False knock update -- AAARRRGGH!

[BillC]

As some of you may know, I've been chasing a persistent false knock problem in my Typhoon since the last Nats. It has been driving me crazy. :x :x :x :evil: :evil:

I really appreciate the advice and input I've gotten, but I still need help.

I just replaced the valve springs. I was sure that was the problem, because two of the old springs had broken dampers. Unfortunately, that didn't fix it.

So, a description of the problem:

The truck has an excessive amount of valve train noise, but only when then engine's warm. When it's cold, I hear a nice, smooth sewing machine noise from the valve train. After the engine's warmed up, I hear a clacking noise that sounds just like a loose rocker arm.

I pulled the passenger-side valve cover, and tried re-adjusting the valves with the truck running. Unfortunately, I couldn't get rid of the noise. I even tried over-tightening the rockers (like a turn-and-a-half extra), but it made no difference.

I have a mechanic's stethoscope, which I used to try to track down the noise. I hear the noise loudest from the polylock on the #4 intake valve. A really loud clanging noise.

I have replaced virtually everything that can be replaced without pulling the heads or the intake. The list includes:

• Rocker Arms
  Valve Springs
  Valve Seals (did this with the valve springs)
  Distributor
  Water Pump
  Throttle Body

Unfortunately, none of that made any difference.

Does this sound like it might be a bad lifter, or does it sound like I need to pull the heads and get them rebuilt?

The motor only has about 12,000 miles on it. I wouldn't have expected any serious problems for a long time.

Thanks for your help, and for wading through this long post.

 

[jwaller]

definatly sounds like it could be a lifter. and your sure it's not pistons? what r u using for pistons?

 

[BillC]

definatly sounds like it could be a lifter. and your sure it's not pistons? what r u using for pistons?

I'm using JE SRP pistons.

The problem also appears to be temperature related. When it first started, it only did it when the outside temperature dropped below 90 degrees F, and seemed to get worse as the temp dropped. Unfortunately, since it's so cold out, I can't check if temp is still a factor (it does it all the time, now).

Engine temp doesn't seem to be a factor, since I have a 180 degree thermostat and a big honkin' radiator. It also doesn't matter whether I'm starting from a stop or cruising down the highway at 64 mph.

The problem also seems to go away when I get into boost. At least, if the knock light is blinking, it will stop once the boost comes up after pressing the gas pedal farther down. Although, I think it might have blinked once or twice at 4 psi boost (kinda hard to watch the light and the road at the same time, especially in traffic).

Unfortunately, I can't tell if the problem goes away because of the pressure increase (which might implicate the pistons), or if because of the increase in the temp of the intake air (which might implicate anything in the intake path).

The motor now has about 12K miles on it. The problems started at about 9K miles, and gradually got worse (of course, the temps also gradually colder during the same time frame).

The extra noise I'm hearing really sounds like it's coming from the valve train. I tried sticking the end of the stethoscope down into the lifter valley, but didn't hear anything unusual. I don't hear it very much when I put the stethoscope on the block. If the problem is the pistons, how do I check them?

 

[JSM]

I am thinking lifters myself, and atleast not something that is TOO bad to replace. Intake removal and valve covers...

Just a guess though...

 

[warmpancakes]

talk with je if you have blower pistons they are noisy, the blower pistons are only designed for 10 psi and arent good for our motors. The same thing happened to a truck up here in michigan

 

[Pittman]

speaking of lifters I have the crane rollers and already the number 2 exh is out. raddles at 1500rpm but goes away as revs go higher. My knock sensor is picking it up too. However its only doing it at 1500 and below.

John what lifters are you using? I think Im going to the comp cams lifters and crane self aligning rocker. I dont know why but I have one noisy valve train.

 

[ghettosled]

talk with je if you have blower pistons they are noisy, the blower pistons are only designed for 10 psi and arent good for our motors. The same thing happened to a truck up here in michigan

the only thing which would make them noisy is if you have the JE piston which is a forged piston, with little silicone. They are actually better for high boost, then the SRP (street piston) which we recommended for our street strip rebuilds b/c of the higher silicone/less clatter. They are designed for street use.