Houndstooth

I have seen a couple of similar posts to this but the suggestions seem to be all over the board so I thought I would post my exact situation. Thanks to a well meaning neighbor my timing was way off on my 302. After messing with it for over a week I finally took a good look at my balancer and found TDC (we were using the wrong mark).

The car had been pinging and after re-setting the timing it seemed to run great for a couple of days. Today, I punched the throttle going down the road and it cut out, then popped really loud. I tried it a few times, sometimes it did it and sometimes it was fine. At home I pulled the air cleaner, pushed the throttle and it hesitated, then backfired through the carb. Is my timing still screwed up or do I have another problem?

tempoffroad

sounds to me like you still have a problem with timing check and make for sure that you are at tdc and go from their. i guess it could be a valve sticking (im not that good with motors just trying to help out) if you have a worn out cam or other internal problems correct timing will be hard to get. check your compression.

Gun Jam

You do have a timing light right?
Dont attempt to adjust timing without one

Houndstooth

Yeah, even with a timing light I've had a real hard time getting the timing right. I've replaced the points, condenser, plugs, cap and rotor. Supposedly the motor was rebuilt 10k ago so the cam should be ok but I don't know for sure. If my dist. is bad could it keep throwing off my timing?

Gun Jam

what number are you shooting for at idle?

you should set it to about 10 deg advanced at idle. When you throttle up you should see the timing advance further to perhaps around 14.

so when you set it, after a bit it changes on its own? If so perhaps a new bolt and the locking piece it presses down on is in order. It maybe worn out and not holding the dizzy in place.

You can try grabbing the rotor and rocking it back and forth and see if there is excessive play in the dizzy shaft perhaps a bearing is way out of tolerance.

-Gun

Houndstooth

Thanks for the help. I have it set at tdc so I will try advancing it a little. It does seem like I get it right and then a couple days later it runs crappy again. I'll try replacing the piece that locks it down too.

Gun Jam

Remember just because piston 1 Is TDC doesn't mean spark is being sent to plug 1 at TDC (which would be bad)

TDC is a rough estimate used for Installing the dizzy with piston 1 TDC the rotor should be pointing to plug 1...That's it.

After that you use the timing light to zero in the actual timing.

IF: when using the timing light the timing indicator (just above the damper wheel) has the number 0 under it ( the deg numbers stamped ON to the damper wheel) the timing is 0 deg advanced and the spark is being sent to plug one the same instant that piston 1 reaches TDC. The engine should run crappy.

Now rotate the dizzy while watching the numbers on the damper wheel under the indicator . Rotate the dizzy so the numbers begin to count up and stop when you reach + 10 deg.

Now the spark is being sent to plug 1 exactly 10 degrees before piston 1 reaches TDC... timing is now 10 deg advanced and the engine should run better.

Tighten everything down and rev up the engine..you should see the timing automatically advance towards 14 or 15 degrees as rpm increases.

If yes drive the car around. If it gets crappy again check the timing before touching anything and see if its still at 10 deg adv at idle.

happy hunting.

-Gun

Houndstooth

I advanced the timing to 10* and the hesitation and backfire is gone but it is now pinging at WOT. I backed it off a couple of degrees and will try again this afternoon when I can get to an open road. I think my curb idle might be set too high but I don't have a tach so I'll have to get one.

I still think I am going to replace my dist., any thoughts on Pertronix v. Mallory v. MSD? Thaey are all around the same price.

67mustang302

Sounds like the carb may be lean.

bodyputtyless

Is the backfiring coming from the exhaust or back through the carb? back through the carb is an indication that your coil is not working properly.