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Carburetor leak
https://www.slantsix.org/forum/viewtopic.php?t=7937		 Page 1 of 2
Author:  Factoids73Dart [ Thu Dec 25, 2003 5:42 pm ]
Post subject:  Carburetor leak
I was wondering if anyone could help. I recently did a Half reassembly of the L6 I have in my 73 Dart, just to replace a couple of cracked valves and worn oil seals. Put it back together, and eventually got it restarted, but one of the cylinders was backfiring into the carb, so I took the valve cover off and readjusted the offending valve. Replaced the valve cover and attempted a restart, no dice. Took the air-cleaner off and moved the throttle lever to see if gas was going in, that seemed fine, but I noticed on the other side of the carb corresponding to the throttle lever that every time I moved it, it squirted out gas out the side of the side of the carb onto the intake manifold. Heres the tricky part, I have the super six 2bbl, I got the model number off the side, but have yet to find anything pretaining to it. Its a Holley 2bbl R-8641 0344, maybe I read the number wrong. Is it time for the carb to meet its maker? or Rebuild it? Or am I barking up the wrong tree altogether? What would be a suitable replacement for the carb if it is indeed time for the carb to retire?
Any help would be appreciated.
Thanks in advance.
Author:  HyperValiant [ Thu Dec 25, 2003 8:45 pm ]
Post subject: 
I would check the timing and make sure the plug wires are installed correctly as that would make it backfire thruogh the carb and cause a nostart problem,check this before ripping into the carb.
HyperValiant
Author:  alienduster [ Thu Dec 25, 2003 9:24 pm ]
Post subject: 
Check if the leak is occurring around the throttle shaft. If it is you will need to have the throttle shaft bushed. Not worth it on that Holley IMHO. I would replace with a Carter BBD. However, if it is not the shaft, just do a rebuild and you should be good to go.
Author:  steponmebbbboom [ Sun Dec 28, 2003 6:32 pm ]
Post subject: 
an obvious question is where is the leak coming from... :)

I wouldnt sweat it too much, worst case is you replace the carb, and the 2bbl off a 318 is common and works well. But Hyper is right, go back and check your ignition for sure if youve had the head off, Ive made that mistake myself more than once.
Author:  Factoids73Dart [ Mon Dec 29, 2003 8:48 am ]
Post subject:  Carb Leak
The leak is coming from the (facing windsheild) the left side of the carb, where the pivot for the throttle is. Sometimes its a little jet, other times it just dribbles out. It only does that when I move the throttle lever.
I readjusted the valves again, so those are fine, there is compression, plugs were regapped. I even tried hooking up the plug wires in the wrong order to see if anything would happen, nothing. Its turning over fine, I can smell gas in the carb. Now, the last time I got it started, my compadre adjusted the two mixture screws at the base of the carb, so it would run leaner, coz the exhaust smelled like gas. Maybe he turned them back too far so that its too lean that it wont catch a spark? Coz I am not 100% how far he turned them back, should I turn them back into the carb and work backwards?
Author:  SlantSixDan [ Mon Dec 29, 2003 1:48 pm ]
Post subject: 
If I'm not mistaken, this Holley has a diaphragm-type accelerator pump. It's possible the diaphragm has a tear in it, which may have been caused or worsened by the backfire. You really should tear down the carb and rebuild it with a kit if you intend keeping this carburetor, but I'm in agreement with those who suggest going to a Carter BBD, because my experience with the Holley 2280 was mostly negative. Of course you need to find and fix the cause of the backfire if you haven't done so already, but fix the carb leak or your car will burn down and render the whole question moot! :shock:
Author:  Factoids73Dart [ Mon Dec 29, 2003 2:29 pm ]
Post subject:  What Gas leak?..... BANG!!!!! ['twisted']
I guess I'll try a rebuild, less expensive than buying another carb at this point. I am hoping that its just the carb.
Author:  Super6 [ Mon Dec 29, 2003 2:51 pm ]
Post subject: 
If it is backfiring through the carb you most likely have a timing issue as well. I would turn the engine over by hand until the intake valve just closes...then continue turning until at TDC compression (timing mark on dampener to zero). Drop in the dist again with the rotor pointed at #1, this should get your timing close enough to start the slant up...then adjust w/ a timing light.

One thing I can say with my limited experience w/ holleys, they do not respond well to backfires (especially through the carb). Every time I have seen a backfire thru a holley (even a mild one) the carb needed a rebuild due to a blown powervalve... (I believe newer holleys have some protection against this, but I am not 100% sure of this...)

-S/6
Author:  steponmebbbboom [ Mon Dec 29, 2003 7:15 pm ]
Post subject: 
Factoid: Are you certain your camshaft was properly indexed to the crank when you installed your timing chain??? If your valve timing is late you can futz around with the ignition timing all you like and never get anywhere. Also check to see the distributor shaft is properly indexed. I have a funny feeling either of those is off a tooth or two.
Author:  Factoids73Dart [ Tue Dec 30, 2003 6:26 am ]
Post subject:  Carb/ Timing Craziness!!
I didn't take the timing chain off or the distributor, all I did was pull the head off and replaced two valves and the oil seals (all of the associated gaskets as well).
The backfiring was happening on only one cylinder, coz it was always at the same interval, either 4 or 6 coz those were the ones that needed the most amount of adjustment with valve lash (more so six than four). All the others were fine in terms of lash.
What about the timing marks on the fan belt pullies? The one attatched to the engine is divided into 3rds, what should those marks line up to?
This prob is either fuel delivery or timing. I hope its fuel delivery.
Author:  steponmebbbboom [ Tue Dec 30, 2003 5:47 pm ]
Post subject: 
ok, well before you throw your rebuilt carb back on you need to eliminate all other possible causes of your backfire, don't want the rebuild to go to waste and I dont think carburetion alone will cause a backfire, unless youre very lean.

You can verify your distributor indexing, valve timing, and timing chain condition all at once like this: Pull out all your spark plugs, your distributor cap and your valve cover and set them aside. Grab a pen or pencil and set it on the right inner fender, youll need it. Now turn the engine by hand until both valves close on #1 cylinder. Grab your pen and hold it in the #1 spark plug hole. Continue to turn the engine until the piston comes up to the very top. You can use the pen to feel it as it comes up. You can also shine a flashlight in the hole and watch, but I find it harder to look and turn the engine over at the same time. The indent on your harmonic balancer should be very close to the center mark on your timing plate attached to the engine. Painting the balancer mark and the center timing mark with paint or chalk makes it easier to read. The center mark is 0 degrees, and the two others on either side are 5 and 10 BTDC and ATDC. Now here's the payday:

Look down at the distributor rotor. It should be pointing to the #1 tower and the points should be closed. If its close enough you can just turn the body to index it right. While youre at it, grab the rotor and wiggle the shaft to check for wear in the bushing. Now turn your engine slowly and watch for any lag in the movement of the valve rockers or the distributor rotor. There should be very little. If you can move the engine in either direction for more than five degrees or so without the rotor or rockers moving, the timing chain is worn out.

The rockers should all be in specific positions at this point as well, you may be a tooth off or so if one or more of the cylinders has a valve open that shouldnt be. But generally if it's been assembled correctly there will be considerable slop in the chain if it's jumped a tooth.

If you havent found anything strange at this point I'll be surprised. But at least with your distributor static timed this way your timing will be close enough to start the engine. Good luck

Oh, I should add this: It's also possible you didnt have the engine indexed properly for each cylinder when you set the lash. I only suggest this because you mentioned you didnt know where the timing mark on the crank pulley was. The lifters have to be at base circle for both valves, ie the cam should be at the power stroke, at TDC. If your cam lobes are "on the rock" (between exhaust valve closing and intake valve opening) your lash will be way too loose as there is some overlap in this position and both valves are actually open a touch.
Author:  Factoids73Dart [ Tue Dec 30, 2003 8:09 pm ]
Post subject: 
Ok, I'll give that a try, won't be able to do anything till new years day coz by the time I get home from work its too dark. You know, working on your car in a parking lot at your apt sucks. Maybe thats whats wrong.
Now which of those marks is TDC? Does it vary depending on which cylinder is at TDC?
Your idea is definatly doable, I even have the old distributor that I can drill the points out of so I can put peice of tape on the old rotor, and go totally crazy. :twisted:
Now that I think about it, when I readjusted the valves the second time, the rotor was pointing to about where the position of #1, and the valve lash for #4 was at spec, and #1 was a little tight. 153624 :idea:
In case you can't already tell, I am a novice at this, I appreciate all the info i've gotten from you all.
Author:  Doctor Dodge [ Tue Dec 30, 2003 9:28 pm ]
Post subject: 
You may want to try adjusting the valves while the engine is running, that can tell you alot about what is going-on. Here is a procedure:

The engine must be hot.

Once valve cover is off, I check the torque on the head bolts, if they don't move ("crack" loose and turn more) by 75 ft.lbs, go to the next, follow the "center-outward" sequence. Also check to see if all the rocker arms are oiling out the center and tip holes. If not, now is the time to change them.

When I do my adjustment with the engine running, I turn the idle down as low as possible and put some cardboard under the car. (if you want your floor to stay clean!)

I start with the intakes, stock cams adjust at .010, watch for the TWO INTAKES side by side in the center of the row (Cylinders 3&4) use the manifolds as your guide.

Come back around for the exhaust valves, they should be plenty hot by now,(remember, the engine is running and you are "feeling" the clearance between the "hits", if unsure, stop the engine for a moment and recheck to help establish your "feel"

The exhaust is set at .020 but shoot for looser to start. (.021 - .022) Find a setting where the idle is smooth but the lifters are mostly quite, yes "mostly" quite, they should make a small bit of ticking noise when correct. When you have things set right, each cylinder should "miss" slightly when you insert the "feeler gauge", this "hangs" the valve open, causing the minor miss.

If you want to try to "sneek-into" a minor bit of performance increase, try setting the intake valves a bit tighter, .008 instead of the .010
If the engine starts running rougher at idle, Go Back To .010, if the idle stays smooth,....how about @ .007? This puts a small bit more duration on the intake valve event, this also works in "consept" with the exhaust but there is way more "risk" of a "choppy idle" and burned exhaust valves, so .020, may-be .019 (HOT) is about as tight as I would go. Bottomline, these lash settings have some "leeway", a little tighter or looser is OK, as long as a smooth idle is maintained.

That's it, Button it up and go for a drive.
DD
Author:  steponmebbbboom [ Wed Dec 31, 2003 11:31 am ]
Post subject: 
Quote:
Now which of those marks is TDC? Does it vary depending on which cylinder is at TDC?
There should only be one mark on your harmonic balancer. Unless the rubber's dried and cracked loose, that mark should correspond with the position of #1 cylinder. With both valves closed and rotor pointing to #1 tower, that mark should line up with the center mark on your timing tag on the engine. Just like Doc says, you can set your valves to spec cold, then readjust them with engine running and at operating temp, this way varying expanded dimensions will be accounted for. Ive adjusted valves on diesel engines this way and there is a difference. Either Mack or Cummins actually specifies clearances be set using this method.
Author:  Factoids73Dart [ Wed Dec 31, 2003 4:49 pm ]
Post subject: 
Hopefully I'll be able to work on the beast tommorrow 01-01-04. Ill let you know what happens.
My beast won't go very far, I've only have put on one of the new leaf springs i've bought. Left side (the one I replaced) sits about 2-3 inches higher than the old one on the right. The only thing holding the right leaf spring together is a pair of trusty heater hose clamps and a piece of rubber on the sides to keep rubbing to a min (I can't help but laugh every time I see that). But thats not the problem, on the right side I brok the stud for the shock (where it attaches to the axle, the stud itself is still there, it snapped at the bolt), and one of the spring mount studs. Since then PB-Blaster has been my best friend..... Damn New England winters.
Is my understanding correct? Is the 73 Dodge Dart 2dr, from the doors forward a "Stand alone year"? I've been hard pressed to find body parts for the fender, and door for a 73. Sounds like a junk yard is my best bet. I am inline to get a fender from a junk yard, while the price for the fender seems to be market value... the S/H is going to kill me. All the way for Or. to CT. The fender itself is $115, in total it will be $290. I can imagine that shipping alone would be 80-90 by itself, packing maybe another 20-30, and removal from the "surrogate" Dart, prolly another 50 (i.e. labor). The fender is in very good shape, minor dings. Or am I being taken for a ride as far as S/H goes?
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