If your motor is idling with the idle mixture adjustment screw all the way in, I'm pretty sure you're getting your fuel because the fast idle speed screw (butterflies) are open too much. The carb needs to be removed for step one to be done, which is adjusting the butterflies.

Last edited by rpm (5/08/2019 3:24 PM)

turns out that "kickdown" feeling is a pretty intense BUCK when the pedal is depressed slowly to that point...
the Spot on the pedal is Consistent, meaning at any RPM and speed it happens at the same Throttle Position.  The Intensity is dependent on how rapid the pedal is pressed....

Aside from that Buck/Kickdown point and the Funky Drivers side Mixture Screw, she is running strong and never thirsty!

on DP with dual Power Valves, should the PV be of equal Value?  (my logic would state one would want the secondary PV to open later as Demand increases, otherwise Jetting would become obsolete at the same point as primaries?  or is that incorrect given the Secondary Butterflies open at different times?

Anyone want to give feedback on the new "kickdown" sensation.......at a very specific throttle position consistent throughout all the gears, after changing the Jet Sizes the car Bucks only at said point.....

how intense the Buck is strictly depends on the rate the pedal is depressed (slowly is mild buck.  Medium pace is a LArge Buck and rapid is like a Kickdown).........if I had to assume the pedal would be 1/3 depressed

Ok Im Stumped....

on this 800CFM with 71/73 jetting it was smooth, seamless and powerfull ----- BUT THE STENCH was eye burning and migraine causing.....

Ive since dropped to 68/71 and power is intense, idle to accel. is just fine But at that 1/3 throttle position throughout all Gears there is THAT KICKDOWN experience.....1st gear is the most Violent and as you progress it gets less BUCK like and more mild kick down like....

I purchase the accelerator pump kit and have changed the secondary to the Brown one cause I have a 50cc there, and changed the primary twice with Minimal change to kickdown/buck experience.....

keep in mind originally with larger jetting there was No Buck (which leads me to believe there is a LEAN point now?? is that wrong?) and turns out BOTH cams WERE the pink one (which to me appears to be the least aggressive and shortest/least volume.....

-PV is 6.5 Primary and 4.5Sec


What esle Do I do?

TKOPerformance wrote:

The condition you are describing could be a lean condition, but I can't see how.  Reducing the jets created more power, meaning it was too rich.  Possibly the bigger jets were covering over something else causing it to go lean.  I'm now wondering if something is plugged up since tuning the accelerator pump seemed to make no difference. 

 
I agree, it sounds like a flat spot. As if it isn't getting a strong enough pump shot. I've run in to this on some carbs many years ago and my go-to was changing the pump nozzle (if enlarging, using a pin drill). I'm running a ThermoQuad and once I leaned up the jetting to what it liked, it too was lean on the pump shot. I stepped it up a bit with a pin drill and lengthened the pump shot duration to solve my problem.

This might be something to consider.

Ok this is excellent info Guys....Special Thank You to TKO and 6Sally, you both always take the time to help out....351Moose youre input is being applied as we speak....

just and update I did order the 50cc kit.....I did this cause as you mentioned TKO the logical thing is a LEAN scenario, which is obviously ODD given its only at 1 specific point, but it must be, so I started with the Accel. Cams thinking changing the duration of the 30cc would rectify it but so far the results are minimal, so perhaps the larger pump and much larger duration/volume will do the trick....

6Sally I can say with absolute confidence No Vac leak.....I did the whole Idle and Mixture Screw thing 100,000x's with all 3 Carbs and nothing got better from that, not saying its not a problem just saying dont know myself how to use that to potentially fix it ---------- but I did identify couple weeks back after trying again that one of the screws did Very Little when screwed inward!  i just cant remember which side so I will report back.....
as for timing Ive also done this 100,000xs and unfortunately I can no longer remember the numbers, but I always relearn TDC from piston 1, I set the initial more modestly this time around so my guess would be 6-8.....
lastly my engine was built 7yrs ago now and all CAM info has been lost in the Move....I know its a Roller Comp Cams with Medium-Higher Duration/Lift and LSA, i just cant recall/find the model number.

I will play a little more and report back!
thanks again guys

regards,
Jeff
 

M1Mustang69 wrote:

So Update:     Lets keep in Mind folks that only variable changed WAS the Jetting and that Bucking Began.....prior to that 0 Carb Performance issues BUT FUMES were unbearable!  jets went from 71/73 to 68/71

*Changed 30cc Primary Pump Cam from Pink, to Red, to White and Now Blue = No/minimal change
*Secondary 50cc Pump Cam changed to Brown = no change
*Primary Squirter was a modest 27......Secondary was 38.  Now primary is 38 and secondary is 40 = No change!!

WTF!?!?!  should I attempt Primary Power Valve? Do I have no choice to up the Primary Jets?  I dont understand how the car can have 0 hesitation, tons of power but 1 consistent DEAD SPOT that buck like a wild horse
 

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ timing will fix that!
 

You said the PV was a 6.5, correct?  How much vacuum is the engine pulling at idle when warmed up?  PV number should be 1/2 the vacuum reading per Holly's tuning advice.

TKO Primary is 6.5yes, vacuum bounces around 12-13.5 area (bounces cause the Cam). 
I can assure everyone all the basic carb knowledge and adjusting Ive Battled with it all for approximately 10yrs or more.....Ive read and researched on all that relatively basic stuff (PV size, secondary curb idle, nozzle changing, idle mixture.)
Where I lack is when something is a skew, or particularly/peculiarly not right, how to rectify it.....With this in particular, 3 Carburetors of different sizes (650, 750 and now 800) ALL SUFFERED from the same Unbearable STENCH regardless of basic/common modifications/troubleshooting...

Sally I always appreciate your input and insight, you are VERY well versed and knowledgeable.  But as stated earlier in this posting 800 maybe too big, but 650 is DEF. too small.  everyone and their mother says 600-650 so I foolishly purchased that costing me close to $1000 and it was in your seat, completely noticeable power and performance drop.....regardless of jetting, PV, nozzle....all it did was make it too lean or increased the potency of the stench!

MS I always appreciate you taking the time to help, in fact it makes me feel important but in the same time makes me realize my issues warrant the attention of a Guru which isnt a good thing cause it could mean "Im Fooked"

I have attempted several positions for the Secondary Curb Idle with definite success on odour potency, but not enough.....
This latest and most important Issue lies with the fact I dropped Jetting and all of the sudden there is a Specific and Constant "Dead Spot" with the throttle position....It feels like a "Kickdown" with automatics but I have a T5 in her....3.73Diff and decently modified 351W (all but stroked)....Ive tried the Curb Idle, Different Accel Cams, Nozzles and PVs and none have yielded the kickdown....

My final attempt is converting the Primary to a 50cc and try playing with that......other than this I think I will sell my 800Holley DP and buy a 750EDEL........I cant take this constant nonsensical battle....

I also have a beauty Holley650 used for 3 summers for sale if anyone is interested, losing my shirt on that one!
 

Apologies, I intended to acknowledge that....14yrs ago when I bought the car I was original original original......then I got bored so thought more more more.....by the end she turned out a little more radical than intended.  The Motor rebuild came out much more than i expected (drive ability wise)  shifting rpm is 2000rpm some what minimum, you could creep under if theres no one on the road or no need to accelerate much at all....
Very Toque.  most this happened from listening to others (a race cousin mechanic) and inexperience....Have half a mind to sell and buy another or start over sometimes cause Id like a bit more of a cruiser/city drive.....The T5 was single handed the best thing done to it, but with that motor the torque went through the roof, I had to put sub frame connectors, esp with the 3.73........Lucky I used a .59OD gear!

Conclusion:

for me to keep this 69Mach I need to get rid of MOST this Smell!  out of all this, that is the thing I can Not tolerate The Most!

do you think Edel will Help?
 

TKOPerformance wrote:

For tunability I'm always going to recommend an Edelbrock over a Holley. 

I've been rebuilding and modifying carbs since the 70's and I got tired ot Holley real fast back then. Carter (now Edelbrock) was the one for me. Dead nuts simple and fairly easy to dial in (jets, rods, nozzles). No power valve to blow out, no pump cams to position and swap out... they are relatively easy to deal with compared to Holley. A couple of important details are:

-  unless you are really good with carbs, throwing things at it to try and fix it usually isn't going to work. MS's advice about getting a gauge in it would be best for your situation. You need to know where you are fat and where you are lean and that's the best way to do it if you're not a carb expert.

- making large changes like changing the nozzle up as many steps as you did may put you on the other side of the problem, leading you to think that nothing was wrong. On my carb I used a pin drill to go from a #29 to #31 to solve my problem. I first made sure I had a second original nozzle before starting and then drilled the original nozzle to a #30. It was better but still flat at the top so I increased the stroke and that fixed the flat area at the top (higher revs). It was still weak in the middle of the stroke so I bumped it up to #31 and that nailed it.

Carbs take patience and a methodical approach to get dialed in. Once set, they are good to go. My 351W has an old Carter ThermoQuad 850 on it that works like a charm. Press the pedal down, set the choke according to the temp (manual), let up on the pedal, hit the key and it immediately lights off. When I started with it it was anything but that...lol! Flat spots, overjetted, float level too high (original carb spec setting) and so on. Patience and a methodical approach solved all of my problems but it did take some time, thus the patience!

Good luck getting it sorted!

Thanks Everyone....the Input is appreciated Tremendously (as trump would say).......

I am no expert but learning comes relatively easy for mechanical things likes this.....with answered questions and good solid input from everyone here I can get it, Although will not lie, very curious on trying an Edel......If I do, would you recommend CFM - to - CFM specs equal from Holley to Edel?  I currently found 750 and 800cfm really make the car come to life, 750 seemed to be most consistent throughout the RPM range and a bit snappier, so that being said would you stick with a 750Edel or did you find they required a bit more to perform relative?

update on my 800 dead spot:

-changed the primary accel. pump to a 50cc that I ordered and the PV to a 7.5hg........also reverted the nozzel to the 27 to give the squirt a longer duration (keep in mind my initial accel. was never an issue, roughly 1/3 throttle position is) and the FLAT BUCK has reduced Drastically.......its like a very light kickdown....Fume Stench and potency has dropped noticeably also.....


Perhaps Lets me ask this, given im not a guru and i feel it will help knowing/understanding how a carburetor and engine should perform:

Knowing and understand LEAN is never good and wanted, how should a carburetor run.......With as small a Jetting to have the car run and drive smoothly and efficiently during normal calm driving conditions, YET when pushed strongly or at WOT the PV comes into play providing "X" amount of proper fuel for the more extreme condition?

Or should the jets always provide the right amount of fuel for both conditions as if the PV was not in the circuit to begin with???