Engine tapping
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 829
Likes: 2
From: Scottdale Pa
Engine tapping
I just started hearing the engine tapping today after a 7 mile drive.It's a stock 350 with 17,535 miles on the car(1980) and it also started to run a little bit rough. Any ideas as to what it could be? 
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 829
Likes: 2
From: Scottdale Pa
It's not the exhaust, sounds like the driver side and one of the cylinders toward the front. More like a knock than tapping and not a steady knock, fades in and out at idle, but louder when you increase rpm's.
Drifting
Joined: Mar 2005
Posts: 1,806
Likes: 3
From: Burlington WI
Quoth the raven, `Nevermore.'
Once upon a midnight dreary, while I pondered weak and weary,
Over many a quaint and curious volume of forgotten lore,
While I nodded, nearly napping, suddenly there came a tapping,
As of some one gently rapping, rapping at my chamber door.
`'Tis some visitor,' I muttered, `tapping at my chamber door -
Only this, and nothing more.'
Or it could be a lifter gummed up from only driving it an average of 701.4 miles per year.
Over many a quaint and curious volume of forgotten lore,
While I nodded, nearly napping, suddenly there came a tapping,
As of some one gently rapping, rapping at my chamber door.
`'Tis some visitor,' I muttered, `tapping at my chamber door -
Only this, and nothing more.'
Or it could be a lifter gummed up from only driving it an average of 701.4 miles per year.
Advanced
Joined: Sep 2005
Posts: 54
Likes: 0
From: Cheshire CT
Originally Posted by fl_rider
Once upon a midnight dreary, while I pondered weak and weary,
Over many a quaint and curious volume of forgotten lore,
While I nodded, nearly napping, suddenly there came a tapping,
As of some one gently rapping, rapping at my chamber door.
`'Tis some visitor,' I muttered, `tapping at my chamber door -
Only this, and nothing more.'
Or it could be a lifter gummed up from only driving it an average of 701.4 miles per year.
Over many a quaint and curious volume of forgotten lore,
While I nodded, nearly napping, suddenly there came a tapping,
As of some one gently rapping, rapping at my chamber door.
`'Tis some visitor,' I muttered, `tapping at my chamber door -
Only this, and nothing more.'
Or it could be a lifter gummed up from only driving it an average of 701.4 miles per year.
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Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 829
Likes: 2
From: Scottdale Pa
Originally Posted by fl_rider
Or it could be a lifter gummed up from only driving it an average of 701.4 miles per year.
Le Mans Master
Joined: Nov 2004
Posts: 6,434
Likes: 0
St. Jude Donor '07
Originally Posted by 80crabvette
That's not the average, over the last two years. I've driven it about 2500 miles per year. The original owner drove it 11,676 miles in 23 years. I just started useing a synthetic blend oil (Castrol) about 700 miles since oil change. I've heard that synthetic oil will clean a engine and sometimes cause leaks and other problems. Any other thoughts?
.Synthetic is pretty pointless if you dont have a new motor, the synthetic allows you to use tighter clearences becuase synthetic is much thinner almost like water . Maybe you have carbon build up in that cylinder and it's increasing compression and causing it to knock 
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 829
Likes: 2
From: Scottdale Pa
Originally Posted by Yellow73SB
Ahh synthetic .Synthetic is pretty pointless if you dont have a new motor, the synthetic allows you to use tighter clearences becuase synthetic is much thinner almost like water . Maybe you have carbon build up in that cylinder and it's increasing compression and causing it to knock
.Synthetic is pretty pointless if you dont have a new motor, the synthetic allows you to use tighter clearences becuase synthetic is much thinner almost like water . Maybe you have carbon build up in that cylinder and it's increasing compression and causing it to knock 
Burning Brakes
Joined: Nov 2005
Posts: 1,143
Likes: 0
From: Leander Texas
Rod knock. The Easiest way I know how to diagnose the problem is to pull each spark plug wire off one at a time at light load. When the the engine stops knocking you found the bad hole.
It sounds bad though.
Good luck!!!
DR. Jay
It sounds bad though.
Good luck!!!
DR. Jay
Drifting
Joined: Mar 2003
Posts: 1,608
Likes: 3
From: Canberra AUSTRALIA
St. Jude Donor '05-'06
Originally Posted by DR.Jay
Rod knock. The Easiest way I know how to diagnose the problem is to pull each spark plug wire off one at a time at light load. When the the engine stops knocking you found the bad hole.
It sounds bad though.
Good luck!!!
DR. Jay
It sounds bad though.
Good luck!!!
DR. Jay
This is how I trouble shot mine on Wednesday. Have someone sit in the car and hold the RPM at the level which you here the noise. Use insulated gloves and a pair of good pliers/multi-grips to pull of each wire fromt the distributor. Remove/replace each wire and listen for the sound to change. The noise will vary as you remove the load from the weak cylinder. I hope yours is not as bad as mine.
Cheers,
Pete
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Here's a crazy idea...how about running down to the oil change shop and giving the ole' girl a quick oill change...worst can happen is a waste of 40 bucks...but maybe it'll help...that would be my first move...just for the heck of it..I'm wondering if you were out hammering on her right before the knock started...if you really had the RPM's up there right before the knock, I'd say ya gots some major problems...
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Try misting water down carb keeping revs up...make sure it is misted in from a spray bottle...I'm betting on the carbon knock...have you tried listening with a long screw driver at valve cover yet ? If the noise is near top of engine,chances are it is not a rod..hopefully...
Edit:I was fooled by a carbon knock once..dropped the pan,and everthing was ok....ever since then,my first move is to probe engine and listen with a long screw driver or wood dowel...never had auto shop,either...
Edit:I was fooled by a carbon knock once..dropped the pan,and everthing was ok....ever since then,my first move is to probe engine and listen with a long screw driver or wood dowel...never had auto shop,either...
Last edited by rihwoods; Nov 13, 2005 at 08:31 AM.
Burning Brakes
Joined: Nov 2005
Posts: 1,143
Likes: 0
From: Leander Texas
Feeding the engine a water mist is a great way to remove carbon deposits from the combustion chamber, and stop predetonation.
I use a primative system that drafts a 50/50 water/methenal vapor mix from a used winshield washer tank that I sourced from a mid '70s chevy pickup. I have a system on my wife's '89 subarban, and I also have one on my '95 z-28.
It really helps lower egt. on the camaro, and It also totally stoped predetonation in the suburban.
Just (Google) "water injection systems". you can find very primitive systems to very high tech. I think that installing a water injection system on any internal combustion engine is a must.
I hope it is just carbon Knock, and not a spun rod bearing!!
DR. Jay
I use a primative system that drafts a 50/50 water/methenal vapor mix from a used winshield washer tank that I sourced from a mid '70s chevy pickup. I have a system on my wife's '89 subarban, and I also have one on my '95 z-28.
It really helps lower egt. on the camaro, and It also totally stoped predetonation in the suburban.
Just (Google) "water injection systems". you can find very primitive systems to very high tech. I think that installing a water injection system on any internal combustion engine is a must.
I hope it is just carbon Knock, and not a spun rod bearing!!
DR. Jay
