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/6 Holley 1920 Tuning

JJordan1173

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Hey All,

I have been trying to tune my Holley 1920 with a manual choke on a 225 slant 6 motor. (Photos attached) I bought the car about a year ago and have been slowly restoring it. Overall pretty good shape. The car is driveable. I will be performing a compression test on my cylinders shortly, due to possibly burning oil in the cylinders.
Maybe relevant maybe not?

In an attempt to not get too far off topic, I feel it lacks power going into first from idle. Or maybe I am wrong and that is just the nature of the slant 6...


I am attempting this tune with the car at operating temp and the choke wide open.

I am attempting all of this in hopes of not having to rebuild the carb. However I did buy a rebuild kit frim the carb Dr., so that is available if I need to go that route.

My first go to is the idle mixture screw. It is unresponsive. It stalls when I screw it nearly all the way in and when I remove it. Anywhere inbetween off or fully in I get no response in rpms. I have taken the screw out and shot carb cleaner through the hole and the screw seems to be in good shape. I am curious why I am not getting any response in any of the turns inbetween.

Thanks for any suggestions.

20230924_130756.jpg


20230321_161856.jpg
 
Are you turning it say 1/16 turn and giving it a second to respond. Then maybe another. And waiting.
It's not about cranking it in, get mad, peel it all the way out, then throw arms in the air.
 
Are you turning it say 1/16 turn and giving it a second to respond. Then maybe another. And waiting.
It's not about cranking it in, get mad, peel it all the way out, then throw arms in the air.
Yes I am giving it time to respond after every turn.
 
Figured it out. My fast idle was way off. I will post the link to the .pdf that gave me the step by step for the Holley 1920 Carberator. Thanks.
 
Hey All,

I have been trying to tune my Holley 1920 with a manual choke on a 225 slant 6 motor. (Photos attached) I bought the car about a year ago and have been slowly restoring it. Overall pretty good shape. The car is driveable. I will be performing a compression test on my cylinders shortly, due to possibly burning oil in the cylinders.
Maybe relevant maybe not?

In an attempt to not get too far off topic, I feel it lacks power going into first from idle. Or maybe I am wrong and that is just the nature of the slant 6...


I am attempting this tune with the car at operating temp and the choke wide open.

I am attempting all of this in hopes of not having to rebuild the carb. However I did buy a rebuild kit frim the carb Dr., so that is available if I need to go that route.

My first go to is the idle mixture screw. It is unresponsive. It stalls when I screw it nearly all the way in and when I remove it. Anywhere inbetween off or fully in I get no response in rpms. I have taken the screw out and shot carb cleaner through the hole and the screw seems to be in good shape. I am curious why I am not getting any response in any of the turns inbetween.

Thanks for any suggestions.

View attachment 1576716

View attachment 1576717
The Holley 1920 is a great carb but it's not without its faults. Suggestion, remove it from the engine.
2. Remove the fuel bowl...4 screws
3. Remove the power valve plunger assembly (top of fuel bowl assembly...3 screws)
4. Remove the main jet's metering plate as it contains the idle mixture fuel passages and air bleeds which seem to be restricted, owing to your idle mixture issues
5. The gasket behind the metering plate also contains the accelerator pump circuit, which, if leaking, could attribute to a difficult control idle mixture as you note.
6. The 1920 is EASY to rebuild. Just use a quality rebuild kit....either by HOLLEY OR STANDARD MOTOR PRODUCTS as the instructions and settings are included and are easy to understand. Just take your time and a good aerosol carb cleaner. The internal screws are small....just don't over tighten....just my opinion of COURSE......BTW...REMEMBER to reattach the vacuum advance hose to the nipple shown in your first pix.
BOB RENTON
 
The Holley 1920 is a great carb but it's not without its faults. Suggestion, remove it from the engine.
2. Remove the fuel bowl...4 screws
3. Remove the power valve plunger assembly (top of fuel bowl assembly...3 screws)
4. Remove the main jet's metering plate as it contains the idle mixture fuel passages and air bleeds which seem to be restricted, owing to your idle mixture issues
5. The gasket behind the metering plate also contains the accelerator pump circuit, which, if leaking, could attribute to a difficult control idle mixture as you note.
6. The 1920 is EASY to rebuild. Just use a quality rebuild kit....either by HOLLEY OR STANDARD MOTOR PRODUCTS as the instructions and settings are included and are easy to understand. Just take your time and a good aerosol carb cleaner. The internal screws are small....just don't over tighten....just my opinion of COURSE......BTW...REMEMBER to reattach the vacuum advance hose to the nipple shown in your first pix.
BOB RENTON
Anyone know what this hole is for? I am not seeing it mentioned in my instruction manuals. Thanks.

20231222_132126.jpg


20231222_132131.jpg
 
The Holley 1920 is a great carb but it's not without its faults. Suggestion, remove it from the engine.
2. Remove the fuel bowl...4 screws
3. Remove the power valve plunger assembly (top of fuel bowl assembly...3 screws)
4. Remove the main jet's metering plate as it contains the idle mixture fuel passages and air bleeds which seem to be restricted, owing to your idle mixture issues
5. The gasket behind the metering plate also contains the accelerator pump circuit, which, if leaking, could attribute to a difficult control idle mixture as you note.
6. The 1920 is EASY to rebuild. Just use a quality rebuild kit....either by HOLLEY OR STANDARD MOTOR PRODUCTS as the instructions and settings are included and are easy to understand. Just take your time and a good aerosol carb cleaner. The internal screws are small....just don't over tighten....just my opinion of COURSE......BTW...REMEMBER to reattach the vacuum advance hose to the nipple shown in your first pix.
BOB RENTON
Thanks Bob. I am going to take it off the engine after the holidays. Merry Xmas.
 
The holly that was on my 225 slant six only had two bowl screws on it....and don't be afraid to advance the initial timing to all it wants. Mine for example liked 15° initial. Anything more than that it would ping a little bit right off idle but it would still run dad gum good.
 
Anyone know what this hole is for? I am not seeing it mentioned in my instruction manuals. Thanks.

View attachment 1577933

View attachment 1577934
The hole you referred to is a VAPOR VENT. it's purpose is to vent any fuel vapors that may occur thst would drip from the booster venturi assembly during a hot soak, engjne off condition. Just about all carbs have one.....no big deal.....just my opinion of course....
BOB RENTON
 
The hole you referred to is a VAPOR VENT. it's purpose is to vent any fuel vapors that may occur thst would drip from the booster venturi assembly during a hot soak, engjne off condition. Just about all carbs have one.....no big deal.....just my opinion of course....
BOB RENTON
Rebuilt the carberator and running much better now. Thanks for all the tips.

I noticed that the float had some bubbles and was beginning to deteriorate. I looked around online and they are going for $100, which I do not think is worth the investment in a holley 1920. Anyone know of a place to get decent floats for this model?
Thanks
 
Photos attached. You can see some float particles. If it clogs and floats are $100+, I may just scrap it and find a new carb..maybe when with a the thermostatic choke, wouldn't that be nice ;)

20240103_134626.jpg


20240103_134635.jpg
 
Rebuilt the carberator and running much better now. Thanks for all the tips.

I noticed that the float had some bubbles and was beginning to deteriorate. I looked around online and they are going for $100, which I do not think is worth the investment in a holley 1920. Anyone know of a place to get decent floats for this model?
Thanks
Looks like someone has over tightened the bowl too. If it doesn't leak, then you're fine....and don't know where you could find a float or even a parts carb. Only had a couple of /6's with the Holley. Throw up an ad in the WTB section and see if anyone responds would be your best bet here. There are some who saved everything. I saved a LOT of stuff over the years but single barrel carbs wasn't one of them. Another good site would probably be the FABO.....lots of older Darts on there and lots of them came with the /6.
 
Rebuilt the carberator and running much better now. Thanks for all the tips.

I noticed that the float had some bubbles and was beginning to deteriorate. I looked around online and they are going for $100, which I do not think is worth the investment in a holley 1920. Anyone know of a place to get decent floats for this model?
Thanks
Have you tried Mikes? Holley 1920, 1-barrel Carburetor Rebuild Kits and Parts
 
Photos attached. You can see some float particles. If it clogs and floats are $100+, I may just scrap it and find a new carb..maybe when with a the thermostatic choke, wouldn't that be nice ;)

View attachment 1585678

View attachment 1585679
This may help you locating a float assembly....from Mike's Carburetor shop

HOLLEY 1920 FLOATS​

Holley 1920 Floats

Holley 1920 Float


The 1920 carburetor used 2 different floats through the years and neither one is manufactured any more. We do find new floats from time to time so check our 1920 catalog. The 1920 float was a Nitrophyl float and over time these floats will absorb fuel and the only way to test your float is to weigh it. We have grouped the carburetor numbers below to each weight and they do differ quite a bit. Floats are weight in grams and since these are very hard to find, you can fudge to the upside 1 to 2 grams and then compensate by adjusting the float 1/32" lower.

The float bumper spring is used to take the bounce out of the float. Good to have, but worst case, you can use the carburetor without it.

Most flooding situations are caused by the needle & seat. Test before assembly.



Holley 1920 Float


This group of carburetor number should weigh in at 12.5 grams.

R-6319A R-2647-1A R-2647A R-2651-1A R-2651A R-3117-1A R-3117A R-3615-2A R-3975AAS R-6266A R-6286A R-2136A R-2303A R-2416A R-2417A R-2418A R-2419A R-2500-1AAS R-2500AAS R-2533A R-2534A R-2535A R-2536A R-2537A R-2765A R-2766A R-2767A R-2768A R-2769A R-2770A

This group of carburetor numbers should weigh in at 7.5 grams.

R-3993-2A R-4405-1A R-4405A R-4487-1A R-4510A R-4542A R-4591-1A R-4591A R-8592A R-4594-1A R-4594-2A R-4595-1A R-4595-2A R-3993-1A R-3993A R-4405AAS R-4487A R-4510A R-7748A R-7864A R-4165AAS R-3228-3AAS R-3271-1A R-3397-1A R-3397A R-3924-1AAS R-3924-2A R-3924-2AAS R-3924AAS R-3982-1A R-3982-1AAS R-3982-2A R-3982A R-3982AAS R-3983-1A R-3983-1AAS R-3983A R-3983AAS R-3984-1A R-3984-1AAS R-3984-2A R-3984A R-3984AAS R-3985AAS R-4012AAS R-4013AAS R-4355AAS R-4356AAS R-4357AAS R-4358AAS R-4359AAS R-4362AAS R-4414-1AAS R-4414AAS R-4416AAS R-4655AAS R-4656AAS R-4659AAS R-4712-1AAA R-4751AAS R-4755AAS R-4756AAS R-6159A R-6202A R-6202AAS R-6876A R-7249A R-7250A R-7583A R-7584A R-7587A R-7747A R-7747AAA R-8213A R-8311A R-8388A R-8400A R-8401A R-8404A R-8405A R-8406A R-8407A R-6153AAS R-6154AAS R-6155AAS R-6156AAS R-6363AAS R-6364AAS R-6365AAS R-6366AAS R-6448AAS R-6595AAS R-6596AAS R-6756A R-7585A R-7585AAA R-7586A R-7586AAA R-4351A R-4351AAS R-4352A R-4352AAS R-4353A R-4353AAS R-4354A R-4354AAS R-4355A R-4356A R-4357A R-4358A R-4359A R-4361A R-4362A R-4363A R-4363AAS R-4641A R-4642A R-4655A R-4656A R-4657A R-4658A R-4659A R-4750A R-4751A R-4755A R-4756A R-6482AAA R-6483-1AAA R-6483AAA R-6153A R-6154-1A R-6154A R-6155A R-6156A R-6363A R-6364A R-6365A R-6366A R-4161-1A R-4161A R-4161AAS R-4162A R-4162AAS R-4163-1A R-4163A R-4163AAS R-4164A R-4164AAS R-4165A R-4192A R-4192AAS R-4193A R-4193AAS R-4194-1A R-4194A R-4194AAS R-4195A R-4195AAS R-2997A R-2998A R-2998AAS R-2999A R-3053-1AAS R-3053A R-3054A R-3057A R-3058A R-3059A R-3060A R-3152A R-3225AAS R-3226-1A R-3226-1AAS R-3226-2A R-3226-3AAS R-3226A R-3227-1A R-3227-1AAS R-3227-2A R-3227A R-3228-1A R-3228-1AAS R-3228-2A R-3228A R-3229-1A R-3229-1AAS R-3229-2A R-3229A R-3271-1AAS R-3271A R-3272-1A R-3272A R-3273-1A R-3273-1AAS R-3273-2A R-3273A R-3274-1A R-3274-1AAS R-3274-2A R-3274A R-3275-1A R-3275-1AAS R-3275A R-3276-1A R-3276A R-3277-1A R-3277-1AAS R-3277A R-3278-1A R-3278-1AAS R-3278A R-3279-1A R-3279-1AAS R-3279A R-3280-1A R-3280A R-3281-1A R-3281-1AAS R-3281A R-3282-1A R-3282-1AAS R-3282-2A R-3282A R-3398-1A R-3398-1AAS R-3398A R-3399-1A R-3399-1AAS R-3399A R-3446A R-3446AAS R-3671-1AAS R-3671A R-3671AAS R-3672-1AAS R-3672A R-3672AAS R-3673A R-3673AAS R-3674A R-3674AAS R-3919-1A R-3919-1AAS R-3919-2A R-3919-2AAS R-3919-3AAS R-3919A R-3920-1A R-3920-1AAS R-3920-2A R-3920-2AAS R-3920A R-3921-1A R-3921-1AAS R-3921-2A R-3921-2AAS R-3921-3AAS R-3921A R-3922-1A R-3922-1AAS R-3922-2A R-3922-2AAS R-3922A R-3924-1A R-3924A R-3985-1A R-3985-1AAS R-3985A R-4712AAA R-4712AAS R-6260-1AAA R-6260-2AAA R-6260AAA R-8403A R-6371A R-6371AAS R-6372A R-6372AAS R-6401A R-6401AAS R-6402A R-6402AAS R-6447A R-6448A R-6449A R-6450A R-6553A R-6554A R-6593A R-6594A R-6594AR R-6595A R-6596A R-7031AAA
BOB RENTON
 
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