Zoomie headers

[power58]

I have a 1953 Desoto Hemi (276 cube) that I want to fab up a set of Zoomie headers. Does anyone know what angle I need from the head. I can get 180 degree pipe in different radius from summit. Would it be a simple 90 degree cut ? I don't want the pipes swept back. Just nice upward from the heads. Thanks for the help.

[jimmy six]

For years JCW has had different radii, diameter, and lengths; now I think it may be aluminized. There are a few header supply places on the net with flanges. Easiest are 90 degree U bends. It takes only 4 to make a set. Good Luck

[interested bystander]

You probably need expend a little effort.
I will GUARANTEE you don't want to cut your exhaust header pipes  90 degrees to the head surface if you want efficient flow.
You're probably gonna have to make the call yourself, but stick a straight edge into the port top and bottom a short distance into the port and you should see the direction that the flow wants to go and you should see that it doesn't match the head face angle. Jocko Johnson and I did this back in '62 on my 241" Dodge hemi.
Methinks Mopar terminated the ports in '51 to get the exhaust out as convenient as possible to the TERRIBLE stock manifolds (that cracked a lot) they created way back then. You can imagine what Detroit's air flow science must have been then -or almost anyone's.
Try to maintain the direction that the straight edges shows you for at least 2" beyond the head- I'm sure that there's loads of header guys on this website (and they may argue with me on all this) that can instruct you beyond this! I ain't one uvem!

[JackD]

If you have a head loose and an exhaust valve out, you can take a healthy water hose stream into the valve pocket and see the result out the port.
Flour and a shop vac can do the same thing.
A straight segment for even a short distance is best but looks are probably a high priority also.
If you desire to put the bend right at the head, the largest mandrel bent shape will of course flow the best and U bends* will always be 180 degrees regardless of the radius.

* I just had to that that for JD.

[Bob E]

I'm in the middle of reading Scientific Design Of Exhaust & Intake Systems by Philip H. Smith and John C. Morrison; one hell of a read if your into that kinda thing. Here's what they say

At this particular point, room is quite likely to be restricted due to carburetters etc., and this will call for a fairly sharp downward bend in the pipe. This bend is not of great consequence in regard to power loss as at the moment of valve opening the pressure difference across the valve is quite high and easily overcomes quite a lot of restrictions. This does not mean that the area can be cramped (as is sometimes done when the gases are passed round a hot-spot) without causing power loss: The calculated area must be maintained at all times.

By calculated area they are referring to primary pipe diameter.

[JackD]

" He can make more words say less than any man I know."
 (A. L. sorta)

[power58]

Thanks for the suggestions. Looking forward to lighting the Firedome's fire soon.
And yes both factory manifolds were cracked.