All Small Six Ford 200 idle slightly shaky vacuum slow movement 18-18.75. At a loss?

This relates to all small sixes
D

Dshak65

New member
Hi everyone,
New to the forum, thanks for having me. I have an issue I just can’t figure out. I bought 65 mustang with ford 200 and c4 auto trans. The engine was rebuilt before I bought it with roughly 300 miles in 10 years and a lot of sitting. After bringing it home I noticed a rod knock and it did run / idle rough with vibration. I tore down the engine and found 3 bent push rods and a slightly bent connecting rod. After taking it up to the local race engine shop we measure the bore, replaced rod, pistons, rings, new push rods fresh hone on Cylinders and new rod bearings. New plugs, wires and adjustments to points, Carb was new but I gave it the once over and adjusted. New fuel pump and filter. Head and values are in good shape. It seems to run pretty well, has good power when driving but at idle it has a slight shake / vibration and when you put it in gear it shakes the car. I set timing 12dtdc checked for vacuum leaks and all is good. Ran a compression test to make sure the rings are seated and all cylinders are within 5% of each other at ~165-170psi. Hooked up the Vacuum gauge and seeing a slow slight variation from 18-18.75 with an idle of 700. When in gear the idle drops to about 550-600. Any thoughts or help on why the vacuum flux? I assume the vibration is tied to this…. Any help / guidance would be very helpful. I feel like I tried everything and can’t seem to solve.
 
Hi, the first thing I would do is check the vacuum advance and vacuum modulator for leaking diaphragms. Besides that, a slow slight bouncing vacuum gauge could indicate a sticky or leaking valve. Can you perform a leak down test? Did you pull a plug wire, one cylinder at a time, and notice a cylinder not responding? Good luck
 
This sounds like a Valve Problem to me there could be one or more that are sticking some or a Valve guide that's a little to tight or a looser one, another thing that can cause this is if there is a Spark Plug Gap that isn't set correctly i.e. it's set too tight. It's easy enough to check a Ford like yours has the recommended Plug gaps setting of .034. I would also check that your Grounds and Electrical connections are all nice and clean of dirt and or corrosion and are snug or tight. Good luck
 
Thanks!! I did gap the new Plugs to .034 disconnected all the vacuum lines and plugged when I tested. Will check the engine electrical connections ( good thought). Was thinking also valve guides but then thought the swing would be a little bigger.
 
B RON CO said:
Hi, the first thing I would do is check the vacuum advance and vacuum modulator for leaking diaphragms. Besides that, a slow slight bouncing vacuum gauge could indicate a sticky or leaking valve. Can you perform a leak down test? Did you pull a plug wire, one cylinder at a time, and notice a cylinder not responding? Good luck
Click to expand...
Thanks. Yup pulled the plugs wire one at a time and everyone will cause a change. The shake it mild in a sense not quite like a misfire but maybe a 1/4 of what a misfire shake feel like. Still noticeable.
 
After everything you've done, I would be suspicious of the carburetor being out of adjustment. Pull the air cleaner and use your hand (carefully) to slightly restrict the air entering the carburetor while watching your gauge. If you have a trustworthy friend, I would also do this with the car in drive while they hold the brake.
 
yes X2 that could also be from a weak or bad Spark Plug wire or lose end connection, might also be just a simple Carb mixture adjustment too.
 
Does your engine still have both a matching SVC type Carb and the stock Load O Matic Distributor?
 
Yes to the distributor but the carb they just replaced before I bought it. It is a henkyo auto lite 1100. Not the original. I did adjust the air/fuel mixture to try and smooth it out. Turn it out til it got rough, turn in until it got rough then put it in the middle. The float is set at 1 3/32. Could be a junk carb.
 
Basic 1965 Mustang 200 Six Tune specs with a C4 Auto Trans, for the quickest and best results they are performed in this order.

Your engine dose have a very good Compression test results, also not a problem in your case but for reference the Fuel Pump should be putting out 4 1/2 PSI.

1.Plugs gaped at .034 that you already checked good.

2. If you are still using the stock type points get set to a basic .025 Gap then they are set to a Dwell of 38 Degrees. The #1 & #2 settings need to be right before doing the #3 Base timing setting. If you are using a Pertronix than the Gap gets checked during the install not a bad idea to recheck them once in awhile though.

3. Stock Base Timing for C4 Auto is 12 Degrees before that you also set it to. good if your dwell is correct to. You can also go a little more on the Base timing like 14 to 18 degrees depending on your locale area conditions and weather.

4. The correct way to tune the carb is with the engine warmed up good and check that the Choke blade is wide open. Then have the Air Cleaner with a clean air filter installed. The Mixture screw is first set to the highest RPM then turn the mixture screw in 1/4 turn this gives you the Lean best idle. You can do this with your Vacuum gauge to setting the engine first to the highest Vacuum setting then turn your mixture screw in 1/4 turn as above for lean best idle. The Carb is right a warm will start quickly without needing to touch the gas pedal.

5. The Curb Idle setting for Non Calif. Emission Spec's are set to 485 RPM with the Trans in Drive have some put their foot on the brake or make sure the Parking Brake is set and wheels blocked good. Sometimes after a rebuild its necessary to repeat 4. & 5. again to get the best mixture setting and curb idle. Good Luck
 
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Ok good that is the right Carb with a SCV for use with a stock Load O Matic Distributor.
 
Thanks, Need to check the dwell angle but all else should be right on. I did adjust the point gap per the Manual .025.
 
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