715 Holley question

[6s855]

Like others on here, I'm struggling to adjust my 715 holley and trying to follow the suggestions made in other posts on tuning.  The carb I'm using is an 80's reissue (1985 Julian date) that I thought had a fuel level sight plug except it's on the primary metering block, not the fuel bowl.  Taking the bowl off shows that the plug hole casting is not open to the fuel bowl and clearly not a sight plug.  A holley schematic/parts list for a 4150 (only picture I could find) names  this part as a "spark hole plug"!   Seems like a curious name to give a part on a carb filled with gasoline.  So does anyone know what this is?  Why poke a hole in the metering block and then close it up with a plug?

[Bob Gaines]

Like others on here, I'm struggling to adjust my 715 holley and trying to follow the suggestions made in other posts on tuning.  The carb I'm using is an 80's reissue (1985 Julian date) that I thought had a fuel level sight plug except it's on the primary metering block, not the fuel bowl.  Taking the bowl off shows that the plug hole casting is not open to the fuel bowl and clearly not a sight plug.  A holley schematic/parts list for a 4150 (only picture I could find) names  this part as a "spark hole plug"!   Seems like a curious name to give a part on a carb filled with gasoline.  So does anyone know what this is?  Why poke a hole in the metering block and then close it up with a plug?

It is a plugged vacuum port not a sight hole. It is supposed to be plugged 65-67 . Correct ones are hard to find.  They are originally plated zinc silver when new.

[Drew Pojedinec]

I zinc plate them and hit them with a short dip in a clear chromate.

[Dan Case]

Trivia, this plated steel part was originally a bare brass part in some specific 1963-64 Ford applications of Holley brand and Ford 4100 carburetors for high performance and racing.

[shelbydoug]

It's for timed vacuum to a vacuum advance distributor. For GT350's, it's used with just a mechanical advance distributor with no vacuum advance.

[6s855]

Thanks to all.  Just thought holley could have chosen a better name than "spark hole".  lol

[6s1640]

Hi Dan,

Please advise we're these can be purchased.  I can't find.  Or do you have a Holley part number and can search on?

Thanks

Cory

[Dan Case]

Hi Dan,

Please advise we're these can be purchased.  I can't find.  Or do you have a Holley part number and can wear on?

Thanks

Cory

Originals I have no idea. The one shown is a new old stock one (my last) I got from Holley® decades ago when I was servicing the Ford carburetors all the time.

I have seen reproductions. The reproductions I bought had a much flatter exposed end and I wouldn't use them.

[Drew Pojedinec]

There are some generic cores that I can steal original plugs from.
(They were used in the baseplate)

[texas swede]

I got one of these from Joe Bunetic some years ago.
Had to do some sweet talking as he only put them on Carbs he restored.
Texas Swede

[gt350hr]

    Corey ,
        I'll try to get a part number for you.

[Drew Pojedinec]

    Corey ,
        I'll try to get a part number for you.

If you know a place to get new ones, lemme know. I'd love to be able to give them out more freely.

[texas swede]

Cory,
I believe the Holley part # is 7R-5 Spark Hole Plug.
Texas Swede

[6s1640]

Hi guys,
Thank you for your help. I could not find the plug with that part number 7R-5.  However I was able to confirm the part name "Holley 180 Degree Timed Spark Fitting".  See image attached for vacuum fitting that goes in the same hole.  I will keep looking.

Thanks

Cory

[texas swede]

Cory,
I got the part # from an old Holley parts list,
Texas Swede