71 Carb Kit

[wbdeford]

Any recommendation on which kit to buy?  I see KEM and Auto-tune on ebay....Walker and Standard Motor on amazon....GP Sorensen from AutoZone and Advance....Echlin from Napa.....

Problems are hesitation when opening the throttle quickly....won't start cold unless i pour gas in the carb.....generally very dirty.

[TJ Hopland]

Standard should still be a good brand.   I have not had any issues with the Napa ones, just did one for a friend this summer.  Cleaning and a new gaskets is a good start but not likely your starting problem.   The kits come with a foam pad that is supposed to help but I usually go with some epoxy on all the bottom plugs just to be sure they don't leak.

[wbdeford]

OK, great...will order the Standard one from amazon....$18.60....when I have it apart I will evaluate whether to use epoxy...thanks, TJ!

[Scot Minesinger]

It is a lot of work to remove carb, clean it, rebuild and then reinstall.  I would use Dayton.  They have a great new needle valve that does not use the thread wires to anchor needle valve to float, much better innovative set up.  I rebuilt a 76 Cadillac carb with this kit and it turned out terrific.  I replaced the float too, which is not a standard replacement part.

When I ordered the carb re-build kit they would not send me anything until I gave them the number on the carb so they could be sure to send the right parts.  That is all they do.  I doubt Amazon is going to go to such lengths to make sure it turns out right.

The symptoms you describe were similar to the 76 Cadillac prior to re-build.  Good luck.

[R Schroeder]

Flat spot could be more than the carb. Leaking vacuum lines can be a problem too.
I used an Echlin carb kit.
After rebuilding I found some bad vacuum lines. Carb works great, and no flat spot now. Flat spot was from bad vacuum line. Replaced all of them too.
Roy

[James Landi]

Make sure to use COMPRESSED AIR through the idle passages... phase separation of ethanol can leave a brown  chalky crude that will create a "flat spot" between dead idle and 1500 rpm. just using spray Gum out through the orifices in NOT sufficient to force out the crud. back out the adjustment screws and force compressed air in.  I recently experienced a lot of pain and frustration before I finally used compressed air on a carb rebuild--the "fix" immediately solved the flat spot problem.

Once you have the carb rebuilt and running right, ALSO,  check your vacuum advance for air leaks and functionality.  Simply take a length of hose from the advance and suck in on it... it should hold vacuum... as well, the stator plate can sometimes move if you can create enough vacuum.  Another idea.... by-pass the electric vacuum valve... connect your vacuum advance directly to the intake manifold port.   You'll be impressed by the difference in moderate-range acceleration.

[Scot Minesinger]

Roy is 100% correct on vacuum hoses, if original or in question, they should be replaced.  It is one of the easiest, least expensive, but ignored 1960/1970's Cadillac essential tune work.  If I hear a complaint about engine performance, that is the first place I look, and the vacuum modulator at transmission short length of hose is the most likely to be original.  If the carb is not off the car, replace the hoses first.  I have a 1970 Cadillac SDV with 32k miles and I replaced all the hoses doing nothing with carb, and it runs perfect.  If you do rebuild carb, get a super high quality re-build kit matched to the correct number on carb, and replace float.

[wbdeford]

Carb is still on the car....got a couple other things I want to do first--mainly, flush the cooling system and road testing the transmission, which I'm hoping to do in the 40 degrees and sunny forecast for tomorrow.  Pavement still has salt, but it is dry, so not worried about a short drive around my neighborhood.  After tomorrow, there is precipitation in the forecast every day through Groundhog Day....

I have already replaced many of the hoses, especially the smaller ones on or near the carb--not the brake booster hose, though, and not the hoses behind the firewall.  The smaller modulator hose is definitely not original as it and the tube are gone and replaced by a longer hose--planning to restore that to the original configuration.  The carb is filthy enough that even if it doesn't need a rebuild, per se, I want to do it anyway.

Thanks, guys!

[mgbeda]

The hard starting without adding gas to the carb could be a bad fuel pump, letting the gas leak back out of the carb line so that you have to crank it a lot to pump the gas back up there.

I'm sure the carb rebuild will not hurt.  I had a "bogging" problem with full throttle acceleration on a '75 Buick with a 455 4 bbl.  The carb rebuild solved that.

And I second (third? fourth?) the comments about checking vacuum lines.

-mB

[Jeff Moffo]

Roy,
Where was your bad vacuum line? 

Scott,
Are there any vacuum lines that "suffer" more than others - i.e. which go bad first?

[wbdeford]

In my case, my worst one was the PCV hose, which actually fell off the carb port it was so hardened.

[R Schroeder]

Jeff, when I bought my car, I went through everything. New tune up parts, carb rebuild, and vacuum lines.
The one I missed was mixed in with some wires that ran along the fire wall. It fed the heater controls, and the brake release for the cruise control.
By the way, that is another spot to look for bad hoses.


wbdeford, that is exactly what I was talking about. You cant always blame the carb. In your case , yours sounds like , it could use a good rebuild .
Roy

[Raymond919]

I may have missed something but I don't think anyone mentioned checking the accelerator pump plunger. When you press the accelerator to move ahead or to prime the engine when starting it, it should send a spray of gas into the carburetor which aids in starting. It's an easy fix and does not require removing the carburetor from the engine. I re-read all the posts and didn't see this listed.
Ray Schuman
#26141

[TJ Hopland]

I suspect no one mentioned it because he was already planning on a kit which includes a new pump.  If you have a carb that is 'very dirty' on the outside chances are good its gonna benefit from a cleaning and new gaskets.  The amount of sitting vs driving these cars do these days and the ethanol found in most fuels is not kind to carbs.

I don't think I have ever heard anyone suggest replacing an accelerator pump on a QJ without first removing it from the engine.  Other than the fuel inlet sometimes being a pain these carbs come off fairly easy.    There are a fair number of small ish screws and parts you have to take off to lift the top off and access the pump.  Besides how long you would have to be leaning over the car I would be worried about dropping something somewhere difficult to find or retrieve. 

I use carb spray on the small passages.  Sometimes it has to soak for a bit.   Be sure to wear safety glasses and be working in an area you don't car about some stains in any direction.  Sometimes a port does not go where you thought when you squirt the cleaner in.  It could be in your face or the side of the car.   I also use the carb cleaner to start cutting the thick varnish and goo on the outside, usually before I start to take it apart.  If you don't do these very often working on a 'cookie sheet' or one of those disposable 'turkey pans' is a good idea so you don't loose any parts.   Flip it over and bang it a few times in the tray to make sure you got everything.  You don't want to looks a check ball or spring in your gravel drive way when you hit it with the air compressor.  Once its all apart and carb sprayed I then use a 'purple cleaner' on it.   There are several brands of the stuff and all I have tried seem to work well.  Its water based and comes ready to go in a spray bottle or a concentrate.   It really cleans parts like carbs good.  I think one of the main ingredients is lye.   That coupled with an assortment of cleaning / tooth brushes can get em looking almost new.  Sometimes I have to go back to the carb spray to get some of the varnish that was under a layer of goo.  After its clean and rinsed out to the compressed air to make sure its dry. 

Check the float level with and without that plastic plug in place.  I have had em where the new needle and seat changes the float level and the float arms hit that plastic plug before the needle seats.   I do this by holding it over my head holding the pivot and or plug with the hand holding the carb so the other hand is free to measure.  If the float arms hit the plug a little work with a file or dremel tool is an easy fix.   

I did a QJ for a friend this summer that was missing the spring from under the primary metering rods.   Thought that was odd so I went to my parts shelf where I have several QJ someone gave me when they cleaned their shop and found 2 more missing the spring.  If either of those had been my first rebuild I would not have known it was missing.    About 3/4 of the time I work on one of these recently the primary rods are stuck.   I have seen them stick both up and down.   Stick up they run decent but down they can end up really lean.  Just getting it apart to make sure that is moving free can help performance. 

Some areas you can still buy what looks like a paint can of carb cleaner that has a little basket built into it.  I have not tried those in a long time, they used to work.   Maybe the fact that some places apparently can't sell it and or transport it is a sign its still got some good stuff in it and it still works.