Nasty valvetrain noise, need some ideas

[86Shelby]

Starting from the beginning of what happened and what I've found, sorry it's long:
Friday I took a trip to my parent's place in the R/T and came back home, about 90 miles round trip. About 35 miles into the trip I come to a stopsign and the car doesn't idle right. No noise that I noticed, but the idle is crap, misfiring real bad. The idle stayed bad for the rest of the trip.

Throughout the trip there were times that the engine felt low on power, and others that it ran just fine. Still got 27-28 mpg overall.

I get back into town and there is a noise from the top end of the engine. Definitely not a good noise. Much, much heavier than a lifter tick, but at 1/2 engine rpm like a valvetrain issue. Doesn't sound like a bottom end knock since it's obviously coming from the head, under the rear valve cover.

I took the valve covers off to inspect everything there. I did find some damage to the intake cam caused by the pins I used to try out my rocker arm fix. I found the issues there and corrected them by moving a few rockers into different positions. I also found that my exhaust cam sprocket had slipped and was now fully retarded. Figuring that those rockers were causing the noise and the bad exhaust timing was causing the bad idle I buttoned everything back up and fired it up. Noise and misfire are still there.

I pulled the valve covers back off, laid out some towels to catch oil and started it. I was able to track down the noise to the exhaust cam, right near the sprocket. It was loudest when I would put my stethescope in the small hole at the end of the head by the rocker shaft, or right behind the cam sprocket. During this I also unplugged the knock sensor thinking the SBEC might be pulling a lot of timing due to the noise, no change after it was unplugged. After this test I saw the sprocket had slipped again, fully retarded timing on th exhaust. I'm getting some washers tomorrow to put under the screws so hopefully it won't slip again.

I am simply at a loss for what could cause a noise like that in that area.


The hole I heard the noise from is the small one, just to the left of the rocker shaft.

[lotashelbys]

Thats no good! I would pull the exhaust rocker shaft off and pull it all the way down and inspect everything. Then you can get a good look at the cam. Maybe even take off the thrust plate and slide the cam out enough to see if theres any scoring in the cam bore or the cam itself. Maybe even try a stock exhaust cam gear if you have one. I dont know just shooting in the dark here. I wish I could be there to hear it run

[86Shelby]

Quote:

Originally Posted by lotashelbys I wish I could be there to hear it run

It sounds just like a rod knock, but from the head. I didn't notice anything out of line when I had the rocker shafts apart while moving rockers around. I guess I'll probably end up doing what I really don't want to - taking the belt off, taking the cam out & inspecting everything. That means I'll have to degree the cams again, once was enough for me!

Can I take the exhaust cam out by just jacking up the passenger side of the engine real high?

[jim34]

If your bolts are coming loose that should explain the noise

[mopar2ya]

Did you make sure the cam plugs are in the end of the cams? If not you will have little oil pressure getting to the lifters. You can pop out the freeze plugs on the back side of the cams and look in there.

Also, did you get the little lifter disks in above the lifters?

[86Shelby]

I looked at everything I could. Over & over & over. Could not find anything that was out of the ordinary. I did a thorough inspection of all 16 rockers & both shafts and everything there is peachy. On the surface everything is great.

Well, I went ahead and popped the exhaust cam out far enough to take a look at the journals and bores. The middle 3 cam journals are trashed. The ones on the ends are fine. The middle three journals have ridges and valleys deep enough I don't need a fingernail to find them, I can feel them with my fingertip. Tough to get a real feel for the bores, but the portions where one would think they would wear -the 2-8 o'clock area when looking from the belt end of the head- are still nice nice and smooth with the original machined finish. I do know that when I took the head apart 2 years ago the 9-1 o'clock area was rough and needed a little polishing to get smooth again; and that was done.


500 FK'N miles and I have to take the damn engine apart again! I waited for 2 years to drive this car again and after 3 short weeks I'm nearly back to where I was when the oil pump went out.

[mopar2ya]

What all did you do to the engine, was it a total rebuild or just the top end?

[86Shelby]

Basically a total rebuild/rering new bearing overhaul. I did everything but overbore the cylinders and use new pistons.

[86Shelby]

Here's a quick pic of one of the exhaust cam journals. They were in perfect shape after Lonewolf did the regrind. I was mistaken earlier about the cam bores, the ones where the journals ran are also tore up a bit as well. While sliding the cam out and then back in it sounded like a zipper. If I didn't have the cam right where it rode before it was quite difficult to turn.

I remember seeing a cam bearing kit listed with NAPA a couple years ago and was able to track down a number on another site. Too bad no one listed the sizes of those bearings online. Hopefully I can find those so I can still use this ported head since machining the bores shouldn't cost as much as the portwork.

[puppet]

Dura-Bond Bearing Co. - Your Camshaft Bearing, Valve Seat Insert, & Valve Spring Booster Shim Supplier
These guys might help out.

[lotashelbys]

Dura-Bond are excellent bearings. They are all I use for I-shaft bearings in these things

[Wizard]

Scoring can be also another sign of bent camshaft. Have these checked and repair the camshafts.

I found two camshafts this way in 8 valve heads, one on my caravan (carb 2.2) and one on the spare 2.5L engine (pulled from junkyard).

Also while head is pulled, DO NOT linebore till head is CONFIRMED flat (wasn't this head milled without straightening the head first?

Cam journal clearance is on order of about .0015 or less and warpage limit is above that. GO FIGURE!?

Cheers, Wizard

[86Shelby]

That is a VERY good point about it possibly not being straight, especially since the center plug was welded. I know that the shop did a valve job after they did the welding because the valves didn't seal perfectly, they also surfaced it...

[lotashelbys]

How big of a weld is there on that center plug? That could of easily warped the center cam bores.

[mopar2ya]

Did the cam turn freely in the head when you installed it? I recall Stephane had a similar problem, it turned out there was a piece of weld slag in the oil galley that gouged the cam.