Author Topic: Qudrajet leaks after shutdown  (Read 1623 times)

Offline gtotech

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Qudrajet leaks after shutdown
« on: November 13, 2017, 08:28:45 AM »
Hello.  First time poster and thanks in advance for any help anyone can give.

I have two GTOs - a 68 and 69 and only one good Quadrajet between the two of them.  I let the 69 sit too long in storage and the QJ on it froze up.  After this, to start it up occasionally, I'd take the QJ off of the 68.  It ran ok with this carb on it. 

I have various other parts carbs and I thought I could build one for the 69.  I didn't know about Cliff's Quadrajets when I started this process.  Using an old QJ book (not Cliff's) and a rebuild kit from APE, I took an air horn top off of a 68/69 Chevy QJ, a main body from a 73 455 Gran Ville and a throttle plate from 70 Pontiac QJ.  The reason I used the 73 QJ was that it was in really nice shape.  The 73 top didn't look right for the car and the 73's throttle plate didn't match up to the linkage so I swapped them out.  The gaskets matched up between these carbs and I thought this combination might work :o

After the rebuild, the frankencarb started the car and I got the car to idle and respond well but it is running a little bit rich (some black smoke), the idle mixture screws don't do much of anything and the carb leaks after shutdown out of perhaps the throttle shaft? on the throttle lever side.  It starts dripping from the shaft about 10 seconds after shutdown and continues with a slow drip for about 30 seconds.  It must also be leaking into the manifold as vapor appears out the air horn and the only way to restart it is WOT.

So... maybe leaking from the bottom plugs and the throttle shaft needs bushed?

My main question is are these parts interchangeable?  If not, I may have the parts around to try another rebuild on parts that are at least from the same year if not the same make.

I've never had the engine out or apart.  The engine is a 400 but it is not original to the car (it's a YS and should be a YZ).  Based on the date on the manifold maybe a 72.  Sounds like it has a stock passenger car cam and it has 3.36 gears and headers.

Any help would be appreciated.

thanks,

Mark

Offline gtotech

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Re: Qudrajet leaks after shutdown
« Reply #1 on: November 15, 2017, 01:12:03 PM »
Talked to Cliff.  Ordered book and rebuild kit for a 70 model QJ with matching top, body and throttle plate. 

He said that it was likely that the mashup of parts that I put together as described above would not work well without advanced QJ technical knowledge.  Parts might need to be drilled/modified to get them to match up.

Offline Cliff Ruggles

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Re: Qudrajet leaks after shutdown
« Reply #2 on: November 16, 2017, 04:46:51 AM »
It doesn't work and begins the leak immediately after shut down because the parts used are miss-matched and not compatible with each other.

It's NEVER a good idea to do any miss-matching right to start with.  Even though parts look similar or even exactly the same, and the gaskets seem to match them, there are internal differences that you can't detect easily that make them not compatible with each other.

Even if the parts were compatible for basic function, which those are not, the calibration would be off due to each part being set up differently, so you are pretty much DONE with that combination before you got started.....Cliff