Per the thread title I am building my 2.25 primary, 4" collector dyno headers with adjustable primary tubes. I have tried a bunch of different calculators that use various input and it seems that the primaries should be 24-34" to the end of the tubes in the collectors.

These are going to be used for my 511" engines to start with. I know the primaries are a little big but it's what I have to work with. If my 2 1/8" primary TTI step headers fit I'll dyno those as well for comparison.

Thoughts on primary length? I was going to make them adjustable to 24", 28", and 34".

Sounds like it would be best to have something between 28 and 34. Pipemax says 31 for my combo if I recall correctly.

Thanks Greg. The wallace site was about 31" for my 511 so I figured I'd start with that.

Do you have a copy of PipeMax? If not, I'd start there.

What is the size of the exhaust valve in your heads? What is the area of the exhaust port at the flange?

My guess is that you can make plenty of power with a much smaller header size than what you are planning. Schoenfeld has BB Mopar dyno headers for $400 which is a good deal. They don't make big ones, but most engines do not need a big dyno header.

I use 2 inch dyno headers on my 514 and it makes more than 900 hp. PipeMax says I could use a larger tube size, but the exhaust valve in my heads is only 1.81 and the exhaust port isn't very large. Even a 2 inch pipe is a large percentage increase in area coming out of the head.

Header guys will tell you that the pipe size should be close to the port size if you want to maintain velocity. This is a very common topic over on SpeedTalk.

Andy that is great news on the Schoenfeld dyno headers. I didn't know they made a set. Was the set you used 1 7/8-2" step with a 3.5" collector? I'd be happy to save all of that work for $400!

No, I use a set of Stahl dyno headers which are 2" tubes. I wouldn't mind trying a set of the Schoenfeld 1 7/8 step headers, my guess is that I wouldn't give up a ton of power. Maybe 20 hp or so.

I do have a set of the smaller 1 3/4 Schoenfelds which we use for the lower performance engines. Anything with a stock exhaust port gets the smaller header.

The trick with dyno headers is that they don't need to be oversized to work since they don't have all of the super tight bends that the passenger car headers have.

If you want dyno headers larger than what Schoenfeld offers then you can get a u-weld it kit from Hedman. All of the bends are there, you just need to weld it together.

Not sure if I can post a link to the Hedman Husler catalog or not but I'll try. If the link doesn't work then just use Google to find it. Hedman has 1 3/4, 1 7/8, 2 inch, 2 1/8 and 2 1/4 dyno header kits.

http://issuu.com/hedmanperformancegroup/docs/husler-race-headers/15?e=1649135/5616318

I'd like to finish the set I started welding over the winter before buying and entire kit and starting over.

To be honest my biggest hold back is welding. It's so dry down here I'm afraid I'll burn the neighborhood down if my shop goes up.

I'm going to call Schoenfeld and see if they make a straight 2" x 4" set. Is 4" overkill? I was planning on running 2-2.125"x4" TTI's. Perhaps I should stick with the 3.5" collector and 3" exhaust that is on the car now.

Lol every time I turn a corner it's time to go back to school on something. Thanks for the insight.

Another option is to buy a small block chevy weld it yourself header kit and use the Mopar BB head flange. Cheaper, and you can get smaller sizes of tube.

What length (avg) are the TTIs for comparison? It would be interesting to test the TTI length with your new dyno headers (2.25) for comparison.

IIRC, the TTI 2" to 2-1/8" step headers have a 3.5" collector, same as their standard 2" like I run. IMO, a 4" collector is way too big for a 2" tube, and maybe even borderline for a 2-1/8". I had some Headers by Ed documentation years ago that was really "picky" on how it sized collectors based on tube diameters and applications. Ol' Ed was into sizing collectors in 1/4" increments, rather than the common 1/2" size changes.

Although the TTI 2" to 2-1/8" step headers do not have the identical tube lengths as mine, I can tell you the 2" TTI B/E-body header have a really wide range in tube lengths (from about 25" to 41") that AVERAGE to approx. 32". They're the epitome of UNequal length as a result of being "designed to fit", rather than "designed to peform". Still, they still seem to work OK.

I wish TTI made a 1-7/8" to 2" step for B/E-body, but will stick w/ my standard 2" since I don't see my combination needing anythying bigger.

FWIW, Steve Dulcich did a header comparison article some years ago where two of the headers tested on his old EMC Chapman-headed 470 B engine (700+ HP) were the Hooker 2" Super Comps (very close to equal-length primaries) and the TTI 2" to 2-1/8" step headers. There were REALLY close across the entire power curve, with the TTI averaging something like only 1/2 or maybe 1 HP more.

I never have understood people using dyno headers. If you want an idea of what your engine really makes when you use it, instead of on a dyno, I don't think you want dyno headers or a deep dyno pan.

I agree that you should test w/ what you'll actually run as closely as possible.

In my case, I had to bring along a set of Hooker 2" Super Comps because they fit the dyno cart, but my more "chassis-fit friendly" TTI 2" headers wouldn't.

Start with the dyno stuff, tune and get the fuel/air data, switch to what you are going to run and retest. That is what I would do, but they said they couldn't hook up to my headers due to the curved collector exit.

You guys are right on target as to why I can't use the headers that will be in the car. I seriously doubt the TTI's will fit on the dyno. I ordered up the Shcoenfeld set so we shall see.

We use dyno headers because it would be a complete zoo if we had to hook up to the customer's headers. Some customers wouldn't have headers, others would bring in rusty junk, some bring in stuff that doesn't fit, etc. All the profit margin goes out the window if you have to spend hours trying to use customer headers. With dyno headers they fall on, fall off, they are already drilled for EGTs, already have O2 bungs on them, etc.

Which headers did you order from Schoenfeld? If you buy them from Summit the shipping is free. Price is the same as direct from Schoenfeld.

If you got the 1 7/8 - 2 inch headers I might want to try them out some time. Or buy them from you after you use them on the dyno if you don't plan to keep them.

Andy I ordered the 1-7/8"-2" stepped headers through Summit due to shipping. Being relatively rural I am very sensitive to shipping prices.

If you are interested in borrowing them let me know ans we can work something out.

As far as EGT bungs should I put in 1/4" and use adapters to get to 1/8" if needed? I have seen some EGT's with 1/4" probes.

I used my complete engine on my last dyno session.. my
headers that I built for the car, my fuel... worked out
great
Get the Pipe Max program.. you cant go wrong... been using
that program for 20+ years and even tried to mess it up to
see how much power was lost

After yet another 14 hours day in the field I came home to these on the door step. Very nice headers for the price IMO. Next up will be welding O2 and EGT bungs.

Benefits of mass production. A person would spend a lot of time trying to build those and they wouldn't come out as nice.

The collector does need to be a bit longer to work right. I think PipeMax will tell you to put a 15 inch collector on it or something like that.

One nice thing about the Schoenfeld headers is that they have the long straight section before the collector so you can cut the primary tube length down if you want to. If you want to run a merge collector then you have the room to cut 10 inches or so off the primaries and weld in a merge setup.

+1 on the collector length; I was going to suggest 18" as a baseline.

The collector design used looks low tech, IMO. Merge or not, you might want to see what options you have to cut those off and replace them with a more efficient design (unless there's more hiding inside than the outside leads me to believe).

That is good feedback. Eventually I'll have more time to revamp my other set and maybe spruce up this pair.

I'm not really looking for some righteous hp number just trying to get a baseline on the engine + nitrous and detect any leaks, squeaks, etc. before it goes in the car. That said if I was trying to sell parts/engines and/or competitively racing I'd be more motivated to try some exhaust header variables.

This stuff is just a side hobby for me so I'm just excited to get my new combo running in the car after four years. Our local track is 45 minutes of back country roads from my house so I'm driving it there on a DOT tire, making some passes, maybe catch dinner and a movie and then putt home.

Maybe if we get serious with the Tunnel Ram/Lenco combo in the black car I'll try some of the stuff mentioned above. I am starting to consider getting an Indy low deck block however the cost seems obscene to me.

I have said for the longest time that the collector length need to
be added on.. in MOST cases it should end up in the 16" to 18" range
but other factors come into play... and a big one is RPM.... I use
to love building headers.. I think I am just over a 100+ sets.. about
14 sets for my own junk... plus doing a lot of 2 cycle chambers.. I
learned a lot of merge stuff working on chambers

Interesting notes Mr. P!

For conversation let's say I am going to run a full 3" TTI exhaust system. Would I want to cut back the 3" pipe on the head pipes and add in, for example, an 18" length of 3.5" to the collector? Is this an open header only thing?

For instance the dyno has 4" flexible exhaust tubing that goes to giant roof mounted mufflers.

Would the results improve if the exhaust was unhooked from the dyno room exhaust system? Obviously this is impractical - anybody want to weigh in on the theory aspect of it?


Also of note: I mocked up a standard Mr. Gasket header gasket to the Schoenfeld headers and the ports will need some clean up to match the gasket. Not a big deal because the surfaced them and then ground away the weld bead therefore some clean up with a carbide burr will be necessary.