Carter bbs problems

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iw378

iw378

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Here we go, 1967 valiant with a 170 slant 6 manual transmission. I got this car a couple months ago and here is what I have done regarding the fuel system. New tank and sending unit, new fuel lines. After I did that it ran fine except for a bad off throttle dead spot. It idled fine and while driving it was smooth. So yesterday I got a notion to replace the accelerator pump. This is when it all went bad, I got a rebuild kit and took the carb apart, the leather piece on the pump shaft was shriveled up to almost nothing. So I cleaned all the parts , blew out all the passages with air, re assembled and it started just fine, the problem now is it idles like crap once the choke fully opens.if I close the choke to less than halfway the rpms rise like its getting too much air at idle. Any help appreciated and yes I do have a FSM with the crappy pictures that leave alot to be desired. I had this carb apart 3 times today and cant find what is wrong with it.
 
Better-than-FSM Slant-6 carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. The kits tend to come with multiple versions of the upper-to-middle and middle-to-lower casting gaskets. Only one of each is correct for any given carb; the others have holes and cutouts for other carb variants and can create air leaks if misapplied. That said, these carbs are all old now, and the bottom flange of the airhorn (top casting) and the top flange of the main body (middle casting) tend to warp. Doubling up on the gaskets is an easy way to make sure the warp hasn't opened up unauthorised air paths, but it does mean you need two kits. Carb kit quality has been in a nosedive for awhile now (low demand). The best kits come from www.daytonaparts.com (their inlet needle/seat is a better design than the usual type); donno if they'll double up on gaskets for you or if you'll have to buy two kits.

(Did you remove the idle nozzle/jet and clean it carefully with carb spray?)
 
I was hoping you would chime in Dan. Yes I did use the right gaskets. And yes I did remove the idle jet/ nozzle and cleaned with carb cleaner and compressed air. My kit came with 2 sets of gaskets and I only used the correct ones. I did notice the bottom of the airhorn gasket surface was not flat but assumed it would flatten out upon mounting it on the throttle body. I'll get some pics up tomorrow afternoon. If it beyond repair could you suggest a replacement carb ? or a place to get one ? I really want to run this slant for awhile till I get a small block built.
Thank you Sir
Luke
 
Good carbs for the Slant are growing difficult to get hold of, but they're not quite extinct just yet. Send me a PM if you need a replacement and I'll go digging.
 
Did you adjust the float level, even accidentally?
If the level is lower than it was, it will have some issues getting gas into the venturi, as it would need to pull fuel over the high point in the metering circuit.
That would be your flat spot off idle.

In the opposite case, if the fuel level is too high, it just flows out to the venturi and drips at idle.
 
And one issue I have read about the BBS is for wear on the throttle shaft bores. Spray a bit of WD40 or something like that around the shafts while idling to see if that changes the idle significantly.
 
I did some spraying and the rpms did not change. This carb ran pretty good until I took it apart, changed accelerator pump.
I did find that the bottom of the air horn is warped, pretty bad. It ran ok like this until I took it apart. The air horn gasket in my rebuild kit is alot thinner than the one that was on the carb.
 
There should be a thick gasket in the rebuild kit (6-7mm)

Put some 600 wetdry sandpaper on a flat surface and sand it flat
 
Tore it apart again today. I bought some gasket material and made my own airhorn gasket out of the better material. I then checked the gasket that goes between the main body and the base and found this. you can seeat about the 2 oclock position the gasket does not compeletly that square notch. The old gasket covered it. So I got out the exacto knife and hole punch and made a new one.
Re assembled and put back on. the problem is not as bad now. so I was able to actually keep it running long enough to spend time carefully squirting carb cleaner on the throttle shaft ends. When applying spray it goes from 900 rpms to about 1500.I guess thats where I'm getting all the extra air from, worn out shaft bores:BangHead:

IMG_0819.jpg
 
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You can have that throttle body rebushed (see the link I previously posted) but you're probably money/time/effort ahead to chase down and swap a better carb.
 
If you are a hard core DYI'er and good enough, there are re-bushing kits out there. If you had the bushings, you could make your own tooling for use in a heavy duty drill press. Just don't drill the bores quite all the way into the bore.

Did you measure the shaft to bore movement to see how bad it is?
 
I didnt measure it but its bad enough to raise the rpm up 600 when I apply carb spray to the shaft. I'm definatly a hard core DIY'er. but this looks to be a little more precision work than I'm set up for.
 
Does not seem too horribly much for a throttle shaft but the RPM change sure is a lot. Are you sure the 'test juice' is not sneaking in somewhere else along with the shaft? Maybe put some clay or heavy grease around the shaft and try it again to be sure? Just curious....

Have you checked the vacuum level below the carb at idle? Sure sounds like a lot of air getting in there.
 
yeah, I just barely let it dribble on the shaft and the rpms went up. I even did a test with spraying just the base gasket just below the shaft but there was no change. when the carb spray is just dribbled on the shaft ends there is an instant rpm rise. Throttle linkage end and the dumb end. I did put wheel bearing grease around the shaft ends, it helped but only momentarily. What I dont understand is when the choke plate is open there is a big hole for air to come in, why in the hell would the air want to take the path of more resistance of the throttle shaft slop ?? Watcha think ?
 
On a side note I could have rebuilt my holley 4 barrel 75 times in the time i have spent messing with this one barrel
 
just thought about it a little more, throttle plate closed at idle the big hole in the top of the carb is closed for air so to speak. air gets sucked through shaft slop.
 
Roger.. on the reason. And yes I am a ham. And Ok, on the thoroughness of the test.

I had to laugh at your 4 bbl rebuild versus this!
 
My replacement carb showed up today. Bolted it on fired it up and adjusted idle speed and the valiant is back on the road. Runs surprisingly well actually
K6XVK
 
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