Baxter61 said

why not just tune what ya got? Theres likely some members in your area that could help you out

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67Dart273 said

There is no reason a 650 DP won't run on that car.

There is several areas of concern, and this is "carb 101"

FIRST Make sure there are no vacuum leaks. Probe around the carb base and other areas on the intake with a scrap length of fuel hose, one end to your ear. Also good for finding exhaust leaks

Check your fuel pressure. You could be pushing fuel right past the needle/ seats at too high pressure

NEXT check the float level.

Then use (water even) in a squirt bottle, short squirts around the carb base, etc. Changes in idle mean a leak

WHAT IS the timing? You want a SHORT mechanical curve and LOTS of initial advance. This alone may clear up the "carb problem"

Next, and ONLY after you get the timing set, investigate the power valve. There are lots of articles on the www, Google it. You will need to tear down the carb and read "what's in" the carb, and about all you can do to tell if it's leaking, is to REPLACE it. But you'll have to measure intake vacuum at idle (AFTER setting timing!!!) to determine if the PV is in the right range.

What you are after with the power valve, initially, is to make sure it is not coming open at idle/ low RPM.

After you have done this, get the engine fully warmed and adjust the idle speed/ idle mixture. You'll need to bounce between the two. Turn the idle mixture screws in until you feel a drop in speed, or watch a vacuum gauge, then bring them slowly out until it "peaks." Then just touch them in (CW for most) towards the lean side until the engine "not quite" drops in speed or vacuum.

Touch up the idle speed, and if you had to change it very much, re-touch the idle screws. IE on something like a stock, stick 318, you don't want to adjust the mixture at 1000RPM and then set the speed down to 600. You want to adjust the mixture as close as you can get to final idle speed.

If you can NOT get a nice idle, and you are SURE the fuel pressure, the float level, and the power valve number is OK, suspect a leaky power valve and replace it.

Next run the car and see where you are. If medium cruise is still not right, see what the plugs look like and only after all the first steps are confirmed OK, do you want to play with jet size.

Random comments.

Cold start. After the carb is correct for warm running, then you can attack the cold start. Do you run a choke? If not, the carb might be jetted on the lean side, or not have enough accelerator pump shot, and you might just expect too much. No carbureted car, example, a "smog" mid 70's car, is going to start and run decent in cold weather without fiddling with the throttle.

Does this problem get worse / better/ no change with outdoor temperature? You could be having fuel boil or vapor lock problems, or you could be having these problems ON TOP of a badly tuned carb.

WHAT KIND of DP is this? Square or spread bore? Example, years ago I had two different Holley spread bore 650's on my 340, and had the same problem with both for a short time. The rear barrels would get "sticky" and would not quite spring completely shut, which once caused the car to act as if the throttle had stuck, and also of course made for high/ erratic and poor idle. You might try a thin tie wire in the rear linkage to keep the rear barrels shut and test drive on the "2 barrel" to see if that affects the problem.

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67Dart273 said

Checking out your timing is easy, but systematic, and you simply must learn to do it. Once you understand it, it's "easy."

First, buy, get, build a "piston stop." This is because you should not assume that your timing marks are correct, as the balancer could have slipped the outer/ inner parts

PIston stop: This are mine I made over 30 years ago for a small block



You can buy them from Summit, Jegs, others. Remove the no1 plug, make sure the piston is "down a ways" and remove the battery ground for safety. Install the device. You may have to adjust it the first time. Gently wrench the engine around until the piston stops on the device. You are NOT trying to stop the engine on TDC but rather with the piston down in the hole somewhat, not critical.

With the piston stopped on the device, carefully make a temporary mark below TDC on your timing tab onto the balancer.

Now do the same thing, rotating the engine CCW. You will now have two marks some distance apart. True TDC will be halfway in between, and if the original mark is correct, that is where it will be.

NOW to check the mechanical advance, you either need to "degree the balancer," buy a "timing tape" for the size of your balancer, or get a "delay, readout, or dial up" timing light. These have either a meter or digi display or calibrated dial. You run the engine up, turn the dial to bring the marks to appear to be TDC, and the readout of the light tells you how much advance you have.

SOME OF these are not reliable. I much prefer a simple light, and degreed wheel.

SO make your choice. Either

1---buy a readout type light

2--measure carefully around your balancer with a flexible tape, ACCURATELY, and figure "degrees per inch," and then scribe marks into the wheel. I usually figure how many inches it takes to equal 40* on the wheel, and carefully measure that off WITH THE TAPE You cannot do that first measurement with dividers. Make a scribe mark with a square and sharp awl/ scribe. You can make them deeper later with a sharp file

Then, using dividers, divide the 40 in half for 20, and add 20 more to the 40 for 60 total. You can check zero to 40 both ways at the 20 mark to be sure your dividers are set correctly.

So now you have marks by 20* out to 60.

Now divide that in half for 10, and again, you can check from 10 to zero and 10 to 20 to be sure the dividers are correct.

3--After measuring around the balancer, you can look at Jegs or Summit, etc for the proper size timing tape and simply, carefully, stick it to the balancer.

NOW you can check timing.

For a "starter" curve, you want 18-22 "in the distributor mechanical, and depending on the cam, "dead stock" or "factory performance" or "somewhat hotter" you'll want anywhere from 10--20* intitial timing at idle, no vacuum

My very mild 360 runs about 15 initial and about 36-7 total (no vacuum) so that means there's about 22 "in the distributor" EXPRESSED IN CRANK DEGREES. This is important, because most of the spec and shop manuals use DISTRIBUTOR degrees, which are HALF of crank degrees.

(On many Mopar mechanisms, the advance degree amount in DIST degrees is stamped on the bottom of the mechanism. This means "crank degrees" are double that amount

This one here, a late 70's smogger is stamped 15*. That means it's a whopping 30!!! degrees!!! at the crank

http://image.moparmusclemagazine.co..._electronic_ignition_system+advance_plate.jpg

Basically, you want all the initial "it will stand" without kicking back on the starter. You can try this a little at a time, and you can also time it for maximum idle vacuum.

Then see what the full mechanical (no vacuum) total is. If you are not comfortable revving the engine, disconnect the belts to disable the fan and other mechanical drives, check with the engine "barely warm" and don't run more than long enough to check timing. Watch the marks, bring RPM up until you get no further advance, and determine how far it is advancing. Depending on cam, heads, compression, fuel quality and a few other things, anywhere from 32to 38 or so may be indicated.

You'll want another 10-12 or so on top of that figure with the vacuum connected, running at "light throttle," "medium to high cruise."

IF YOU HAVE a stock "smogger" distributor, these typically came with a very long, very slow advance, which means you can NOT simply "bump up" the initial timing, because a the top end it will be FAR over advanced.

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