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Discussion Starter · #1 ·
Well, it turns out the Q-Jet on the truck's small block 400 needed a full rebuild, it was leaking like mad. The urgency is that I need this truck to get us and the Chevelle to Nashville in a few days! This is making me nervous!

I rebuilt it tonight and plan to throw it on the motor tomorrow first thing. But my dilema is I'm not sure which carb-to-manifold gaskets to use for the best results. I have two options:

1. a really thick gasket with plastic lugs at each bolt hole. This gasket is basically an outline of the outer rim of the carb base plate with no gasket material extending between the barrels of the carb.

2. this is a three part set designed to keep the carb cool I think. The first is a thin gasket, then a gasket shaped thin aluminum plate and then another gasket. One gasket is kind of rubbery and the other is typical paper gasket material. These gaskets have individual holes for each barrel openning unlike the one mentioned above. If I should use this set I'm also unsure which gasket should go toward the engine and which toward the carb.

I hope there are some Q-jet experts tuning in tonight. I'll check for responses in the morning to hopefully point me in the right direction.

TIA!

*EDIT* A picture speaks a thousand words. Click the link for a picture of the gaskets in question. The one on the left is the extra thick one, the right hand set are the three piece set up mentioned in #2.

http://www.amhost.com/scooter/gasket.jpg

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[This message has been edited by Rich-L79 (edited 06-02-2001).]
 

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Rich,

I have used the thick style gasket many times. It has worked well for me. The only thing that I would suggest is that you first set the gasket on the manifold and check to see that it will seal all of the intake holes completely. And then flip the carb up side down, and place the gasket on the bottom of the carb. Once again check to see if it will properly fit the base of the carb. I have run into gakets that are not the proper shape for he carb and they would look good from the outside when installed but they would create a vacumm leak because they did not line up properly with the carb or the manifold. Good luck.


P.S. I just have to bragg because I took my maiden voyage today in my new to me '72 Chevelle and boy am I excited!
 

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Discussion Starter · #3 ·
The new thick gasket is exactly like the one the came off the engine today. Both styles fit just fine because I've been where you metioned with huge air leaks so I checked that out before I asked.

I've also re-epoxied the caps on the underside of the carb body as these tend to leak as well.

Any more insight anyone can offer? I don't think I'll use gasahol ever again since this may have contributed. I'll also be retorquing the carb body screws every time I stop for gas on the way to Nashville.

If anyone sees a stranded maroon '69 Chevy truck with a maroon '65 Chevelle on a trailer along I-70 between KC and St. Louis or along the interstate south from there to Nashville, please stop and help me rebuild the carb again!
 

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I'd put the thick one on.....thats what came off, so there are no doubts
 

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Discussion Starter · #5 ·
But in some bizarro way could that thick gasket have contributed to my leaking carb and loose carb body screws? I'm grasping at straws here I know but I'm really nervous to drive this thing across country right now!

I rebuilt this carb when I rebuilt the motor about 3-4 years ago. I used the thick gasket then since that's all I had and I don't recall what was on the motor when I got it. I really think a carb rebuild should last more than 4 years and I also think the screws should stay torqued as well. I found the two screws from underneath were really loose. Maybe I should get some small lock washers in the morning before I put it on the engine.

Yeah, that WOULD make me feel a little better and is cheap insurance. I have to wonder if the fact that I don't drive the thing too often could accelerate the deterioration? I'm sure the gas evaporates out in between the times I drive it. It often sits for weeks and months at a time between uses.

Thanks all for the input, I'll check in again in the morning. I'm going to bed now, I really need to rest!
 

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Rich, I believe the gasket/shim/gasket is what came from the factory on most Qjets. The shim seals off a hole/slot in front of the primaries that is open to the heat riser (BB). If yours doesn't have the hole open to the heat riser then it's not important. It's easy to get the gasket upside down, then when the carb is installed a portion of the gasket sticks out and interferes with the throttle shaft (can't remember if primary or secondary or which side), causing a vacuum leak. Just trial fit the gasket(s) to the bottom of the carb and you'll be fine.

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I know my brothers L48 Corvette had that gasket.........maybe for your carburator, it was just "its time"
 

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Rich, Does you manifold have an exhaust/heat crossover channel in front of the carb bolts closest to the front of the car? If so then you must use the thin gasket on the manifold that leaves this channel open, then the metal gasket that will CLOSE it off, then other thin gasket. From 65?-69 this is the case (SB and BB?). Otherwise the thick gasket would be fine since it its a "wide open" gasket. I found this out the hard way.
 

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Discussion Starter · #11 ·
There is no heat cross over at the front, just the one under the carb area right in the center. This is small block if it matters and has a stock cast iron (truck) intake that belongs with this motor. Other than the cam it is bone stock mechanically.

I decided to run with the three-piece set. It just makes more sense to match the carb bores with the round holes in the manifold more exactly. Better air flow I would think. I have the thick gasket in the truck in the event something happens on the trip.

After a few runs around town and down the highway and back it seems to be working just fine. It took a bit for the secondaries system to get working (must have had to fill up the passages or something) and it even seems to be free of leaks. I only wish there was a way to double check the fittings at the base of the carb are no longer leaking after my new epoxy treatment.

Let's just hope it stay together long enough to get us there and back!
 

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Rich,

I also had a problem with my carb bolts backing out. This begins to cause a vacuum leak that just doesn't get better.

I solved it with lock washers on each bolt. Torqued them to about 14 ft lb. I haven't had a problem since.


Good luck,

Tom.
 
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