Author Topic: Hay Cliff Needle and seat area in need of help heli coil?  (Read 128 times)

Offline Mr.Pontiac

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Hay Cliff Needle and seat area in need of help heli coil?
« on: February 13, 2020, 08:18:30 AM »
Well i got lucky and bought a 70 carb. part no. 7020264 carb. basket case for parts and noticed the Body needle and seat had a pressed in needle& seat. Lucky enough to get it out and wondering if its possible to install a 3/8 heli-coil & try and save this carb.???O.d. right now measures close to .430 so no threads are left. Do they make special 3/8 oversize heli-coils for this application?? Do you have any??Interested in taking a look at it??? Rich in WV

Online Cliff Ruggles

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Re: Hay Cliff Needle and seat area in need of help heli coil?
« Reply #1 on: February 14, 2020, 03:07:39 AM »
You are in trouble if its got the pressed in double "O" ring deal.  Even if you could get a heli-coil in there successfully there will not be any material left for the seal to sit on.......

Offline Kenth

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Re: Hay Cliff Needle and seat area in need of help heli coil?
« Reply #2 on: February 14, 2020, 05:56:30 AM »
If you can tap the hole to 1/2"-20 you should be able to install needle & seat oversize insert with 1/2"-20 Male Thread x 3/8"-24 Female Thread? Gasket seals on the insert.

Online Cliff Ruggles

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Re: Hay Cliff Needle and seat area in need of help heli coil?
« Reply #3 on: February 15, 2020, 02:57:58 AM »
Kenth, every single carb that has came in here with that repair fails a pressure test, no exceptions.  I've even had a few come in with pressed in thread inserts and those failed as well.

Probably why I got all of them in the first place.  A small leak on the pressure side of the system makes fuel control impossible as the fuel level varies some depending on engine load and how fast fuel is being consumed.  Once the engine is shut down any remaining pressure continues to fill the fuel bowl until the pressure goes to zero.

A bad scenario all the way around........Cliff

Offline Kenth

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Re: Hay Cliff Needle and seat area in need of help heli coil?
« Reply #4 on: February 15, 2020, 10:46:41 AM »
I would install the inlet seat with gasket into the insert first, then install the assembly into carb and seal the outer 1/2" threads with Marine Tex as a last resort to rescue a rare carb.

Offline Mr.Pontiac

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Re: Hay Cliff Needle and seat area in need of help heli coil?
« Reply #5 on: February 16, 2020, 11:04:46 AM »
TIME to say good bye to it

Online Cliff Ruggles

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Re: Hay Cliff Needle and seat area in need of help heli coil?
« Reply #6 on: February 19, 2020, 04:53:55 AM »
I'm NOT fond of using Marine Tex or any other type of epoxy to glue the seat into the casting to save a rare carb.  I've done it a few times but it's risky.

The best repair is to have the carb sent to a competent machinist and bored out for a large threaded insert interference fit into casting at the correct depth.  TALL order for most machine shops and I save that deal for trying to save the most rare and valuable units.

I had a good source locally to do this at one time but they closed down their shop a couple of years ago.  I tried another source a few years back who was basically a self-proclaimed carburetor "guru" and full time machinist.  It was NOT a good experience so never went that route again and found a source about 2 hours North of here to do them.  Sadly they retired/closed a few months ago so currently I don't have a machinist that can effectively repair a main casting that has no threads at all and no viable way to fix them with a heli-coil or any other easy repair.......Cliff

Offline Mr.Pontiac

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Re: Hay Cliff Needle and seat area in need of help heli coil?
« Reply #7 on: February 19, 2020, 05:44:46 PM »
Always honest always there when i need you, thanks for the imput.