Backfiring

[Tommyt]

I have recently purchased a1971 Mustang Mach 1 with a 351 Cleveland. I haven’t been able to get it running yet. New points, condenser, coil got it started. I keep getting a backfire on the 1-4 side. Have shot fire out the tailpipe a few times. Cyclinder 1 and distributor line up tdc does not. I’m guessing cam has been changed. Have tried two carbs 750 and 600. Tried new wires still got backfire. Plugs were new but will try new again on them the 750 was too rich and I believe I ruined those. Should I try a new carb? Afraid I’ll mess it up with a backfire. Am I overlooking a simple? Any help ideas appreciated.

 

[ArtBBQ]

I have recently purchased a1971 Mustang Mach 1 with a 351 Cleveland. I haven’t been able to get it running yet. New points, condenser, coil got it started. I keep getting a backfire on the 1-4 side. Have shot fire out the tailpipe a few times. Cyclinder 1 and distributor line up tdc does not. I’m guessing cam has been changed. Have tried two carbs 750 and 600. Tried new wires still got backfire. Plugs were new but will try new again on them the 750 was too rich and I believe I ruined those. Should I try a new carb? Afraid I’ll mess it up with a backfire. Am I overlooking a simple? Any help ideas appreciated.

The backfire tells me that it's out of time. I would verify that you have the distributor and the timing set correctly before trying a carburetor?

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[Don C]

Check for correct firing order. The distributor rotor rotates counterclockwise and the firing order is 1-3-7-2-6-5-4-8. The passenger side cylinder numbering is 1-2-3-4 and the driver side numbering is 5-6-7-8.

 

[Kilgon]

As mentioned above it sounds like a timing issue.  Shooting fire out the exhaust would indicate ******** timing or a bad exhaust valve.  Backfiring out the carb indicates early timing, foul plugs or burnt valve.  I would make sure you are bringing number 1 to tdc and that you are not 180 out.   Rotor turns ccw so to advance the timing you need to turn the dizzy cw. With having fire shooting out the exhaust I would consider doing a compression test to make sure you don't have any valve issues. Plugs will burn off once you get the engine running correct unless they are extremely fouled.   Replacing the carb is not the answer.  

 

[Tommyt]

Sound advice thanks. Watching that fire come out the tailpipe not a good feeling. The engine is the h code 2barrel and has had the edlebrock 4 barrel installed. I’m gonna plug the vacuum port temp. To eliminate that as my source of back fire. I’ve been doing the blow your finger out of number one and set the distributor at number one. I have wondered if I might be off by one notch. When I get it running the dist. is pushed into the radiator hose. That means I’m pushing the dist. in a cw direction. Thanks for your help. I’ll drop in some clean plugs and stick with 600 carb as I move forward. Thanks again Tom

 

[Tommyt]

Timing is direction I’m going thanks for all the replies I’ll add posts as I go. Great to have this site. To the guy in Michigan your red Mach is super sharp. I have a friend with a m code 4 speed strong engine 

 

[Kilgon]

Sound advice thanks. Watching that fire come out the tailpipe not a good feeling. The engine is the h code 2barrel and has had the edlebrock 4 barrel installed. I’m gonna plug the vacuum port temp. To eliminate that as my source of back fire. I’ve been doing the blow your finger out of number one and set the distributor at number one. I have wondered if I might be off by one notch. When I get it running the dist. is pushed into the radiator hose. That means I’m pushing the dist. in a cw direction. Thanks for your help. I’ll drop in some clean plugs and stick with 600 carb as I move forward. Thanks again Tom

If you are turning cw and hitting the rad hose to get it running then I would say you are off a tooth.  Trying resetting the dizzy by moving the rotor one tooth ccw.

 

[Tommyt]

Will do 

 

[Carolina_Mountain_Mustangs]

You did not say you changed the dist. cap either. After you are sure you are timed correctly and if you still have an issue try spraying the inside of the dist. cap with WD-40 if there is a crack it temporarily keeps from cross arching. If if helps get a new cap and rotary button. If the car has not been ran in a while make sure the points plate in the dist. if not frozen and can rotate. Also if it has not been running in a while you might have stuck or sticking valve. Pull the valve covers and check for bent push rods which are caused by stuck valve. If a valve is stuck open the piston will hit for sure and you will have to pull head and replace. They will snap off the head from flexing if bent. 

 

[Tommyt]

Update- all the easy ones eliminated. I have her at a shop. We got it running but it’s up and down like half the cylinders are working. Mechanic thinks maybe timing chain incorrect.

 

[Jeff73Mach1]

pull the valve covers and check for a valve that isn't moving or isn't moving fully, sounds like a bad cam lobe to me.

 

[Fabrice]

@Don C

" the firing order is 1-3-7-2-6-5-4-8"

I just realise I can never remember my own phone number, but know my 351c firing order by head

 

[Don C]

Yeah, we tend to remember the important things. No reason to remember your own phone number, unless you like calling yourself

 

[Stanglover]

I remember numbers.......... it's names I have trouble with!!

 

[Don C]

I hear you about the names. Back when I was working full time I received a lot of phone calls from people I didn't know, if I didn't write their names down as soon as they introduced themselves by the time the phone conversation was over I would have forgotten their names. Same way with face-to-face introductions. Faces I remember, just not always the name that goes with them. After I read someone's name I usually remember it. Name tags at conferences were great.

 

[Tommyt]

I did pull the valve covers and every cylinder was functioning. The one before me has been trying to get it to run for 3 years. Good chance something assembled incorrect, or maybe oil without zinc has been used. 

 

[Kilgon]

If you done all the above then at this point I think your best bet is to bite the bullet and pull the timing chain cover and see what is going on in the valve train.  If the timing marks are off by one tooth you can still get an engine to run but it will not develop full power and will exhibit the problems you are having.  I know it's a lot of work but you can continue on getting no where or start here and know exactly what you have.  If the marks are off problem solved.  If not off then pull the cam and  check all the lobes.  If all does check out ok then at least you can eliminate that part of the system.  Good luck.

 

[Stanglover]

I hear you about the names. Back when I was working full time I received a lot of phone calls from people I didn't know, if I didn't write their names down as soon as they introduced themselves by the time the phone conversation was over I would have forgotten their names. Same way with face-to-face introductions. Faces I remember, just not always the name that goes with them. After I read someone's name I usually remember it. Name tags at conferences were great.

Yes, I'm the same way, but I too easily forget faces as well. The other day when I was getting gas in the Mustang, two separate people started talking and called me by name, who were they? No clue, but I know I should have known who they were. I would have felt a right *** asking their names, so I just bluffed it. If people had numbers, I wouldn't have as much difficulty.

Now, back to Tommyt's post.

 

[Tommyt]

Finally. Bad distributor. Learned all about pulling the cover and checking timing chain. Can’t see anything wrong visually with the distributor but the new one fixed it right up.