Port divider welded to the header flange

I

indyman13

Active member
I've read and read and read about port dividers. Big question seems to be concern about welding on cast iron or running the risk of burning out the header.

How about welding a tab to the header flange itself that fits into the exhaust port? Seems logical but hell, so did the Edsel!

Thoughts?
 
Like you said it makes sense, but if your header ever warped or the divider got stuck/rusted inside the head you'd have a terrible time trying to install and/or remove the header.
 
Why would you think the ports need to be divided....are they siamesed or individual runner! The only reason an exhaust port should be or need to be divided is if you are building a killer Flathead V8, these have the center exhaust port siamesed, and the 90 degree firing of the two cylinders that share the port create reversion issues when large camshafts are used. In an inline, the firing sequence is spread farther apart(120 degrees), and doesn't effect the shared ports as much as in a V-style engine....if your meaning a siamese port!
 
They are siamesed. The concern, I believe, is since the port is roughly twice as big as the rest of them it could cause a flow imbalance. Though I am no expert on port design.
 
Yes, 3 ad 4 are siamesed on my 200. I'll go with what the Ford engineers worked out on their slide rules and let 3 and 4 fight over handling the exhaust gases without a divider.
 
Airflow into and out of an engine is extremely sensitive to changes of this type, and if he still feels compelled to attempt to do this, should do so with the aid of a flow bench to comfirm that indeed there is a significant difference in flow between the larger port vs. the smaller ones to warrant this type of modification. And second to confirm that dividing the port doesn't hurt the flow more than it helps. Never assume that because the port is larger than the rest, that it flows more or better. Also, the larger port would have to be roughly twice the size of the smaller ones to be able to divide it equally to match the smaller ones, instead, by dividing it he will make it much smaller than the other ports. Take this simple example to see: If the large port was an 1-1/2" diameter, and the smaller ones were 1-1/4" diameter. Now divide the 1-1/2" port into two equal divisions....you now have a much smaller cross section by dividing the port. To start with the large port was only about 17% larger than the 1-1/4" port. Now by dividing it you made it 50% smaller than it was, and 40% smaller than the small ports are now! You created far more unbalance now than was there to start with....I say leave it alone.
 
Looking at the cost for headers, brackets for relocating the a/c compressor, differing opinions on port divider or not, two flowmasters (or equivalent), exhaust tubing and the single digit percentage increase in power I'm going to save up a little more and do the v8 swap.
 
CNC-Dude":2tu45k8w said:
Airflow into and out of an engine is extremely sensitive to changes of this type, and if he still feels compelled to attempt to do this, should do so with the aid of a flow bench to comfirm that indeed there is a significant difference in flow between the larger port vs. the smaller ones to warrant this type of modification. And second to confirm that dividing the port doesn't hurt the flow more than it helps. Never assume that because the port is larger than the rest, that it flows more or better. Also, the larger port would have to be roughly twice the size of the smaller ones to be able to divide it equally to match the smaller ones, instead, by dividing it he will make it much smaller than the other ports. Take this simple example to see: If the large port was an 1-1/2" diameter, and the smaller ones were 1-1/4" diameter. Now divide the 1-1/2" port into two equal divisions....you now have a much smaller cross section by dividing the port. To start with the large port was only about 17% larger than the 1-1/4" port. Now by dividing it you made it 50% smaller than it was, and 40% smaller than the small ports are now! You created far more unbalance now than was there to start with....I say leave it alone.
Click to expand...

The center port is roughly 2x3", and the individual ports are 1 1/4 or so. I don't think there is much of a measureable difference on the dyno when the divider is installed, though. Pretty sure it would help with header gasket issues!
 
There's always been active debate on Ports, Porting, Polishing etc...

Good point about the header gaskets. I remember reading of a racing class that doesn't allow head mods so the divider was attached to the header-bolted I think.


After all the work it sure feels faster...





PORTDIVIDER1WEB.jpg


250PORTPOLISHWEB.jpg
 
One of the potential disadvantages of having siamesed ports is the temperature abuse the exhaust valves take from having exhaust blown at them from there backside just as there trying to cool down on the seat :shock: .

Probably not too important at stock output levels, but may become more important as power levels rise (especially Turbos). I would suggest that if you are really going to "use" the headers, a port divider is "Best Practice".

Has anyone tried oven-brazing a divider into a head?

Larry
 
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