Thread: Engine Knock
Hybrid View
-
09-09-2010 06:40 AM #1
Engine Knock
My 74 two bolt 400 SBC developed a severe knock over the past couple of days. Could only be heard at 3k+ rpm but then moved quickly into the lower ranges until it could be heard at idle. Sounds like it is coming from the mid center or top center portion of the engine although it is hard to tell. Video link below shows that it comes and goes which is what I can't exactly figure out. I'd like to have a better idea for a diagnosis before I just break into it. Any theories?
http://www.youtube.com/watch?v=IleBauFOnS4
-
09-09-2010 03:30 PM #2
Try the easy stuff first, take a look at your flexplate (assuming it's and automatic) and see if it might be cracked? Pull one plug wire at a time and see if the knock quits on a certain cylinder or not...Yesterday is history, tomorrow is a mystery, Live for Today!
Carroll Shelby
Learning must be difficult for those who already know it all!!!!
-
09-09-2010 03:43 PM #3
Flexplate would be my first guess too.
-
09-09-2010 04:07 PM #4
I don't know I think I'd pull the valve covers sounded like a rocker to me but not being there its hard to tellCharlie
Lovin' what I do and doing what I love
Some guys can fix broken NO ONE can fix STUPID
W8AMR
http://fishertrains94.webs.com/
Christian in training
-
09-09-2010 06:27 PM #5
Take a short piece of broom stick or PVC pipe one end to your ear and the other different places on the engine and see if that helps to localize the noise.
-
09-11-2010 06:52 AM #6
ok, i've had a little time to mess with it this morning. The knock is the loudest under the oil pan. Broken piston skirt?
-
09-11-2010 06:59 AM #7
actually, i'm thinking more and more that it is the flexplate. time to get to work and actually look.
-
09-11-2010 08:29 AM #8
initial inspection of the flex plate turned up nothing. Of course it's still in the vehicle so I may have missed something. I pulled the oil pan and all the rods look ok, all are still attached and there are no noticeable stray marks on the underside of the engine, no debrie in the oil pan. I'll likely head back to the flexplate and tranny bolts. Anyone know any rough torque specs for this area? If that doesn't turn up anything I'll pull the valve covers.
-
09-11-2010 09:34 AM #9
on a whim I filtered the oil I just drained and I found some copper shavings/flakes. Sound like bearings? Where is there copper in this engine?
I can't remember a singular event that triggered this nuttiness so I'll say it was being born. After we moved from Kansas to Chicago (I was 5 then) we'd drive back down each summer to visit the...
How did you get hooked on cars?