Carb question again

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statsystems
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Re: Carb question again

Post by statsystems » Tue Oct 31, 2017 12:45 pm

Tuner wrote:
Tue Oct 31, 2017 12:01 pm
PVC is Poly Vinyl Chloride, a form of plastic.

PCV is Positive Crankcase Ventilation. PCV is a good thing because it reduces the amount of water and fuel that otherwise accumulates in the oil and forms acids and other nasty things.
Any ideas why I'm chasing my butt here tuner? Ever heard of anything like this? I just drove the car and it runs good. Probably a touch rich at cruise and I need to junk that 6.5 PV and go a 9.5 if they make it, maybe 10.5 to help clean up the little bit of tip in issues I'm having, which I think is lean from the PV opening too late.

The damn no vacuum at the PCV valve is breaking my balls.

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Re: Carb question again

Post by Tuner » Tue Oct 31, 2017 1:54 pm

You have it connected to the 3/8" nipple under the secondary float bowl, don't you? You mention the small nipples under the primary bowl, but the PCV connects to a 3/8" nipple with 3/8" ID hose. You should be able to remove the valve from the hose and blow through the hose into the carb and feel very little restriction, the carb connection should not restrict flow noticeably over that of the hose alone. But, did you say you already tried that?

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Re: Carb question again

Post by F-BIRD'88 » Tue Oct 31, 2017 1:55 pm

Wait till you get the pcv sorted out before evaluating and adjusting the jetting poeer valve choice etc..
The pcv air flow has a overall effect on the whole tuneup,
so without it the tune is going to be shifted fatter a bit.

The carb was set up to work with the pcv.
Some don't appreciate that effect and intent.

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Re: Carb question again

Post by statsystems » Tue Oct 31, 2017 3:33 pm

Tuner wrote:
Tue Oct 31, 2017 1:54 pm
You have it connected to the 3/8" nipple under the secondary float bowl, don't you? You mention the small nipples under the primary bowl, but the PCV connects to a 3/8" nipple with 3/8" ID hose. You should be able to remove the valve from the hose and blow through the hose into the carb and feel very little restriction, the carb connection should not restrict flow noticeably over that of the hose alone. But, did you say you already tried that?

The PCV is connected to the 3/8 fitting act the back of the carb. The two 1/4 fittings (IIRC...maybe 5/16) at the front are where I have the vacuum gauge installed. The inboard of the two looks to be timed vacuum and the one I have the gauge hooked to is full manifold vacuum.

I just verified that the hose is not plugged and the 3/8 fitting is open to manifold vacuum.

What hair I have that isn't grey, and what was grey is falling out. I'm missing something. Why does disconnecting the hose from the back of the carb has zero affect on idle speed? I'm am stumped.

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Re: Carb question again

Post by statsystems » Tue Oct 31, 2017 3:34 pm

F-BIRD'88 wrote:
Tue Oct 31, 2017 1:55 pm
Wait till you get the pcv sorted out before evaluating and adjusting the jetting poeer valve choice etc..
The pcv air flow has a overall effect on the whole tuneup,
so without it the tune is going to be shifted fatter a bit.

The carb was set up to work with the pcv.
Some don't appreciate that effect and intent.

Yep. That's why (one reason) I want to use the PCV valve. I think they run better when they work, and they keep the oil cleaner and other things. I'm sure what's happening is affecting the tune up.

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Re: Carb question again

Post by F-BIRD'88 » Tue Oct 31, 2017 3:42 pm

Stick you finger over the rear 3/8" tube hole while its running..
Vacuum? no.....?

If not take the carb off. its blocked.

If there is vacuum there yet it does not effect idle speed when you block that you have a even bigger leak somewhere.

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Re: Carb question again

Post by F-BIRD'88 » Tue Oct 31, 2017 3:48 pm

While you have the carb off flip it over and check the pri and sec throttle T slot exposure at idle (throttle blade opening at idle.. Reset as req... about .020" .030" T slot showing on a 4 barrels.. (start point).

Potential wrong base gasket, carb body to throttle base gasket... Powervalve gasket..... other leak... intake manifold?

carb body not seated on throttle base....

Some secondary metering blocks hit t the base plate
stopping the base plate from seatibg on the body..
big vac leak.
Minor clearance grinding to fit.

Some carbs must have the air cleaner stud installed or vac leak.

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Re: Carb question again

Post by cjperformance » Tue Oct 31, 2017 4:23 pm

What carb part/list number.?
Im correct in reading that you can remove the entire pcv hose from the carb with the engine running and it has no effect or big vac leak?
Some carbs had an undrilled boss for the pcv, who knows how its been played with, people do some strange things.
It should be pretty simple with the carb removed to see if the pcv fitting is clear or not. Have you got the carb off yet?
Craig.

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Re: Carb question again

Post by statsystems » Tue Oct 31, 2017 4:28 pm

cjperformance wrote:
Tue Oct 31, 2017 4:23 pm
What carb part/list number.?
Im correct in reading that you can remove the entire pcv hose from the carb with the engine running and it has no effect or big vac leak?
Some carbs had an undrilled boss for the pcv, who knows how its been played with, people do some strange things.
It should be pretty simple with the carb removed to see if the pcv fitting is clear or not. Have you got the carb off yet?

I have 2 carbs. A BLP BX4 750 and a brand new ProForm 750 and they both act the same. And yes, I can take the hose off and nothing happens.

I checked the BLP when I pulled it off and it's drilled and open. And I double checked the PF before I put it on.

What's really crazy is there must be a vacuum leak somewhere, but it doesn't act like it. It will idle down to 850ish without an issue. You can drive it and it never acts like it has a vacuum leak. Always comes back to idle.

I've never been fan of spraying carb cleaner around to find a vacuum leak but it looks like I need to. I'm out of other ideas.

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Re: Carb question again

Post by cjperformance » Tue Oct 31, 2017 5:27 pm

statsystems wrote:
Tue Oct 31, 2017 4:28 pm
cjperformance wrote:
Tue Oct 31, 2017 4:23 pm
What carb part/list number.?
Im correct in reading that you can remove the entire pcv hose from the carb with the engine running and it has no effect or big vac leak?
Some carbs had an undrilled boss for the pcv, who knows how its been played with, people do some strange things.
It should be pretty simple with the carb removed to see if the pcv fitting is clear or not. Have you got the carb off yet?

I have 2 carbs. A BLP BX4 750 and a brand new ProForm 750 and they both act the same. And yes, I can take the hose off and nothing happens.

I checked the BLP when I pulled it off and it's drilled and open. And I double checked the PF before I put it on.

What's really crazy is there must be a vacuum leak somewhere, but it doesn't act like it. It will idle down to 850ish without an issue. You can drive it and it never acts like it has a vacuum leak. Always comes back to idle.

I've never been fan of spraying carb cleaner around to find a vacuum leak but it looks like I need to. I'm out of other ideas.
Get out the carb cleaner spray!
Craig.

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Re: Carb question again

Post by statsystems » Tue Oct 31, 2017 5:48 pm

cjperformance wrote:
Tue Oct 31, 2017 5:27 pm
statsystems wrote:
Tue Oct 31, 2017 4:28 pm
cjperformance wrote:
Tue Oct 31, 2017 4:23 pm
What carb part/list number.?
Im correct in reading that you can remove the entire pcv hose from the carb with the engine running and it has no effect or big vac leak?
Some carbs had an undrilled boss for the pcv, who knows how its been played with, people do some strange things.
It should be pretty simple with the carb removed to see if the pcv fitting is clear or not. Have you got the carb off yet?

I have 2 carbs. A BLP BX4 750 and a brand new ProForm 750 and they both act the same. And yes, I can take the hose off and nothing happens.

I checked the BLP when I pulled it off and it's drilled and open. And I double checked the PF before I put it on.

What's really crazy is there must be a vacuum leak somewhere, but it doesn't act like it. It will idle down to 850ish without an issue. You can drive it and it never acts like it has a vacuum leak. Always comes back to idle.

I've never been fan of spraying carb cleaner around to find a vacuum leak but it looks like I need to. I'm out of other ideas.
Get out the carb cleaner spray!
Am I the only chicken weenie worried about a fire with carb cleaner? I'm worried about getting a fire started. I do have two fire extinguishers in the shop. Of you think it's safe, I'll go for it. I'm not a fan of fire.

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Re: Carb question again

Post by rfast racing » Tue Oct 31, 2017 6:51 pm

Borrow or rent a smoke machine excellent and safe machine for finding vacuum leaks oil leaks exhaust leaks and all sorts of other leaks u might be surprised of all its uses

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Re: Carb question again

Post by statsystems » Tue Oct 31, 2017 7:37 pm

I just checked for air leaks with carb cleaner. Good news. The and car didn't burn down.

Bad news. I can't find an air leak. It will idle clear done to 700ish and just sit there and run. I don't like to let it idle that slow so I keep it around 900-1000.

With it idling away, I can pull the PCV hose off the carb and it doesn't do anything. Just keeps banging them off like nothing. With the hose off the idle RPM should have went way up but it doesn't. In fact, I can put the hose back on and pull the PCV valve off and I can't feel any suction on the hose.

Wouldn't you feel something even with 8.5-9 inches of idle vacuum?

I know the hole is open because I pulled the carb off and verified it.

I am mortally stumped. It's a good thing I don't drink or smoke dope. Otherwise I'd be rolling a Philly sized blunt and sipping off a pint of Old Bushmills.

I'm out of ideas.

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Re: Carb question again

Post by amcenthusiast » 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)
XRV8 Race Parts > for AM's '56-'67 Rambler V8: http://amcramblermarlin.1colony.com/favorite_links.html

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Re: Carb question again

Post by statsystems » 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.

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