Flathead Rear Exhaust Port Cut-a-Way

I had posted before on cutting up a junk 8BA block and cylinder head http://www.jalopyjournal.com/forum/showthread.php?t=319141 and decided to cut into the rear exhaust port to see what it looks like. The picture may not show to well but I took off just the roof of the port and the depth of the port is 1 1/2". Nothing shocking but does show the shape and the path of the exhaust, might come in handy when porting the exhaust ports.































Vergil

 

thanks for that view, looks like you can do allot right at the exhaust with out pulling a motor apart like getting rid of that little casting gnome and cutting that square corner off

 

Vergil:

Thanks a lot. Hopefully in a week or two, I'll be porting my lump. These pictures help immensely.

 

Ditto on the week or two, engine block getting checked out now.

Vergil

 

Great post, I'll bet it took a few cut-off wheels to it that fare.

The exhaust patch actually looks a lot better than I thought it would.

 

That's real interesting! Looking down thru the deck, I thought the exhaust was a tube that didn't connect to the back wall.

 

thats not too bad of a port and tunnel, just a little straightening work at the exit is needed. not much else necessary, or worth the effort.

 

Cool Reference post.....
Thanks
Skot

 

Very interesting, nice job, something you don't see every day. I'd really like to see the siamese center port.

 

Never looked inside a flathead, learned a few things. Thanks.

 

Cool photos. You could definitely improve things near the outlet with some hand grinding. I wonder if anyone's ever tried to Extrude-Hone these ports? There's a whole lot of rough areas in there that there's no way to get to with a die grinder.

 

Gotta wonder why Henry put that "Gnome" in there! At least you can reach it with a grinder. Thanx, man, I learned a lot about flatties here. Never realised the port went right to the back block wall, weird! You'd think there'd be one hell of a hot spot there? I see now how some oldtimers ran the ports straight out the front and back.

 

There is a hell of a hot spot there! When you put a blower on top and crank up the horsepower, this area gets a bit "charred" on the outside. As noted, you can see why the "quick way" exhausts were not terribly hard to fabricate on race motors.

 

Those pictures prove how easy it is to clean up the four corners on the engines exhaust. About thirty minutes and its done. thanks for all the work and sharing.

 

a neighbor comes by the shop now and then,
he has a 40 sedan with a pretty mean flathead in it.

If you look closely,
there are 3 threaded ports on the bottom side of his engine.
I guess there was tubing connecting them straight from the water pump,
shooting cooler water to these hotspots.
He said another trick was to have a tube inside the water jacket,
shooting water to the rear of the block from the cold water inlet on the radiator.

Now I can see more clearly why and how that would work.

THANKS FOR POSTING THOSE PICS!!

TP

 

HD there is a cut a way of the center port here http://www.jalopyjournal.com/forum/s...d.php?t=319141 but may not show as much as you would like to see.

Vergil

 

Thanks Vergil great pictures.

 

It is remarkably smooth in its wanderings...it must work pretty well, or supercharging a flathead would be much less productive than it is...

 

So if you drilled a round hole in the back of the block you could run an exhaust pipe from there about 1 inch from the valve. Do it from the front also. It would run cooler, breath better, and you would really have some spaghetti style headers. Now if you could only do something with the center exhaust path. Just thinking & ramblin.

 

Yep, if you look at some of the old time flathead diggers, you'll see they did just that.

 

I agree Bruce it is pretty smooth in fact I was expecting a very rough port. After cutting the engine open to where I could actually see how the ports were shaped I realized my thinking was not what was actually there, for example the picture below, I have looked at the ports and valves in the block and looked at the cylinder head chambers but my mind did not put together how the intake air path and the ski jump in the head was related or maybe it isn't but it sure makes a pretty picture if everything was a straight shot as the feeler gauge shows.




Vergil

 

Well, look at that. Man, this thread is really going somewhere.

It's a shame Fatdog wasn't still with us to share his vast knowledge about this topic.

 

Flatdog believed in sharply slanting the header pipe and cutting edges of port to follow that final turn towards the center of engine, cutting mostly on the ledge in there.
Ski jump fascinates me since I realized it actually closely follows Yunick and Vizard's descriptions of flow off of seat...air can only turn in limited steps, like the 60-45-30 of the seat and into the jump-and-pocket area. Found some traditional support from that route in a Navarro drawing, Don Francisco build, explorations by Holleran. Don't have a flow bench, but I still have difficulty in figuring out how normally aspirated flow can like turning down into a block relief...seems like the stiock head relief is right where it should be.

 

I have read Flatdogs posts (great reading) and looked at the cut a way ports, (have Ol' Ron's book and JWL's new book) and was thinking the same thing about the cutting away the edges and have the headers at a sharp angle. The engine I am running now I cut some of the exit edges but not enough to utilize the true benefits of custom headers. I am using Sanderson center dumps and the front header pipe is somewhat on an angle but not enough so compromised the porting a little. Dang didn't want to fabricate a set of headers for the engine in the works but might have to, oh well wanted longer header pipes anyway. Picture below is one of the ports on the engine I am running now.





Vergil

 

This has been done before. Most notable exponent is long time drag racer John "Mr Flathead" Bradley.

Photo courtesy of Steve McGuiness

 

It also shows how notching the head for more valve lift would help. Its pretty obvious that there isnt any flow over the top of the valve. Can,t argue with Ken Kloths 267 inch, 140 mph 49 Merc sedan. Also he doesnt use any external exhaust pipes sticking out the sides of the block.

 

Flatdog said there was minimal airflow over/around the valve, but enough to respect. Most flow is up and out the side of valve facing piston, obviously, but experiments with letting the valve go into a close pocket in head lost enough flow to worry about, and current thinking was very slight clearance over the valve like 040. He died while I was still thinking about this...
The old school idea held by a minority of tuners that pocket behind valve should be hogged out seems to be conclusively dead.
There seems to be a growing suspicion that exhaust flow is much better than one would suppose...if it were really bad, supercharging would be a very limited endeavor.
Also cut into head over valve should be at actual angle of top of valve. This has started me thinking of ways to apply the valve piston notch cutters sold by the cam grinders for piston clearancing...seems like they could be run in a flathead guide to notch out an aluminum head for someone without a machinest on retainer.

 

And it also shows how some cleaning, and extra help in getting cooling water to the various hot spots in the block would be beneficial.

 

well it shows how much flatheads can benefit from blower,flow is hard to get in any flathead.

 

"...I have looked at the ports and valves in the block and looked at the cylinder head chambers but my mind did not put together how the intake air path and the ski jump in the head was related or maybe it isn't but it sure makes a pretty picture if everything was a straight shot as the feeler gauge shows..."
Also the "ski jump" in the block between seat and cylinder ties into that path.
Flatdog's mantra on flow: "Air don't like to turn!"