What exactely is your engine number?
Do you have the 4.2L M119.975 in there?
I know that the E430 has the 3valve technology, but I am not too familiar with any significant variations of the 4.2L.
If you have the 4.2l engine that was introduced in 92 for the W124 400E/E420 and the W140 420SEL, it's a good engine that usually won't go bad unless it has taken some significant abuse, like overheating( cracked heads or even block etc) or has been run low on oil for some time ( no compression on a number of cylinders worn out rod bearings etc), as I have been told. This is a very powerfull engine and mistreating it can cause it to go bad quickly. A MBZ tech told me that they can achieve around the same mileage as the earlier M103's. The best I have seen so far on a 92 400E/E420 is 250K, running strong.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)