Knock knock

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

   I hope it's not a rod knock.  I'm looking for some suggestions as to what it might be.
Last time I took the boat out, doing nothing significant it developed a knock. I've gone through things like removing the plug wires one at a time and didn't notice any difference. I've adjusted the pre-load on the lifters twice with no change. The link bar roller hydraulic lifters make a racket and I couldn't pinpoint any place that was different. I finally took the Intake manifold off and a couple of the lifters wouldn't bleed down, and a couple others bled down somewhat fast,  but there are different opinions on whether that makes a difference or not. 

I just installed a new damper flex plate and wonder if that could make that sort of noise if it came loose? 

Anybody have any ideas?

Thanks

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
AlfaDon Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 407	Post Options Post Reply Quote AlfaDon Report Post Thanks(0) Quote Reply Topic: Knock knock Posted: November-12-2021 at 1:53am
	I hope it's not a rod knock. I'm looking for some suggestions as to what it might be. Last time I took the boat out, doing nothing significant it developed a knock. I've gone through things like removing the plug wires one at a time and didn't notice any difference. I've adjusted the pre-load on the lifters twice with no change. The link bar roller hydraulic lifters make a racket and I couldn't pinpoint any place that was different. I finally took the Intake manifold off and a couple of the lifters wouldn't bleed down, and a couple others bled down somewhat fast, but there are different opinions on whether that makes a difference or not. I just installed a new damper flex plate and wonder if that could make that sort of noise if it came loose? Anybody have any ideas? Thanks

MrMcD Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750	Post Options Post Reply Quote MrMcD Report Post Thanks(0) Quote Reply Posted: November-12-2021 at 2:29am
	I worked in the engine field for 30 years, I am not aware of any test that determines lifter health by bleeding them down engine off. Personally I think that was a waste of time. If you think you have loose lifters causing noise grab a rubber hammer. Place the wood end on the rocker arm with engine running, press on the rubber end putting pressure down on the push rod side of the rocker arm, this will quiet a noisy lifter.. This forces it to adjust, hold it a minute and release, I am thinking about 25-40 lbs of pressure not a light push. It should adjust again right away and run smooth. If it does not react properly you found the bad lifter or the location of a loose lifter. The cause could be a bad lifter or a cam going flat. Engine off you might find a collapsed lifter just by checking each push rod but to do this you would need to check each cylinder while that cylinder was at TDC on the compression stroke to be sure both lifters should be loose. All 16 lifters at TDC compression stroke should have very similar play if not identical play. Hydraulic lifters adjust all the time in normal use, you are looking for one that no longer adjusts in normal use or is sticky. Get a mechanics stethoscope or take about 4' of 5/8 heater hose and hold it to your ear. Search the running engine with your scope or hose trying to find the location of your sound. It very well may be your damper or even a loose bolt somewhere in that area hitting on something. The rhythm of the sound should give a clue if it is a piston, rocker arm or rod bearing. The damper would have a faster rhythm. Hope you find it and it is minor.

Gary S Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096	Post Options Post Reply Quote Gary S Report Post Thanks(0) Quote Reply Posted: November-12-2021 at 6:08am
	An exhaust leak at the junction of the exhaust manifold and the head can sound like a knock
	69 Mustang HM SS 95 Nautique Super Sport

AlfaDon Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 407	Post Options Post Reply Quote AlfaDon Report Post Thanks(0) Quote Reply Posted: November-12-2021 at 12:02pm
	Gary, Thanks. The gaskets show a clean mark around the perimeter of the port and I didn't think to check them when it was running. McD. I can't check the operation of the lifters with the valve covers off because the EFI manifolds are in the way. The test I was trying to perform and got an answer for was to see if a lifter was collapsed. They all had good spring pressure, except the one that wouldn't bleed down. And the one's that bled down too fast. The bleed down could be a factor of where the lifter is in the bore, although I checked them all at the same position. Thanks

Knock knock

About CCF

Donate

Partners

Contact