6 Pack carb questions

[440fish]

Have two questions that i think people here may know off hand...

1. Do the six pack carbs have backfire protection for the powervalve? (everything i can find says no but there is some info that points to it being a non issue on them) My car started running really rich at idle and the plugs are really dark. Vaguely remember a backfire last fall when i started it up on a cold day and think it may have damaged the power valve. Once off the idle circuit she runs very nice. Also noticed stone cold (no choke) it will idle which confirms a rich situation

2. Is it possible to remove the center carb without the others? Ive read you can modify an open end wrench to get at the tricky nuts and slide it out to the passenger side.


thanks!

 

[Bill Monk]

Have two questions that i think people here may know off hand...

1. Do the six pack carbs have backfire protection for the powervalve? (everything i can find says no but there is some info that points to it being a non issue on them) My car started running really rich at idle and the plugs are really dark. Vaguely remember a backfire last fall when i started it up on a cold day and think it may have damaged the power valve. Once off the idle circuit she runs very nice. Also noticed stone cold (no choke) it will idle which confirms a rich situation

2. Is it possible to remove the center carb without the others? Ive read you can modify an open end wrench to get at the tricky nuts and slide it out to the passenger side.


thanks!

There is no backfire protection on the originals, I'm not sure about the newer ones but I doubt it. Yes, you can take the center carb off without removing the other 2 but good luck on those fuel lines, they are a royal pain to try to get loose without tearing something up. It's easier to take them all off. It's hard to find just one of the carb gaskets anyway, they usually sell them as a set of 3.

 

[lewtot184]

if your using factory fuel lines you have to take the rear carb off to unbolt the center carb. i never had a set that had the back fire protection.

 

[62MAX]

Just a note to anyone on removing fuel lines the easy way.Flare a piece of soft copper tubing the same size as the fuel line,cut off the flare and and insert it in the end of the fitting,you'll be surprised how easy fuel line fittings come off.

 

[440+6]

You can easily add the blowout protection with a kit from Holley, I did mine many years ago.
You can remove the center carb only, just remove the fuel lines to all three carbs first, I just did this a month ago to install a smaller squirter.

 

[lewtot184]

You can easily add the blowout protection with a kit from Holley, I did mine many years ago.
You can remove the center carb only, just remove the fuel lines to all three carbs first, I just did this a month ago to install a smaller squirter.

this involves disconnecting the fuel lines at the carb. i never do that because of leak complications and simply the nuisance of getting wrenches in place. the old original carbs had an 11/16" hex for the fuel line fitting on the center and rear carb which was a big help. i disconnect the lines at the tees and always at the same spots. there are 12 places for leaks at the carb fuel lines. can be a real headache.

 

[440fish]

this involves disconnecting the fuel lines at the carb. i never do that because of leak complications and simply the nuisance of getting wrenches in place. the old original carbs had an 11/16" hex for the fuel line fitting on the center and rear carb which was a big help. i disconnect the lines at the tees and always at the same spots. there are 12 places for leaks at the carb fuel lines. can be a real headache.

Ok, so at the end of the day it makes more sense to just take them all off instead of inviting fuel leak issues at the carbs?

Also, do any of you think im on the right path of a blown powervalve with the symptoms im experiencing? Also noticed a drop in fuel mileage. (not that it was good before!)

 

[62MAX]

Ok, so at the end of the day it makes more sense to just take them all off instead of inviting fuel leak issues at the carbs?

Also, do any of you think im on the right path of a blown powervalve with the symptoms im experiencing? Also noticed a drop in fuel mileage. (not that it was good before!)

For what it's worth,direct from Holley !

THE TRUTH ABOUT POWER
VALVES USED WITH HOLLEY
CARBURETORS
There still seems to be a lot of misconception about
Holley carburetors blowing power valves. Nothing
could be further from the truth. Holley performance
carburetors built since 1978 have utilized a power
valve check system that effectively eliminated this
infrequent problem. Consisting of a spring, brass
seat and check ball, the check ball system is 100%
effective protecting the power valve diaphragm
from damage due to engine backfire.
The power valve check ball is designed to be
normally open but quickly seals to close off the
internal vacuum passage when a backfire occurs.
Once closed, the check valve interrupts the pressure
wave generated by the backfire, thus protecting the
power valve diaphragm. There is no way that the
power valve’s diaphragm can rupture due to an
engine backfire!

 

[440fish]

For what it's worth,direct from Holley !

THE TRUTH ABOUT POWER
VALVES USED WITH HOLLEY
CARBURETORS
There still seems to be a lot of misconception about
Holley carburetors blowing power valves. Nothing
could be further from the truth. Holley performance
carburetors built since 1978 have utilized a power
valve check system that effectively eliminated this
infrequent problem. Consisting of a spring, brass
seat and check ball, the check ball system is 100%
effective protecting the power valve diaphragm
from damage due to engine backfire.
The power valve check ball is designed to be
normally open but quickly seals to close off the
internal vacuum passage when a backfire occurs.
Once closed, the check valve interrupts the pressure
wave generated by the backfire, thus protecting the
power valve diaphragm. There is no way that the
power valve’s diaphragm can rupture due to an
engine backfire!

Thanks. I understand my carbs have technically been "built" after 1978 but the six pack repops are probably not redesigned with backfire protection as they didn't have it back in the day and i cant see Holley retrofitting the original design with it out of the box.

 

[62MAX]

Thanks. I understand my carbs have technically been "built" after 1978 but the six pack repops are probably not redesigned with backfire protection as they didn't have it back in the day and i cant see Holley retrofitting the original design with it out of the box.

The two window power valve is used exclusively in everything including current production,shouldn't be an issue.

 

[Daves69]

.............
http://documents.holley.com/techlibrary_power_valves.pdf

https://www.holley.com/products/fuel_systems/carburetor_components/power_valves/parts/125-500

http://documents.holley.com/199r9898-2.pdf

 

[440fish]

Thanks for showing me that Dave. Has anyone here done this to their center carb?

 

[440+6]

Yes as stated in a earlier post, takes a minute to do once you have the base plate off.
I have a spare one if you want it, the kit came with two

 

[RJRENTON]

Gentlemen,
I routinely remove the center carb for service, at least once per year, due to a leak ov the fuel bowl gasket (yes, I'm using the blue holley gaskets). The tricky part is the fuel lines...i loosen all lines, remove the rear line and the center carb tee and line coming from the front carb tee. You MUST USE flare nut wrenches on the inverted flare nuts and you MUST hold the carb fuel inlet nut (11/16" hex) with an open end wrench...i use a MAC angle wrench....its thinner. After all pieces and parts are removed, the center carb can be removed easily.
Yes....i used the holley power valve blow out kit on the carb...very easy. I used a small drill press to ensure accuracy...very easy. Always use a new base plate to manifold gasket and spray it with a silicon spray to keep it from sticking when you take it apart also an anti seize compound on the bolt threads.
Bob Renton

 

[440fish]

Guys

Thank you for your responses. I plan on installing this in the next week or so. 440+6 i appreciate your kind offer but i have a buddy with a 6 pack and need to do his too so if the kit has 2 we will need them!

 

[440fish]

Question. If i completely close my center carb idle enrichment screw should it stall or do i have to close the outboard adjustments as well. Want to do the quick powervalve test to see if it is leaking before i tear into it.

 

[Bill Monk]

Question. If i completely close my center carb idle enrichment screw should it stall or do i have to close the outboard adjustments as well. Want to do the quick powervalve test to see if it is leaking before i tear into it.

Should stall. There shouldn't be enough fuel coming from the outboards alone to keep it running

 

[440fish]

Thanks. I ordered gaskets so i could get inside to verify but wanted to do a quick check in the meantime

 

[RJRENTON]

440fish,
Since you are going to tear down the carbs, consider installing Holley's power valve blow out protection kit...its cheap and relatively easy to do.
FYI.....the power valve enrichment circuit at idle wil be inoperative ....the power valve circuit adds fuel into the main metering well emulsion tube ONLY when the power valve is open and is metered thru the power valve channel restrictions. The power valve opens when manifold vacuum drops below the calibrated value, stamped on the hex and is in inches of vacuum....ie, 6.5". Unless the booster venturii are feeding fuel into the air stream the power valve circuit will have no effect.
My experience is Holley's will run best if the fuel kevel us set at one R-C-H BELOW the sight plug threaded opening with the engine running. Use ONLY Holley rebuild kits as they will have the corrrct inlet needle assembly. Spray all gaskets with silicon to prevent sticking, including the base plate gaskets. Use an anti-seize compound on the carb to manifold bolts.

 

[440fish]

440fish,
Since you are going to tear down the carbs, consider installing Holley's power valve blow out protection kit...its cheap and relatively easy to do.
FYI.....the power valve enrichment circuit at idle wil be inoperative ....the power valve circuit adds fuel into the main metering well emulsion tube ONLY when the power valve is open and is metered thru the power valve channel restrictions. The power valve opens when manifold vacuum drops below the calibrated value, stamped on the hex and is in inches of vacuum....ie, 6.5". Unless the booster venturii are feeding fuel into the air stream the power valve circuit will have no effect.
My experience is Holley's will run best if the fuel kevel us set at one R-C-H BELOW the sight plug threaded opening with the engine running. Use ONLY Holley rebuild kits as they will have the corrrct inlet needle assembly. Spray all gaskets with silicon to prevent sticking, including the base plate gaskets. Use an anti-seize compound on the carb to manifold bolts.

First off Thank you for the help. I appreciate the comments from everyone

Update!

I just came in from the garage. The idle enrichment adjustment screw did NOTHING when i closed it which confirms my suspicion that the powervalve has failed. Upon close inspection you can see there is a heavy, steady drip of fuel on the center carbs boosters which i believe is the smoking gun in this case. No wonder it burns your eyes at idle. My god there is a lot of fuel going in there... I seriously noticed a drop in fuel economy.
My questions:

1. Now i need to order the correct rebuild gaskets. Anyone got a P/N handy? I noticed my rear carb base gasket has "rear" stamped in the exposed gasket surface area. I thought they were all the same?


2. So the consensus is to leave the fuel fittings alone that go into the carbs and disconnect at the junctures where they T off to the individual bowls?

3 Any hints on disconnecting linkage that makes lifer easier at disassembly? I.E order of operation. (again my intent is to remove the center carb so im open to any tips.) Seems some take only the center out and others take the rear and center off every time.

Anyway, on the course to getting this fixed. Man that 6 pack linkage is like a rube goldberg cartoon.... A lot more going on than a four barrel!