claysmoker

Good thoughts Doug. I checked all that during assembly, and can't believe I missed anything, but who knows? I also looked at all the bottom end bits when I put the second oil pump in and didn't see any evidence of interference.

Since I have no other alternative, I will probably start tearing it down today. It's gonna be hell if I don't find anything.

AZDoug

The crank on my motor didn't give any indication it would hit the oil pan rail during assembly, but it sure did when running once it was torqued down, I had to dimple three small spots on the OP. .010" was all it took to make the noise go away.

I would check the rod bolt areas for the slightest of marks, if that was it, it wasn't bad enough to break the motor, just make a bit of noise.

claysmoker

As soon as the shop warms up I'm going to start tearing it down. I hate the mess and oily parts, but I can't just let it go and wait to see what fails. Too many $ tied up in parts to let that happen.

When I figure out what's going on, I'll post my findings. Good thing I have nothing much to do this time of the year.

AZDoug

Cam clearance is something one wouldn't normally think about unless you start doing stroker stuff, try to put 10 pounds in a 5 pound make makes for some issues. Watch all the stuff barely miss while rotating the motor was interesting, I now have about .080" clearance between cam lobes and rods/rod bolts.

Doug

EDinPA

No, I have a hydraulic roller cam from comp cams. It is a retrofit for a 427 that originally had a flat tappet cam. They specify either a bronze or composite gear for both the hydraulic and solid roller cams because of cam shaft material used.

They also require a bronze tip fuel pump rod, but I am using an electric in tank pump for fuel injection.

http://www.cpgnation.com/forum/selec...gear-5604.html

AZDoug

FWIW, the Hyd roller custom grind Comp Cams cam (from 2007) I have in my 427 SB has a pressed on cast iron gear, so no special dizzy gear is required.

IIRC, the out of the box comp XR I have in my 327 doesn't require a special gear either, as I seem to recall asking them about that. Or maybe they told me the stock GM dizzy gear was OK with the cam, I don't recall. The gear looked fin when i had the dizzy out at 1000 miles to fix an oil leak.

Doug

AZDoug

It wouldn't surprise me if they went to pressed on cast iron on all the steel cams due to issues with dizzy gears.

Doug

claysmoker

I have an XR 282 HR in the 383 currently in the car and it doesn't require any special distributor gear either. As an aside, I called Howard earlier just to make sure, and no special dist. gear is required with the cam I am running.

So far, the pan is off and I can't find any interference between the cam and rods. All the cam lobes look perfect and I can see that all the rollers are running very close to center on the lobes.

Guess I will continue the teardown.

Westlotorn

Sorry about the mess, you will figure it out and we all will gain some information that may help in the future.
I have seen several distributor gears that failed, this was when Roller Cams were first introduced. I don't recall anyone saying it sounded like a lifter or Rocker arm noise.
When you pulled the distributor the gear teeth were worn to knife edges. I think these were torn down because of timing fluctuation not noise but it has been over 15 years ago and memory fades.

cv67

Anxious to hear your findings I know that exact noise youre talking about .
Had it out tonight and clear as a bell cant figure it.
350 or 383 same exact noise.

Smilie 388

This may be a strange question but what oil pan gaskets are you using ? On the last 383 I did in my 97 Vortec the crank rubbed on the one piece pan gasket . They are steel core and made a noise when turning the engine over .

claysmoker

Well it's apart. And the bad thing is I can't find a rub mark, wear mark or anything else that looks out of the ordinary. I have not measured the bearing clearances, but the bearings look virtually unrun, and the crank throws look perfect.

There's not a mark on the cam, rods, pistons, crank or block. It looks just as it was put together.

I'm not sure I know how to proceed now, but I'll let it be for a day and go do something else.

One interesting thing I noticed is that the tops of the pistons had what I can only describe as a thin coating of grease. I can only think that this is what the coating that Mahle put on them turns to when it gets hot. I wiped them off with a paper towel and the tops are completely clean, but the coating is now gone. Does anyone know what this coating is?

Dave

cv67

ED in pa you can use an Everwear gear by Lunati also if you dont care for the bronze, compatible with any steel gear.

EDinPA

cv67

Claysmoker I have a thread about this on speedtalk got a good tip

Apparently the intake bolts can touch the pushrods or hit when the pushrods flex? Never thought about that. Maybe check yours for signs of contact?

claysmoker

Good thought, but no marks on the pushrods that I could find. They are black oxided so it would be easy to see.

Thanks for the heads up.

claysmoker

I may have found the problem. Maybe. Too much piston clearance. The Mahle pistons are made to run tighter than most all the other brands, and never having used them before I think I screwed up big time! I wish I was wrong, but that's the only measurement I can find that's haywire.

Now I have to go spend more money. Whoopee!

Plasticman

Wouldn't all the pistons be making that noise, not just one? Your initial description of the noise appeared to be once every other engine rotation. Your description was "like a loose rocker" (not rockers).

Hate to see you spend the money for new pistons, & find it was still there....

Plasticman

claysmoker

It could well be all, or some of them. It's the only thing that looks like it could be an issue. The noise resonated in the bellhousing, but maybe that's only because it's like an amplifier back there.

For forged pistons, these seem to need clearance like hypereutectics. I bought them from a Mahle outlet and was told that the clearances were to be the same as any forged piston. Now I'm finding out that they like to run half the clearance of other brands of forged piston. I typically run forged at .005 or .006, and I'm hearing now that these should be .0033 max and .0025 min. unless you are running nitrous or a puffer.

Since I can't find any other reason for the noise, I'm kinda stuck with thinking this is the cause. My LS in the C5 has always rattled until it warms up, and I've had other cars that did the same, but this thing doesn't change as it warms up, so the piston material must be very low growth.

Plasticman

My C5 (2003) does the same thing, and have had high mileage other vehicles do it, but piston slap when cold, does not make a sound (to me) like a rocker.

I would talk to Mahle directly. Also, you had stated that you did not hear any noise up front.

Plasticman