[BrianBodzenta]

You don‘t have to have a PCV. A lot of guys just run filters on those. I wouldn’t think that is your issue.

I know the PO tinkered with a lot of stuff so I wouldn’t check those things off the list. There are plenty of new parts that I’ve put on that take a lot of work to get running properly. Unfortunately with all the things that have been touched you really have to run down the entire system from fuel tank line to pump to filters to carb to timing to vacuum lines and such. Make a big list and just start checking stuff off.

What’s your vacuum pressure at idle (check when warm) and is it steady?
What is your cold idle?
What is your hot idle?
What is your initial timing?
When does your timing advance come on and how much advance does it give?
Does your choke close properly and then how long does it take to electronically open?
Check fuel pressure in the lines, should be 4-7psi.
Float set properly? Open it up and make sure there isn’t debris in there (If he replaced all the lines, typically you want to purge the lines with a gallon or so before hooking it to the carb.)

I’m betting one of those gets you on the right track.

Follow Milliagan’s recommendations above this will provide yourself with more information to diagnose the problem.

 

[daveplatt]

So I agree that the PCV may be the issue, but its not likely. Like Matter stated the PCV ports/locations can be left open, the engine will run the same. This is not true for the port on the carb spacer that the PCV hose connects to. If this port is left open you will have a vacuum leak which will cause the engine to run rough. Was the port on the carb spacer plugged or left open?

There are many possible causes for the issues you are experiencing. Likewise a lot of good information has been listed above. Be sure to diagnose the issue first. Do NOT throw parts at the problem hoping for a solution, this just causes aggravation. Additionally when the time comes only change one part at a time this way you know for sure what fixed the problem. This will allow you to expand your knowledge and will make diagnosing issues easier in the future.

The chances of this being your timing chain are very unlikely. Perform a compression test first. Yes a replacement timing chain is cheaper than a compression tester but like I stated above knowledge is power. Additionally what happens the next time you have engine troubles?

Keep in mind a timing chain replacement requires new oil, coolant, gaskets, and a harmonic balancer puller at the minimum assuming you have basic hand tools. This all adds up and the more you spend the more aggravating the hobby becomes...

Just food for thought.

I appreciate the reply. So the hose from the carb wasn’t left open, it was run to a PCV valve which was stuck into the oil cap. The valve didn’t seat in the grommet properly, and wasn’t even completely in. I’m assuming this caused a vacuum leak? It needed to be addressed anyways so that’s what I’ve been doing for the last hour or so. I’m not convinced that it’s the timing chain either.

 

[daveplatt]

This is what it looked like before. The hose connected to the PCV ran to the carb.

 

[Matter]

For diagnostic purposes you could plug the fitting at the base of the carb and see if that helps your drivability issue. Won't hurt a thing but it may run a little rich. Just leave the pcv in wherever it is or leave it on the workbench if you want, it doesn't come into play with the port plugged.

 

[daveplatt]

For diagnostic purposes you could plug the fitting at the base of the carb and see if that helps your drivability issue. Won't hurt a thing but it may run a little rich. Just leave the pcv in wherever it is or leave it on the workbench if you want, it doesn't come into play with the port plugged.

I might go ahead and try that. At this point why not, it’s nothing but time. I’m not sure when I’ll get to it but I’ll let you know how it goes!

 

[awhtx]

If the timing chain has jumped 1 tooth the engine will not run with the timing set at 10* or 12* BTC.
The timing chain in my '69 Mach 1 jumped 1 tooth causing the engine to die and I had to reset the timing to get it started again. A few days later it jumped another tooth and resetting the timing would not get it started. I was forced to replace the nylon tooth cam gear that had worn teeth.

 

[daveplatt]

If the timing chain has jumped 1 tooth the engine will not run with the timing set at 10* or 12* BTC.
The timing chain in my '69 Mach 1 jumped 1 tooth causing the engine to die and I had to reset the timing to get it started again. A few days later it jumped another tooth and resetting the timing would not get it started. I was forced to replace the nylon tooth cam gear that had worn teeth.

I’m sure that my chain is worn but I don’t think it’s skipping teeth. My engine starts up like a charm 3/4 times and doesn’t have an issue until heavy acceleration.

 

[BrianBodzenta]

I’m sure that my chain is worn but I don’t think it’s skipping teeth. My engine starts up like a charm 3/4 times and doesn’t have an issue until heavy acceleration.

I agree if your engine has ever been rebuilt there is a good chance the nylon timing gears have been replaced therefore timing chain skipping teeth is a very rare problem.
I agree with awhtx the nylon gear design wasn’t the beat idea and many have had timing chain slipping issues.

My point is run as many teats as you can first and learn what each one of them is telling you. Id take a look at your spark plugs as well and check to make sure your points are operating as desired.

 

[daveplatt]

I agree if your engine has ever been rebuilt there is a good chance the nylon timing gears have been replaced therefore timing chain skipping teeth is a very rare problem.
I agree with awhtx the nylon gear design wasn’t the beat idea and many have had timing chain slipping issues.

My point is run as many teats as you can first and learn what each one of them is telling you. Id take a look at your spark plugs as well and check to make sure your points are operating as desired.

I’m not sure if the engine has been rebuilt before or not. I can send the P/O a text and ask him. Points were replaced in May, I will check them anyways and make sure they’re set properly. I changed the spark plugs and plug wires a few weeks ago. I gapped them to .035 and double checked before installation…those should be fine. Removed the nasty Bosch platinum plugs and put Autolite coppers in, someone mentioned copper is best for these older engines since that’s what they were originally made with.

 

[BrianBodzenta]

I’m not sure if the engine has been rebuilt before or not. I can send the P/O a text and ask him. Points were replaced in May, I will check them anyways and make sure they’re set properly. I changed the spark plugs and plug wires a few weeks ago. I gapped them to .035 and double checked before installation…those should be fine. Removed the nasty Bosch platinum plugs and put Autolite coppers in, someone mentioned copper is best for these older engines since that’s what they were originally made with.

I agree that the autolites are fine and I’m not telling you to re gap the plugs. Im telling you to read the plugs to see if the engine is running rich or lean…

 

[daveplatt]

I agree that the autolites are fine and I’m not telling you to re gap the plugs. Im telling you to read the plugs to see if the engine is running rich or lean…

Gotcha. They’re all very dirty but they’re not overly fouled like you’d see with a rich mixture. They actually look pretty clean. Cylinders 3 and 6 have a white ground electrode. There isn’t that sandy buildup, just white color.

 

[kellysedars]

I skimmed this and didn't see any mention of a possible power-valve rupture on the backfiring that you've had. Sometimes the pressure of the backfire will rupture the diaphragm in the power valve rendering it useless from that point forward. This would certainly cause further problems on acceleration, may make you chase your tail a bit. Easy enough thing to change too. Just wanted to add that to the list of things to check.

 

[Matter]

A weak ignition can also cause the symptoms you describe. When you accelerate you have a richer mixture and if you ignition is weak it will be unable to fire completely. Possible coil, coil or plug wire and your new points, cap, rotor are even a possibility.
Just usually an intake backfire is mostly symptomatic of a lean issue.

 

[daveplatt]

A weak ignition can also cause the symptoms you describe. When you accelerate you have a richer mixture and if you ignition is weak it will be unable to fire completely. Possible coil, coil or plug wire and your new points, cap, rotor are even a possibility.
Just usually an intake backfire is mostly symptomatic of a lean issue.

Yeah that makes sense to me. I was looking into all the Pertronix stuff as I’ve heard hood things about their products. I wasn’t going to replace anything since it was all new, but maybe it’s worth looking into. Is there an easy way to test whether the ignition is weak? At this point i’m open to trying just about anything, but I think I need to get some better tools to run some tests like someone mentioned I should.

 

[Matter]

You can hook up a timing light, tape the trigger down and tape it to your windshiield and go for a test drive. Watch the light and if it stops blinking or is erratic when the car is missing that is a clue. If it does it on a plug wire, then move the induction clamp to the coil wire and see if is does it there. That will help isolate the problem.

 

[daveplatt]

You can hook up a timing light, tape the trigger down and tape it to your windshiield and go for a test drive. Watch the light and if it stops blinking or is erratic when the car is missing that is a clue. If it does it on a plug wire, then move the induction clamp to the coil wire and see if is does it there. That will help isolate the problem.

Wow. I would have never thought that would work. Thank you, I’ll try it out.

 

[awhtx]

The yellow spark indicates weak ignition. It should be blue, look like a lightning bolt and jump across a minimum of a 3/16" gap.

 

[Matter]

The yellow spark indicates weak ignition. It should be blue, look like a lightning bolt and jump across a minimum of a 3/16" gap.

This when you check the spark at the coil wire or plug wire, should be a very audible "snap" at the spark.

 

[daveplatt]

I plugged the port on the back of the carburetor and went for a drive. Started right up almost as easy as my 2019 Jetta. No stalling on the first accel, and no popping from the carb when I floor it. Runs like a Mustang should. There is still a slight hesitation but I’m guessing that’s due to my mixture and timing. Thank you all for the help and suggestions, I’ve learned quite a bit just by reading your responses. Happy driving

 

[Milligan]

Good news! I’d recommend getting yourself a vacuum gauge, they are only around $15. A vacuum gauge can tell you stuff like that instantly and much more. They usually come with a little sheet to tell you what the different readings mean.

The hole on the back being unplugged would have had your idle vacuum below 10 I’m sure which would have been the read out of the bottom left on that chart. Very handy to start with for troubleshooting!