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Author Topic: 57 Plymouth Belvedere 301v8 w/ 4brl running poorly  (Read 1073 times)

Robert Rottman

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« on: September 30, 2010, 05:36:35 PM »

I bought the car this way...This is what it's doing...It starts right up fine but runs rough...like it's missing a cylinder. Originally, I just thought it was a bad wire or plug on the passenger side because it sounded like it was missing from the passenger side exhaust pipe. Right away, I noticed the plug on the passenger side closest to the firewall was fouled pretty badly...so I replaced all the plugs and dist. cap but car still ran poorly...no change.  Then I checked all the wires by checking spark at the cap as I pulled the wires one by one. Some wires seemed to have stronger spark than others and the stronger sparks seemed to make a bigger difference as to how the engine ran when I pull them one by one. When I listen to the dual exhausts as the car is running the "miss" is on the passenger side when the engine is cold and moves to the driver side when it's hot. The "miss" sounds like an "extra puff" in the exhaust and the side that exhibits the "extra puff" also is much stronger in flow. Summing it all up...I replaced the plugs, dist cap, checked the wires (they look new)...sanded the points/re-gapped them...checked timing, Looks very steady...did not set it to spec yet. Just watched it for a few seconds and noticed it was very steady...it's not bouncing around at all. History: The car sat for a long time...in humid South Carolina...The guy hardly ran it at all from what he told me...especially the past several years. He bought it in 1985 from second owner in NC and restored it himself in 1995.  Odometer works and it shows 1960 miles....probably 101,960 or 201,960? Anybody got any ideas as to what I can do to it next?.just
 
furyfever2010-10-04 09:37:45
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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #1 on: September 30, 2010, 05:49:48 PM »

Two reasons the spark plugs would foul, being low compression (do a copmression check to compare pressure cylinder to cylinder), or something with the valve themselves (leaking umbrella oil seal or bad valve seat/guide). Even if spark plug wires look good and are flexible, carbon core or suppression core wires can go bad simply by disconnecting them too many times. Another thing to check would be the carburetor itself, ensure the float is set correctly and no junk near the jets. Not positive of what the valvetrain is, but the valves needing to be adjusted may be another option. dana442010-09-30 22:51:12
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Robert Rottman

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #2 on: September 30, 2010, 06:12:28 PM »

Oh...Forgot to mention...I did check the compression on 7 out of 8 cylinders when I replaced the spark plugs...forgot to do 3rd one back on driver side. All were 105-110 psi...Looked up in book, should be 140 when new.furyfever2010-10-04 09:38:13
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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #3 on: September 30, 2010, 06:22:12 PM »

YOu do have adjustable rockers on this 301 A engine, they may be a little bit on the tight side, a couple thousandths can do the strangest things with running smooth, and compression (more than likely the head gaskets are thicker than the stock steel shims and dropped it that way). Just means you could pour a gallon of water in a low tank of gas and she will make it to the next gas station in an emergency (JUST KIDDING ON THAT ONE).
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Steve

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #4 on: September 30, 2010, 06:40:53 PM »

If that extra puff sounds like a ffffttt  ffffftttt  fffftttt, it could be one of two things.  As Ed mentioned, a problem in the heads or poor cylinders.  You could have a burned valve or a valve not closing all the way.
 
The clue to me is the guy hardly ran it.  Therefore I am inclined to think you may have sticky valves.  Take it out for a long ride up 81 and see if that clears it up.  Maybe put some lighter oil in it, 10/30 maybe, before you run it.  It could also be carboned up too.  You can get some decarboning agent and run it down the carb, by the instructions.  The best I ever used was the one from Mopar.
 
Another thing to look at.  With it running take the oil fill cap off and see if you have allot of puffing going on.  There's no PVC, the only thing there is the vent tube.  See if that is excessively wet or dripping.
 
Also, think about flushing the crank case.  Let's do this on the cheap first.
 
Did you listen to the exhaust with the new plugs?  I didn't see that.
 
Polaraco sounded like that right after I put this motor in.  It turned out to bad fuel injectors.  The plugs had a puffy white on them
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Steve

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #5 on: September 30, 2010, 06:41:45 PM »

Quote from: dana44
YOu do have adjustable rockers on this 301 A engine, they may be a little bit on the tight side, a couple thousandths can do the strangest things with running smooth, and compression (more than likely the head gaskets are thicker than the stock steel shims and dropped it that way). Just means you could pour a gallon of water in a low tank of gas and she will make it to the next gas station in an emergency (JUST KIDDING ON THAT ONE).
 
Good Point.  I forgot about that.  Tyhey are mechanical lifters on that.  They may be too tight as he said.
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Robert Rottman

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #6 on: October 02, 2010, 05:59:45 PM »

I did a compression check before pulling the valve covers today...found cyl # 5 (driver side) low @60 PSI...all the rest on that side were 100-105 PSI...So I adjusted the uppers rockers (intakes) to .012" and all the lowers (exhausts) to .019" on both sides for all 8 cylinders. I found Cyl. 5 (exhaust) was too tight...After adjusting them...engine smoothed right out and now cyls. 1,3,5,7 (driver side) are all 90-95 PSI. I haven't rechecked compression on passenger's side yet...But...The main thing...No more rough idle...no more puffing exhaust. I'm stoked...First time I ever did this. Thanks guys very very much...
 
furyfever2010-10-04 09:38:46
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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #7 on: October 02, 2010, 09:41:49 PM »

Good, now go put some miles on her, like at least a good hour of running. Solid cams have a habit of getting a dusting of rust on the seats of the valves if they aren't driven very much, so they need to be basically heated up really good, valves smacking the seats, and cleaned up really good that way, which may actually raise the compresssion a bit, too.
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Steve

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #8 on: October 02, 2010, 09:59:18 PM »

How could the compression go down Bob.  It should have gone up
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Jason Goldsack

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #9 on: October 03, 2010, 05:49:16 AM »

I was thinking the same thing..

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Jason

(Eileen)1965 Chrysler Windsor, 361/727/2.76 16.49 @ 86 mph

Robert Rottman

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #10 on: October 03, 2010, 07:30:11 AM »

Quote from: POLARACO
How could the compression go down Bob.  It should have gone up

I was talking to a good friend about that last night...and believe me, I don't understand what's going on in there...He said that I have the average now...(for that side of the motor)
 
Before the rocker adjustment...Compression of Cylinders 1,3,5,7 respectively were 105,105,60,100 = 370/4 = 92.5. Now...after the rocker adjustments (per spec) I have 90-95 on each of them...I thought I was in real trouble with that low one...you guys and one of my 57/58 Plymy buddies all encouraged me to do the rocker adjustments...Car is running so much better now...and these are just observations I have recorded along the way... Can anyone with the full understanding of what's going on in there chime in and explain? Note: I did the compression tests on that side several times before any adjustments so I'm sure of those compression readings.
_popupControl();furyfever2010-10-03 12:39:08
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Steve

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #11 on: October 03, 2010, 09:09:42 AM »

I did a few of those motors over the years.
 
So lets take it one step at a time.
 
How does it start now?
 
are the valves making any noise at all?
 
When you checked the compression, was it hot or cold?
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Jason Goldsack

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #12 on: October 03, 2010, 10:56:01 AM »

Where did the 301 fit in with the engine classes?.. is it a smaller version of the  318 poly?

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Jason

(Eileen)1965 Chrysler Windsor, 361/727/2.76 16.49 @ 86 mph

Robert Rottman

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #13 on: October 03, 2010, 01:11:44 PM »

Quote from: POLARACO
I did a few of those motors over the years.
 
So lets take it one step at a time.
 
How does it start now?
 
are the valves making any noise at all?
 
When you checked the compression, was it hot or cold?

Steve, initially I checked compression in 7 out of 8 cylinders all hot...the one I forgot to check i just did the other night (60) ...initially I did it cold so I was hoping that's why it was low...(60)...The next day I repeated a few more times this time...after heating the engine up...It was still at 60...While I was at it I checked that whole driver side again...the others were up near 100-105 like they were when I originally checked them...After I set the rocker arms to spec last night...uppers @ .012" lowers at .019" and rechecked....the whole driver side is now at 90-95...
 
furyfever2010-10-04 09:39:10
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Steve

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57 Plymouth Belvedere 301v8 w/ 4brl running poorly
« Reply #14 on: October 03, 2010, 02:15:22 PM »

Are the lifters making any noise?  Or id the motor stone quiet?

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