some info on flat head porting

[oldfatguy]

Flathead Porting
I found this and wanted to post it, there have been a lot of posts lately about asking about how to port or cut eye brows on a flat head. I hope this helps those interested to get a better understanding of how to do it with the pictures of what it should look like.

 

[minidragbike]

Nice info, but it's a lot different from porting a small flathead racing engine.

 

[korndog]

I was just reading an old thread over on 4cycle debating this. Just what is the prefect eyebrow cut without decking? I have seen some guys recommend very light blending and others saying to cut just above the top ring, some say channeling, some only milling the head around the intake valve, etc. What is the best way to fill the cylinder?

 

[minidragbike]

Everyone has there theorys
So what the after market big jr dragsters motor guys have done is have the blocks made so the valves seats sit at 0 degree. That way the valve goes 100% straight up, and no eyebraw cutting is needed at all.

 

[korndog]

Everyone has there theorys
So what the after market big jr dragsters motor guys have done is have the blocks made so the valves seats sit at 0 degree. That way the valve goes 100% straight up, and no eyebraw cutting is needed at all.

So, does an angled deck job accomplish the same thing or similar?

 

[oldfatguy]

I would think that what ever works on a full size car flat head should work on a single cylinder. making the rounded ramp in between the valves and cylinder should help. Minidragbike knows more than the rest of us what works or doesn't. Please post pictures of what a proper briggs eyebrow job looks like.

 

[korndog]

Here's one from 4cycle

 

[oldfatguy]

nice job fitting that valve in there