Off Roading Forums banner
1 - 16 of 16 Posts

·
Registered
Joined
·
2,348 Posts
Discussion Starter · #1 ·
I am getting a strange noise from my jeep, and I am pretty sure it is coming from the engine.
The motor I have in my Jeep is a 350. It has hydro lifters in it, and I am wondering if maybe one is bad? The engine only has 1700 miles on it at this point.
The noise I am getting only happens some times. The rest of the time the engine runs like a dream.
I think I would describe the noise as a "clatter" (it kind of sounds the same as when my last jeep had a cracked flex plate) (this Jeep is a standard, so it has no flex plate)

I get the sound, only when the RPM's in the engine are low, and the jeep is under hard accelerate.
So, say I am in 1st gear, and I shift into second, and apply a heavy throttle... I get a clatter for a bit. If I let off a little the clater will go away. And once the RPM's come back up a little, the clatter goes away.
The only other time I hear it is if I am in 4th gear, and I am going up a long hill.. If I apply more throttle, sometimes I will get the same caltter. Basically when the throttle (carb butterfly) is open more than needed for the given Motor RPM (under very low manafold vac) I seem to get this clatter.

I am hopefully going to get a local motor builder to go for a rid with me some time this week, or next. I would just like to be clued in a little before I talk to him about this.

Does this sound like maybe a bad lifter to anyone? Anyone have any other ideas?

Thanks for any help, I know that sounds are hard to diagnose in this manner, I figure I would try.
 

·
Official Curmudgeon
Joined
·
4,706 Posts
Sounds like timing knock to me.
 

·
Registered
Joined
·
2,348 Posts
Discussion Starter · #3 ·
Taz,
Thank you for the quick response.
I must admit that I have never heard of timing knock before. Can someone explain what it is? And how to go about fixing it?

It would make perfect sence if this was a timing issue. I had to replace the dist. about a month ago. I thought I had everything timed back in correctly but it seems like maybe I don't.

If what I am experencing is timing knock, how would I go about getting rid of it? I hope that I am not doing any damage to the engine in any way..

Thank you
 

·
Registered
Joined
·
556 Posts
Agree with Taz, knock can ruin any motor... so do not hit the throttle hard until you fix the problem...
Retard the spark.
Depending on what changes you have in the motor. You may have a knock sensor that is not working or not connected. Changing the distributor you may have the wrong spark advance curve.
I suggest you have the engine set up by some one who is qualified to check all of the above. A SUN Test meter is needed to do the complete check.
 

·
Registered
Joined
·
875 Posts
You're getting too much spark advance, from the distributor, at the wrong time, for the engine. You're probably getting to much total advance.

Your distributor needs to be tuned to your engine's needs.

I'm sure someone here can explain this better to you than me. It's not that complicated, or hard to do, most of the time. But someone who's very experienced at it, could explain it better.

Maybe someone will give you a link that explains how to correct it.
 

·
Registered
Joined
·
10,815 Posts
Timing knock --- also known as "Ping."

Sounds like a bunch of marbles flying around.

Try something - remove distrubutor cap - note which way the rotor turns when you bump the starter.
Replace cap
move the distributor a little in the SAME direction the rotor turns.
Drive it - helps?
Keep doing that till it doesn't ping.
 

·
Registered
Joined
·
13,432 Posts
The first thing you do is to trot down to your local autoparts store and buy a mechanics stethoscope for about $7. Then listen for where that noise is coming from, and under what repeatable circumstances. Otherwise
  • your whistling in the wind..
  • it could be this...
  • it could be that...
  • it may be thus and so.
You say the noise is only understandable at low RPM and under load. That's a clue, but it may also be noticeable using a stethoscope when the engine is not under load.

IMHO... more information is needed to determine the problem and it's fix.
 

·
Registered
Joined
·
10,815 Posts
New distributor (discount store rebuilt?) -
Betcha -
1. intial timing too high
2. too much advance due to:
A. Wrong vacuum
B. Mechanical advance too fast/too much (light springs)
C. Vacuum advance diaphram moves to far.

An advance timing light would be very helpful.
 

·
Registered
Joined
·
2,348 Posts
Discussion Starter · #9 ·
Thank you all for the feedback. It sounds to me like what I have going on is Timing knock.
It sounds Exactly like a bunch of Marbles flying around.
My engine does not have a knock sensor, there is no computer.

I do have a stethoscope, and I have listend just about everywere I can think to listen with the jeep sitting in the driveway running. Nothing sounds funny until the engine is under a load.

I did replace the Dist with a rebuilt from a parts store.
There is a very good chance that my inital timeing is too high. This afternoon after work I will try turning the dist a little, and give it a drive. Hopefully that will do what I need, and eliminate the knock. I have never recurved a Dist before. It seems to be a confusing task from what I have read. If it comes down to that, I may need to seek help from a pro.

Hopefully all I need is a little turn of the dist.
thanks again for the help
 

·
Registered
Joined
·
2,348 Posts
Discussion Starter · #10 ·
I do have an advance timing light, but I have never used the "advance" before. I have only used it for setting inital timing..
 

·
Registered
Joined
·
10,815 Posts
It's possible that's what went wrong.
For thje initial timing, m,ake sure the knob is in the click position. Then read the timing on he marks on the engine.
If the knob isn't at 0 - click, it will throw you off.

Notice if you turn the knob till the marks on the engine say 0, the reading on the knob reads the intial - should be the same.
One ot the other, not both.


Once the initial is set, rev it up to about 2500 RPM - cruise speed. Turn the knob till the marks on the engine read 0.
Read the knob, that's the total advance.

The knob actually slows or delays the flash of the light, the more you turn it, the more it delays. That's an easy way to see the advance.

You can even plot the curve, with and without vacuum at different R's.
Really a handy tool.
 

·
Registered
Joined
·
830 Posts
Listen at the end of this video clip, and you will hear some ticking as the rocker is loosened.

 

·
Registered
Joined
·
830 Posts
Here is another one. Imagine this noise a bit more clattery. That is what a lifter knock sounds like. But yours sounds different.
 

·
Registered
Joined
·
3,833 Posts
Not to Hijack the thread, but I have another kind of tick.

Every now and then, and not that often. I'll be sitting at an idle and I'll here a tick that lasts only 1-2 seconds and goes away. when it starts it's kinda quiet, then gets louder and diminishes and goes away. It may tick only about 10-12 times in that 1-2 second period, only at idle and always sounds the same.

I'm kinda guessing it has something to do with AMC V8 oiling issues, but that's only a guess on my part. any ideas?
 

·
Registered
Joined
·
2,348 Posts
Discussion Starter · #15 ·
Well, I am happy to report that what I have is timing knock. last night I played with the timing a little, and I was able to make it better. However I was unable to eliminate it.
It seems to me like I am going to need to adjust the Dist and re-curve.
As I had mentioned above, this is somthing that I have never done. Is it doable for a shade tree guy, or am I going to be better off, and time ahead just bringing my Jeep to a good motor shop. I have a freind who works at a really good shop in the area.

Thank you
 

·
Registered
Joined
·
10,815 Posts
Before throwing lots of money at it - now that you've reduced the knock -
Try adding a bottle of Techron to the gas tank. A full bottle to 1/2 tank works great as a slow decarbonizer.

Since the timing's been off, it may have built up carbon deposits in the combustion chambers. The Techron is the best SAFE decarbonizer around.
Sure, some folks will tell you to pour something down the throat, ATF, carb cleaner, kerosene, Marvel oil, water etc. That works, but if there's heavy deposits in there, they can break off and do considerable damage. Best not to take the chance.

Use your advance timing light to check it at cruise speed - it should not exceed about 35 degrees. If it does, isolate whether it's advancing too much from the mechanical or vacuum advance.
Each system should only advance it 12-15 degrees. Often times a rebuilder mixes and matches parts giving too much advance, or too soo an advance.
Timing advance is cumulative, each sytem adds to the total. You cannot easily limit the mechanical, but you still can isolate and measure them.

Measure the total, then pull the vacuum line and try it.
The difference is what the vacuum did.

In theorey -
Initial 8
Mechanical 12
Vacuum 15
That gives a total of 35

Much more than 35 almost garantees ping.
Advancing too soon, coming in at lower RPM does too.

Type of fuel also causes it - high alcohol content is best avoided - Arco gas has so much alcohol that a tiny bit more they'd have to label it gasohol. BMW owner's manuals say not to use Arco. Arco sued them for making that statement, Arco lost! There must be something to it!
Many "independant" stations buy from Arco too, but call it by their own name. Try switching a tankful to a big name brand.
 
1 - 16 of 16 Posts
Top