To add my tiny .02 to the discussion, my 7.3L Ford has planetary gears for timing - basically for life. The T1N on the hand has the chain with apparently cams being the weak points. So my question is can the engine be rebuilt in situ or does it need to come out of the van ? If rebuilt for the cam damage I am guessing there will be metal slurry in the bottom end and bits of crap everywhere at the top end, the head will have to be pulled and I would be looking at a solid 10-20hrs of commitment ?
A clarification is needed here.
My apologies for being a bit pedantic but you would only find PLANETARY gears in the E4OD transmission (gearbox) attached to the back of that 7,3 engine !
An example :-
https://www.google.com/search?q=pla...o94MKHfajBwcQ9QEIiQEwDA#imgrc=EesKgbHCRz7slM:
In fact for clarification the engine you mentioned does have a SPUR gear timing set to drive the camshaft and HPOP pump etc etc . Helical tooth form is prefered in this application.
https://www.google.com/search?q=spu...hXD4IMKHRDvAwkQ9QEILjAB#imgrc=JfCJ0JMVosac8M:
For information on engine architecture/design MB (like many manufacturers) prefer a timing chain for the application, simply because the engine is used in passenger cars and engine quietness is a strong consideration.
Conversely the 7,3 International Navistar engine was principally designed as a truck engine for medium duty truck applications like the IH 404. --404 is of course 400 CU Inches or 7,3 litre!
Ford of course adapted this engie for light duty PU applications where noise was less of a consideration.
As for the camshafts you mention that are weak!
Essentially they are not, but rather being a cast induction/ case hardened item, they fracture when impacted by sudden arrest! (Such as in a valve hitting a piston when the timing chain arr' lets go!) in short they are not very ductile as in most applications.
The weak area is in fact the spokes on the exhaust camshaft chain wheel which fracture/shatter in some cases.
The issue is not a prevalent one but more a weakness created by mass production and induction hardening processes is the cause.
It is preferable to tear down the engine which in any case dictates removal!
Why you might ask?
Principally metal fragments and swarf are dumped into the engine oil pan/sump.
The oil pan can be removed from the engine in situ but its much quicker to pull the engine as a complete powerpack for a clean out.
In any case the head will have to be removed and the piston crowns inspected for valve impact damage. In some cases the impact can be severe and this will damage the top ring land rendering the piston as scrap.
For that very reason alone, it is preferable to pull out the pistons and carefully inspect them for impact damage. Equally the rods checked for alignment when repairing this engine after such a failure.
As with most repairs be thorough for the best results.
Dennis