Lack of bore notching on big $$$ engine builds
 

This may be a stupid observation, but as people post pics of their big money builds I’m not seeing much bore notching happening. It’s seems like easy HP with no drawbacks, so I’m surprised to not see it on every refreshed/built engine. Am I missing something?

It might depend on finish bore size and chamber, how much notching would you do on a 4.6 bore block with .240 between cylinders.

Likely too much cost for maybe a small gain. It is also hard to isolate the impact of bore notching with all the other upgrades involved in a fully prepping block.

My head guy that bore notches my 454 blocks says that the valves are unshrouded enough on 4.5" bore and don't benefit from it. But, on a built 454 that has good heads and air flow he has seen 20HP on the dyno. He pulled the heads on the dyno, notched the bores and made a few more dyno pulls. These are not 330's these are more 600Hp 454's.

https://cimg4.ibsrv.net/gimg/www.off...e5378bd6d2.jpg
https://cimg2.ibsrv.net/gimg/www.off...0488116359.jpg

As said on the bigger bores it really doesn't help enough to make it worth it.

Notch
 

Are you talking about unshrouding the valve around the edge cylinder bore area. 4.600 bore (:

Just make sure you don't grind down into where your top ring is going to come up the bore.
On a 454 it makes a big difference. On a 502 or 540 it helps enough to make it worth it to do.
Anything bigger in bore size I wouldn't do at all.
I have done this myself to all of my engines up to the 598. On a 4.6 bore there isn't much between the cylinders so I don't want to make it even smaller.

Biggest issue hindering airflow is typically valve shrouding on a bbc. Alot of heads have chambers designed to fit smaller bores, like a 4.250 bore. Especially an issue when you get into 2.25+ diameter intake valves.

Also, I am willing to bet bore notching would show bigger gains when tested with a stock like 26* valve angle head, vs say a 24* angle or shallower head with a better canted angle.