Rod vs. Valve knock

eboutin88

New Member
Authorized Seller
Joined
Jan 18, 2009
Messages
11
Location
Vermont
How can you tell the difference between a rod knock and noisy valves?

I am trying to figure out which problem I have before I go removing the engine.
 

airhead04

New Member
Authorized Seller
Joined
Aug 21, 2009
Messages
1,489
Location
Lima, Ohio, United States
How can you tell the difference between a rod knock and noisy valves?

I am trying to figure out which problem I have before I go removing the engine.
I personally think, valves noise sound like clicking pens, just sometimes a little louder. (my valves make noise too)

Rod knock sounds like somebody knocking on a counter top.

At least thats what i think it sounds like.
 

Txsupra

Professional Driver
Authorized Seller
Joined
Aug 23, 2008
Messages
239
Location
Texas
Use a long screw driver, put the handle up to your ear. Touch different parts of the head and cam covers. Listen for where the noise is loudest or at all. Then do the same for the block if ya can, maybe from under the car. You should be able to pick up a cheep mechanics stethoscope at your local auto parts store. This will give you a general idea of where the noise is coming from.
PLEASE use extreme caution when doing this as you have to lean over a running engine. Have someone else watch out while you work. NO loose clothing
Rod knock is usually pretty loud compared to valve tic.
 

GrimJack

Administrator
Staff member
Administrator
Authorized Seller
Joined
Dec 31, 1969
Messages
12,378
Location
Richmond, BC, Canada
If you are going to remove the engine, why worry now? Just pull the oilpan, the main caps, and check the bearings. If one is roasted, it'll be rather obvious.
 

grimreaper

New Member
Authorized Seller
Joined
Jul 2, 2008
Messages
2,180
Location
Dallas
valves - sewing machine when in clearance. Valve noise should be .5 : 1 with rpms and starts at idle and just gets louder with higher revs. Other noises will drown this out in higher rpms though. When mine were out of clearance, it made quite the racket/ clatter from 1000-2500rpms or so. I could easily make the noise with the slightest blip of the throttle when at idle.

rk should be 1:1 with rpms and should be most obvious from 2000-3000rpms. Should not come and go, should be louder when the motors at operating temp (early on set).

I should add that like the post above, there is no "mold" rk follows. Some have lost oil psi, others say they never saw a drop in psi. Some have it start at 1800rpms and others higher up. A lot of things can knock with so much metal under the hood, grimjacks advice is simplest at this point.

or IJ's if your not pulling it
 

89supra7mgte

New Member
Authorized Seller
Joined
Sep 20, 2009
Messages
797
Location
colorado
IJ's advice is probably one of the easiest ways to to verify, another way would be to ground out each plug wire with a test light (hooked to ground) and slightly pierce the wires be careful to not create a hole this will cause the spark to jump. This takes the load off the selected cylinder due to no fire, as with removing the injector clip, there is no forcing of the piston down. Dont quote me but i do believe when you do this and there is still the knocking noise you would have a lifter issue, being that the lifter movement is mechanical and the rod/piston movement is based around ignition in the cylinder.
 

radiod

Supramania Contributor
Authorized Seller
Contributor
Joined
Dec 13, 2007
Messages
1,342
Location
Abbotsford, BC
If you've got a mechanic's stethescope (or long screwdriver/baseball bat/broomstick to ear), you should be able to hear very easily whether it's in the top end or bottom end even if you don't know what you're listening for. Put the stethescope (or whatever you're using) to different places on the top end of the engine (valve covers, injectors, etc.), see where the noise is louder. Then go to the bottom end and listen from the oil pan. You should be able to hear where it's louder and where it's quieter at the very least. If it's loudest on top, it's definitely not rod knock. Shouldn't be too hard to tell what you are closest to while testing, and that should give you a good idea of what could be making the noise.

IJ's injector clip trick is another good way of ruling out rod knock.
 

eboutin88

New Member
Authorized Seller
Joined
Jan 18, 2009
Messages
11
Location
Vermont
From the first second I start the car you can hear the knocking. At idle you hear it and when you rev it up it is ridiculously loud. The reason why I thought it was a rod knock is because of how loud it is. I may be wrong, How loud could a lifter or a valve noise be.
 

IJ.

Grumpy Old Man
Authorized Seller
Contributor
Joined
Mar 30, 2005
Messages
38,726
Location
I come from a land down under
From the first second I start the car you can hear the knocking. At idle you hear it and when you rev it up it is ridiculously loud. The reason why I thought it was a rod knock is because of how loud it is. I may be wrong, How loud could a lifter or a valve noise be.
Did you try my advice?
 

StrikeIS

New Member
Authorized Seller
Joined
Apr 1, 2009
Messages
61
Location
Va
Great I read this post and the next day my car starts making ridiculously loud noises. I think its in the head. Im begining to hate this motor.
 

grimreaper

New Member
Authorized Seller
Joined
Jul 2, 2008
Messages
2,180
Location
Dallas
not the motor... its all the "great" maintenance its had over the past 20 yrs ;).
 

eboutin88

New Member
Authorized Seller
Joined
Jan 18, 2009
Messages
11
Location
Vermont
Took IJ's advice "Get a helper to hold the throttle at the knocking rpm then pull and replace each injector clip, if it's RK it should stop"

Found that Cylinder number one and Four were the noise makers. One a little, Four, huge difference when unplugged. I guess, it is officially the death of the just rebuilt 7M. Stock too, thats the part that pisses me off. Now I am building one with ACL bearings, eagles H Beam Rods and Wiseco Pistons. Hopefully this will last.

Thanks IJ for the advise.
 

89supra7mgte

New Member
Authorized Seller
Joined
Sep 20, 2009
Messages
797
Location
colorado
Too bad they werent companion cylinders, just kill the plugs and fuel and make it a four cylinder lol!!!!!! Did you rebuild it or have it rebuilt?
 

IJ.

Grumpy Old Man
Authorized Seller
Contributor
Joined
Mar 30, 2005
Messages
38,726
Location
I come from a land down under
Took IJ's advice "Get a helper to hold the throttle at the knocking rpm then pull and replace each injector clip, if it's RK it should stop"

Found that Cylinder number one and Four were the noise makers. One a little, Four, huge difference when unplugged. I guess, it is officially the death of the just rebuilt 7M. Stock too, thats the part that pisses me off. Now I am building one with ACL bearings, eagles H Beam Rods and Wiseco Pistons. Hopefully this will last.

Thanks IJ for the advice.
Welcome Dude, my condolences...
 

dusthead

C-C-C-C-COMBO BREAKERRRRR
Authorized Seller
Contributor
Joined
Aug 10, 2009
Messages
100
Location
New London, CT
what kind of repairs would happen if it WAS from the head/valves? i'm having this issue now - i'll be doing IJs method tomorrow but interested in both possibilities for knowledge.
 

Koenigturbo

Well-Known Member
Authorized Seller
Joined
Oct 4, 2006
Messages
1,598
Location
Oxnard CA
If you are going to remove the engine, why worry now? Just pull the oilpan, the main caps, and check the bearings. If one is roasted, it'll be rather obvious.
I'm with Grim Jack, even if it was a rod knock you would still have to replace the bearings and/or do machine work. If it was the valve would still have to replace the valve and/or the piston, if youv'e gone that far, then I would just do the whole engine. From my experience from the past, if you did the valve job, the presure would just blow your rings out. Then you end up losing progress, then all the money, effort, parts, would just be a waste of time, money.
 

Bri7man

"Yeah! Take the lemons.."
Authorized Seller
Contributor
Joined
Jul 17, 2009
Messages
580
Location
Torrance, CA
^^
Here's rod knock.

The quality is shit and I didn't rev it because I don't want to scratch up the crank anymore than it may already have, but I think it's pretty obvious.
 

GrimJack

Administrator
Staff member
Administrator
Authorized Seller
Joined
Dec 31, 1969
Messages
12,378
Location
Richmond, BC, Canada
That one *is* pretty obvious, however, there are much lighter cases of rod knock. I've dealt with one where you couldn't hear anything at idle, only a tapping when you let off the throttle and the load on the bearings went from accel to decel.
 

Bri7man

"Yeah! Take the lemons.."
Authorized Seller
Contributor
Joined
Jul 17, 2009
Messages
580
Location
Torrance, CA
yeah before i took my engine out nobody could hear it but me from 5+ people and people that watched the vids I posted of it here. To me i think its something only an owner knows at first because only you know what your engine normally sounds like.

But I definitely do believe RK and valve tick is a miles difference but I'm not gonna elaborate on it cause I think most people disagree and my ears are better than anyone I know.
 

shaeff

Kurt is FTMFW x2!!!!
Staff member
Super Moderator
Authorized Seller
Joined
Mar 30, 2005
Messages
10,590
Location
Around
Found that Cylinder number one and Four were the noise makers. One a little, Four, huge difference when unplugged. I guess, it is officially the death of the just rebuilt 7M. Stock too, thats the part that pisses me off. Now I am building one with ACL bearings, eagles H Beam Rods and Wiseco Pistons. Hopefully this will last.
OEM parts had nothing to do with your engine failure. OEM parts are fantastic, and many guys on stock rebuilds make 400+rwhp all day long for years. The flaw was likely in the build or machine work.
 

Moy

It's broken...
Authorized Seller
Joined
Aug 6, 2008
Messages
2,432
Location
Beach Park, IL
why would you need to do that?
To find out if it's RK or valve tick...
Ian, if I made add to this...

When you pull the injector clip, the injector is getting no voltage, therefore is not being told to open. If the injector doesn't open, no fuel is being sprayed into the cylinder. No fuel means no combustion in that cylinder, meaning much less load on that bearing. (feel free to add to or correct any of that)

If it was valve tick, it would always be there, because the cams are always rotating as long as the engine is running.
 

black89t

boost'en down 101
Authorized Seller
Joined
Oct 27, 2007
Messages
954
Location
humboldt, ca
To find out if it's RK or valve tick...

IJ i understand that. :icon_roll


i have used that trick on other motors. its just i don't see why you would have to replace the injector clip. i know you wouldn't say that for fun. i was curious as to why.

didn't you notice the bold. lol.
 

89supra7mgte

New Member
Authorized Seller
Joined
Sep 20, 2009
Messages
797
Location
colorado
Well with the engine running, everytime you pull the injector clip the engine has a misfire. You only have 6 injectors and if you leave them unplugged the engine will run like shit if at all, thus preventing you from finding any noticeable change between cylinders.

Listening to the engine is how you determine what the problem might be.
 

shaeff

Kurt is FTMFW x2!!!!
Staff member
Super Moderator
Authorized Seller
Joined
Mar 30, 2005
Messages
10,590
Location
Around
Well with the engine running, everytime you pull the injector clip the engine has a misfire. You only have 6 injectors and if you leave them unplugged the engine will run like shit if at all, thus preventing you from finding any noticeable change between cylinders.

Listening to the engine is how you determine what the problem might be.
Negative, Ghostrider. If you do it right, pulling an injector clip is probably the easiest way to tell. You won't have a misfire, that cylinder just won't fire, period. When you first remove a clip, the engine will bog, but then go back up to the RPM you were holding it at. When the knocking goes away (which it will as there's no load on the bearing), you've found the cylinder that's knocking.

I've done this a few times, and it's worked every time.

Edit: you seem a bit confused. You unplug one injector at a time. If the sound doesn't go away, you plug that injector back in. You shouldn't have more than one unplugged at a time. And you ARE listening to the engine. Dunno what else you're going to do, because you certainly can't LOOK at it to diagnose RK without pulling the bearing caps.
 
7

787m

Guest
haha! Was gonna try IJ's injector trick, but the bastard spit out a headgasket first! Now I could care less if it's any of the three, time to go JZ...
 

IJ.

Grumpy Old Man
Authorized Seller
Contributor
Joined
Mar 30, 2005
Messages
38,726
Location
I come from a land down under
IJ i understand that. :icon_roll


i have used that trick on other motors. its just i don't see why you would have to replace the injector clip. i know you wouldn't say that for fun. i was curious as to why.

didn't you notice the bold. lol.
Won't run with too many cylinders down of course ;)
 

89supra7mgte

New Member
Authorized Seller
Joined
Sep 20, 2009
Messages
797
Location
colorado
Negative, Ghostrider. If you do it right, pulling an injector clip is probably the easiest way to tell. You won't have a misfire, that cylinder just won't fire, period. When you first remove a clip, the engine will bog, but then go back up to the RPM you were holding it at. When the knocking goes away (which it will as there's no load on the bearing), you've found the cylinder that's knocking.

I've done this a few times, and it's worked every time.

Edit: you seem a bit confused. You unplug one injector at a time. If the sound doesn't go away, you plug that injector back in. You shouldn't have more than one unplugged at a time. And you ARE listening to the engine. Dunno what else you're going to do, because you certainly can't LOOK at it to diagnose RK without pulling the bearing caps.
I know how this works i was replying to the post that was asking IJ why you replace connector after unplugging. And if a cylinder does not fire isnt that along the same lines as a misfire? on a more controlled basis?

EDIT: read quote from IJ post above that was what my post was referring to. Sorry for your confusion
 

Bri7man

"Yeah! Take the lemons.."
Authorized Seller
Contributor
Joined
Jul 17, 2009
Messages
580
Location
Torrance, CA
The knock sound won't go away by pulling the inj clips, it will just not sound as loud. At least in my case. So listen carefully.
 

supraguy@aol

Active Member
Authorized Seller
Joined
Dec 30, 2005
Messages
4,247
Location
Atlanta
LOL!

I think 89supra7mgte is asking why IJ says to replace the injector clips!
I mean really, IJ- why would I want to cut off and splice in new injector clips, just to verify rod knock??
:yelrotflm

I think this was just a case of misunderstanding. IJ means that after you've unplugged each injector clip, you place it back on the injector- IE; replace it.
 

dusthead

C-C-C-C-COMBO BREAKERRRRR
Authorized Seller
Contributor
Joined
Aug 10, 2009
Messages
100
Location
New London, CT
wow i didn't catch that...i thought he was just totally missing something...