Author Topic: I could use some help, please  (Read 4875 times)

Offline King Scooter

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I could use some help, please
« on: March 22, 2017, 06:43:24 PM »
I recently purchased a rebuild kit from Cliff. This is my 1st q-jet rebuild/mod. I am doing my best to follow his book, but have to admit, I'm a bit overwhelmed by all the new terms, circuits, recipes, configurations and such. But I'm having a good time.
My set up is...1972 full body Monte Carlo. 355 sbc, OEM 487x heads, 8.2:1 cr, cam is HFT .464, 214d @ .050, 110d LS with ICL @ 105. Cam is degreed and valve train geometry is correct. The cam specs listed are measured and what I'm actually getting. Stock cast iron intake, points converted to electronic module w/hotter coil, 1 5/8" headers w/dual 2.5" full exhaust, TH350 with Coan 2400-2600 stall, 3.31 posi. Power brake and A/C car. Not a daily driver, but I like to drive it aggressively and it's my long distance cruiser.
Carb is 7022210 QE 2381=1972 C-10 pick up, A/T, non California. Cliff supplied me with the sr rebuild kit as well as .125 fuel inlet seat .076 main jets, 43B primary MR and DA secondary metering rods.
Information gleaned since beginning the rebuild, and after getting the rebuild kit:
Idle tubes .039
Idle down channel .051
Lower air bleed .070
Upper air bleed .089
Accelerator pump discharge holes .074
Main air bleeds: Air horn & main body .042
Secondary POE well restriction .040
Secondary POE restriction .051
Secondary tube restrictions...one is .024 and the other is .038. Looks like 1 tube was replaced and maybe damaged during install, restricting flow to .024
Secondary MR hanger G
Idle bypass air .094
No holes in throttle plates
Can someone look at these specs and tell me what I need to do to maximize what I have? My numbers don't seem consistent with any of the recipes listed in the book. What parts can I use, what needs to be changed?
I'll try to answer any questions you may have.
Thanks
Scott


Offline Ethan1

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Re: I could use some help, please
« Reply #1 on: March 23, 2017, 04:25:21 AM »
 Scott,
 I would go with Recipe 1 in your case. It sounds like you have have a pretty mild cam/setup.

 .036" Idle Tubes
 .046" Idle Down Channel
 Your Lower IAB is good at .070".
 .069" Upper IAB
 .027" Accelerator Pump Discharge Holes
 .070" MAB's in Airhorn and Main Body
 .035" Secondary POE Well Resitriction
 .054" Secondary POE Restriction
 .036" Secondary Tube Restriction
 Secondary Hanger "K" or Higher ("G", I don't think will work)
 .050"-0.080" Idle Bypass Air

 What choke do you have also? Also, aren't those secondary metering rods a tad on the rich side?
 
Ethan

1972 Chevelle

(oo______oo)

Offline King Scooter

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Re: I could use some help, please
« Reply #2 on: March 23, 2017, 06:36:43 PM »
Ethan:
I'm running the stock heat stove, divorced choke. I haven't accurately timed the release yet, but it seems really fast, like less than 1 second based on sucking on it.
I can't say if the secondary metering rods are on the rich side as I have no idea. That is what was provided in the kit, so I trust it's what I need. But to be fair, Cliff didn't have this much info to work with. Is the large size maybe compensating for some other oversized orifice or circuit?
I did get a better measurement on the accelerator pump discharge openings of .022. I was measuring the opening at the air horn, not the actual discharge. Remember, I'm a rookie.
Now my questions:
-Is there a way to reduce the openings on my upper IAB? I'm at .089 and you suggest .069.
-Can you explain the secondary hangar lettering system? You say K or higher. Does that mean K, H or I or does it mean I, J or K. I'm not sure what direction means higher.
-One last thing, what is the proper way to measure the secondary air flap opening?
Thanks for your time & understanding. I'm sure I'll be ordering more parts in the near future, once I get this stuff sorted out.
Scott

Offline Ethan1

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Re: I could use some help, please
« Reply #3 on: March 24, 2017, 08:06:45 AM »
Ethan:
I'm running the stock heat stove, divorced choke. I haven't accurately timed the release yet, but it seems really fast, like less than 1 second based on sucking on it.
I can't say if the secondary metering rods are on the rich side as I have no idea. That is what was provided in the kit, so I trust it's what I need. But to be fair, Cliff didn't have this much info to work with. Is the large size maybe compensating for some other oversized orifice or circuit?
I did get a better measurement on the accelerator pump discharge openings of .022. I was measuring the opening at the air horn, not the actual discharge. Remember, I'm a rookie.
Now my questions:
-Is there a way to reduce the openings on my upper IAB? I'm at .089 and you suggest .069.
-Can you explain the secondary hangar lettering system? You say K or higher. Does that mean K, H or I or does it mean I, J or K. I'm not sure what direction means higher.
-One last thing, what is the proper way to measure the secondary air flap opening?
Thanks for your time & understanding. I'm sure I'll be ordering more parts in the near future, once I get this stuff sorted out.
Scott

 Scott,
 I believe you can stick a check ball in the hole and re-drill it. I am pretty sure that is what, Cliff, has done in the passed. Maybe even soldering up the holes?

 As for K and higher:
K      .565"
L    .570"
M    .575"
N    .580"
O    .585"
P    .590"
R    .595"
S    .600"
T    .605"
U    .610"
V    .615"

G is  .545"

The difference between those are the height at which they keep the rod in the jet. A hanger that is adjust higher will give you full rich faster as your secondaries open.

So, K or higher would be .565" or higher of lift.

The secondary air valve opening is a little tricky. I am not sure on it, Scott. I think I remember reading you have to take dial calipers and measure down from choke to when the secondary air valve is fully open. If I am wrong, I am wrong. Sorry. :(
Ethan

1972 Chevelle

(oo______oo)

Offline Ethan1

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Re: I could use some help, please
« Reply #4 on: March 24, 2017, 08:10:21 AM »
 Or it's from the back of the edge of the Qjet to the edge of the secondary air valve fully open. Try both methods. I think it's the latter of the two. :)
Ethan

1972 Chevelle

(oo______oo)

Offline Cliff Ruggles

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Re: I could use some help, please
« Reply #5 on: March 25, 2017, 03:28:40 AM »
The stock MAB size on that carb should be .120".  Has it been commercially "remanufactured" at some point?.....Cliff

Offline King Scooter

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Re: I could use some help, please
« Reply #6 on: March 25, 2017, 07:05:02 AM »
Ethan
Thanks for the info and help. I'll look into resizing the upper IAB & I'll check my others carbs for a K or higher hanger. Otherwise I'll be ordering.
Cliff:
According to receipts I got with the car, yes it was "rebuilt" in 1996. I found they closed off the idle bypass air passage through the main body then drilled the throttle plates to compensate(?). I removed their plugs and swapped out the throttle plates so I think I'm back to ground zero again other than the orifice sizes, which I'm working on.
BTW, love your book. As a newbie to Q-jets I just wish it had an index so it would be easier to find the different circuits and terms.
Thanks again
Scott

Offline Cliff Ruggles

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Re: I could use some help, please
« Reply #7 on: March 26, 2017, 10:10:34 AM »
The MAB's should not be .046", so they also need to be removed to use the .076" jets and 43B primary metering rods.....Cliff

Offline King Scooter

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Re: I could use some help, please
« Reply #8 on: March 28, 2017, 08:09:36 PM »
So here's where I'm at:
-Since my upper air bleeds are so large @ .089, I read in the book that my idle tubes should be .003-.004 larger than normal recipe, so I left my idle tubes at .039. Hope this is correct.
-I left my idle down channel at .051, since I can't reduce what I have to the recommended .046
-Can't find any drill bits smaller than .040 so I'm stuck with my accelerator pump discharge  at .022 vs recommended .027
-I drilled out the brass inserts that were installed in my MAB's from .042 to .070. I can remove these inserts if I need the MAB's to be the original .120.  Cliff: do I need to do this or is .070 going to be OK with .076 jets and 43B PMR?
-Secondary POE restriction left at .051 vs recommended .054 since I can only get a .060 drill bit
-I drilled my smaller secondary tube restriction to .040 vs recommended .036. Again I could only get .040 drill bit.
-Secondary hanger is now L since I had one from another carb
-Idle bypass air is now .0625
I'd like to think what I'm doing will be WAY better than what I had. Is this a safe assumption or am I still off base?
If anything looks out of whack please let me know & I'll try to correct it before final assembly, hopefully this weekend.
Thanks
Scott



Offline Cliff Ruggles

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Re: I could use some help, please
« Reply #9 on: March 29, 2017, 04:50:47 AM »
76 jets will be too large they are designed for the .120" main airbleeds.....Cliff

Offline King Scooter

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Re: I could use some help, please
« Reply #10 on: August 02, 2017, 07:49:31 PM »
UPDATE: So I've had a few months to run my rebuilt/modified q-jet on my 355.
I want to say thanks to Ethan & Cliff for all the help.
I am thrilled with how this carb works. It cold starts quickly and idles nicely with just a few pumps of the gas pedal. The only cold start issue is that it sometimes wants to die after a few seconds if I don't hit the gas pedal, but then it straightens right out. Warm starts are flawless as long as I don't touch the gas. I have no hesitation from idle to instant WOT and no dead spots while slowly accelerating or cruising. I'm very pleased, to say the least.
My question: I'm still running the .070 MAB's with the 76 jets.  Plugs are a bit black and I'm disappointed with my 14 mpg. Will mpg (and performance) improve if I open the MAB's to .120 as Cliff suggests, or would I be better off with smaller jets etc?
I almost hate to make any changes at this point since I'm so pleased otherwise, but I'm up for it if that's what's needed.
Thanks.
Scott

Offline Cliff Ruggles

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Re: I could use some help, please
« Reply #11 on: August 03, 2017, 11:12:22 AM »
I'd leave the MAB's at .070" and reduce the jets to 72's or 73's, that should do the trick....