Crankshaft is different stroke on a 304 to a 253/308. Plus 304 and 308 crankshaft is weighted differently to a 253 crankshaft to balance with the heavier pistons on the 4” bore engine. Rods are interchangeable between all of them from the first 253 and 308 through to the last 304 in VS however the rod design changes during VK to use a larger rod bolt (basically L34 rods) and again to a different design at the start of A9L engines. Camshaft, lifters and even rockers and bridges etc are the same except for the last roller cam engines in late VS (also used in parallel with VS in VT).

Edited by user Tuesday, 7 July 2020 6:52:06 PM(UTC)  | Reason: Not specified

I forgot about the timing chain, but having said that I haven't seen too many in the last 5-10 years sporting their original chain! Most are changed when a new cam is fitted.

Same with camshafts, you wouldn't be utilising an original camshaft today.

304/308 cams are pretty easy. From HT through to HQ the camshafts are the same for 253 and 308, they just retarded the cam on the 308 by using a different camshaft gear. HJ 4.2 ran the same cam.

From HJ through to VL the cam is the same for 308 and later 304 and it used the HT-HQ 253 cam gear (no longer retarded). The only exception on any GMH vehicles being the VK Group A engine. HDT may have fitted a different cam to some engines but those aren't GMH vehicles.

There were a few variations in the 4.2L cam. The first XT4 4.2 camshaft (9936254) was changed to another one around October 1977 to eliminate valve gear noise in the range 2400-2600rpm. From memory there was another one fitted when the XT5 engines were released.