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Yesterday, 12:15 AM | #1 |
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Join Date: Apr 2019
Location: Fort Lauderdale, Florida 33311
Posts: 103
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Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
Super frustrated, fellas.
I've got a 71 with a basic SBC 350/700R4 combo and I'd been daily driving it in south florida for literally 2+ years without any issues. (Hedman mid lengths, Erson 1.5 rockers, edelbrock intake manifold, Holly 650 carb, full Magnaflow exhaust, etc...) With little more than occasional maintenance, the truck always started on the first hit of the key and idled/ran/drove like a champ the entire time. After a long drive from Florida to central NC, the truck hasn't run right since. Now, when I start it, it runs rough & I've got to give it a little gas until it warms up. If I don't, it'll stall any time I even put it in drive. I'm not even sure where to START looking, since it seems so random and out of the blue. If anyone has some advice, I can't tell you how much I appreciate it. It's also had a knocking sound that's been nagging me for months. It comes and it goes and I thought a new crank balancer would resolve the issue, but no such luck. (it's loudest when the truck is cold and it's quiet when it's warm) Really trying to not pull my hair out here... Video of the noise I've been chasing https://youtu.be/mC7LzL19K6g?si=v_HAxJV4iIsbzDkD Last edited by BigTopGT; Yesterday at 12:21 AM. |
Yesterday, 01:18 AM | #2 |
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Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,611
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
Knock sounds like exhaust leak. Those can be hard to chase. Don't overlook the intake exhaust crossover. Yes, a bad intake gasket can cause an exhaust leak.
Take all the belts off and give it a short run. Possible the 'knock' is one of the accessories being EOL. If things get quiet with no belts, go through the process of elimination until you find the noisy accessory. May also be easier to track down the leak or internal noise without the fan and other noises. Just don't get lost in noise tracking that you forget the short run part. Rough running could be a simple as it needs a tune up. |
Yesterday, 02:20 PM | #3 |
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Join Date: Mar 2022
Location: Surrey BC
Posts: 915
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
probably two things going on.
On the rough startup, I'd check choke is coming on properly, check timing and pull plugs for a look. your knock is hard to hear, is there a lifter tick or a knock? Things DP suggested and also look at the flex plate. I had a van I thought had a bad main, but the noise was only at low unloaded RPM. Finally figured out the flex plate was cracked all the way around the bolt circle at crank and the noise was the torque converter banging around. the noise went away when the TC had power applied as the crack jammed into itself. It was a high mileage van (250k+miles), the knock came on suddenly for no apparent reason. I could wiggle the TC & flex plate around from the inspection cover |
Yesterday, 02:26 PM | #4 | |
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Join Date: Apr 2019
Location: Fort Lauderdale, Florida 33311
Posts: 103
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
Quote:
I'll get her up in the air tomorrow and start turning over some stones. I'll report back as I start ruling things out. |
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Yesterday, 04:50 PM | #5 |
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Join Date: Dec 2016
Location: Canon City, Colorado
Posts: 124
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
I'd also check the valve lash/preload/rockers. Make sure you don't have some that have loosened up.
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Yesterday, 06:14 PM | #6 |
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Join Date: Oct 2013
Location: Maine
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
Hmmm, sounds pretty bad. It doesn't sound quite like a rod knock but it does seem to come from the bottom. It does not sound like a lifter tick to me. Those flexplate knocks can be kinda tricky. I think I would bet my money on a bad flexplate.
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Yesterday, 07:23 PM | #7 |
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Join Date: Dec 2016
Location: Canon City, Colorado
Posts: 124
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
I bought a steel crank 454 from some friends once. They thought it had a rod knock, and pulled it. Crank was fine. But, a couple of cam lobes and lifters were wiped out.
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Today, 11:54 AM | #8 |
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Join Date: Jan 2000
Location: Wyoming USA
Posts: 2,449
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
Has it ever been over heated, had one do that and warped a cyl (rod) thing ran great after it happened.I actually ran it for a couple years with not one issue besides the knock.
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Today, 12:31 PM | #9 |
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Join Date: Jan 2000
Location: Wyoming USA
Posts: 2,449
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
Has it ever been over heated, had one do that and warped a cyl (rod) thing ran great after it happened.I actually ran it for a couple years with not one issue besides the knock.
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2001 Silverado K-1500 2005 FXDWG stage3 69 CHEVY Short/Step 327/4L60 373 posi 63 IMPALA 327 Last edited by kaycee; Today at 12:33 PM. Reason: Delete |
Today, 12:38 PM | #10 |
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Join Date: Jan 2000
Location: Wyoming USA
Posts: 2,449
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
Has it ever been over heated, had one do that and warped a cyl (rod) thing ran great after it happened.I actually ran it for a couple years with not one issue besides the knock.
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2001 Silverado K-1500 2005 FXDWG stage3 69 CHEVY Short/Step 327/4L60 373 posi 63 IMPALA 327 |
Today, 03:15 PM | #11 |
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Join Date: Feb 2013
Location: central California
Posts: 2,775
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
A bad fuel pump can make a knocking sound.
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Today, 05:59 PM | #12 |
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Join Date: Sep 2023
Location: randolph va
Posts: 158
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Re: Daily driven 71 now runs like crap after a 700 mile trip (and WTF is this sound?)
flex plate cracked or loose , converter bolts loose
ez to check david
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