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Holley carb.

If adjusting mixture screws screws up your timing you have other problems(disconnect vac.advance,stiffer mech.advance springs in dist.)
 
Couple of questions on 4150. It is on a very high performance 440 (.040" over), ported, 915 heads, headers, MSD, cold air intake, Dominator intake manifold, headers.....so, close to 600 hp. All of this and a "bog" upon hitting WOT. I am running a 373 rear end.

First question....the carb has sight glasses for float level. I was told when I bought the car that the level needed to be at half way in the site window. I have read posts and watched numerous Holley YouTube and they all emphasize setting the level at the bottom of the glass (just wetting the threads on a plug). I picked up some literature on a Holley HP dbl pumper and it said that if you have glass, to set the level at halfway and if you have a plug, set it at bottom thread. Then, for the 4150 it only covers the level with a plug. I'm confused. I do know this, I have a had time setting the carb up if I use the bottom of the glass, and, I am running too rich at half way. Common sense would say that I set it at 1/3. What are the members opinion and experience?

Second question. If I set the auxiliary pumps so I have an accurate .015" at WOT, then I do not get shots right at the slight movement of the primary and secondary throttles. Should I cheat and set it for instant shot, or go with the book on the .015 at WOT?

OK, got a third......Where is the "square" transition slot? and when I find it, is it best to set it at Square? Where is that adjustment screw.

Finally, is there an opinion on cams and screw location? I am not worried about the hole shot, I just want mid range response. Thank you for any response(s).
 
With the glass site yes half way up. Older brass plug set up, trickling out.

Transition slot is adjusted with your idle adjustment screw. Flip the carb upside down. Open the throttle and you will see the slot. Set the primary side so you can see a perfect square when looking at it from underneath throttle closed.
 
Personally I just set the primary side and then make small adjustments with the secondary side to set the idle.
 
Well if your not getting pump shot right away then you need to look at pump cam.You need the .015" clearance so the pump itself doesn't bottom out at WOT.
 
Will do both things. I'll set the primary transition slot and make sure I'm back all the way to .015" Then I'll set the idle via the secondaries. I planned on having to empirically find which cam worked the best. Gotta put it back together and run it up and down the road to see what works. Thanks to you for helping me out. My objective is to one day be able to pass information I have collected on the Mopar onto others with less experience.
 
Sputnik it sounds like you need to look at Holley tuning, there's a lot of acc.pump cam profiles to choose from, but a bog at WOT ain't gonna be fx'd by acc.pump.
 
Oldbee, thanks for your post. Like I said on my first post today, I have been reading and watching Holley, Summit and any other reputable source. I have talked to racing mechanics, supply houses and anything or anybody I can get my hands on. Am I confused? Not a lot, but enough to not take the Holley the extra step, or to assure that the advise I follow is correct for my given situation. Take the subject of power valves. Go back and read the posts on this site, go to publications that you should trust, and read the papers and videos made by experts. I would venture to say that if you through out your experience and knowledge that you too would be asking questions that there seems to be multiple answers for.
Oldbee, please don't think I'm focusing on you, I am not. I am more frustrated because I come from a science background and I find that the Holley is not a scientific marvel. Getting back to my confusion. This is what you posted on post #27...." if your not getting pump shot right away then you need to look at pump cam". Here is what was posted on #29......."there's a lot of acc.pump cam profiles to choose from, but a bog at WOT ain't gonna be fx'd by acc.pump." Everything I have read about the pump cam, everything, does not tell you which one to chose to start with and why. Everyone talks about changing them but it seems there is no direction to lean on. This is where experience comes into play. With Holleys', I am limited. I have read books on theory and some in great detail, but not all they talk about are relative to a double pumper for a 4 speed 440 HP. I'm sorry I took so much space on the post. I do have two more books from Holley that I will read before I consume so much space and time. I do thank you and others for your advise. I appreciate it. Off to the garage to attack those windmills.
 
You may want to richen up the secondaries. If it has a bog near WOT, then you are probably running a little lean. As I said earlier, I ran my 850 dbl pumper carb with 88 main jets all around and it ran great! Nice tan color on the plugs. 451 with 915 heads, headers, Street Dominator intake, 509 cam.
 
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The reason you have .015" clearance on the acc pump arm at closed throttle, is to prevent engine vibration at idle to cause the squirters from pumping in fuel. Any tiny movement of the throttle pedal is going to pump a little gas out of the nozzles. So the .015 clearance prevents this from happening.
 
Garys1969rr, a couple of good points and a good explanation of the .015" at idle. How much richer on the secondaries vs secondaries?
 
Garys1969rr, a couple of good points and a good explanation of the .015" at idle. How much richer on the secondaries vs secondaries?
The 850 has the same size jets all around from the factory. I would go up 2 or 3 numbers in jet size on all 4 jets. Remove your front float bowl and see what size main jets you have now, and let us know.
 
Sputnik- heckuva last post; I've always liked to read so I devour a lot of paper & somewhere yrs ago I read (pre-internet)something on the cams/colors; duration of shot,height of cam,beginning of movement. It had to be an old Holley tuning book. Good luck you'll figure it out, sometimes takes awhile.Jeff
 
The reason you have .015" clearance on the acc pump arm at closed throttle, is to prevent engine vibration at idle to cause the squirters from pumping in fuel. Any tiny movement of the throttle pedal is going to pump a little gas out of the nozzles. So the .015 clearance prevents this from happening.

Well, not exactly, Gary. The .015" clearance is checked with the throttle held all the way open. The purpose is to insure that the accelerator pump diaphragm doesn't bottom out or tear. There should be NO clearance between the arm and the throttle assembly at the idle position so that ANY movement of the throttle moves the pump arm as well. Some of the videos on the web are confusing on this adjustment, but Holley got it right here:
Hopefully, this video will clear it up for Capt. Jim. BTW, the stock pump cam that Holley installs works for most situations. They provide a variety of cams for those who want to fine tune their engines...
 
Well, not exactly, Gary. The .015" clearance is checked with the throttle held all the way open. The purpose is to insure that the accelerator pump diaphragm doesn't bottom out or tear. There should be NO clearance between the arm and the throttle assembly at the idle position so that ANY movement of the throttle moves the pump arm as well. Some of the videos on the web are confusing on this adjustment, but Holley got it right here:
Hopefully, this video will clear it up for Capt. Jim. BTW, the stock pump cam that Holley installs works for most situations. They provide a variety of cams for those who want to fine tune their engines...

I may have to dis-agree a little bit. The clearance between the pump arm and the adjuster may not be that tight with the throttle closed. It is more important for the arm not to push the diaphram so far as to tear it. And so there may be more clearance when the throttle is closed. Ask me why I had to replace my pump diaphram today ! It might be because of the cam profile too. ................................MO
 
So, let me see if I have this right....You adjust the accel pump on both the primary and the secondary so each arm and adjuster are touching. The primary at idle and the secondary at the point the throttle begins or open. Then adjust both the primary and the secondary at .015" at WOT. Now here is what I am having a problem with. When I make the final .015 adjustment on the secondary, it throws off the primary setting. Assuming I have done it correctly, would this mean I should change the cam until I can achieve the .015 on both accel pumps at WOT and still have the primary just touching the arm at idle? I have a feeling I may be trying to split atoms here. It is strange that one measures the .015" (clearance) by sliding the gauge between the arm and the adjuster and to be satisfied when the arm moves up and down. I can't see where this is "clearance", it seems more like interference and a gap less than the .015". How much is enough when letting the arm move? Do I let it move .005, which means the gap is actually .010?
 
So, let me see if I have this right....You adjust the accel pump on both the primary and the secondary so each arm and adjuster are touching. The primary at idle and the secondary at the point the throttle begins or open. Then adjust both the primary and the secondary at .015" at WOT. Now here is what I am having a problem with. When I make the final .015 adjustment on the secondary, it throws off the primary setting. Assuming I have done it correctly, would this mean I should change the cam until I can achieve the .015 on both accel pumps at WOT and still have the primary just touching the arm at idle? I have a feeling I may be trying to split atoms here. It is strange that one measures the .015" (clearance) by sliding the gauge between the arm and the adjuster and to be satisfied when the arm moves up and down. I can't see where this is "clearance", it seems more like interference and a gap less than the .015". How much is enough when letting the arm move? Do I let it move .005, which means the gap is actually .010?
There is a good YouTube video put out by Summit racing that explains very well how to adjust a Holly accelerator pump. You don't want the arm touching solid the pump adjusters at rest. Most important is that the pump lever is not extended to the point that the diaphram could be ruptured at full throttle. In my case, that makes more than .015 clearance at throttle closed, but I don't think that makes any difference. The pump stroke has only a certain amount of travel. . It may be that a cam could be found that would contact the the pump lever with less clearance, But I don't think that is important. This is not a critical adjustment , however the cam profile determines how the pump "sqirts" the fuel. There is also a video that explains the cam profiles. Obviously, I am not a teacher LOL.........................MO
 
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