Tower Or Nub On The Timing Cover?

[HOrnbrod]

I have the 1997+ power steering setup with the newer intake manifold. I use a serpentine belt for the 1999 and up XJs and route it the same way as in the pic below. I noticed yesterday some fraying on the belt, and when I pulled it, I could see the belt had been riding across the nub pictured below (not my pic) on the timing cover which tore it up over time. I broke out the old Dremel tool and cut it down about 3/8", replaced the belt, and now have plenty of clearance for the belt to ride. My question is: What is the purpose of that nub sticking up near the timing marks? Anyone know?

 

 

[HOrnbrod]

No one knows huh? Well, I don't either. Anyone have a guess?

 

Also, anyone have a 97 and up XJ? Curious if the timing cover on those has that protuberance/boss/nub or whatever it's called.

[Geonovast]

My 99 does not have it.

 

I've seen 4.0s with them and without them, never seemed to be any rhyme or reason for it.

[Alexia]

My 1997 does not have it. It may have been for the original casting process.

[HOrnbrod]

Thanks Correy. Looks like the cover part number changed in 1994. Maybe it's there for casting purposes.  :dunno:

 

EDIT: You beat me Alex. 

[64 Cheyenne]

I've seen this on different vehicles with a hole all the way through. (so the timing marks could be seen?)

I always thought it was a "target" to shoot a timing light through, a "fixed reference point" if you will, that does not change.

Maybe a fixed target on some vehicles before/after centrifugal or vacuum advance.

[HOrnbrod]

Good a guess as any. When I cut the top off it was a hole all the way through.

[Geonovast]

Makes sense, looks like the 258 uses the same cover, and changing the casting unnecessarily would have been a waste of money.

[Keyav8r]

My 88 has the hole all the way through. I was thinking if it could have been an alternate CPS mount on some version of the engine. The harmonic balancer would also have to be different if that were the case.

[FrankTheDog]

If you used a Goodyear gator belt it would of chewed right through that nub until it was self clearanced.

That's what happened to my son in law. Didn't notice it and the belt just ground it away, it didn't do anything to the belt.

[HOrnbrod]

If you used a Goodyear gator belt it would of chewed right through that nub until it was self clearanced.

That's what happened to my son in law. Didn't notice it and the belt just ground it away, it didn't do anything to the belt.

 

That's exactly what happened Frank. I had a Goodyear Gatorback belt installed. It did groove out the nub as you said, but it also frayed/flattened out two of the six ribs on the belt. I only noticed the fray on the belt when I replaced my distributor and was checking the timing marks with a timing light. Probably would have been fine for awhile more, but I chopped the top off the nub and installed a new belt to eliminate the rubbng.

[Comanche County]

Magnum engines have that nub too. 

[AMCJeepMJ]

My 2.5 has the nub as well.

[HOrnbrod]

Magnum engines have that nub too. 

 

Magnum engines? You mean the 5.2/5.9 V8s?

[MJ_Milam]

No one knows huh? Well, I don't either. Anyone have a guess?

 

Also, anyone have a 97 and up XJ? Curious if the timing cover on those has that protuberance/boss/nub or whatever it's called.

those are for an inductive timing light pick-up wand. old technology, I'll see if i can find a picture

[MJ_Milam]

it hooks up to an old Sun oscilloscope and fit's in the hole and used for timing. I've seen long metal ones also but couldn't find a picture. It works like a hall effect and triggers like a timing light on the scope. sorry about the small picture, it was the best I could do

[Comanche County]

 

Magnum engines have that nub too. 

 

Magnum engines? You mean the 5.2/5.9 V8s?

 

Its kinda pyramid shaped into the magnum timing cover,,,not really the same shape, the belt doesn't ride as closely as in the 4.0L.  I only mention it because its a larger sort of piece cast into the timing cover.  I think it just to aid in acquiring the timing.  I sold my spare 5.9 engine and I couldn't get a clear pic on my DD.  Either way, its non-consequential, I only mentioned it because I also thought it strange to cast in a large piece of metal that's really not needed.  FWIW....?

[64 Cheyenne]

it hooks up to an old Sun oscilloscope and fit's in the hole and used for timing. I've seen long metal ones also but couldn't find a picture. It works like a hall effect and triggers like a timing light on the scope. sorry about the small picture, it was the best I could do

 

I like this answer, learned sumthin new...

[HOrnbrod]

it hooks up to an old Sun oscilloscope and fit's in the hole and used for timing. I've seen long metal ones also but couldn't find a picture. It works like a hall effect and triggers like a timing light on the scope. sorry about the small picture, it was the best I could do

 

I remember those Sun Analyzers and MJ_Milam's answer makes perfect sense. Probably had the holes on the old 4.2 engines drilled all the way through the nub for the wand to time them, then kept casting the covers the same way w/o punching the holes when the distributors became fixed. Thanks for all the answers.  :cheers: