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2 circuit metering gaskets
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Author:  Coloradoracer [ Sun Oct 21, 2012 11:11 am ]
Post subject:  Re: 2 circuit metering gaskets

I was using a pair of the gaskets that Mark showed in my carb this year. I did have to enlarge the dowel holes just a bit, as they were off on my stuff, but that was it. I like them. they didn't leak, stick or anything else like that, and I had them off plenty!!! No permanent indentions either. I can't say for sure if they ever made a difference in the calibration, as the gaskets that I had on it before were swollen quite a bit and seems like they partially blocked some of the passages, but that wasn't an issue with those. I'm going to get another set for my other carb and a spare set in case I do something stupid...........The nice thing is they last.......buy them once and that's it...

Author:  nomad [ Sun Oct 21, 2012 1:30 pm ]
Post subject:  Re: 2 circuit metering gaskets

Pics!

Standard 2 circuit block

Image

QFT 3 hole block w/ vacuum provision

Image

BLP and QFT block comparison. Look how low the BLP idle crossover passage is.

Image

BLP 5 hole block. See how close the hole in gasket is.

Image

4500 mainbody. In oldstyle 750 Dominators the bottom of this cavity is drilled for timed vacuum. Works well at vacuum. As engine speed increases vacuum sucks gasket back and opens bowl to manifold vacuum. Instant 5th jet. NonHP 4150 carbs may also have this problem.

Image

Hp type carb has no drilled passage.

Image

Solutions are:

A. fill 4500 cavity with epoxy if required.

B. use only BLP or QFT gaskets.

Author:  74 firebird461 [ Sun Oct 21, 2012 2:13 pm ]
Post subject:  Re: 2 circuit metering gaskets

Bruce Is this hole okay if you are using it for vacuum?

Image

Author:  Beretta [ Sun Oct 21, 2012 2:34 pm ]
Post subject:  Re: 2 circuit metering gaskets

Great post Bruce!!!!!! Thanks for spending the time to point it all out!!!!!!!!! \:D/
Ken, This needs to be a sticky IMO

Author:  nomad [ Sun Oct 21, 2012 3:02 pm ]
Post subject:  Re: 2 circuit metering gaskets

firebird, my eyes can't see that very well. Can you post a clearer photo?

Author:  Beretta [ Sun Oct 21, 2012 3:06 pm ]
Post subject:  Re: 2 circuit metering gaskets

Bruce my 7320 & 9377 has that vacuum cavity but there is no hole to the throttle plate..

Author:  74 firebird461 [ Sun Oct 21, 2012 3:41 pm ]
Post subject:  Re: 2 circuit metering gaskets

Bruce I took that pic a couple of weeks back with my phone, The guy that did my 750 dom that he made a 1050, turned around the main body putting that big vac port in back so i could use for brakes etc, and then drilled another hole in what used to be the back connecting the two holes that went into the throttle bore so i could have vac advance. It works perfectly, the only thing He forgot to do was plug that original front hole that was now in back, cause when i first got the carb it would drain the back bowl, and i couldn't figure out why til i told him about it. I then just used jb weld to cover that rear hole and no more issues with it.

Author:  nomad [ Sun Oct 21, 2012 4:11 pm ]
Post subject:  Re: 2 circuit metering gaskets

74 firebird461 wrote:
Bruce I took that pic a couple of weeks back with my phone, The guy that did my 750 dom that he made a 1050, turned around the main body putting that big vac port in back so i could use for brakes etc, and then drilled another hole in what used to be the back connecting the two holes that went into the throttle bore so i could have vac advance. It works perfectly, the only thing He forgot to do was plug that original front hole that was now in back, cause when i first got the carb it would drain the back bowl, and i couldn't figure out why til i told him about it. I then just used jb weld to cover that rear hole and no more issues with it.


I had the same problem when my engine was new. Now i have cyls 3 and 4 showing 12% leakage. Probably been like that since the beginning.

Author:  just primer [ Wed Nov 14, 2012 5:49 pm ]
Post subject:  Re: 2 circuit metering gaskets

Guy's, I don't know how you feel about this, but I have been putting a very thin layer of chap-stick on all of my metering plate gaskets for years. Weather they are non stick or not. On the advise of the owner of are local hot rod shop. He is very sharp and raced for years. I never have a problem. Even years later I have reused gaskets sometimes in other carbs. Once I skipped the chap-stick and the non-stick gasket tore into separate peaces. Don't know much about the clear gaskets.

Question: on some of my plate gaskets the rectangle opening coming from the vent tube is partially blocked at one corner. What is the reason for this? Restrict the air coming in?

Also I know most of you do not use power valves ,or just on one side, but have you see the power valves that come in the Quick fuel rebuild kit. They have four rectangle openings instead of two. Is this any kind of advantage to this?

Just Primer

Author:  Ken0069 [ Wed Nov 14, 2012 6:40 pm ]
Post subject:  Re: 2 circuit metering gaskets

just primer wrote:
I know most of you do not use power valves ,or just on one side, but have you see the power valves that come in the Quick fuel rebuild kit. They have four rectangle openings instead of two. Is this any kind of advantage to this?

Just Primer


Those are what is known as "High Flow" power valves and that's what we normally use on the primary side "IF" we run a PV that is.

Author:  just primer [ Wed Nov 14, 2012 8:34 pm ]
Post subject:  Re: 2 circuit metering gaskets

I have always use the Holley "high flow". They only have two rectangle ports and they are not as tall (in the opening). I normally run 4.5 but these are 6.5.

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