Closer inspection of the cam sprocket against the old one and it appears that while the teeth and overall thickness of the sprocket is the same the new gear isn't as "deep" on the inside allowing the washer and bolt to seat in far enough for the cover to go on.  I put the old gear on and the cover goes on fine.

I've found the old style gear on eBay, and can probably just order one.  However it has the nylon teeth and would rather use the new gear which is all metal.

Any thoughts?

Tom

On the old one the front is "dished" out more than the new one, allowing the washer and bolt to sit in further and allow the timing cover to clear.

When I put the new one on and torque down the bolt, the timing cover actually rocks on the bolt, I would say there is a good 1/16" gap between the cover and the block.  I could grind off the back but if the cam is bottomed out in the recess (I think it is) then grinding off the back might work by allowing the cam to go further into the block.

Headed back to the parts store to see if they have another one, maybe this one is defective.  If that doesn't work I'll probably just buy the nylon one. 

Replace it. China strikes again?

Start cobbling on the back side all you need is gear wobble.

I've ordered the nylon gear and will use it.  Guess it will be an unsolved mystery.  

Thanks,

Tom

The Seal Power KT3493S gear has the recess for the washer.

i just changed the timing set in my 199 a couple weeks ago. the original plastic gear, 198,000 miles. noticable wear on the teeth, chain slack, still quite a ways from failure.

i have nothing else to offer here, other than i got a Mahle kit, i think it was, with the repair sleeve.  all steel sprocket, no clearance issues. the rear is of course recessed with the locating pin.

what *exactly* is hitting? dab some paint on various places and check.

Just to be clear on the issue though in case someone else runs across it in the future -- with the timing gear, washer and bolt installed on the cam -- the bolt makes contact with the nipple inside the front of the timing cover before the cover is seated onto the block.

I put everything together on the desk so you can see.. timing cover is on the desk, bolt, washer and gear are upside down.  I put a straight edge across the back of the timing cover and you can see the timing gear is about 1/16" proud.  The issue could probably be resolved by either machining out a dish in the front of the gear for the washer or using a thinner washer.  Neither idea I'm particularly fond of.

I think machining the back down might also work but that is assuming the cam is not already as far into the block as it will go.

I couldn't find the Seal Power part number Trader suggested anywhere in any catalogs or online.

I ended up buying: Perfect Circle S-354T Engine Timing Nylon Camshaft Sprocket J3172306  A NOS off of eBay.  Although I believe you can get them under the Autozone brand:  Duralast Camshaft Timing Gear S-354N.

I also bought:  Omix-Ada 17454.07 Camshaft Gear off of Amazon.  It is cast iron also and the casting appears different in the picture from the S388s you see all over under different brands.  At least in the picture.  Who knows what will be in the box but easy enough to return to Amazon if it ends up being incorrect.

My experience that the nylon will fail..  especially on an old part.

The Omix-Ada might be the ticket -- they are a big supplier of Jeep parts and would know the difference between early and late cam gears, and correct any complaints early. The mainstream parts stores are slow to make corrections, as the parts numbers that are "condensed" are usually slow sellers anyway.

I'm with both TomJ and gtoman! A new production nylon gear shouldn't be a problem. 100K+ miles easy. An NOS gear... well, it depends on just how old it is. Nylon is pretty durable or it wouldn't last at all in this application, but it does get brittle with age like all other plastics. Probably not as fast as others, but it does age.

Most people who have experienced problems with nylon coated gears have had older engines, not brand new ones. They will generally last 10+ years, 100K+ miles -- at least under normal use. Heavy use (lots of racing or heavy loads/towing) puts more stress on them and they may not last as long. We all curse things that don't last forever in old cars -- nylon timing gears and vacuum wiper motors get a lot of grief -- even though they do their designed job well for the time they were expected/designed to do it.

Thanks everyone for the suggestions. 

Tom

that;s just freakin' weird, but parts these days... glad it worked out!