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  • 1 Post By Gaz64
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  #1 (permalink)  
Old 12-08-2019, 12:13 PM
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Default Holley 750 vacuum/can I remove this?

Iím installing a turkey pan and the linkage attached to the vacuum canister is in the way. The manual doesnít even show this setup. I believe itís the area that would allow the cable for a manual choke. Whatís this for and can I just remove it? Iíve seen pictures of other people having a turkey pan with a vacuum carburetor. Thanks...
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Old 12-08-2019, 12:32 PM
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That's just the manual choke linkage. Unbolt all the brassy colored stuff that's attached to the vacuum canister and then put a little zip tie inside the grey housing area so as to hold the choke fully open all the time. There is a debate as to whether your carb runs better with or without the big butterfly choke plate removed, or left on as is. I left mine on.
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Old 12-08-2019, 12:55 PM
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Thanks Pat, done....
One more question, I was surprised to find a plug in the line going from the pcv valve in the intake manifold to the bottom of the carburetor. Someone must have thought it was causing oil consumption, but the real cause was a bad intake gasket. Should I remove the plug while I’m in here or is it better to have the pcv valve functional? No sense drilling the turkey pan to run it if it’s plugged anyways.
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Old 12-08-2019, 02:10 PM
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I like a PCV for a predominantly street driven car. That said, I think the ME Wagner adjustable PCV is probably the best I've found. Add to that the Moroso oil separator and you've got a pretty nifty system. I did mine like this:

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Old 12-08-2019, 05:59 PM
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Sweet setup. Thanks Pat...
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Old 12-08-2019, 07:56 PM
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And while you are in there, if your float levels are verified correct, I would drop the secondary level a few flats, and blast all the air bleeds with carb cleaner.

Gary
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Old 12-09-2019, 06:37 AM
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Gary's absolutely right. With today's gasoline and, I'm guessing your carb might be tilted a bit as well, you can no longer rely on the fuel level at the bottom of the sight hole method for setting floats (which you could on a nice Galaxie with Sunoco 260 in the tank). What I do is set it to the bottom of the holes, run the car until it's hot, pull the air cleaner and watch the boosters drip. Light up a Lucky Strike while one of your kids/grandkids films you with his phone. Once the car cools down, drop the floats slightly and repeat. Keep doing that until you no longer have booster drip from shi**y gas percolation. That's the best way to set your floats. For the air bleeds, blast a good carb cleaner though all eight bleeds, then set your compressor down to about 40psi and blast some air down through them. Then repeat. Your carb is now 75% dialed in. Setting the idle mixture screws just right (mine are set at 1 and 3/20ths turns out from lightly seated) is your next step. Then set your primary throttle plate so there's just a little bit of the transfer slot below the plate (you do not need to pull the carb off to do this, you can see this by looking down the top of the carb). Then get your idle RPMs just right by adjusting the secondary. You're now better dialed in than 98% of the carbs out there.

EDIT -- Don't light up a smoke while you're checking out the gas percolation cloud.
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Last edited by patrickt; 12-09-2019 at 06:49 AM.. Reason: Added the cautionary note on smoking....
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Old 12-09-2019, 07:34 AM
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With a Holley 750 vac secondary, I can't emphasize enough how having the idle/transition circuits tuned just right can make a HUGE difference in your overall quality of life. Seriously, the idle/off-idle/transition circuit is really important when you're just driving around town, at low speed, and gently accelerating. It's the difference between the carb being "just ok" and it being great. And to get that circuit just right, easily, you replace the hidden screw on the underside of the carb, that controls the opening of the secondaries, with a 25 cent mod like I have right here. You then adjust your idle RPMs with a little Allen wrench. That screw, btw, is 10-32.

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Old 12-09-2019, 07:39 AM
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Wonderful information, Thank You...
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Old 12-09-2019, 12:54 PM
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There is one last tweak that will make your Holley 750 Vac Secondary as easy to adjust as it can possibly get, and that is replacing that vacuum canister with the QuickFuel adjustable vacuum secondary canister. Having to change out the springs to get the secondaries to open at just the right pace is a PITA. Turning a screw to get it just right is a breeze. Here's a pic of the part, and a shot of my carb with the QF installed and the adjusting screw circled. A sharp eye will also find the zip tie that holds the choke open that I mentioned in a the previous post.



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Old 12-09-2019, 01:07 PM
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Ö and my modification to the hidden secondary screw was done after the vacuum advance cannister change out, so it does not appear in that photo.
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Old 12-09-2019, 02:02 PM
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Default Air Bleeds

Can't emphasize enough how important it is to keep them clean and clear. They will gunk up over time and cause issues. I went through it with them. If you are not familiar with them, there are some YouTube videos on cleaning them. Good luck.

PS I noticed you are in CT and no choke.

Fred
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Old 12-09-2019, 03:20 PM
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Quote:
Originally Posted by patrickt View Post
Gary's absolutely right. With today's gasoline and, I'm guessing your carb might be tilted a bit as well, you can no longer rely on the fuel level at the bottom of the sight hole method for setting floats (which you could on a nice Galaxie with Sunoco 260 in the tank). What I do is set it to the bottom of the holes, run the car until it's hot, pull the air cleaner and watch the boosters drip. Light up a Lucky Strike while one of your kids/grandkids films you with his phone. Once the car cools down, drop the floats slightly and repeat. Keep doing that until you no longer have booster drip from shi**y gas percolation. That's the best way to set your floats. For the air bleeds, blast a good carb cleaner though all eight bleeds, then set your compressor down to about 40psi and blast some air down through them. Then repeat. Your carb is now 75% dialed in. Setting the idle mixture screws just right (mine are set at 1 and 3/20ths turns out from lightly seated) is your next step. Then set your primary throttle plate so there's just a little bit of the transfer slot below the plate (you do not need to pull the carb off to do this, you can see this by looking down the top of the carb). Then get your idle RPMs just right by adjusting the secondary. You're now better dialed in than 98% of the carbs out there.

EDIT -- Don't light up a smoke while you're checking out the gas percolation cloud.
1 and 3/20ths?

Gary
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Old 12-09-2019, 03:34 PM
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1 and 3/20ths?

Gary
Yes. I know it sounds a bit anal, but I have a clickable very small ratchet that has exactly 20 clicks for one complete revolution. I use that tool to adjust the idle mixture screws. The perfect amount for my calibration is 23 clicks out from lightly seated. Not 22, and not 24. There's actually a feelable difference from just one click, one way or the other.
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Old 12-09-2019, 03:51 PM
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Quote:
Originally Posted by patrickt View Post
Yes. I know it sounds a bit anal, but I have a clickable very small ratchet that has exactly 20 clicks for one complete revolution. I use that tool to adjust the idle mixture screws. The perfect amount for my calibration is 23 clicks out from lightly seated. Not 22, and not 24. There's actually a feelable difference from just one click, one way or the other.
Ah yes, makes sense, and now for others following as well.

Gary
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Old 08-26-2020, 05:02 AM
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Default Pat and Gaz know it all!

I followed their sage advice and it cured my awful low running/big cam carb issues. Thanks guys if you didn't see my thanks on the earlier posts. Here's my secret screw/secondary idle fix, that almost nobody knows about, certainly not in the UK, that's for sure.
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Old 08-26-2020, 05:10 AM
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Pat and Gaz know it all!


Your subject line says it all.
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Old 08-26-2020, 08:25 AM
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I adjust that screw for the seconaries so as the transision slot is covered by the seconary throttle plates just leaving a little square hole------on some comp/more agressive type builds I adjust the throttle plates to just lightly seat on the bores(completely shut except loose enough that when cool they won't stick------then -------------
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