It may be that your L28 is de-rated through design due to smaller carb and smaller exhaust..... thus your results

I found this cool cedric post with a nice satin blue http://retrorides.proboards.com/index.cgi?board=readersrides&action=print&thread=48875

Yep, that's probably true and the reason why there is such a jump in power with modifications. Seeing the results were so encouraging was more than enough for me to continue searching for more power.

Cheers.

PS Nice thread on Cedrics, thanks!

This is one of those frustrating reports where you don't know if the added performance equipment is very good, or the replaced equipment was very bad. No offense oz, I've enjoyed reading your comments over the time I've been around this forum. But is there any way to compare the Cedric's 2.8 L engine exhaust components to a 1978 280Z's, for example, for the Z crowd? Without knowing what you started with, there's no way to measure the benefits for the rest of us. Do you still have them, and could take a look and a measurement or two?

Since 1978, who knows what previous owners have done to the exhaust system. My exhaust pipe was smashed to half-diameter from a misplaced floor jack.

Your report goes against the bulk of what I've read, so it's some interesting stuff, considering the ease of getting it done.

edit - To be clear - 23% from an exhaust system modification is an enormous gain! That's why I'd really like to know more. I have never heard that the stock Z exhaust was that bad.

Edited June 16, 201113 yr by Zed Head

Yeah, that's a good call Zed Head. I'll see what I can dig up and photograph and measure. I'll post up ASAP.

I enjoyed reading the whole thread and the results are amazing, thanks Mark for the info, it gave me a lot of ideas to do on my L26 (260C), I could use a Z intended header from MSA and change the single carburettor for twin SUs and see what happens!...

Soemthing tells me the holley conversion is misleading. I have not clicked on the readings, but how is the driveability compared to SU's. When my SU's were fresh from Z therapy, they were fanfreaking tastic. The numbers Blue posted are interesting, but I would like to know more of the comparison. Was the Holley new and the SU's old and worn out? What was the total area under the HP/torque curves for both. Peak HP does not mean nearly as much as total area under the curve.

Soemthing tells me the holley conversion is misleading. I have not clicked on the readings, but how is the driveability compared to SU's. When my SU's were fresh from Z therapy, they were fanfreaking tastic. The numbers Blue posted are interesting, but I would like to know more of the comparison. Was the Holley new and the SU's old and worn out? What was the total area under the HP/torque curves for both. Peak HP does not mean nearly as much as total area under the curve.

Mark (Ozconnection) is talking about an L28 from a Cedric 330, which only has a single carburettor.

As Oz said, the real information is in the relative changes in the horsepower numbers, not the actual numbers themselves.

The purpose of this thread is to continue a comment that I made about the benefits of modifying the original Datsun L28 exhaust setup and replacing it with headers and a bigger single system.

So, I have a dyno sheet that shows the difference what headers and a nice exhaust make to the L series. The original exhaust manifold and 1.75 inch was replaced by a set of HM39 (Aussie brand) and a 2.5 inch exhaust with two mufflers.

I don't want to shoot my own argument down here by saying that the discussion only involves headers and not the rest of the exhaust but I kinda see it as a whole package really. If you didn't want to upgrade the whole pipe and muffler shebang your power gains probably won't be as much as mine. Still worthwhile?.......absolutely.

The question about the value of adding "Headers" is still left unanswered. The OP did exactly what the manufacturers and sellers of Headers do - change out the entire exhaust system - and claim that the Headers were responsible for the HP gains.

When a larger and free flowing exhaust pipe is added to the stock exhaust manifold's header pipe after opening it up, combined with free flowing mufflers - you will see a 10 to 15 HP gain on most dyno's. If you then add expensive Headers to an otherwise stock or mild street mod engine - you won't see any significant additional HP gains above what the free flowing exhaust system gave to begin with.

Bottom line is don't waste your money on headers if you are looking for performance increases. All you will get is more heat and noise under the hood. If "Looks" is what you are after - go for the headers...

FWIW,

Carl B.

Replaced the original exaust in the 73 automatic last summer; wanted to see the diff, so timed about six zero to 60 runs with a stopwatch, best time was 9.43. Put a 2 1/4" pipe and turbo muffler, ran a 8.34 first time next day. That's about 12% faster. BTW, did a dyno run last month - I was shifting too late.

A 25% or even 10% improvement in horsepower or performance is probably a bit optimistic...

But I don't doubt that replacing the stock exhaust has to help the engine quite a bit, look at how restrictive the stock y-pipe was on my 280:

Edited July 10, 201212 yr by 8DC

Saw your post about your collector pipe on another forum and though for sure that someone would respond that it was not stock.

I have three 280Z collector pipes and they all look like the attached picture. I have a portion of a ZX pipe also and it looks similar.