Inliners International Forums General Discussion Hi Performance Lets talk about flathead combustion chamber shapes

A friend and I am designing a new Mopar Flathead head(but the same principles apply to ALL flatheads). We're to the part where we need to come up with how we want our combustion chamber shaped. Pictured below is a cast from the stock chamber. The intake side is the right(high) side, and the spark plug is almost directly above the intake valve. My main goal is to increase flow into and out of the cylinder. More flow = more power, but only if the chamber is more efficient as well.

Here's my thoughts on improvment. I want to increase the area around the valves(the intake in particular) so they're less shrouded. I'd like to move the spark plug to the edge of the intake valve(torwards the center). I'd like to add more volume about the intake valve as well. To make up this added volume, I want to shorten the area over the cylinder. I think if I make it shorter but steeper, I can gain back compression without loosing to flow into the cylinder it's self. Looking at currently avalible heads, they all have a more abrupt transition to the cylinder than my stock chamber has.

Did I miss anything? Any other ways it could be improved? What makes for a good performing Flathead chamber? Anything that should be avoided? Thanks for the input.

Wow, must be hard to guess at the rest -
Assuming you have some area of "squish" above the piston to generate swirl? Flathead is such a different animal -

I never thought about it much tho I learned on Model "A" and Ford 221/239 - there's kind of a second intake port - the piston has to pull across the "bridge" to the intake valve, then thru the intake valve itself. So the cross-section of that "bridge" between the piston & intake valve has to stay big enough that it doesnt restrict -

If it was me doing something like this, I'd study the Briggs and Briggs clones that are used in some cart racing and the Jr Dragster classes. They have a few aftermarket heads and I'm sure they've been well thought out.

When I was in my last semester of college as an Industrial Arts major, I had to take a small engines class and rebuild a lawnmower engine for a class project. I used a B&S flathead mower engine, and since I never could resist hopping up an engine, I ported and relieved the little bugger while I was rebuilding it. Long story short, in stock form it put out 4 hp on the dyno, and after my "improvements", it put out 5 hp, an increase of 20%(or maybe 25% depending on how you look at it). You might get more results from improving the fuel/air passages in the block rather than redesigning the combustion chamber. Or at least you could possibly get more efficiency from improved breathing in addition to improving the combustion chamber design.

hey, you just have to love a true hot rodder - hopping up a lawnmower engine in class!!! And you even got to learn something in the process. Horray for you