popping noise

[airforce guy]

Ok, I had the starter rebuilt, and a quick Re-wire job to the push button start switch that was in place... finally got it started:Brow: , but now I hear a popping noise coming from the engine it appears to stop when the engine is reved up a little.. I think its a valve sticking thats making that sound.. I have not made all the final adjustments, or broke the engine in yet by letting it run for 20-30 minuets @ 2000-2500 Rpm. Any ideas ?? Will I have to tear the engine back down Or will this auto correct once the engine is broken in and timed??:Do No:

[66electrafied]

First question; - did you rewire the entire starter circuit, and if so, did you include a balast resistor?

Your ignition is out of tune, or your carb is. Run the engine up to 2500 for at least 20 to 30 minutes, and shut down. Allow to cool. Restart, and do your final tune. Chances are you will have to make more adjustments as the engine breaks in. But it's crucial that the engine is run up for those first 20 or so minutes to temper the cam. Failure to do this could cause premature camshaft failure.

If you feel confident enough to, do some of the set up while the engine is doing it's primary run-up; - check for vacuum leaks, and play with distributor settings. Hook up a vacuum gauge and turn the distributor to try to reach the highest vacuum that engine will deliver, and then back it off a few degrees; - that should be pretty close to the best setting for a preliminary time without a timing light. Check the dwell. Best dwell angle for a Buick is something around 29 degrees. Too little or too much will affect idle, and possibly give you popping noises. Is the cap and rotor new. or are they the old ones? Are they on properly? These are just some of the things you should check. Here again, using a vacuum gauge, turn in the idle screws on the carb until the vacuum starts to fall off, and then turn them out until you reach the highest number the engine will deliver. That should set your idle close enough to drive.

[LARRY70GS]

Simply hooking up a vacuum gauge and observing needle movement will give you a good indication of engine condition. Vacuum gauges are cheap and a must have item for any one working on engines. Look for a steady needle. Level will depend on whether you have a stock or performance cam. Stock cam will make about 18-20", a performance cam, 13-17". Do you have any valve train noise?

[DaWildcat]

I'm with Marc...don't run it at low speeds anymore until you're finished with camshaft break-in. Hopefully it will run well enough for that. For break-in I try to get ignition timing where it needs to be, and run it at various speeds while watching temp and oil pressure. Have a spotter watch for leaks and smoke.

If timing is right but it still won't rev, it could be a carb/fuel delivery problem which will have to be solved before you can continue.

Devon

[airforce guy]

First question; - did you rewire the entire starter circuit, and if so, did you include a balast resistor?

Your ignition is out of tune, or your carb is. Run the engine up to 2500 for at least 20 to 30 minutes, and shut down. Allow to cool. Restart, and do your final tune. Chances are you will have to make more adjustments as the engine breaks in. But it's crucial that the engine is run up for those first 20 or so minutes to temper the cam. Failure to do this could cause premature camshaft failure.

If you feel confident enough to, do some of the set up while the engine is doing it's primary run-up; - check for vacuum leaks, and play with distributor settings. Hook up a vacuum gauge and turn the distributor to try to reach the highest vacuum that engine will deliver, and then back it off a few degrees; - that should be pretty close to the best setting for a preliminary time without a timing light. Check the dwell. Best dwell angle for a Buick is something around 29 degrees. Too little or too much will affect idle, and possibly give you popping noises. Is the cap and rotor new. or are they the old ones? Are they on properly? These are just some of the things you should check. Here again, using a vacuum gauge, turn in the idle screws on the carb until the vacuum starts to fall off, and then turn them out until you reach the highest number the engine will deliver. That should set your idle close enough to drive.

I did not rewire the whole ignition, I just went under the hood where the wires connect from the push button start switch to the wire(s) coming from the firewall. I have a pertonix coil and "Bug" for electronic ignition.

[tomthacher]

did you put an oil containing zddp to break in the cam??? Please do your self a favor and google this cause the new oils are not good for tappet engines when new(and probably never)

[66electrafied]

I don't know too much about pertronix units, except to avoid them.

However, a vacuum gauge is the cheapest diagnostic tool you're ever going to buy. If you are sure your igniotion is firing correctly, and that the firing order is correct, then I'd check for vacuum leaks. Plug off any unecessary connections except for the line to the distributor. That should be hooked up to the front right about 1/2 inch up from the manifold on a stock four bbl carb. Then check vacuum at idle. It should be anywhere from 16-21 in/hg depending upon the car's tune, and your altitude above sea-level. For every 1000 ft above sea-level, add one point, so 16 becomes 17, and so on. Most vacuum gauges have a moveable dial for this purpose. What you will look for is a steady needle; - anthing else indicates a problem. If the reading is low, (10 or less) there's a definite leak. If the reading is around 14 and the needle swings alot, it could be rings or valves. If you figure the vacuum is low, look for an obvious leak on a hose, or a line. It could be you have the vacuum pump hooked up wrong. So plug off everything except for the manifold port that you're hooking the gauge to and the vacuum advance on the distributor. If you suspect a vacuum leak, place your hand over the throat of the carb when it's running, - if the engine dies, you haven't got a leak; - if the RPMs pick up, you've got a leak. You can then spray carb cleaner around the base of the carb, manifold to head connections, any vacuum port, in order to see if there's a leak. Usually if you spray carb cleaner on an idling engine, it'll kill the motor, (that would be where the leak is) however to be on the safe side, have a fire extinguisher handy.

If no leaks are found, then try adjusting the idle screws on the carb until you get the highest vacuum reading. Start by closing the screws in until the motor just about quits, and then open them up carefully, trying to obtain the highest number possible. This would mitigate too lean an idle setting.

This is all of course, after you've set the timing, and set the ignition up, used new plugs and wires, and the distributor cap is new. One hopes that the timing chain and sprockets are all properly lined up. Set the engine up to TDC using a coat hanger or welding rod in the spark plug hole, and with the valve cover off watching to make sure that both valves are closed. Check firing order making sure that it is set to number 1, which is on the passenger's side front plug. Sometimes the order can be set to fire on the #6 first, but it's better to set it up to #1. Note that this coat hanger trick should be done carefully, and make sure you get it all out and don't bind iit up in a cylinder wall. A nail will run at 0 degrees, but likes 5 BTDC better, but it should start. Here again, with your trusty vacuum gauge, you can maximize your tune. The risk you run into is that you'll plug in too much advance and the motor will ping when you step on it, so be prepared to back it off a bit.

I usually set up a new engine with just a vacuum gauge during the initial run-up, and then do a final better tune once the motor has been run at 2000-3000 RPM for at least 20 minutes to break in the cam. ZDDP in the oil is a must! There are guys shot-gunning cams within the first 1/2 hour of run time because they didn't use ZDDP or run up the motor to higher RPMS. This is a crucial step.

So; there you have it; - try all of the above, and you should be able to troubleshoot that motor. Hope this helps.