jeffkilgo

I have a 66 Mustang Hardtop with a 200 six and C4 Auto Trans (owned about 4 months now). I just tuned it up earlier today...new points, plugs, condenser, rotor...waiting on the new distributor cap and plugs wires. I adjusted the timing to 12 degrees as per the manufacturers specs and the car starts and seems to run much better than before. Unfortunately though I noticed some loud valve chatter when I get in to the gas. I didn't have this before and was wondering if anyone had any thoughts about what I can do to correct this. Of note when I tested the timing after installing the new parts I noticed that it didn't register...way below TDC. I figured the timing was off but didn't think it was off that much. I'm petty sure that the timing is at 12 degrees now...just want to solve the valve chatter issue. Thanks in advance. Jeff.

MonsterBilly

check your firing order. If the distributor is off a tooth or the plug wires are a terminal off, that may explain the timing mark not lining up. So, when you adjusted it to where you think is 12* it may actually be far off.

jeffkilgo

Thanks...I'll give this a check. Supposed to get new plug wires today so it will be easy to make sure they firing order is correct.

Xargon321

also if it is a old damper the outer ring could have slipped as the rubber gets old. might have to find TDC on #1 piston and check to see if the timing mark is at 0

jeffkilgo

My timing light has an adjustment dial on the back that allows you to dial in a certain timing setting...I'm assuming this is for engines that have a limited range on the harmonic balancer scale. When I timed my engine I started with the dial on zero and adjusted the timing to 12 on the engine scale. When I turn the dial on my timing light to 12 the timing mark goes to zero...I was assuming this was an indicator that the distributor was installed correctly...any thoughts?? I'm going to replace the distributor cap and plug wires today...so I'll see if this makes a difference. Also I noticed the new points I installed were of a much cheaper quality than was was in the car originally...I'm wondering if these new points are defective somehow.

scott_m_mil

Ditto on timing being off. Its also possible you have now advanced the timing far enough to be getting pre ignition ping. VERY BAD. That being said my 66 200 that was just rebuilt is set to 12 degrees. But I also know that my timing mark is correct since I just put the engine together. Try taking the timing back to say 10 degrees and see if it goes away. If it is pre-ignition and you are 100% sure you're at 12 degrees it could be cruddy fuel causing pre-ignition. A premium fuel (which you shouldn't need for only 12 degrees), or fuel from a different gas station could remedy the problem.

Another possibility, though a longer stretch is that with the added advance you've been able to get higher into the rpm range. Doing so on an engine some mileage on it can cause you to get the piston higher into the cylinder causing the top piston ring to hit a lip that has built up in the cylinder, breaking the piston ring. I did this on my old 200 when I switched to an electronic ignition. That's what spurred the rebuild

jeffkilgo

Roger all...thanks. I re-timed my engine a few days ago and dropped it back to 6 degrees...surprisingly this helped quite a bit. It still appears from the timing light that the timing mark is accurate...but I wouldn't swear to this. The bad gas theory may have something to it...we can only get the ethanol blend here in this part of Virginia and I've always wondered if this could be an issue. I will probably try the mid grade blend next fill up and take your suggestion for a different brand of gas. Definitely a perplexing problem...thanks for weighing in...I'll update my post later when I try the differenet gas

scott_m_mil

I'll be interested to hear after a fuel change. Just a couple of extra notes:

The way many old school racers adjusted timing was to turn it up until ping and then bring it back a few degrees. I wouldn't be surprised if you could get 8 or 10 degrees.

All say 87 octane fuels are not created equal. I and several others I know have better luck with one brand of gas vs. the next. Old gas is also very bad, caused me some issues last spring.