Technical Flathead Porting: Soup to Nuts . . . Pictures, Details and Opinions

How is this done? Im in a similar situation right now.

 

Plug one hole in the pattern and redrill it.

 

"... Soup to nuts..."? Where are head chambers discussed- I may have missed it?

I may have something to contribute (hint: think valve unshrouding).

 

Just contribute.

Valve unshrouding is well documented in the modern flathead books. Generally, it is done on machines not available to the backyard builder...unlike porting.

 

I haven't read any "flathead books". I'm curious if it's now common practice to barrel-shape the chamber walls surrounding the valves? The point being, to maximize flow while minimizing loss of compression ratio.

 

Joe Abbin, who has probably done as much flow bench work as anyone on flatheads, now recommends a simple plunge cut above the intake with a radiused cutter - I don't have the dimensions handy.

Not quite sure what you mean by 'barrel-shape' though.

 

Joe Abbin, who has probably done as much flow bench work as anyone on flatheads, now recommends a simple plunge cut above the intake with a radiused cutter - I don't have the dimensions handy.

Not quite sure what you mean by 'barrel-shape' though.

 

Barrel-shaped is the most simple description. The objective being to give greater valve-head-to-wall clearance while the valve head is off the seat, than when seated. It can't be accomplished by a plunge cut straight down from the deck surface of the head; a dynamic boring head on a CNC mill is the elegant approach. When I built billet heads for one-lung alky engines (for modified garden tractor pulling) I used a normal offset-boring head on a manual mill, feeding the head laterally into the rotating radiused tool (both intake and exhaust). I never got the heads (w/blocks) onto a flowbench, but the customers had good results on the track.

 

Well, there is a bang for the buck perspective too. A plunge cut with a radiused cutter is going to be significantly cheaper than a CNC program...bear in mind, you're talking relatively small improvements in flow in only the upper RPM ranges. Not viable for street use, really...

 

What do you guys think about this sharp edge before intake valve seat (shown in picture between numbers 3 - 7)? My friend told me I should porting the short side of intake port just like this before the valve seat, not make it smooth and round. Air flow would be better in tight turn.

 

Air doesn't like tight turns! I'd try and 'straighten' it as much as possible.

 

I agree with you, but he justify it that sharp corner suck air flow to valve. He hear that from "cylinderhead expert"... And that pic was in internet too...

 

What you think about exhaust baffles, any proven benefit or is flow getting worse?

 

My understanding is, as the air/fuel passes through the port some of the fuel droplets will be moving against the surface of the 2, 3, 7 side, as the air moves over the sharp edge the fuel will be sticking and sliding on the surface and pool under the sharp edge making for large droplets which will be harder to atomize in the chamber for combustion.

Vergil

 

That didn't work for me.

 

Did the sharp edge help for you?? I like different experiences that worked for others.

Vergil

 

I have a hard time believing a sharp edge will be beneficial, even if it were on the Internet, or CNN!

I think what most here may be overlooking, is the fact that all this pretty, really cool looking porting ,may not be doing much good!

Ask anyone who ports for a living, and has a flow bench.To a man, they almost all say what they thought worked before they had a flow bench, isn't what really worked! That's why I laugh when someone says they know how, "because they just do", or say they do it "by the seat of there pants"! Lol!

I think we can all agree, knocking off the sharp edges, and 'straightening' out the corners, as much as possible, will be somewhat beneficial. IMHO, though, without putting it on a flow bench, to measure results, you'll never really know how much you COULD have improved the head, with the same amount of effort.

 

No sharp edges.

 

Joe Abbin has spent quite a few hours on the flow bench with various mods. He's got some good data.

 

Why are we discussing a view of an OHV port in this thread about flathead breathing?

 

Awesome thread!!!

 

Hey D

If your gona use the the baffels, and they came with studs that are threaded all the way? Don't use them, as they will stretch very easy.
Use stock studs or order a set of ARP ones.

..............................
Taildragger&fenderless

 

I have ARP studs.

 

The problem with these ports isnt just the sharp radius but the angle of entry is very curved & there is not much that can change that. The biggest single gain in manufactured ports is in the pocket behind the valve. Reducing any sharp edge & straighten the port in that area.

 

Looks great!!

i decided to leave the exhaust baffles out, not enough time to do it last year but i have no data to say its beneficial or not.

 

bump, and save it for me, will do the same
thanks for the good info

 

Ode to Flatdog, I miss him and think of him almost daily. When our coupes were running in the fifteens, mine mid and his low he lamented his quest to get into the fourteens was frustrating and chose to go supercharged. At that time he challenged me saying if I could show him a 14.999 or lower timeslip he'd take the blower off his '34 and continue his quest N/A.

I set my goal at 14.5 and got it, but not before he checked out.

I concentrated my efforts on chamber shape and continue to tweak it. Latest rendition pictured here.

http://i646.photobucket.com/albums/uu187/Flat32/CHAMVOL_zpsb388c1c8.jpg

Flat32

 

Flat32, that's a real interesting shape! I'd sure like to see a side shot, to more fully understand the shape.

I'd sure be interested in talking to you-I'd like to try that chamber design on my blown flathead, and compare the results!

 

yes please flat32, will you exsplane the chamber shape.
thanks

 

Open where the air wants and needs to go, closed where it doesn't to keep CR high, 10-1 on my engine, and angled to enhance rotation (swirl) into the cylinder. Side of chamber opposite exhaust side is cut deeper, closer to the stud, and beyond the gasket line, yellow in the picture.

Intake is shrouded at back and when open has little clearance over the top.

Exhaust flow may seem somewhat blocked off at the cylinder, but Flatdog flow tests on exhaust showed flow out of the chamber tends to go sideways from the intake side and it makes sense that the flow is influenced by the exhaust port flow direction past the valve.

Picture is a tweaked version of what's on my engine now. Good enough to get me a 13.822 timeslip, but needs the tweak to get targeted 13.5.

Flat32