ronbo97

All -

I rebuilt a quadrajet for a 1970 442. The threads that the fuel inlet filter housing screws into are stripped, so that the housing won't tighten and instead, keeps rotating. Does anyone have a repair for this ? I don't want to junk the carb, so don't suggest that.

Thanks,

Ron

compedgemarine

someone makes a replacement inlet that is over sized threads for just that fix. I dont recall who but I have bought them at "good" parts houses before.

jensenracing77

If that is a rare number carb i would not go with the over sized inlet. Sparky's can fix it for $60. i am sure there are other places that can fix it also.

http://www.sparkyscarbs.com/

joe_padavano

This is sadly all too common. There are several possible fixes, with different prices and results. The best fix is a helicoil. This is an unusual size, so unless you WANT to own the tap and installation tool, Sparky (or another Qjet specialist) is a good choice. Second is the aftermarket inlet with the oversize, self tapping threads. These are available from Dorman Products. The problem with this solution is that the next time you remove the fitting to change the fuel filter, you run the risk of stripping the threads again. I used one of these fittings but converted to an external inline filter. This way I only had to screw it in once and never touched it again. Worked fine for that application. The final option is to epoxy the fitting into the carb housing. This also works, assuming you get the surfaces completely clean, but again you need to use an inline filter.

ronbo97

How easy is it to install the Helicoil ? Also, any idea as to what the tool costs (I assume it's a tap) and where I can get it ? I understand that it's a 7/8 x 20 thread size.

I'm trying to figure if it's worth it to do this myself, or just send it off and have it done.

Ron

compedgemarine

just look up 7/8-20 helicoil kit. they are around $150 for the kit.

joe_padavano

Yeah, Google is your friend. Here's one for only $144...

http://www.blindrivetsupply.com/Reco...ts_p_2902.html

Octania

This is one task I have not done, but for ONE carb, I'd say just send it out to have done.

Besides the tooling costs, I would assert that unless you have a Bridgeport mill to perform the process with, the chances of success are fairly slim. You'd want at least 1 or 2 carbs to practice on first, right?

joe_padavano

Keep looking - here's the same kit for $112. Given how many Qjet vehicles I own, I may have to buy one for that price.

http://www.rivetsonline.com/unique-s...ze-7-8-20.html

MDchanic

Not a bad price - an enterprising soul could charge a bargain price of $50 per repair and do well with that.

- Eric

Hurst/Olds 73/74

I just dealt with this problem on the original 2V carb on my '71 Cutlass Supreme convertible a week ago. Everything I've tried in the past few months still left the carb leaking or worse...spraying. I tried rubber O-rings, Seal-All, Goop...nothing stopped the leak. Finally, I bought VersaChem's 60 Sec. Epoxy at Autozone. Have everything ready, because you have about 30 seconds once it's mixed. It is the only thing that has worked! I put a second coat around the outside just to make sure it stays sealed. It's not great for a show car, but it's fine for my driver...and the air cleaner hides the fix anyway. I've driven it probably 100-200 miles in the past week or so with no more leaks!!! Just make sure to leave the filter out and put in an in-line aftermarket filter.

It is nice to know there are better fixes out there, though, if you want to spend the money to do it right.

MDchanic

No question if you clean the threads well and use a good quality epoxy (either fast or slow curing), it will seal and stay sealed.

An epoxy repair is not a one-way street, either, as you can soften epoxy and remove the parts with heat (a heat gun, or gentle heating with a propane torch, is fine) if you later decide you want to do a fancier job.

- Eric

The_Jeremiah

I used to work at a carb shop, we did this to special quadrajets more than once, If they werent special, we would toss them and build another carb. ship your carb off and have it done, its a good repair and you cant notice it once you screw in the fuel inlet.

ronbo97

So if I went the epoxy route, could I keep the inline filter inside the housing, or would that have to be removed prior to epoxying ?

MDchanic

No, it has to come out.

If the filter should become clogged later, it will be tough to open the chamber up to remove (or even inspect) it.

Take the filter out, install an inline filter in the rubber hose before the fuel pump, and you're all set. That way, if the inline filter picks up any crud, you can change it easily.

I have done this before, myself, but not in the last 20 years or so.

- Eric

joe_padavano

Well, if you left it in, you'd never be able to change it once it plugged up, so what do you think?

ronbo97

Yeah, I realized that. But figured that with the amount of driving that the car would receive, it could probably stay in there for decades.

I'm definitely leaning toward the Helicoil and I'll have it done by Sparky's or similar shop. I'm helping out a friend on this one, since she's had the car for years and is not mechanical.

Hurst/Olds 73/74

The package on the 60 Sec. Epoxy said "seals most liquids" but the package on the 5 Min. Epoxy said "seals water". I wanted the extra time, but was worried about the packaging wording. That's why I went with the 60 Sec. Epoxy. Maybe it was just older packaging on the 5 Min. stuff.

MDchanic

Far as I know, any good 2-part epoxy will seal out gas, but I could always be wrong.

Never met one that didn't though...

- Eric

shortstroke425

I know this is an OLD thread, but this might help someone out! JB Weld WILL eventually leak and create a fire risk. The epoxy you need is Permatex "Cold Weld" steel reinforced epoxy, product #14600. It is impervious to gasoline, diesel, antifreeze, etc. Other epoxies do not make that claim.
I chose to leave my filter in place since the epoxy can be softened with a butane pencil torch and the inlet removed. I only run a few tanks a year through mine anyway and didn't want to have a non-original filter on it.
When removing, make sure to plug the back of the carb inlet with a piece of a rag and thoroughly clean the threads, or in my case, the helicoil, with a small brass brush, making sure all debris is removed (I use a vac to get it out).
Has anyone ever had a helicoil not leak on a carb? No luck here.

shiftbyear

I buy my rebuild kits from Cliff Ruggles. He stresses that the only way to get the heli-coil in correctly is with a mill or Bridgeport, which is what he uses. If it's not perfectly straight the gasket won't seal. good luck


http://cliffshighperformance.com/ser...-thread-repair

joe_padavano

The helicoil does NOT form part of the seal on a Qjet inlet fitting. There are two styles of fittings, the old ones with the seal gasket OUTBOARD of the thread and the new ones with the seal INBOARD of the threads. In the former case, the seal is between the screw-in fitting and the float bowl. The threads are completely inside the sealed volume and do not contribute to sealing the fitting. In the latter case, the the threads are completely outside the sealed volume and again contribute nothing to the seal path.

Old style:



New style:

shiftbyear

As Joe said the heli-coil doesn't do any sealing what-so-ever. But if the heli-coil is not perfectly straight it will affect the gaskets sealing abilities. The only way to duplicate the precision of the Rochester tooling is with a jig fixture on a Bridgeport or mill.

Greg Rogers

EXACTLY!!! I learned this the hard way. After having my original carb completely rebuilt from a reputable "carb" shop in California, my fuel inlet started leaking and needed new threads. (this was not their fault) I sent it back to them and they put in a helicoil. After that I couldn't get the inlet to seal. The helicoil was installed crooked so it wouldn't seal at the intended inner gasket ring. I sent it back to this "carb" shop and they said nothing was wrong! It was so crooked you can see the tilt. I have since gotten another carb. This ended up being quite costly with shipping being $60.00 each round trip to allow this "carb" shop to ruin my original Quadrajet. I shouldn't mention the name of this "carb" shop, but maybe you can figure it out. I would avoid them.

Via3d

What are your thoughts on sealants? I want to hear some war or horror stories on proper sealants being used on Rochester Fuel Inlet fittings.

I find it interesting all the back and forth editorial on dozens of sites regarding use of sealants, epoxies, etc.

I understand the hesitation to use sealants, I really do.... however familiarization with aviation and marine applications - sealants, putties, etc. are used all the time for fuel/chemical fittings, lines etc., matter of fact it is often required to meet specs ! And the environment can be much more dangerous. Think about the below deck environment on marine craft and the stringent safety requirements necessary! Do you think it is plausible they will ever risk a below deck fuel leak? KABOOM!!!
Think about the inspections and standards that aviation craft must adhere too. Mayday Mayday!!!

There are a lot of sealants out there that are resistant to gasoline and ethanol.... providing a flexible yet high strength seal.
Just Permatex alone has half dozen solutions that are made for fuel fittings and are gasoline resistant...

I looked at all these viable Permatex Tech Data sheets:

• Aviation Form-A-Gasket No. 3 Sealant
• High Temperature Thread Sealant 59214 (I have seen several comments this worked for folks on Rochester Inlet fittings)
• High Tack Gasket Sealant 80062 (suggested carb applications)
• PermaShield Fuel Resistant Gasket Dressing & Flange Sealant 85420
• SEAL+LOCK Thread Compound (fuel supply fittings, injectors 155% strength retained against gasoline, plies to nearly type metals used)

....and these are not all.
Before it is asked, NO, I have zero affiliation with Permatex

Other products/brands that appear to be applicable:

• Gasoila makes a gas resitant sealant
• Marine Tex epoxy (better than JB Weld debate)
• Permatex Stripped Thread Repair (yea, what about tread repair products)?
• Loctite 28654 Form-A-Thread Stripped Thread Repair Kit

Yeah, Yeah... I hear of teflon tape being used ... of course a no no !! Only certain ones are resistant to gas and ethanol but the biggest problem of All of them is it shreds and wears with assembly/disassembly over time....
Nugget: It's illegal in Washington State to use white teflon tape on gas lines for a reason !!!!!!!!
Proper Sealants though will not break down from gas, ethanol, water, or air. So does it sound like cockamimi bull about getting sucked up in the carb and junking stuff up??
Doesn't seem likely.... and all I am saying is look at the marine craft or aviation industry and/or even talk to large marine craft and aviation mechanics..... BTW Rochester Quadrajets were marine craft carbs too.

I see so many negative with no real life experience stories of failures... of those, failures an be attributed to other issues.... Like a serious cross thread issue to the point the fitting can slide and wiggle out. I evenread twice that they popped out !!?!? LOL, c'mon! sure, there is a point of no return.

------------------------------

Question: What was the mfg. suggested interval to change the fuel filter? every 12k or 15k miles right ????? Well after doing that several times... the "soft" thread metal in the carb housing can easily get slightly worn....
so we should all then go to our closest mechanic that has the expertise and tools for heli-coil repair?

joe_padavano

If the threads are stripped (which was the topic of this thread you resurrected), then no amount of sealant is going to fix that.

If the threads are not stripped, the seal is NOT made on the threads. No amount of thread sealant is going to fix a leak if the primary seal (the plastic circular gasket or the flare on the fuel inlet tube is going to fix that either. Scroll up and look at the photos of the fuel inlet fitting seals. The threads are NOT intended to seal. On a flare nut, the nut is not intended to seal either. In that case, put all the sealant you want on the threads - how do you seal between the tube and the ID of the flare nut? The answer is, you don't - the flare is the seal, not the threads.

allyolds68

FWIW I will add that there are Q-jet aftermarket fuel filter inlet housing nuts that are crap and will never seal. I rebuilt the carb on my boat and no matter what I did I couldn't get it to seal (the inlet threads were fine). Eventually after loosening and trying various inlet gaskets (the plastic rings on the nose) I got it to seal. I took the boat out for a ride under full engine load for five minutes and it FINALLY didn't leak. The next boat ride with my wife and two kids in the boat the engine stalled after idling about 5 minutes. I lifted the engine cover and as soon as the fresh air hit the motor it went up in flames. The top of the motor was covered in gas. Fortunately I had a fire extinguisher close and I was able to immediately put it out. No one was hurt and nothing was damaged. I got towed back in and called Cliff Ruggles (who I bought the rebuild kit from). He asked me to send him a pic of the inlet housing nut. As soon as he saw it he told me to throw it away. He said it was an aftermarket nut and the sealing surface was crap. He sent me a new one and I haven't had a problem since.........

This is a pic of the bad nut (yeah.... I know it's a Chevy.... ). It's the "new style" that Joe refers to above

scrappie

Wow, you were lucky. that could have been so much worse. Im thinking a fire extinguisher is a must have with these cars for many reasons.

My442

Sparky fixed my Q-Jet with stripped threads with a heli coil. It came out perfect.

allyolds68

I was very lucky. It actually went up in flames a second time a minute or so later when I was mopping the gas up off the manifold and accidently bumped a piece of the air cleaner assembly across the starter solenoid which caused a spark. I put that out too. There was a lot of white powder to clean up but you'd never know it happened now

johns72olds

Boiler_81

He fixed mine as well - perfect.

Via3d

Mechanical fix the most popular best option (heli-coil)

Temporary fix: ( tested and has been working great )
A very new product by Permatex: Permatex Seal + Lock Thread Compound. Part #57535

Tech Data Sheets (TDS) :
made for fuel line fittings
150%+ resistant to gasoline, ATF, engine oil, etc
120 lbs sq in locking;
1000 psi seal;