Bore Notching
 

I will be be bore notching a +.030 over 454.

Do I notch to match the cyl. head combustion chamber?

Thanks

Scribe the head gasket chamber. Stay away ring depth.

Bore notching is said to be worth about 30hp or so on a 454-468cid engine and is a simple/easy free HP job---just so you know and be aware that your compression ratio will drop some when bore notching the cylinders though. Have fun.

DONT SCREW UP THE BLOCK BY MAKING THE VALVE RELIEF NOTCH CUT TOO DEEP DOWN length of THE BORE.

.........otherwise the top piston ring will not seal....!!!!

3/16" into the bore and gasket as template is ample, all you're trying to do is unshroud the intake valve

I agree,...and I should also add that the "30hp gain" is something that was told to me by someone years ago from some back to back dyno testing that was said to have been done here locally so, not exactly sure how true or accurate the "30hp" claim is, but logic would say there should at least be some HP/TQ benefit from the un-shrouding the valves. Whether it is worth 30hp or not I do not know as I have nothing to back up that quote.

The GM factory did it on their 454 blocks...although it appeared to be kind of a crude machining type of fly-cut process, they must have still thought they had a good enough of a reason to make it worth doing.

Also consider whether the block was decked. If somebody shaved 020 to zero deck the pistons the rings are up that much higher. I would assemble and check where rings actually top out before notching...

The block has been decked .020 making the piston to deck zero. I will be using layout dye and making templates to keep each notch the same. I plan to stay .100/.125 from the top ring. The compression ratio calculators say I should be right around 10 / 1 so lowering it a bit will be just fine with me.

Thank you for the advice.

How is your valve shrouding situation within the combustion chamber itself? What heads are you using?

I will be using AFR 305 heads once they get to me.