Datsun Roadster Forum-311s.org

I have a racing friend who does a lot of work with tuned exhaust, he is crunching the numbers for me, I will let you know what he comes up with, given the engine specs and target performance range (autocross) Using his input we made almost 20 WHP over commercially available systems on my RX7, with a nice fat power and torque range. (over 4000 rpm wide!)
The 1 5/8 number came from some long time roadster racers, but they road race, a different place than where we are going so it may not be a good number. Autocross requires drive-ability over a fairly wide band, much like street only we need more top end, and a little less at the very bottom

Send me your #'s via PM. I'll run it and we'll see how much different we are....
Need peak horsepower @ RPM, compression, valve sizes & lift, duration @ .050".

So I just finished reading this 9 year thread this morning and it looks like there is a 4-2-1 header in my future for the stroker I'm having built. As I was looking into ceramic coating I came across Eastwood's internal coating that claims to reduce heat. Anyone have any insights to the value of this? http://www.eastwood.com/ew-hi-temp-inte ... on-tu.html" onclick="window.open(this.href);return false;

A blog about headers from a pro! Calvin Elston of Elston Exhaust.....
http://www.exhausting101.com/" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

A quote from Calvin:
"A 4-2-1 header is lighter, easier to build, offers more ground clearance and broadens your power band. There are few reasons to consider any other layout if your engine runs under 8500 rpm. One of those is simply not knowing this. So Madbill is forgiven.... "

And another interesting thread @ SpeedTalk:
http://speedtalk.com/forum/viewtopic.php?f=1&t=41836" onclick="window.open(this.href);return false;

In case anyone thought the reading/research was over and done with.....
http://speedtalk.com/forum/viewtopic.php?f=1&t=43818

There are definitely some detractors to the merge collectors, which I am surprised about. I still believe a good 4-2-1 design would be an improvement for our cars. That being said, the currently available header was likely designed for these cars as they are, and without back to back testing (dyno or track), there is no way to tell how significant the gains would or could be, and gauge the cost factor. Among those costs would be the frame modification because I'm pretty sure a properly designed header would be longer, and of course when you start compromising on length, you lose power...but how much?? Depending on the rpm you drive on a regular basis that is....higher rpm = shorter header, lower rpm = longer header.....there are many variables to account for.
Interesting to note that if the header is working REALLY well, a cam change as well as a re-tune may be required, not easy for the R engines.
A quote by Ron E in the above thread:
"A custom set of merge/tri-y, stepped headers is probably only justified in a class racing/ non-index environment."
YMMV

I run a stepped header on my Roadster that I got from Randy Carter several years ago and it works very well, with solid numbers on a dyno. It is a BRE style header with Large primary tubes into a 4 to 1 merge collector and 2.5" exhaust with a small race muffler.

Check out Columbia Mandrel for all things needed to roll your own header. A bunch of the hot rod guys around here use them when they build headers.

Here's an interesting thread - Carb issue which turns out to be a header issue.....
http://speedtalk.com/forum/viewtopic.php?f=1&t=45148

And now for something completely different:


I really didn't see that coming!

What the ? That is against everything we know about exhaust flow. The header company need to just sell them with a few dents Like when jeans with holes were cool.

A series of venturi - restrictions can be helpful

Daryl Smith wrote:And now for something completely different:


I really didn't see that coming!

Solex68 wrote:What the ? That is against everything we know about exhaust flow. The header company need to just sell them with a few dents Like when jeans with holes were cool.

Actually there are engineering principles to explain why this occurs. The simplest being, another component(s) influences flow restriction to the degree the introduced header constriction is insignificant. Engine modeling software would identify the limiting component and why.

Yep. The primary pipes themselves are probably oversized for the displacement, so they just aren't the limiting factor anyway. If they had started with smaller header tubes in the first place, such that they WERE the limiting factor, crushing the pipes would have had a more pronounced effect.

Also, the silliness about 1,2,3 HP resolution in 480 is meaningless. Most industrial measurement systems have about a 1-10% error or so (not the digital hardware, but the analog transducers and hydraulic system and control system providing the input). I'm sure the absolute measurement range of that dyno is well over 1000-2000hp, so even a 1% error is more than what they were discussing.

Their measurement approach was fundamentally non-scientific in that if they were trying to learn anything in the 1-5 hp range, they would have to do multiple runs to the identical RPM, with no changes, throw out the measurement outliers and average the rest.....basic laboratory type measurements that are done everyday even with very high precision systems.

They probably did prove that bashing the big headers on a big V8, did not cost it 30 hp. Otherwise the rest of the discussion about minor improvements etc was not based in reality...J

I think they proved that restriction from a venturi is less and different from restriction down a smaller tube.

They stated that tube size is still important.

So I am guessing the little pinch Kevin and I put in mine to clear the steering probably didn't hurt it..lol