The Dodge Challenger Message Board

Hi

I am starting work on a header program for my 440 that is mounted in my Jensen Interceptor – I could use some help checking the specs before I have them made up. I may have other sets made up for sale and I therefore need to consider different OEM / S/R heads.

Please note that this car will see road use only. It will rarely if ever see much more than 4500rpm and has a redline at 5200rpm. Low down torque is what I am looking for.

My main question regards the length of the primaries?

The car has the following specs:

Engine 440
Speed Demon 750 Vac
Edelbrock Performer
Hughes HEH 1928 BL Cam – 219/228 @ .050” 111 LSA .489”/.524”
Edelbrock Aluminium heads – 10.25 C/R
Standard (Stock Torque Converter)
TF727 with 0.78 Gear Vendors Overdrive
3.54 rear end – 2.75 when in overdrive
Tire size = 25.25”
Car weight 4000 Lbs
The headers will feed into a 2 ½” system.
X pipe or crossover pipes may not be possible. For this reason the left and right side would be independent – each will have a 6”x21” round muffler and resonator. I have been thinking of using the Dynomax Super Turbo Muffler.

The original exhaust manifold that I will be replacing was #3769103, the centre dump truck manifold.

Perhaps you would care to comment on these design ideas:

1. Use 3/8” header flanges?

2. What do you think of the Schoenfeld header flanges/shape? http://www.schoenfeldheaders.com/0435DIMPRINT.htm

3. Perhaps the part 12120 www.dtprofab.com/tabzone/04_CATALOG_WEB.pdf would be better ?

4. Different heads may require a different flange shape? (E.g. angled verses straight plugs) Edelbrock and Chrysler OEM C.I. items only – No Indy, Bulldog etc Any thoughts?

5. Do you agree that a single piece header flange is preferable to three short flanges even with angled plug heads and possible access problems?

6. The basic design would be 1 7/8”OD x 36” (equal length) primaries that feed into a 4 into 1, 2 ½” merge collector. Is 36” the correct length for my use?

7. Material – At first I thought that Stay Bright 304 stainless tubing would be the way to go in spite of the extra cost it wouldn’t rust. Stainless doesn’t transmit as much heat as standard mild steel but it expands by 45% more than mild steel and is a lot more brittle. Stainless steel headers also sound different, sort of “tinny”. The real problem comes if you ceramic coat stainless – I have been told that because of the expansion, the coating last ½ the time it would on mild steel. The material option is now not so obvious! Mild steel or stainless 304? Rust is a big problem here!

8. Tubing thickness or gauge? 16 = 0.065”, 17 = 0.058”, 18 =0.049”. What should I consider thick walled pipe to be?

9. Mandrel bent bends.

10. Consideration will be given to starter motor (standard type) removal and fitting without the need to remove the headers.

11. I like the idea of a ball and socket header to tail pipe joint. Do you see any downside to this? http://www.drgas.com/Ball-Cone-Adapter-Joints.asp

12. Under hood temperatures are very high with the Jensen and I therefore believe that ceramic coating is vital (internal and external). Do you agree and do you favour anyone coating make/system?

13. The merge collector I have in mind would look like this http://www.burnsstainless.com/MergeColl ... ay_big.gif (that’s if we can make it fit the Interceptor).

14. AFR Bungs x 2. htp://www.widebandcommander.com/product/bung.htm

Your plans sound well researched and well thought out.

I am not an expert on these things but I know there are books on the subject available because I have seen some of our Mech Eng. students at the university here using them.

I general I seem to remember that the longer the primary tube the more low rpm torque and the less high rpm torque you will make. Same with diameter i think?

I can't trust my memory though and cannot remember where I used to have some info on this.

I do think you should consider a tri-y design or a collector that joins two pairs of pipes before merging into one collector. I think Flowmaster used to make a collector like this. depending on which two tubes you merged first it made more HP or more lbs/ft.

I also think you should seriously consider using a mini starter. Not only will it make life easier but they turn the engine over better too. Plus they save a few lbs in weight of course.

As far as I know there is only one company in the UK doing ceramic coating. http://www.camcoat.u-net.com/

You will find some information in the book Power secrets by Smokey Yunick. The information is not up to date and Smokey is a Chevvy man but I think it is well worth reading anyway. I can post some pages from the book if you like.