Originally posted by Was_II I just can't find any references to gasket-matching the exhaust ports except on sport-compact-buildup boards, and one mention on these boards where a guy said he killed his low end by opening the exhaust and intake ports too much.


Ever heard of an import with a Ford small block? No? Then I think you can open up the exhaust ports as far as possible to eleminate the #1 restriction in stock sbf heads.

I did some porting a while ago on a set of D8OE heads for a supercharged engine:





Exhaust ports shoudn't be completely matched to the gasket, you usually leave one edge protruding into the port as a "reversion dam". This keeps burned gases from re-entering the combustion chambers as pulses travel back and forth through the exhaust system.

Also I heard from several people that intake runners shouldn't be polished, a slightly rough finish will keep atomized fuel from sticking to the runner walls and leaning out the mixture.
Polished exhaust runners will however help to prevent carbon buildup, the same applies to combustion chambers, but removing material here will drop compression ratio, so remove as little as possible unless the engine will be supercharged (meaning a low static compression ratio is required)

Here's a pic of my combustion chamber polishing work:



The most work is necessary on the peanut sized exhaust ports, as I wrote above they are what really restricts airflow.

However if you want to put a ricer engine in your stang porting may reduce airflow velocity to a degree where it actually hurts performance

Hope this helps...

-Simon