[Doc4421]

Folks,

I've been working to restore the ol' Mustang and I've hit a snag. I usually gun the engine twice before I shut her off and usually, nothing bad happens. Today, however, I got a major backfire. When I looked under the hood and cranked her up a couple times, I saw a flash between the couplings that hold the exhaust to the engine along with a pop.

I had been working under the hood most of the week and when I pulled the valve covers, I had to remove the spark plug wires. I checked them all and they were all in the right order. I then went to the supply store and bought a new set of wires (when I pulled one, it gave funny, so I thought I'd have screwed something up there). Changed them and the plugs: no better.

Here's what I've done to the car as part of the restoration recently. Anything that you see that raises a red flag or anything that might be causing this would be appreciated:

- Replaced valve seals
- Painted the fire wall.
- Painted the valve covers
- Cleaned gunk out of valve covers
- Painted the air cleaner system
- Oil change
- Replaced plugs and wires
- Replaced choke tube (old one broke)

If you've got ANY idea as to what's causing this and any step-by-step instructions on how to fix it, I'd greatly appreciated it.

Best,

Doc

[Veronica]

Hello. Are you talking about where the exhaust manifold bolts to the cylinder head or where the pipe bolts to the exhaust manifold? Either way, it's an exhaust leak, but, if it's where the exhaust mainfold bolts to the cylinder head, you could have a scorched valve which isn't seating properly anymore. I would start with fixing the exhaust leak and see if that helps. It would be a very good idea to stop doing that 'gun the engine twice' thing. That's the source of the fuel for that flash. You're pumping a lot of fuel into the system right before you shut it down. The motor doesn't have enough time to clean out the unburnt fuel. That is going to cause your plugs to foul and need replacing far more often than they should, and the accumulation of raw fuel will still cause that backfire sound, you just won't be able to see the flash after you repair the exhaust leak.

[Doc4421]

I am uncertain which it is, but it's right by the engine itself. Again, I'm kind of a moron on this end.

If it is an exhaust leak, what can I do to solve this problem?

Also, it only seems to happen when the car is parked, not when I'm driving.

Am I harming the car by driving it and how do I fix this?

[Print Dad]

What's up doc? - sorry i couldn't resist.

It sounds like you need some help here. I am thinking you are young or very new to working on cars. This is not a big deal.....we all started from knowing nothing.

Veronica is right...cool it with the revs. as she explained it is not good for the motor.

Now we get down to business
1. - I think perhaps what you did was replace the valve cover "gaskets" and not the valve seals. I point this out so that you will know the difference adn others won't think you messed with the valves themselves. That could lead to other issues.

It would be very helpful if you could post a few pictures of where you are saying the leak is from.
I have so many suggestions for you that i am not sure where to start.
1. - Get a motor manual for your year car. This will help you with terms and will have lots of info to help you.
2. - When you installed the spark plugs did you "gap" the plugs before you installed.
Some people think the plugs are set at the factory. When you installed the plugs did you tighten them up enough?
3. - Do you understand and know what the fire order of the motor is?
it is vital that the spark plug wires go to the correct plug in the correct order.it is easy to get this wrong if you are just starting out. I also would suggest until you get a bit more experience, change one wire at a time.
4. - Do you know if the motor has headers or stock exhaust manifolds?
5. - Did you do anything to the exhaust? There is a gasket that goes between the motor (head) and exhaust manifold.
6. - Check to be sure that all the bolts on the headers or exhaust manifold are tight.

I think it is likely, you have messed up the wires. All the other things you list except the choke tube are considered cosmetic and would not affect the motor.

Do you know how to find TDC of the number 1 cylinder?
If you do....then I would take #1 to TDC on compression stroke....the timing mark will help you.. Once the #1 is a TDC...lift off the distributor cap and see if the rotor point is under the # 1 spot on the cap.

Your firing order is 1-5-4-2-6-3-7-8 (Number 1 cylinder on right bank, nearest radiator)

As you look from the front of the car at the engine, the cylinders on the passengers side closest to you is NUMBER 1, then 2, then 3 and the one farthest back is NUMBER 4.
The drivers side the closest one to you is NUMBER 5, then 6, then 7 and the farthest one in back is 8
REMEMBER THE DISTRIBUTOR ROTATES COUNTER CLOCKWISE!

Check to see if the wires go to the correct cylinder. It is easy to mess this up. Just start with # 1 and then go counter-clockwise. So the next wire should go to the first cylinder on the driver side (#5) then your next wire goes to the last cylinder on the pass side (this is #4). Follow this procedure till all the wires are checked.

I will stop at this point as I think you have enough to do. Check the wires, recall if all the plugs are gapped correct ( .034).

I am sorry if this post seems to simple for you. I will of course continue with more advanced posts but ....... if there is anything in this post you don't understand....please just ask.

A long time ago, I was a young kid messing up just about everything I tried to do.
I will never forget all the people who helped me learn.

Once you check these few things we can move forward. You may need a vacuum test, compression test etc. Don;t be concerned with that yet. Let's see what yo find... Print DAd

[Doc4421]

Print Dad-

Thanks. You're about half right: I'm not very young (or at least as young as I would like to be) but I am very green. 30-second recap of life: Wanted to be a mechanic, went to work in a garage with a guy who let me do oil changes, tires and an occasional spark plug swap. Every time I tried to learn something, he'd say, "Just let me do it." Dropped out of there and went to college instead. Having an early midlife crisis so I'm back to my roots of wanting to play under a hood.

With that in mind, let me go through a couple things. I really do appreciate the simplicity of the post. I am dumb as hell with this. Even when I did stuff at the garage, the guy would tell me, "Look, here's what you do. Now do it." I was literally a grease "monkey."

- Revving: Understood. Will stop that right now if not sooner.

- Valves: Yes, good grief, am I dumb. I meant valve gaskets. That was harrowing enough. I wouldn't mess with the inner workings of the engine. On the plus side, I must have done OK with them, as they're not leaking.

- Attached is a picture of where I'm seeing the flash and hearing the pop. It's where the pipe (I'm pretty sure the exhaust. attaches to the engine just behind where the choke tube is. (that's why I figured it was something I screwed up with the choke tube).


- Manual. Good tip. I ended up buying two a few weeks ago. Still learning to read the stuff, but some things make sense.

- Plugs: Gapped them to .035 like the guy at the parts place said. To clarify, this was happening before I changed the plugs. I changed them and the problem is still happening.

- Wires: I numbered the wires when I took them off and put them back in the same order. I checked the diagram for firing order when I noticed this problem. The order was right. That's why I figured I screwed up the wires themselves. I changed the wires one at a time, rechecked the order and was still right. I'll check again, but I'm not thinking that this is it.

- Exhaust: This was literally the car that was owned by a little old lady who only drove her on weekends. She bought it in 1968, owned it her whole life, stuck it in a barn for 15 years and then it came out for sale when she died. The dealer from whom I bought it did most of the tune up work to get the engine to run well. The exhaust, I'm assuming, is standard. They didn't put much onto her in terms of anything beyond need stuff. I didn't do anything to the exhaust.

- Tightening stuff: Will do. Havne't done that yet.

- Tap dead center: Don't know how to do that and I don't have the gun to measure timing. How hard is this?

Is she safe to drive? Am I doing damage to my car if I keep running around with this going on? She seems to handle great when I'm out driving around and this only happens when I'm in park and I give the engine a couple quick bursts. (Yes, I'll stop that, but something tells me it shouldn't be happening anyway.)

More advice would be greatly appreciated. I really do love the help here!

[Veronica]

Hi again. Here is the picture that you posted with a couple of marks added to it. Are you seeing the flash in the area with the red stripe or the the area with the green arrow pointing at it? If the it's the area with the red stripe, that means that you need to replace the donut gasket. If the flashing is in the area indicated by the green arrow, that means that you need to either replace the exhaust manifold gasket, or, it means that the exhaust manifold is cracked there, and will need to be replaced. It kind of looks like it might be, but, it's hard to tell. None of those are complicated things to do, but, they all can be very aggravating.

[Doc4421]

Hi Veronica-

Thanks for taking the time to help me. You have no idea how much I appreciate it.

It's in the area where you've got the red line, so it sounds like the donut gasket.

How does one go about replacing this? How hard is this?

And do you think this will solve the problem?

[Print Dad]

Hello Doc,
I was just about to send a picture and see Veronica has already done that.

As far as changing the donut gasket. You have 2 options.
Option 1 - is to remove the bolts that hold the exhaust manifold
to the head....then pull the manifold and replace the donut.
The problem with this is you could wreck the gasket that goes between the
manifold and the head. The manifold is held in place with the 8 bolts
on both sides of each runner (near the green).

The second option is to take the 2 nuts off the crossover pipe. These are the 2 bolts to the left of the red line. You may have to do this on both sides of the motor because the pipe called a "Y " pipe goes to both heads.
It forms a Y and then goes to a single pipe and then the muffler.
This is of course if you have single exhaust.

If you pull the nuts off both sides, you may be able to push the pipe toward the rear of car enough to get the gasket off. I am fairly sure this will work. In the worse case, you may have to drop a hanger near the muffler, but I really don't think you will have to. In my opinion this is the way to go.
The nuts could be hard to remove and you may want to apply a little heat with a blow torch. OF COURSE be very careful with flames.

I think your timing and wires are probably fine. What you may have is a valve that is a little sticky from sitting for many years. This is common.

What you could try is to use a little "seafoam" in the carb. This product can be found at local parts stores. Follow directions but be aware the car will smoke for several minutes.

See if you understand the gasket replacement and try that. If at all unsure post back. I almost forgot, the nuts on the exhaust may unscrew the bolts they are attached to.....No problem there. Just remove the 2 studs.
I would try to remove the pass side and see if you can slip the donut out. It just slides over the pipe. It will take a screw driver and a little force but it will pop.

If unsure of anything....Post Back...... Print Dad