is there a difference between the normally aspirated head and SC cylinder head on a 95-97 X300? Thanks Nick

 

Hi Nick,

According to the Electronic Parts Catalog (EPC), which you can download from this forum, the part numbers for the N/A and SC cylinder heads (less cams and valves) are different:

N/A to engine 128486: NBC2510BA
N/A from engine 128487: NBC2510CA

SC: JLM12075


My assumption would be that the SC head is designed for lower compression than the N/A head, but one of our tech gurus will know for certain.

Cheers,

Don

 

Thanks Don ,I had thought the compression ratio was set by the piston choice.If it is controled by the head choice maybe a SC head could be modified to use on a NA engine? Nick

 

Andy and others will know the answer.
I may be the lower SC compression is a mix of both lower piston height/shape, and larger cylinder head volume
I will be interested to find out...

 

The difference in compression ratio between naturally aspirated AJ16 engines and the supercharged versions was achieved entirely through the design of the piston crown, which was dished on the AJ16 SC engine. After 20 years I can't remember using different cyl heads castings in development, so it must have been quite a subtle / late change. My guess is that higher exhaust valve seat insert material was specified for the SC engine, if the part numbers for the two bare heads are different. In which case, the two heads would be physically interchangeable and the cyl head for an NA engine would probably last on an SC engine unless you were conducting an engine dyno durability test (eg >100hrs running at peak power - not really likely in a car)

 

Thanks thats the info I was looking for. I picked up a new in the box sc cylinder head at a good price. It's good to know that it will work on my NA car as well if needed Nick