I am having trouble dialing in the timing. Static timed to 10 deg BTDC. Engine is running rough like it’s missing. Have tried plugs, wire set, cap, rotor, ect. Has an intermittent tapping that could be pre-ignition but not sure. Recently had head off. Valve timing is spot on with good compression. I’m not sure what to try next.
Thanks
Make 100% sure that you have the firing order correct: if you do, then what you should do is, with the engine idling, pull individual spark plug wires off the plugs with insulated pliers and isolate which cylinder or cylinders are not hitting.
…That’s a good plan to find misfiring cylinders. With everything you have done…it would be good to know if it was the same cylinder…or random. Most of mine occur at startup. Sometimes it pops in and out…and may clear up. If you don’t wait too long…you can lift the bonnet and run your finger down the Exhaust Manifolds. ’ Ouch - Ouch - Warm - Ouch - Ouch - Ouch '. … If you wait too long, the Cast Iron distributes the heat and it is all hot. You can use one of those neat Laser Pointer Temperature Sensor Guns to locate the cooler Exhaust Runner…but it’s not as much ’ Fun '.
" Recently had the head off " Any chance of Intake Leaks…lean conditions?
Ran well before recent work?
Have you timed it with a strobe timing light?
With a strobe, you will immediately know if your problem is ignition or fuel related.
In addition to setting the timing, you can put the strobe on each spark plug wire in turn and see if you get a regular spark for each firing. If not a regular spark, then you have found the problem in ignition.
Dennis
69 OTS
Ok so firing order is correct. Did find that I have and air leak in the vac check valve so I plugged line for now. All plugs are firing (checked with heat sensor and timing light). Books aren’t helping with dynamic timing. What should i set it for 10deg BTC? With the vac line to the advance plugged? I also have an intermittent loud tapping (like valve shims not right but it comes and goes and is louder at low idle.
I have recently seen reproduction caps & rotors that touch the pins inside the cap when you turn the distributor. This makes using a timing light near impossible. If left long enough it will damage distributor internals. My fix was to use older original Lucas cap & rotor. Only way to find this is remove the distributor & turn by hand.
Setting timing statically is only good enough to get the car started. Undo the clamp on the dist and, while the engine is running, rotate the distributor.both ways. If idle smooths out and rpm increases, you know it was the timing. Typically as you advance the timing the rpm speeds up and the engine runs smoothly. Some guys set it that way - that is advance to where it is idling the smoothest with the max rpm. Back off the dist. 5 - 8 degrees and you are there. Listen for detonalion under heavy throttle in the 2500 - 3000 rpm range, and retard if necessary.
Could be a loose tappet sleeve. Try identify where with a stethoscope, probably on the exhaust side. Will need a stake down kit, search for a number of posts on that subject.
I set my timing at 10 degrees advanced with a timing light. This gives good results. A bit more (say 12 deg) might be even better. With this car the vacuum port on the front carb is not open until the throttle is open a small amount. In this case we don’t need to plug the vacuum line to set the timing with a light. The SU blocks it for you.
Thanks for all the help. Curently set at 12 deg btdc. seams to idle well but still is a little bit rough. no tappet noise until it warms up. them there is a random noise that will come and go. did install hold down kit on exhause side.
Thanks
Paul
I put the tapet guide hold down on my car when it was rebuilt around 10 years and 22,000 miles ago. This is working well. When the engine was dismantled 5 years ago to fix low oil pressure (long story) we found a broken timing chain roller in the pan. Close. If the lower timing chain breaks the engine will never run again.
During assembly 5 years ago we found the lower timing chain tensioner did not work correctly. When bolts were tightened the tensioner was locked. Not good since this tensioner is operated by oil pressure and when locked could not do anything. The car always had a bit noisy timing chain. The bad tensioner came in an OEM box and looked perfect. We purchased another tensioner for 4.2 liter engine (different P/N) and all is now good.
Yesterday we finally got my fuel supply and distributor problems sorted. Car now goes like a rocket and all is well with the world.