SM Head Modifications on a budget

Yup.
I’ve had people argue with me about it, but when you have them sitting on the bench next to each other, and run your finger over the SSR…….. it’s quite obvious.
And I’ve had X and J heads in the shop at the same time on multiple occasions.

In my assessment, the X head has the better intake port as cast. The SSR apex is shaped and placed in the correct location for a 2.02 valve, because that’s all they came with.
The apex of the J head is moved towards the guide to be able to work with a 1.88 valve.
When the 2.02 is installed, the corresponding bowl cut ends up making the final approach of the SSR into the bowl much more abrupt and steep.
Which is why an untouched X head outflows an untouched J head.