New/Modified Header Design?

[Daryl Smith]

CSP - If you are looking at the bends, they will be smoother bends than my mockup....

I think the biggest 'choke' point is at the intake manifold. Smooth slow bends are best, having the intake right there forces a pretty quick bend to avoid it. Custom intake manifolds could move the obstruction further away from the head.....
After that, yes, without the starter there you would be able to angle the pipes toward the back of the engine bay, and have a couple less bends, but it's not terrible as is, and we've all seen a lot more complicated headers than this. The fewer bends the better as each bend adds restriction.

All that being said, comparable Volvo, Triumph, and BMC engines are getting plenty of power from similar setups, and Lou Mondello and Rebello seem to be getting 180+hp with the currently available headers. What we have is workable for the R16/18/20+ and the U20 (225+ hp?).

For me, this excursion with the 4-2-1 is less about peak horsepower (tho I expect an increase) than it is about throttle response and power 'under the curve'. I expect (tho no gaurantee) a very noticeable increase in both, due to what I think is both a better design and sizing.
The race prep manual for these cars showed a picture of a 4-2-1 header saying it was good for 9 hp. Nothing said about throttle response or the torque curve. I look at that picture and think...no attempt at equal length primaries, collector designs could be better, and what size pipes were they using?

There is also the fact that almost every OEM exhaust I've seen for the inline 4 cyl is a 4-2-1. Almost everything I've read says a properly designed 4-2-1 header gives up almost nothing under 8,000 rpm for peak power, and increases the torque curve substantially - this covers 99% of the cars out there.

The big question is...Are the gains, if there, worth the cost? We are not talking about a $300-$400 header, even mass produced I'm sure it would be substantially more. I'm told a very well designed header exhaust system is worth 10-12% power increase over early OEM designs.
What would it be over the currently available header if at all?
How much would the increased throttle response and low end torque be worth? Likely to also increase fuel mileage...
What would that be worth if it all works out as advertised?

[Jdurban94550]

I'm looking to redo the exhaust on my 70 1600 so am thinking I would pull the trigger on a header sooner rather than later. Dean at Datsun Parts has two headers for a stock R16. Stock motor use 1895 or 2530. I honestly cannot tell the difference between these two headers other than manufacturer and price. Any thoughts on these two headers? Preferences of one over the other?

He also has a performance header part #2877 that appears to be for a stroked R16. If I plan to stroke the R16 in the future, should I just go with the 2877 now? Are there any downsides to using a performance header with a stock R16?

[Daryl Smith]

Jdurban,
Dean's own testing with Rebello has shown that the 1 1/2" header is good for 180 hp.
Unless you plan to spend a good chunk of money building the stroker for horsepower, the standard 1 1/2" header will be more than adequate, and is, from my reading, already 2 steps too big for a stock, or even modified 1600 or 1800, unless you are making over 120 hp. jmo.

[Pjackb]

Are there any downsides to using a performance header with a stock R16?

In my opinion, on a completely stock R16, all you’re likely to get from a performance header is more noise and heat. Performance headers, especially a 4-1 design like you're looking at are tuned for higher RPM performance, but your stock R16 will barely hit 5800 RPM. This means you won’t really see the benefit of the increased flow in the RPM range where the engine spends most of its time. Additionally they have 1.5” primaries, which are too large for a stock engine making ~80hp net at the crank This can actually hurt exhaust velocity and scavenging, reducing low-end and mid-range performance—where a stock R16 spends most of its time.

Even if you plan small upgrades down the road, like a better cam, I’d argue that the stock roadster manifold is very well-designed for this engine. Its 4-2-1 design is specifically tuned for a good balance of low-end torque and mid-range power, which is what makes the car enjoyable on the street. Unless your R16 is making 125 HP or more (which is a lot for this engine), the stock manifold might actually provide better usable performance for street driving.

So, unless you’re building a high-RPM race engine or planning significant upgrades, the stock manifold is probably the better choice. It’s efficient, reliable, and already optimized for the kind of performance your R16 is designed to deliver.

Let us know what you decide, though—it’s always fun to experiment and see what works for your setup!

[Daryl Smith]

"...I’d argue that the stock roadster manifold is very well-designed for this engine. Its 4-2-1 design is specifically tuned for a good balance of low-end torque and mid-range power,..."

Pjackb, respectfully, I have to disagree with this statement. Tho I have never seen, nor heard of a comparison test of the stock manifold vs the 1 1/2" header, I would personally go with the header every time at least it separates the 2/3 cylinders all the way to the collector..
The stock manifold is NOT a 4-2-1 ....it is a 3-2-1 as the 2/3 cylinders are combined into a single pipe as soon as they leave the head. As well, all three pipes are much larger than the 1 1/2" pipe of the header. I know the Brits have done pretty well with the 3-2-1 headers on their 5 port 4 cyl heads, but, it is far from the best design. I think "specifically tuned" might be giving more credit than due, tho likely much better than a log manifold.
We are stuck with a 1 1/2" header because that is the size that covers the exhaust ports. If the ports were sized to the output of the engine, they would be equivalent to a 1 1/4" header...or smaller.

I had a 1 3/8" primary (made to work with the port) 4-2-1 header built years ago that I didn't accept because I didn't like the welding. It was bought by someone on here and is floating around somewhere. it is a decent design but did have a flaw in that it hung down a bit to low. If that were fixed, I'm guessing that header would be good for somewhere around 140 hp or better. Find that header, fix it and ceramic coat it and you'll have a dam good header for a built 1600, an 1800, or a median built 2L stroker.

Happy New Year!!

[Pjackb]

Pjackb, respectfully, I have to disagree with this statement. Tho I have never seen, nor heard of a comparison test of the stock manifold vs the 1 1/2" header, I would personally go with the header every time at least it separates the 2/3 cylinders all the way to the collector..
The stock manifold is NOT a 4-2-1 ....it is a 3-2-1 as the 2/3 cylinders are combined into a single pipe as soon as they leave the head.

I won’t argue you may be right , it’s my opinion but I have not tested them back to back so it’s all guesswork on my part , regarding the size of the pipes I know the OD of the pipes are typically much larger because of thickness of the manifolds so I’d be curious to know what the ID is

What I can say for certain however is that I’ve tested something similar in my 510 using the stock manifold and the performance is undeniable
It’s common practice to use the 1600 manifold with longer down pipes for mild 2.0 and 2.3l builds that are in the 140-150hp range as it outperforms most headers on street builds save the long tube 4-2-1 units
Here’s a few pics of my build

[Daryl Smith]

No problem Pjack,
I'm guessing you haven't actually seen a stock 1600 exhaust manifold?
It is not a cast unit. It is welded sheet metal and the pipes are not round.....and they are prone to cracking.....
The L series were a MUCH better design!

Happy New Year!

[Daryl Smith]

Picture of the stock exhaust manifold on ebay right now.....
https://www.ebay.com/itm/315686296373

Okay....some of the pipes are round....

[tangoterje]

Here’s a 1.5" header I bought from Lou Londello. Still not wrapped up this engine, but will hopefully find out how it performs before this spring (meaning summer).

[david premo]

That is a beautiful header, one quick comment the engine mount in the picture is the passenger side mount. It might be a little bit of a problem as it will not orient the engine properly in the car.

[Pjackb]

Here’s a 1.5" header I bought from Lou Londello. Still not wrapped up this engine, but will hopefully find out how it performs before this spring (meaning summer).

I spoke with Lou about this set but the cost and shipping to Canada did not make economic sense and I might end up doing something similar locally

[Pjackb]

Here’s a 1.5" header I bought from Lou Londello. Still not wrapped up this engine, but will hopefully find out how it performs before this spring (meaning summer).

I spoke with Lou about this set but the cost and shipping to Canada did not make economic sense and I might end up doing something similar locally

[tangoterje]

That is a beautiful header, one quick comment the engine mount in the picture is the passenger side mount. It might be a little bit of a problem as it will not orient the engine properly in the car.

Ah, possibly, I can’t remember This was just a quick mockup for a couple of pictures. Lou made me a custom engine bracket though, to avoid having to use the exhaust brace (or whatever it is).

[tangoterje]

Here’s a 1.5" header I bought from Lou Londello. Still not wrapped up this engine, but will hopefully find out how it performs before this spring (meaning summer).

I spoke with Lou about this set but the cost and shipping to Canada did not make economic sense and I might end up doing something similar locally

They certainly aren’t cheap. Not as much aftermarket support as our plentiful L-engines. But hot diggity, I remember the first time I drove my U20, couldn’t stop smiling. Very different from my «very serious» Z car, haha.

[Gregs672000]

When I contacted Lou he pointed out that his header will only work on right hand drive cars due to the steering rod interference.