INLINE SIX EXHAUST HEADER

[maxeffort]

Feel free. They were only a "secret" till I opened the hood. Hey, I "cameup" with the idea when I saw a NASCAR upside down in a photo. The pictues are also on the GMC Truck site. Good Luck

Nothing I do will be as beautiful and exotic looking as those headers and its a much different chassis.

This will be DIY headers. I will do some mock-ups of dual headers and single. I will consider dual headers, single header with single merge / collector and also the triple merge of your design.

The exhaust port has no divider and the port is so weak now that I'm very reluctant to divide it.

At least we have some ideas and dimensions from your dual headers to work with.  On the dual header where outer  pipes were 1-5/8" ,  the shared ports were 1-7/8".  That means 2.07 sq inches on the single and 2.76 sq inches area respectively. I had suspected that the shared port would not require double the area of pipe.

What diameter collector did you run on those?

Also on the single header, its tough to count pipes on those headers, but it looks as if the the share ports are still using one pipe. What are the diameter of primary pipes and merge collectors? (excluding steps, just average diameter of both the single and dual port primary tubes)

A friend was trying to help calculating from mini cooper headers, but I believe that worked out way too large.

The dual header dimensions seem more in order.


BTW, on the intake we did use a divider, starting well past the entry  were the port opens up for two valves.  I think we would have had more flow without a divider, but less quality.

Thanks,
Keith

[jimmy six]

On the duels the collectors are 2-1/2". On the single they are 4 pipes as the picture shows. They still have a single on the shared exhaust port. The rest is hard to answer as the exhaust is currently on the car and wrapped the entire length. They did start with the same diameter as my duals because of the it mating the exhaust port of the head. The steps were 1/8" up for a total of 27-28" before the first merge. Out of that merge the ID is 2.100" The ID of collector at its merge is 2.600". The collecter is a meg as shown.

If you go to www.burnsstainless.com and open their catalog you will get a better idea. I could duplicate all of this in mild steel mandel bent u bends from one of the many sites on the net. I have made my own GMC header flanges from 3/8"  so they would not be a problem. There are some header flange suppliers out there so look then up even for your application, there may be some.

Also the design on mine is very specific to my engine. Cam lift, duration, RPM, comp ratio, etc....Good Luck

[Milwaukee Midget]

Cam lift, duration, RPM, comp ratio, etc....Good Luck

All critical points on shared exhaust ports, and I would include overlap.

A friend was trying to help calculating from mini cooper headers, but I believe that worked out way too large.

And that would make sense.  On a six, your power strokes occur every 120 degrees - on the Morris engine, your strokes occur every 180, so on a six, you have less time to evacuate the combustion chamber before the neighboring exhaust valve opens.   

[panic]

Yes, the Mini-based primary OD looks too big, but only compared to your valve & port size.
The downside of small primaries is backpressure (= increased pumping loss), and perhaps a bit more residual gas in the chamber (except during favorable wave return conditions). After leaving the head, the pumping loss from exhausting a 65" cylinder through 40-50" of 1-5/8" pipe is considerable even after allowing for reduced VE. Larry Widmer has demonstrated that really high gas speed in the exhaust port isn't necessarily fatal, and Blair says that the instant speed at the port is perhaps 6 times as high as the "mean" speed as used for calcs in a well developed engine.
The upside of small primaries is reduced reversion at low to moderate speeds (which will make carb jetting easier) and a stronger return wave especially at moderate speeds.
If your VE at peak is 75% (fairly bad - we hope this is an understatement!), the engine is still effectively 284", giving about a 2-1/16" primary.

[Blue]

Early in this decade, I spent the better part of two years trying to make the ideal in-line 6 header and then used Burns Stainless' design software.  Nothing beats it.  The siamesed ports are a big issue, e-mail them and find out what their solution is.  They are incredibly helpful and have the best prices for tubing and far-and-away the best collectors.

www.burnsstainless.com

[comp]

good link