Author Topic: Re-rebuild?  (Read 595 times)

Offline CJ7Pilot

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Re-rebuild?
« on: May 22, 2018, 06:38:51 PM »
Hello, I have an '82 Jeep Scrambler that has an '82 GMC pickup engine installed (CA legal, 350).

I'm putting together a new GM stock replacement crate engine for it, and in the interest of minimizing down time, I bought a used, but recently "rebuilt" Quadrajet. 

I took it apart to see what's in it, and it looks like a pretty clean home rebuild.  However, the primary shaft has all kinds of play in it, so at the very least, I'll need a bushing kit.

It doesn't look like any of the passages have been drilled out, but the needle seat is .130, and the main jets are .073.  These are the sizes you list for a mild performance engine (recipe #1).

Would you recommend I go back to a stock needle seat and jets?  I'm perfectly happy with a stock 350 in my Jeep... I just want it to run like new.

The model number is 1708 4226, followed by 2933 HCD.

Thank you!

P.S. - I'd be happy to buy a full rebuild kit from you, and re-do the whole thing, if that would help eliminate some unknowns.  8)
« Last Edit: May 22, 2018, 07:00:52 PM by CJ7Pilot »

Offline CJ7Pilot

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Re: Re-rebuild?
« Reply #1 on: May 24, 2018, 08:22:35 AM »
I went ahead and ordered an HP rebuild kit for my model number, as well as a primary shaft bushing kit.

If you guys see this post, and have any other recommendations, I'd appreciate it.

Cheers!

Offline CJ7Pilot

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Re: Re-rebuild?
« Reply #2 on: May 27, 2018, 06:16:38 PM »
I got my HP rebuild kit and bushing kit today... SUPER quick shipping!

I broke the head off one of the throttle plate screws, which was kind of a bummer.  I tried drilling it out, starting with a #60 bit, and going progressively bigger.  I never got it to budge, and I ended up having to completely oversize the hole, and tap to 8-32. 

The shaft bushings themselves went a little better.  The self guiding drill bit is fantastic!  The bushings were a little hard to start, so I put them in the freezer for about 1/2 an hour.  They drove right in after that. I did have to ream them out with a 5/16 bit to get the throttle shaft working smoothly, but that part was a breeze.

Tomorrow I'll get the base plate re-assembled, and move on to the rest of the re-build. 

Offline Cliff Ruggles

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Re: Re-rebuild?
« Reply #3 on: May 29, 2018, 04:04:45 AM »
I didn't see the thread, sorry. 

We are experts at removing twisted off shaft screws, must have been a pretty big hole to go all the way to 8-32, but it will be fine provided you opened up the hole in the throttle plate to provide some "wiggle room" and you use a pan head screw so it doesn't block much air flow.

Make sure the power piston hanger arms are level and EXACTLY even, biggest problem we see here with all "rebuilt" and remanufactured units, 99 percent of them will have the primary metering rods hanging at different levels.

Make sure to use the new power piston retainer to hold the PP down during assembly and carefully slip the tongue of the top gasket under it w/o bending the hanger arms.

If you need tuning parts we recently had some really nice primary metering rods made with a full taper from .050" down to the .036" tips for those carburetors.

Since it's going on a "stock" crate engine it shouldn't need a lot of idle fuel beyond the stock specifications, but may need some additional part throttle fuel as those carbs were emission calibrated and quite lean on the primary side........Cliff

Offline CJ7Pilot

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Re: Re-rebuild?
« Reply #4 on: May 29, 2018, 08:54:46 AM »
Thank you for the reply. 

I did use a pan head screw for the throttle plate, and it worked out nicely.

I got the rest of the carb assembled yesterday. 

I spent quite a bit of time on the power piston, and you're right, the hanger arms were not even.  They're dead-even now though, and I was very careful installing the gasket.

The APT screw seems to be just a lower limit adjuster for the power piston.  I set it so the step of the metering rods is even with the opening of the jet (inside the slot).  If I need a little more part throttle fuel, I could back out the APT screw a little, right?

I used the light blue spring, which seems to be as good a starting point as any, until I get the engine running.

My main jets are .073, so we'll see how they do fuel-wise.

Do you have any initial setting recommendations for the idle screws? 

The old screws were 10-1/2 turns out (just barely hanging in there), so I'm thinking whoever was working on it before didn't have the right tool, and didn't feel like running them back in with needle nose pliers. 

I ran the new screws down to the seat, then backed them off two turns to begin with.

Thanks again!

Offline Cliff Ruggles

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Re: Re-rebuild?
« Reply #5 on: May 30, 2018, 04:45:59 AM »
"I spent quite a bit of time on the power piston, and you're right, the hanger arms were not even."

Last time I checked the books I've worked on 12,900 q-jets since 2003 and can only remember a dozen or so Q-jets that came in here where the arms on the power piston were EXACTLY even!

The later carburetors used fine pitch metric idle mixture screws and most will have very tiny holes under them, so it's about 2 turns to 1 compared to the pre-1979 units with the 10-32 screws.  5-6 turns out is a good starting point unless the holes under them are opened up some.

I'd advise against opening them up much as you can very quickly go too large and have to start cutting coils off the mixture screw springs to get them to seat.......Cliff

Offline CJ7Pilot

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Re: Re-rebuild?
« Reply #6 on: May 30, 2018, 08:18:47 PM »
My Frankenstein... TBI accessories on a Q-Jet engine! 

I'm hoping for new 1982 Chevy pickup performance in my old 1982 Jeep Scrambler.

Once I swap it in, I can rebuild my existing Q-Jet as a spare... or maybe set it up as a "performance" carb, and use this one as a "smog" carb.  ;)


Offline CJ7Pilot

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Re: Re-rebuild?
« Reply #7 on: September 23, 2018, 06:37:28 PM »
I got everything installed, and it runs like a champ!

Initially, I couldn't get the idle settled down, but then I remembered that Cliff mentioned the later model Q-jets have finer threads on the adjustment screws.

I ended up with about 4 turns out, and I couldn't be happier!

Thanks, Cliff! 

Offline Cliff Ruggles

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Re: Re-rebuild?
« Reply #8 on: September 24, 2018, 03:18:58 AM »
Good news, thanks for the update.....Cliff