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Old 12-16-2010, 12:29 PM   #7
Flathead Fever
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Join Date: May 2010
Location: Yucaipa, CA
Posts: 1,091
Default Re: exhaust port dividers

Years ago I went to visit John Bradley “ Mr Flathead’ who at one time had the world’s fastest flathead dragster. He told me he did not like the bulky cast dividers and preferred to tack weld in an 1/8” steel plate divider. I had a pattern laying there that he let guys trace so they could make their own. I’m pretty sure on a street engine that the tack welds would eventually break, but on a race engine that has had the water jackets filled solid and exhaust ports coming out places that never had them I don’t think a broken tack weld was a big concern to John.

Another guy I interviewed was Pete Henderson. Pete was good friends with Randy Shinn who held the SCTA Roadster record back in 1947 and 1948. Pete credited Randy Shinn as being the first guy who came up with the idea of using port dividers. Pete seemed to think the dividers made a difference on an all out dry lakes car.

There is probably a benefit to using exhaust port dividers with a big high duration cam. On a mild street engine I’m not sure they make much difference. I went ahead and installed the cast dividers in my 59A engine that has a Winfield SU1A cam, just so I can say they are in there, it’s a nostalgia thing. I ground down the dividers to remove a little bit of their bulk, then I made them pretty with a Roloc disc.

I own Dave Mitchell’s Olds powered pickup from the fifties. I had to recreate the original 1951 left header which was made from a ’35-36 Ford Driveshaft with ¾ inch thick flanges, it took me a month of my spare time to build it. These early Olds V8 engines only use three exhaust ports, the center two cylinders share one port just like a flathead does. While I had the header off I noticed that the Olds head has a factory built-in port divider (see photo) I think the GM engineers stole this speed secret from the flathead Ford guys.
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File Type: jpg Mitchell Hedder 042 copy.jpg (480.6 KB, 51 views)
File Type: jpg olds.jpg (319.9 KB, 78 views)
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