Carb question again

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Baprace
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Re: Carb question again

Post by Baprace » Tue Oct 31, 2017 7:57 pm

statsystems wrote:
Tue Oct 31, 2017 7:40 pm
amcenthusiast wrote:
Tue Oct 31, 2017 7:38 pm
Without meditating on all that's been said so far, this seems like a troubleshooting question that would be better served by going to a forum pertaining to the particular make and model of the car... to sort out the confused vacuum lines?

Otherwise one might easily become a fan of Chilton's Repair Manual 'Troubleshooting' section. (get a repair book on your car and spare yourself the grief and hassle of hit or miss troubleshooting techniques)

1973 Dodge Dart. 340 and the only hoses are the PCV hose and the vacuum gauge I have hooked up. I don't run a vacuum advance.
you should pull the carb and blow air through the fitting, it has to be blocked, perhaps the gasket ?

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Re: Carb question again

Post by statsystems » Tue Oct 31, 2017 8:19 pm

Baprace wrote:
Tue Oct 31, 2017 7:57 pm
statsystems wrote:
Tue Oct 31, 2017 7:40 pm
amcenthusiast wrote:
Tue Oct 31, 2017 7:38 pm
Without meditating on all that's been said so far, this seems like a troubleshooting question that would be better served by going to a forum pertaining to the particular make and model of the car... to sort out the confused vacuum lines?

Otherwise one might easily become a fan of Chilton's Repair Manual 'Troubleshooting' section. (get a repair book on your car and spare yourself the grief and hassle of hit or miss troubleshooting techniques)

1973 Dodge Dart. 340 and the only hoses are the PCV hose and the vacuum gauge I have hooked up. I don't run a vacuum advance.
I'll pull it off and check it.

you should pull the carb and blow air through the fitting, it has to be blocked, perhaps the gasket ?

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Re: Carb question again

Post by tresi » Tue Oct 31, 2017 8:57 pm

I know you have pulled the hose off of the PCV valve and got no vacuum. Have you pulled the hose off the carb while the engine is running? If there is no change it can't be as clear as you think

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Re: Carb question again

Post by cjperformance » Tue Oct 31, 2017 9:02 pm

With 9ish hg of vac you will definetly 'feel' and hear a leak the size of which removing a pcv hose from the carb will produce.
You have got the correct fitting havnt you? Typically 3/8" tube sticking out of carb base and typically 1/4" to 3/8" hole leading thru the carb base thats open to the intake manifold below the buttlerfys.
Can you show a pic?
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Re: Carb question again

Post by grandsport51 » Tue Oct 31, 2017 10:26 pm

In the first place pulling you pcv Hose at the tube on the baseplate with 9" will be noisy affect the idle either up or down on the idle speed and suck a finger therefore r and r the carb make sure the Gasket isn't blocking the pcv tube on the baseplate correct as required or my suggestion buy a Trans Dapt 2582
1" 4-bbl Carburetor Spacer Open Plenum with PCV for $30'and see if that solves your problem.
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Re: Carb question again

Post by statsystems » Thu Nov 02, 2017 4:16 pm

I have verified that both carbs have open ports for the PCV valve yet I can still pull the hose and it won't affect idle speed.

I have a picture of my carb that I'm putting back on. The borrowed carb was brand new and it has the same issue. I can't figure out where the vacuum is going. No vacuum at the port means the PCV valve is nothing but a vent and that sucks.

How do you post a picture on here?

Figured it out I think.


Nope, can't do it.

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Re: Carb question again

Post by F-BIRD'88 » Thu Nov 02, 2017 7:22 pm

Pull the hose off the PCV port and then stick you finger over the hole.
Do you feel any vacuum when its running? Yes No....
If no then that passage is not open.
Don't look to see if it effects the idle speed feel with your finger over the hole. It either has vacuum there or it don't.

If you want to post a picture from your camera or phone first
resize it so it is a reasonable size resolution and file size.
make it about 640x480 MAX 450x??? is plenty big.
Resave as a JPEG (.JPG) file type. about 50KBits to 100KBits file size.
The raw digital picture from your camera or phone are WAY TOO BIG and
the wrong file format.
Use this free small footprint windows pc program to resize correct pic brightness etc
and resave as a JPG... Then post from your computer.
WWW.irfanview.com

On the Proform billet carb base if the steel tube has been driven too far in the hole on the baseplate then most all of the vacuum flow will be blocked.

If the carbs throttles are way too far open at idle (usually incorrect timing at idle) and or if there is a even bigger vacuum leak or 3 or 4 then that amount of vacuum is not going to effect things.
Are the throttle blades drilled for extra air flow?
You can either use this method to get enough air flow at idle or the PCV air flow at idle but not both at the same time.
With the PCV working as designed ....,, drilled throttle plates are not necessary.
The 2 combined is too much.

Is this a auto transmission car or 4 speed car?

ignition timing at idle?

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Re: Carb question again

Post by statsystems » Thu Nov 02, 2017 7:56 pm

F-BIRD'88 wrote:
Thu Nov 02, 2017 7:22 pm
Pull the hose off the PCV port and then stick you finger over the hole.
Do you feel any vacuum when its running? Yes No....
If no then that passage is not open.
Don't look to see if it effects the idle speed feel with your finger over the hole. It either has vacuum there or it don't.

If you want to post a picture from your camera or phone first
resize it so it is a reasonable size resolution and file size.
make it about 640x480 MAX 450x??? is plenty big.
Resave as a JPEG (.JPG) file type. about 50KBits to 100KBits file size.
The raw digital picture from your camera or phone are WAY TOO BIG and
the wrong file format.
Use this free small footprint windows pc program to resize correct pic brightness etc
and resave as a JPG... Then post from your computer.
WWW.irfanview.com

On the Proform billet carb base if the steel tube has been driven too far in the hole on the baseplate then most all of the vacuum flow will be blocked.

If the carbs throttles are way too far open at idle (usually incorrect timing at idle) and or if there is a even bigger vacuum leak or 3 or 4 then that amount of vacuum is not going to effect things.
Are the throttle blades drilled for extra air flow?
You can either use this method to get enough air flow at idle or the PCV air flow at idle but not both at the same time.
With the PCV working as designed ....,, drilled throttle plates are not necessary.
The 2 combined is too much.

Is this a auto transmission car or 4 speed car?

ignition timing at idle?

No vacuum at the port.
Had my finger over the hole, but there is nothing there at all. I'm sure the gasket isn't blocking the hole. I'm back to the BLP BX4 now, and I physically verified all vacuum ports are open. There are only two.

I'll see if my wife can help me post a picture.
Blades are drilled with .125 holes and the throttle blades have barely any slot exposed. I can turn the idle screw out and drop it down to below a 700 RPM idle.

4 speed car.
Timing is 36 locked out.

Like I said, I'm stumped. Hard.

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Re: Carb question again

Post by jmarkaudio » Fri Nov 03, 2017 10:02 am

Can you blow air into the vacuum port while it's running? That should shake it up a bit...
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Re: Carb question again

Post by statsystems » Fri Nov 03, 2017 10:36 am

jmarkaudio wrote:
Fri Nov 03, 2017 10:02 am
Can you blow air into the vacuum port while it's running? That should shake it up a bit...

Great idea!!! I never thought of that.

I'll hit that bugger with some air in a bit and let you know.

I'm so damned stumped right now I can't believe it. I just don't get it. A good shot of air should tell us something!!!!

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Re: Carb question again

Post by F-BIRD'88 » Fri Nov 03, 2017 12:23 pm

What happens if you cover the 2 holes in the throttle plates
say with black electrical tape and run it
Any vacuum at the pcv port now?

Are there 2 holes or 4 holes in the throttle plates?

power brakes connected to intake manifold?
What intake manifold? just for reference.

340 LA motors are cool

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Re: Carb question again

Post by statsystems » Fri Nov 03, 2017 2:28 pm

F-BIRD'88 wrote:
Fri Nov 03, 2017 12:23 pm
What happens if you cover the 2 holes in the throttle plates
say with black electrical tape and run it
Any vacuum at the pcv port now?

Are there 2 holes or 4 holes in the throttle plates?

power brakes connected to intake manifold?
What intake manifold? just for reference.

340 LA motors are cool

IDK about plugging the holes in the throttle plate. I can try it.

One hole each plate.

Manual brakes.

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Re: Carb question again

Post by JDR Performance » Fri Nov 03, 2017 2:42 pm

The engine wouldn't run without vacuum below the carb. I would put a spacer with a vacuum port between the carb and manifold to check how much you have and look closely at the bottom of your carb and mounting gasket to see why it isn't seeing it at the port.

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Re: Carb question again

Post by F-BIRD'88 » Fri Nov 03, 2017 3:21 pm

Is there any vacuum at the 2 little fittings on the front of the carb at idle.?
One is full manifold vacuum other is ported vacuum ( no vac at curb idle
but some vacuum as you open the throttle some.)
Any vacuum at these spots?

Ya got me stumped now... ha ha

Both of your carbs are doing the same thing?

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Re: Carb question again

Post by In-Tech » Fri Nov 03, 2017 4:15 pm

statsystems wrote:
Mon Oct 30, 2017 10:12 pm
I'm fighting my tune up. I want to run a PCV valve. And I think it's causing issues.

I just pulled the PCV valve from the valve cover and there is no flow through the valve. So I pulled it off the hose. There is virtually nothing moving through the PCV valve port. It idles at 900-950 and has ~ 10 inches of vacuum at that idle speed.

I'm stumped. It would seem that even at that low vacuum I should still have some air movement through the hose. And I think I should see the idle speed slow down when I plug the PCV valve hose and speed up when I unplug it.

Cam is 281/281 advertised 255/255@.050 and gross lift of .620 on a 105 at 105 on 340 CID. So I get why the idle vacuum is on the low side. I still think there should be some air movement through the PCV valve at idle.

Am I nuts or is something wrong.
Very first post he said he has vacuum, so he's checking it somewhere so obviously his other vacuum cavities aren't.
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