

Hi Steve, sounds like you've tried everything, but if the car still runs with idle screws all the way in then you have a circuit operating at idle that shouldn't be. This is not likely to be a metering block issue. The QF blocks are great to properly tune the carb, but I think it might be better for you to nail the fundamental problem first. You could try running the throttles so closed that you can see none of the transition slots from underneath (and keep the car running by pulling the unported vacuum line off to introduce more air if you need it etc etc). With no transition slots exposed to the underside of the throttle blades, you should definitely be able to kill the engine with the screws and have full mixture control. You can then sneak up on throttle position until you lose idle mixture control, take the carb off and have a look at where that critical position is w.r.t. transition slot.

Final thought - there's not some weird extra feature or circuit for idle control built into the demon is there? Never used one personally - my fav carb is the proform 750DP (by QF) - best 750 by far of all the ones I've tried.

Good luck! Cheers, Andrew

 

[Steve26]

Hi Andrew,
my inability to communicate is showing! I can kill the engine at idle with the four corner idle adjustment. They should be turned out from seated between one turn and two turns, I'm at about 5/8th or less so I have no fine controll. The point where I start to get lean enough is less than 1/2 a turn and I then have a stumble on acceleration so I turn the screws out until I loose the stumble. If I continue to go in on the screws I can kill the engine. At this point I'm to rich so I would like to lean up the Idle restrictions to see if that helps. Thank you for your help, I do really appreciate it. I should have the Quick Fuel blocks by this weekend and I'll let you know what I find. I agree with you on the Quick Fuel carbs, if I buy another one it will be the Quick Fuel HR that is fully adjustable. Thanks again bud

Steve

 

[Andrew Robertson]

Hi Steve - I get you now! 1/2 a turn out from seated is not unusual on a 4 corner idle carb. Once you get lean best idle, then work on the IFR size and throttle plate position w.r.t. transition slot to cure the flat spot. It sounds to me like your IFRs might actually be too small, or you don't have the primary throttle plates set so you can see the first wee bit of the transition slot, or you might have play in the pump shot actuating lever. Anyway, you'll get the adjustability you need with the metering blocks to find out. Cheers, Andrew

 

[Jac Mac]

Steve, has your Demon got the 'EZI-IDLE' setup in the center of the base between all four barrels, if it has that is where you set your base idle speed after you set the throttle plates correctly in relation to the transition slots, not just on the throttle plates, if it has not you might wish to look at buying the kit from Demon/BG, makes life real 'EZE'..........

 

[Steve26]

Andrew and Jac you guys ROCK! I should have the metering plates tomorrow or the next day so I'll let you know what happens. Jac, I don't have the Idle-eze but at this point I might purchase one, would I need to get new throttle plates since I have already drilled holes in them? This carb works so well everyware else I would like to make it work. Thanks again for the help

Steve

 

[Jac Mac]

Andrew and Jac you guys ROCK! I should have the metering plates tomorrow or the next day so I'll let you know what happens. Jac, I don't have the Idle-eze but at this point I might purchase one, would I need to get new throttle plates since I have already drilled holes in them? This carb works so well everyware else I would like to make it work. Thanks again for the help

Steve

You 'could' get new throttle plates, but what I would do is get friendly with someone in an aircraft repair facility or your local Sport Aviation group & get four suitable sized alloy aircraft rivets to fit in the holes you have drilled, get him/her to squeeze them 'in situ', rather than hammer [ with the base removed from carb body of course ], job done...