Holley gurus: ID a leaking port please!
#821345
10/04/10 02:21 AM
10/04/10 02:21 AM
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Joined: May 2009
Posts: 35
Aurora, CO
Manifold
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Aurora, CO
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I picked up a used Holley Street Avenger 770 which has a primary Proform billet metering block. Not sure if this problem existed the whole time or not (though, I suspect it did), but it is leaking while simply sitting even when not on the engine. The leak was coming from the front passenger corner of the carb and appears to be the source of a problem I was chasing down. After I ensured the front bowl and metering block were snug, I checked to see if the leak disappeared but it didn't. It was coming from inside the passenger side primary venturi. I removed the base plate and filled the bowls back up. I figured out which port is leaking, but I don't know its purpose. I poured over two Holley books I have, but do not know what this port is. The only thought I had was the power valve had gone bad and was leaking, but I see the built-in power valve protection and figured this fed the valve and the port in question wasn't connected to that circuit. I verified several times the float levels were correct. I took several pictures of both the bottom of the main body and the body side of the base plate. I've marked the port from where the gas is leaking. If someone would clue me in on what this port is and what I need to do to get it to stop leaking, I would greatly appreciate it. I'd like to make the last test-n-tune session this Wednesday with this carb (I pulled off a Carter AFB 625 in favor of the Holley) to see if I can dial it in some and run quicker. Thanks for any insight anyone out there may have! Bottom of main body (If I should remove the gasket for easier identification, then I will but would rather not if possible)  Closeup of bottom of main body  Main body side of base plate  Closeup of base plate 
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Re: Holley gurus: ID a leaking port please!
[Re: Manifold]
#821348
10/04/10 10:25 AM
10/04/10 10:25 AM
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Joined: Jan 2003
Posts: 75,020
U.S.S.A.
JohnRR
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I Win
Joined: Jan 2003
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Quote:
Very close! It doesn't feed the port on the base plate, as that hole leads directly into the venturi. But since I was desperate for some help, I cross-posted this on a few boards and got an answer. That port feeds the timed vacuum port which is found on the side of a standard Holley primary metering block. The Proform block I have does not have this provision, and sometimes with these aftermarket pieces or non-timed vacuum port equipped blocks, you will get fuel leaking out of this passage. Plugging up this port at the metering block face of the main body will eliminate the leaking. I was considering losing the race-oriented tuned block (67150C) for a standard block (67166C) to get the timed port back, so I may just swap the block instead of plugging. I suppose I could plug it with some epoxy which could later be drilled back out should I swap the block out.
I'm just glad the problem I was chasing wasn't a bad head gasket or cracked block/head. One bank was sounding sick and emitting white smoke/steam on startup. Instead of burning coolant, it was trying to burn off all the fuel. I best check the oil to see if it is thinned out from the fuel.
Thanks for your help.
Be careful with the type of epoxy you use , many are not alcohol friendly and the leak will soon return.
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Re: Holley gurus: ID a leaking port please!
[Re: JohnRR]
#821349
10/04/10 01:11 PM
10/04/10 01:11 PM
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Joined: May 2009
Posts: 35
Aurora, CO
Manifold
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OP
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Aurora, CO
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Quote:
Quote:
Very close! It doesn't feed the port on the base plate, as that hole leads directly into the venturi. But since I was desperate for some help, I cross-posted this on a few boards and got an answer. That port feeds the timed vacuum port which is found on the side of a standard Holley primary metering block. The Proform block I have does not have this provision, and sometimes with these aftermarket pieces or non-timed vacuum port equipped blocks, you will get fuel leaking out of this passage. Plugging up this port at the metering block face of the main body will eliminate the leaking. I was considering losing the race-oriented tuned block (67150C) for a standard block (67166C) to get the timed port back, so I may just swap the block instead of plugging. I suppose I could plug it with some epoxy which could later be drilled back out should I swap the block out.
I'm just glad the problem I was chasing wasn't a bad head gasket or cracked block/head. One bank was sounding sick and emitting white smoke/steam on startup. Instead of burning coolant, it was trying to burn off all the fuel. I best check the oil to see if it is thinned out from the fuel.
Thanks for your help.
Be careful with the type of epoxy you use , many are not alcohol friendly and the leak will soon return.
I used some JB Weld. I'm not running alcohol, just regular gas. JB Weld should be fine AFAIK. I've used it on carbs in the past with no issues.
Here's what I found on my carb. Looks to me that a previous owner never installed the Proform metering block gasket, or installed a used Holley gasket. The hole in the Holley gasket for the bottom of the channel for the timed spark port just cuts into the bottom of the (IIRC) idle or emulsion well - in other words, it's open to a part of the metering block it isn't supposed to be. I've attached some pictures in case someone else runs into this problem of fuel draining from the carb regardless of being in use or not.
I suppose the proper fix is to get the correct gasket, but AFAIK none of the stores near by carry the Proform gaskets. Though, they carry the Holley gaskets. So, I decided to seal off the passage and use Holley gaskets.
Holley metering block gasket used with Proform block. Gasket still has impression from original metering block with timed spark port provision (marked in yellow). The overlap of the bottom hole in the gasket for the timed spark port and the impression in the gasket from the bottom of the well marked in red.
Metering block with the gasket shadow/residue showing the small portion of the hole overlapping the bottom of the well:
New Holley metering block gasket set onto Proform metering block. I marked where the fuel was leaking in - you can see the overlap.
Stock photo of Proform gasket with no hole for the timed spark port. If this gasket had been used, this problem would have not existed.
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Re: Holley gurus: ID a leaking port please!
[Re: Manifold]
#821350
10/04/10 01:25 PM
10/04/10 01:25 PM
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Joined: Jan 2003
Posts: 75,020
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,020
U.S.S.A.
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Quote:
Quote:
Be careful with the type of epoxy you use , many are not alcohol friendly and the leak will soon return.
I used some JB Weld. I'm not running alcohol, just regular gas. JB Weld should be fine AFAIK. I've used it on carbs in the past with no issues.
Just a heads up , I'm not sure about gas where you are but most gas sold now has ETHANOL in it .
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Re: Holley gurus: ID a leaking port please!
[Re: JohnRR]
#821351
10/04/10 06:04 PM
10/04/10 06:04 PM
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Joined: May 2009
Posts: 35
Aurora, CO
Manifold
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member
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OP
member
Joined: May 2009
Posts: 35
Aurora, CO
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Quote:
Quote:
Quote:
Be careful with the type of epoxy you use , many are not alcohol friendly and the leak will soon return.
I used some JB Weld. I'm not running alcohol, just regular gas. JB Weld should be fine AFAIK. I've used it on carbs in the past with no issues.
Just a heads up , I'm not sure about gas where you are but most gas sold now has ETHANOL in it .
We haven't escaped the blend fuels, unfortunately. I have faith in JB Weld.  If it starts to leak, it'll be obvious. I'll just break down and get the correct gaskets at that point.
Thanks!
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Re: Holley gurus: ID a leaking port please!
[Re: scratchnfotraction]
#821353
10/05/10 04:18 PM
10/05/10 04:18 PM
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Joined: May 2009
Posts: 35
Aurora, CO
Manifold
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OP
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Joined: May 2009
Posts: 35
Aurora, CO
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Quote:
that was very interesting indeed 
you did a super job of figuring it out and posted more than one solution to the problem 
I bet thats why they sold it,it no worky 
I like to think I would have figured this out on my own, but it was late, I was tired and frustrated and wasn't in the mood to tear down the primary bowl and metering block again that night (as one of the bolt holes stripped - will have to helicoil down the road; for now, there's a slightly longer bolt installed which is holding). So, I took pics and posted it up. Once I took it back apart the next day, it was pretty obvious.
The PO told me he bought the carb with the Proform block installed and had "no problems" with the carb. After seeing the Holley metering block gasket with the impressions from a stock/standard block in it, either the problem existed the whole time and he somehow never saw it (don't believe that considering how much fuel was leaking out - it took me only a short amount of time to see that there was an issue... lots of fuel leaking to include pooling in the combustion chambers), or (here comes my benefit of the doubt piece) when the PO was reinstalling the stock jets, the metering block gasket was damaged and a used Holley gasket was slapped on. I find it REALLY hard to believe that the PO had no issues if this problem existed during his ownership.
I will say that I got the carb for a real good price, so it wouldn't surprise me if he knew of the problem and didn't have the heart to sell it for market value.
After fixing this issue, the carb is working really well (in comparison to the Carter I pulled off). I hope to have some fun Wednesday night!
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