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iTrader: (2)

I am in the process of breaking in the new 383 I just built and I have had it together for around 4 months.

Something I noticed after driving on the highway for awile was that it has developed a ticking noise. I can hear it getting louder when I am on the highway at 1800-2000 RPM. Not especially loud but just barely noticable.

Then when I slow down and come to a stop the tick gets very loud and the engine runs rough like it has lost a cylinder. This is accompanied by light knock counts. Oil pressure has always been very good with this motor as the lowest I have ever seen even at idle is ~40PSI.

By the time I get to two more stops after being off the highway (20-30 seconds) the noise is barely noticable again and the engine idles smooth.

Any ideas as to what I should check?

The motor is a 383 with a retrofit hydralic roller cam and promag roller rockers all from comp. I have readjusted the lash on the valvetrain with the engine running (made a nice mess of oil) and that did not help.

Thanks for any help.

joe350

Consistant ticking like this is usually caused either by an exhaust leak or lifters somehow. There is a difference in the noise they make, but the difference is difficult to describe. How new are the lifters? It could be that they are getting old or have somehow collapsed.

88305tpiT/A

iTrader: (2)

Lifters are brand new - less than 4 months old. the fact that I lose engine power and get a rough idle makes me think that its not just an exhaust leak.

speedped79

sticking valve? weak spring?

88305tpiT/A

iTrader: (2)

Other than replacing all the valves and springs how would I know thats what it was?

I just used my GM service manual and it says that a fast bleeding lifter (defective) can cause the syptoms I am seeing -- noisy at slow idle or with hot oil.

I am about to go drive it on surface streets about 5 miles by the way so if you have any suggestions for diagnosing I am all ears!

Thanks for the help.

88305tpiT/A

iTrader: (2)

So I drove it out to the park and back (5 miles 1 way). It definately is always there now and gets worse as the engine has been running longer. I think this would mean it gets worse as oil temp gets higher. I notice that if I maintain a higher power level at a higher RPM for awhile and then bring it back to idle its much worse. So bad the Knock sensor picks it up as mild detonation and the motor runs rough like I said before.

When I pulled it back into the garage I opened the hood and did some experimenting to see if I could locate the sound. Unfortunately I couldent hear it at all since it had been idling for a few seconds as I was opening the garage door. So I revved it to 2500 and held it there for 10 seconds to see if I could induce it but no dice.

Help?!?

Cat59

Suggestion? Use the poor man's stethoscope. A BIG Long Shaft Screwdriver, touching it to different area's on your motor while placing the molded handle end to your ear. It might help you in locating the origin of the knock, thereby possibly helping you in your diagnostic quest(s).

88305tpiT/A

iTrader: (2)

thanks -- I have an old broomstick I use for just that purpose. Only problem is getting the noise to happen when its parked.

88305tpiT/A

iTrader: (2)

TTT

Supervisor42

Put wood blocks in front of all 4 tires, park brake on and idle it in drive.
A/C on if you have it. Watch for ignition sparks near the sparkplugs.

88305tpiT/A

iTrader: (2)

So you think its the plug wires shorting? I dont get why you would want me to put the blocks and put it in drive if Im just looking for spark arcing?

Sorry for the second guessing but I work better when I know why Im doing something.

Incidentally I have been putting a wideband LC1 kit in today but I pulled all the plugs to check the color. They all look great, white with a touch of tan. No signs of misfire on the plugs.

Thanks for the help.

Supervisor42

If it's a "part-time" misfire, you won't see it on the plugs.
Putting it in drive puts a load on the engine and raises the compression. This places a greater demand on the ignition raising the voltage. Voltage leakage at the sparkplug will only happen when the voltage is up. Like during a stall test. Same procedure as above except the throttle is opened above idle. Limit stall time to 10 seconds with 30 seconds in between for cooling.
This only takes a few minutes to do and will eliminate the ignition system breaking down under load as being the problem.
A high voltage ignition system will make a loud ticking sound accompanied by misfire when it arcs.

88305tpiT/A

iTrader: (2)

Thanks Ill try that!

88305tpiT/A

iTrader: (2)

No spark arcing that I can see in the garage. Albeit, it isnt super dark in there but the noise wasnt present either so...

On a good note I got my LC1 and O-Meter wired in and man this thing is great. Once the wiring was done (4-hours for me) - setup is super easy and I can already tell its money well spent.

88305tpiT/A

iTrader: (2)

Ok so I called the guy who did the machine work for me and he agrees with my diagnosis. Essentially he believes it is a lifter that bleeds down excessively fast compared to the others. He says this is a common phenomenon with high performance anti-pump up lifters. The faster bleed down helps keep the lifter from pumping up at high RPM. However if the tolerance is too lose then you get the problem I am describing.

He said that I need to find the bad one so he can send it (the pair actually) back and get credit from comp. Only problem is the ticking doesnt seem to stick around very long after getting off the highway. Its almost as if I would have to pull off the highway real quick and remove the valve covers and find the ticking one all in about a minute.

The machine shop guy suggested that I bump the motor over with a remote starter switch and look to see which lifter bleeds down faster than the others. This seems like a very inaccurate way of doing it but I am essentially stumped as to how to find the bad one..

Anyone have an idea of how to find the bad one?

Thanks.

SpitotRs305

it goes away after you get off the highway? whats your oil pressure at 1500RPMs?

88305tpiT/A

iTrader: (2)

45+ PSI

SpitotRs305

okay you are using the "FAST" bleed lifters? with i am guessing a 10:1 cr or abouts with a zz4 cam?

SpitotRs305

i was thinking you might be experiencing some slow speed detonation due the those lifters and your CR well my guess at your CR... fast bleed lifters shouldn't be used with in a engine that has an decent CR for the cam used... they should only be used with a lower than necessary CR to help restore some of the low end and vacuum

88305tpiT/A

iTrader: (2)

No no. I am not using fast bleed lifters. The lifters came with the retro fit roller cam kit from Comp Cams. They are the lowest priced retrofit roller lifters you can get from comp.

Also -- this is not the motor in my sig, its a 383 I built for another car. This motor has a 210/214 duration cam (very small for 383).

Static CR is about 9.5 to one and I have a knock sensor system on it (MSD).
No slow speed detonation that I can see.

88305tpiT/A

iTrader: (2)

Well I tuned the carb a little beter than it was before. It used to cruise at 15.5 to 1 or closer to 16 I am guessing. I tuned it so it cruises at 14.7 now and I cant seem to replicate the problem anymore. I am hoping that if the problem was preignition from lean mixture that I didnt do any damage. I think I would almost rather have it be a bad lifter than have had bad hotspots on the pistons or the valves for any length of time.