70 engine miss

On the intake valves, there is no drip hole. I assume that any oil placed on an intake stem would be sucked into the engine thus causing exccesive smoking and/or oil consumption. Mine was rigged with holes all around but then somebody else went in and soldered up the intake drip holes - I assume that my poor old Johnny had at least two prior mechanics working on her and one wasn't all that bright. Now I'm wondering if I can avoid your problem by making the exhaust valve drip holes larger to help oil up everything in the 'top' end?

I'm just curious to know which valve stuck on yours and if it was due to a plugged oil drip hole for one of the exhaust valves? Thanks.

Sounds like it was the rocker arm that was the actual trouble? When you go to work on it make sure that oil drips from both ends of that oil tube, I suspect that the left (flywheel) side or number one side hole doesn't drip as much as the right. Some of that sludge build up might be inside the tube too, possibly blocking the hole?

The intake valves are the two inner ones and the exhaust valves are the two outer ones. Symptoms would have been wild in any event :) Nice to get a handle on the ole girls' weaknesses like this - Thanks.

~Start with the obvious, open the carb bowl drain valve & see if you have a pencil sized stream of fuel for at least 30 seconds, [if not, find out why, possibly a plugged strainer, either at the carb inlet or strainer assembly].

~Does running with the choke partially closed help the problem? If so suspect a carb internal problem.

~If you are getting black smoke when the problem occurs suspect a malfunctioning choke [just because the linkage is in the off position doesn't mean the choke valve is actually open inside the carb [common problem].

~Make sure there isn't any water in the air cleaner cup. [it doesn't hurt to check the obvious]

~If the fuel flow is good then move on to the ignition... Start with the points, open the gap to about .025" to see if a worn distributor cam or distributor bushing is causing a lack of proper point opening when hot [closed up points will act like it's running out of power & hitting on only one cylinder]. If the point adjustment doesn't help, suspect the condenser is possibly going away when hot [long shot]. It could be a plug wire but they are usually worse when cold & damp. That 70 [unless an LP] uses a 12 volt internal resistor coil & no ballast resistor [you have a 56 so who knows if it's a late one though]. If you have installed a 6 volt coil, or a 12 volt coil that needs a resistor, it might be cutting out when hot. Is the coil getting real hot when the problem occurs? If so, suspect a 6 volt coil or one that needs an external ballast resistor. If you have an ohm meter, measure the primary resistance between the (+) & (-) terminals on the coil & if under 2 ohms it needs a resistor. [if over 3 ohms it has the correct internal resistor].. If the coil isn't getting real hot when it's acting up, try a jumper wire from the [BAT] terminal on the voltage regulator to the non-distributor terminal side of the coil to see if the problem goes away, if the jumper helps suspect a high resistance in the ignition switch, [common on a tractor that sits for extended periods].

~If the ignition system doesn't appear to be the problem see if adding some heat to the carb by setting the manifold heat valve to hot helps. [maybe the carb is freezing up inside].

~If all above doesn't help you might pull the rocker cover when hot & push on the valves to look for a sticking valve [long shot but possible].

~Go through everything & verify that you have good fuel flow, proper operating choke valve, good voltage to the coil, proper coil, points at proper [or even a little bigger] gap, good hot compression, no water in the air filter, & new spark plugs. Something should show up to point you at the problem.

~Let us know what you find?..... .

You might first remove both plugs and observe if each has about an equal blue spark across its gap (both should have about same gap of 0.030 or so) or, if one is better than the other??? If one side always has a hotter bluer spark, I suspect a plug wire or plug or distributor cap problem (carbon track or crack), or maybe a worn distributor bushing or low gap, but I doubt that .

A compression test on BOTH cylinders may pinpoint the problem (if one is considerably lower than the other) to be a cylinder, not an ignition problem.

Then (if both sides compresssion is about equal), before suspecting a bad coil or condensor, I would first try swapping wires and plugs (or just install new Autolite 388's and wires, especially if they arent solid wire core, you need to have them NOT carbon auto supressor type) to see if its still always one particular cylinder that causes the problem, or it was a bad wire or plug etc on that one side.

If after warm up and she starts to miss out, look at the plugs and see if one is all black and sooty or has any apparent shiny black oil fouling problems, while the other is clean and gray (as should be)??? If so, I suspect a cylinder or fuel over an ignition problem.

NOW, if both sides have about similar sparks and compression and no one particular side seems to foul a plug, BUT a warm up still causes missing, THEN I would suspect a bad condensor or possibly coil. Take a look at the points first, however, to be sure they are not pitted or burned or carboned or have a gray coating, (all bad signs) and re gap them or beter yet, replace them if they were burned or pitted . In addition to misses after warm up problems being a condensor or coil, the points can often be the culprit.

TRY Simple things first, like plugs or plug wires, equal compression both sides, clean crack and carbon free distributor cap, then points (clean and gapped or replaced), then condensor, then coil. Good luck, Ol John T Nordhoff in Indiana