Jeep Strokers

dwg86 wrote:I have also heard that a hyd cam is ground to keep the cam in the block, but most engines have some sort of cam retainer. And engines that were not manufactured with a cam retainer, have some sort of after market retainer (SBC).

Also, I don't know if it was the 4.2L or 4.0L but one of the engines originally didn't come with the pin and spring to begin with. It was added later and there is an AERA bulletin on that being a fix for a knocking sound. And Jeep did switch to a retainer plate in the last years.

I have also heard that a flat tappet cam is ground to pull the cam back into the block. Then what would be pushing it forward? The oil pump?

I mocked the engine up yesterday(head on w/ old gasket, torqued down, solid lifters, rockers, engine mounts, etc) and couldn't find any issues. I left the timing chain off so I could just feel the cam and valve train with out any interference from the crank and pistons. With the head on, and engine mounts on, the cam still turned fine. With the valve train on I didn't find anything that indicates any binding. With the full valve train on initial torque to get the cam turning is 265-390 in lbs, depending if I started it when a valve was near the full open or not. Constant rotating torque is 159-160 in lbs, again depending if a valve is opening or not.

I also measure how far forward the cam can move with its the spring and pin setup. .105" and with the valve train out it didn't require much force to get it to. I don't see how that would hold the cam in the block with any real force against it. If the cam is bouncing back and forth it would certainly explain that knock sound that was always present.

The cam is forced rearward by the helical cut in the dist/oil pump drive gear, that end play is zero while engine is running. One thing I came across in the FSM regarding timing case cover was "if there is evidence of rubbing against timing cover, by end of camshaft, examine the oil pressure relief holes in the rear cam journal to ensure that they are free of debris". WTF? Oil pressure relief holes in rear cam journal? Can the plug in the back of the cam tunnel be inserted as to block anything; is it put in like a freeze plug, or put in reverse from a freeze plug. Could there be the lack of venting or "burping" of air at the cam journal oil galleries that prevents flow there? While the cam is being forced backward by the helical gears, could the timing gear be allowing the cam to move too far rearward differently than the stock one blocking anything?

One other thing on rod end play: Spec is .010 to .019". Is that total or per side? That's got to be total or .005 to .0095" per side.

I6FAN wrote:The cam is forced rearward by the helical cut in the dist/oil pump drive gear, that end play is zero while engine is running.

Techinically that might be true, but its not how it works in real life. Im not refering to my engine in particular, but at least the I6 in general. If that cam was always back in the block they wouldn't have added the spring and pin after reports of a knocking sound. Nor would they have switched to the thrust plate.

One thing I came across in the FSM regarding timing case cover was "if there is evidence of rubbing against timing cover, by end of camshaft, examine the oil pressure relief holes in the rear cam journal to ensure that they are free of debris". WTF? Oil pressure relief holes in rear cam journal? Can the plug in the back of the cam tunnel be inserted as to block anything; is it put in like a freeze plug, or put in reverse from a freeze plug. Could there be the lack of venting or "burping" of air at the cam journal oil galleries that prevents flow there?

There is a hole on the last journal to let pressure out from between the cam shaft and the cam plug. I had inspected it in the past, but I will take closed look now that you mention it.

While the cam is being forced backward by the helical gears, could the timing gear be allowing the cam to move too far rearward differently than the stock one blocking anything?

Doesn't look like it. I don't see any alignment issues with the lobes or journals.

I6FAN wrote:One other thing on rod end play: Spec is .010 to .019". Is that total or per side? That's got to be total or .005 to .0095" per side.

Yes, that is total. You insert the feeler gauge on one side to get the measurement.

this could be a long shot, but i saw on tv one of those car shows was building a v8 where they had to actually pound the timing cover with a rubber mallet to adjust cam end play. could you try that or would the cover just shatter?

That would work for a steel cover and i have seen that done. Out aluminum covers would just crack.

I pressure checked the gallies this weekend and saw no bubbles or anything to suggest its cracked. I also replaced the stock cam button setup with a static one. I currently have .0055" cam end play, with some RTV it will probably increase a bit. I've been trying to think of what would push the cam out of the block, if it is doing that. Its a flat tappet so it pulls the cam into the block and the oil pump should do the same. But even on stock engine they had an issue with the cam walking w/o the stock button. I also checked the cam and crank timing gears and they were in line with each other. One thing i did notice that on the previous assembly what the #3 cam journal had a lot of lube left on it when the cam was inserted then pulled back out a bit compared to the others. Not so this time. I guess its time to put it back together and see what happens. Really, the only change was the coated cam bearings and someone else installing them.

This is new. A few of the valves are like this. I can't feel it with a finger nail. That line in the middle of it is where the valve seal is.


Some more images:
http://jeep.blackonyx.net/forum/valves/

What is it? Gauling? I don't see how as the valve guides aren't new and it was a rebuilt head. This is the first time I have seen it in the failures.

How about the restictors to top end? Or maybe debris embedded in seals from the failures? Are they intakes and exhausts, or limited to one or the other?

Not limited to either intake or exhaust. Possibly crap from failure but IIRC I replaced the seals at some point. Maybe the restrictors could have played a part after the bearings failed and the pressure dropped.

How can there be wear marks down from the seal contact??? Unless there some crap in the guides too? But I find it weird.

edit : looks to me that the problem is inside the guides. But it seems to be only on one side of the stems, am I wrong?

Yes, not all the way around the stems. The line you see is where the seal rests when the valve is stationary. and the line is only in the wear area, not all the way around as well. Also, the wear is also below where the seal is as well.

Looks like the valve seats are not concentric to the valve guides. Or maybe the guides are out-of-round or worn out of specs?

Its not the rocker arm to valve issue.. the wear pattern is even all the way across the stem. Even if the roller locked up it would just act like a stock rocker... so its not the rocker to valve relation. Someone mentioned the spring pad not being cut square with the valve stem. But would a non concentric valve seat cause wear to that extent? I would think it would only be when it gets near the seat.

I guess the valve seats would not cause wear on the stem to that extent, you're right. So I would think the valve guides are worn, either out of round or out of specs. That's one theory.