GROSS JET REPAIR

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speedytinc
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GROSS JET REPAIR

Post by speedytinc » Fri Aug 25, 2023 9:04 am

A previous post asked if a gross jet can be cured of intermittent sticking shut & open.

@ last nights T party, a member brought one in to show how to get one to work properly again.
{the following information was gleaned from our meeting & I share with permission}
They seem very susceptible to getting varnished up & sticking open & closed.

The gross jet has 2 ball bearings. The one on top is large, around 1/4" (looks like the top of a roll on antiperspirant bottle), Under that large ball is a second, smaller ball, around 5/32". That smaller ball seats in the body to regulate fuel flow.

Well, turns out it can be disassembled & made good again. Well, as good as was new.

Take a 3/32" punch thru the jet base & tap on it. The pressure will release the upper, large crimped in ball. (careful to not lose either ball)
Take a sharpened wood dowel & rotate it in the seat.
Notice a black residue deposited on the dowel point. Thats the varnish causing the seat ball to stick.
Reassemble. The large ball will pop back into position & doesnt need to be re crimped.
Test for function. (suck & blow test)
Good as new.

HOWEVER, GOOD AS NEW AINT GOOD ENOUGH. The fuel flow passage is .093", Like an unmodified viaton unit, its TOO SMALL & will present as such on a non improved T's fuel system during high demand situations. (The original NH orifice was .125") May work adequately with the extra head pressure of a 26-7 cowl tank.
This is where a high volume, modified viaton needle/seat excels in fuel flow & not leaking. Available thru Scott Conger.


Gross jet
Gross jet
96092 gross valve.jpg (81.35 KiB) Viewed 750 times
Picture from a someone else's previous post.

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TWrenn
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Re: GROSS JET REPAIR

Post by TWrenn » Fri Aug 25, 2023 9:21 am

Yes, very easily. REPLACE IT with the "other jet" that has the needle point! :lol:

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TWrenn
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Re: GROSS JET REPAIR

Post by TWrenn » Fri Aug 25, 2023 9:22 am

TWrenn wrote:
Fri Aug 25, 2023 9:21 am
Yes, very easily. REPLACE IT with the "other jet" that has the needle point! :lol:
And oh, while you're at it, get ahold of Scott Conger and see if he has any of his excellent "full flow" version of the aforementioned jet! They work great!

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DanTreace
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Re: GROSS JET REPAIR

Post by DanTreace » Fri Aug 25, 2023 9:45 am

speedytinc wrote:
Fri Aug 25, 2023 9:04 am
A previous post asked if a gross jet can be cured of intermittent sticking shut & open.

They seem very susceptible to getting varnished up & sticking open & closed.

Well, turns out it can be disassembled & made good again. Well, as good as was new.
HOWEVER, GOOD AS NEW AINT GOOD ENOUGH. The fuel flow passage is .093", Like an unmodified viaton unit, its TOO SMALL & will present as such on a non improved T's fuel system during high demand situations. (The original NH orifice was .125") May work adequately with the extra head pressure of a 26-7 cowl tank.
This is where a high volume, modified viaton needle/seat excels in fuel flow & not leaking. Available thru Scott Conger.

Agree with your conclusion! That photo of the carb with Grose Jet Needle was mine, always a problem. So now all my T's run the best, and spare rebuilds on the shelf get the same treatment......"Scott Congerized" ;)

IMG_3536 (640x395).jpg

Grose Jet out and "Full Flow Needle Valve and Seat" ready to go in!
Full flow valve close.jpg

This is the gain....look at that big bore to pour gas into the bowl, spectacular result of added power....a must do!


Full flow valve seated.jpg
The best way is always the simplest. The attics of the world are cluttered up with complicated failures. Henry Ford
Don’t find fault, find a remedy; anybody can complain. Henry Ford

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JTT3
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Re: GROSS JET REPAIR

Post by JTT3 » Fri Aug 25, 2023 10:39 am

You guys are just saying that, well because it’s true. A world of difference and the tool Scott makes keeps the whole exchange easy peasy.

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Oldav8tor
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Re: GROSS JET REPAIR

Post by Oldav8tor » Fri Aug 25, 2023 10:40 am

Couldn't agree more. I installed Scott's valve and no longer have fuel flow issues when the tank is low or climbing hills.
1917 Touring
1946 Aeronca Champ
1952 Willys M38a1 Jeep (sold 2023)
1953 Ford Jubilee Tractor

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