Jon O.
Well-Known Member
I have a 72 Newport. My grandfather came and looked at it today and told me that it sounded like it was running on 7 cylinders. How do I tell if I really am? Ill try posting a video tomorrow. He could be wrong too.
Running on 7 cylinders
- Thread starter Jon O.
- Start date
bigmoparjeff
Senior Member
The best way to check it is to have it tested on an engine analyzer. Finding a shop with one is tough to do these days.
You may want to give the car a tune-up: new plugs, wires, cap & rotor, and see if that helps. A vacuum leak can also make the car run rough. I'm assuming you have a 400 2bbl in the Newport. The Holley two barrel carburetor used on that engine is very troublesome, and also a possible source of rough running.
Jeff
You may want to give the car a tune-up: new plugs, wires, cap & rotor, and see if that helps. A vacuum leak can also make the car run rough. I'm assuming you have a 400 2bbl in the Newport. The Holley two barrel carburetor used on that engine is very troublesome, and also a possible source of rough running.
Jeff
Jon O.
Well-Known Member
Honestly I think it runs fine. It was rebuilt a few years ago. I was told by him though, and he used to be a manager at ammco transmission in the 80s.
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70bigblockdodge
Old Man with a Hat
If it is smooth on acceleration it is probably fine
Jon O.
Well-Known Member
https://www.google.com/url?sa=t&sou...CqEQtwIIHjAA&usg=AOvVaw30relBULYoytdrhgDoBpVu
The car sounds dead on exactly like this. It passed inspection this year.
The car sounds dead on exactly like this. It passed inspection this year.
Xenon
Senior Member
Pull the plugs and see if any are fouled or excessively black...
Then do a compression check on all eight..
This will probably give you the answer you are looking for....
Then do a compression check on all eight..
This will probably give you the answer you are looking for....
The Horvaths
Young man with a cowboy hat
What he said ^
Check your plug wires to ensure they are fully seated as well/are in good condition.
Check your plug wires to ensure they are fully seated as well/are in good condition.
An ignition scope would let you watch each cylinder's plug firing traces. Many of those will allow you to kill cylinders in succession. Then you can watch the tach to see how the rpm drops or doesn't drop as each one is shorted.
The "analog" approach would be to pull each plug off the plug with the engine running. Or from the ignition cap. Just don't bet "bit"! Especially if you're leaning over the fender! Again, the weak cylinder will be obvious as the rpm will not drop when that wire is removed.
Another approach would be to hook a vacuum gauge to a manifold vacuum port. Each time the cylinder "misses", the gauge needle will drop. Won't tell you which cylinder, just that one is not hitting.
When you load the engine against the foot brake, is it still smooth or does it miss? Smooth at cruise but misses on acceleration and/or has lower power on acceleration?
IF there is a burnt valve, the plug will fire normally, but be rough under power situations.
Upon what is this "running on 7" orientation based? Just curious.
CBODY67
The "analog" approach would be to pull each plug off the plug with the engine running. Or from the ignition cap. Just don't bet "bit"! Especially if you're leaning over the fender! Again, the weak cylinder will be obvious as the rpm will not drop when that wire is removed.
Another approach would be to hook a vacuum gauge to a manifold vacuum port. Each time the cylinder "misses", the gauge needle will drop. Won't tell you which cylinder, just that one is not hitting.
When you load the engine against the foot brake, is it still smooth or does it miss? Smooth at cruise but misses on acceleration and/or has lower power on acceleration?
IF there is a burnt valve, the plug will fire normally, but be rough under power situations.
Upon what is this "running on 7" orientation based? Just curious.
CBODY67
Jon O.
Well-Known Member
Not even sure if it is right, I was told by someone that it sounded like 7
commando1
Old Man with a Hat
What's the matter with you guys? Sheesh.
You pull one plug wire at a time and...
GJS
Senior Member
I don't know what your exhaust system is but it certainly sounds more aggressive than that car would have sounded off the showroom floor. I can't make out anything that sounds like a "miss" from that video. It's entirely possible that your Grandfather is mistaking the exhaust sound for a problem.
oliver
Senior Member
Quick easy check: with the engine idling, feel the exhaust flow with your hand at the tailpipe. If the flow is even and smooth, your engine is hitting on all 8. If you feel an uneven flow with hard "puffs", one cylinder could be misfiring.
If that turns out to be the case, then start doing what @commando1 suggested in order to identify the culprit.
If that turns out to be the case, then start doing what @commando1 suggested in order to identify the culprit.
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Let's recap... Grandpa, who used to run an Aamco trans shop says "it sounds like 7 cylinders". I envision a guy old enough to be my.... uhhhh .... brother holding a cane and shaking it at the car.
You post a video of some car in Finland with an exhaust leak at the manifold and say it sounds exactly like your's.
You say you think it runs fine and the engine was rebuilt a few years ago.
Have I got it?
Given those facts, here's my answer....
Two options.
Fix the exhaust leak. If the engine was rebuilt, they probably used gaskets on the manifolds and they've blown out. This will make the engine sound like crap (and how the Finnish car sounds to me) at idle and still run just fine.
You might make it better by tightening the manifold bolts. If the engine was assembled correctly (no manifold gaskets), a bolt or three might be loose.
or...
Leave it alone and drive the car. Eventually, because it will get worse, you'll end up pulling the manifolds, cleaning them up and putting them back on without gaskets (like the factory did it) but you aren't hurting anything.
You post a video of some car in Finland with an exhaust leak at the manifold and say it sounds exactly like your's.
You say you think it runs fine and the engine was rebuilt a few years ago.
Have I got it?
Given those facts, here's my answer....
Two options.
Fix the exhaust leak. If the engine was rebuilt, they probably used gaskets on the manifolds and they've blown out. This will make the engine sound like crap (and how the Finnish car sounds to me) at idle and still run just fine.
You might make it better by tightening the manifold bolts. If the engine was assembled correctly (no manifold gaskets), a bolt or three might be loose.
or...
Leave it alone and drive the car. Eventually, because it will get worse, you'll end up pulling the manifolds, cleaning them up and putting them back on without gaskets (like the factory did it) but you aren't hurting anything.
Hold on now... That's waaaayyy too simple.. We can't have that.
What's the matter with you guys? Sheesh.
You pull one plug wire at a time and...
The variation of this is to take a red shop towel, hold it around the end of the tail pipe, so all flow goes through it. If it's a burnt valve, you'll see a negative pressure pulse and the rag will be sucked into the pipe. Have to look quick! But it's evident as the other cylinders push the rag out and the burnt valve cylinder sucks it in. And that's with "all 8 firing".
CBODY67
Correct, NO exh manifold gaskets between the exh manifold and cylinder head. On our '66 Newport, it has a "tick" on light acceleration, but it went away when the rear exh manifold bolt was tightened about a 1/4 turn or so. That's with the OEM cast iron manifolds, headers do need a gasket (hopefully the "black one" with the higher-heat material and an internal mesh).
CBODY67
CBODY67
Jon O.
Well-Known Member
He is more like one of those people that thinks they know everything and finds a problem in everything when they really know nothing - but that's a different story. Even though I think he was pulling something wrong with the car out of his ***, I figured I would ask because it could be a problem if he really was right. Obviously you all know much more than me about these cars - or I wouldn't be here. (Thanks for all of your knowledge by the way.) I posted that video because that is what sounded closest to my car. So are you suggesting that I tighten the bolts on the manifold?
Yes, tighten the bolts... You have nothing to lose.
If there is no gasket, it could quiet it down. If there is a gasket, it may or may not help. Definitely can't hurt.
Jon O.
Well-Known Member
Thank you.
- There aren't a whole lot of 70s Chryslers rolling around so I am not sure what it should sound like anyways.
oliver
Senior Member
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