Exhaust Manifold - Advice Needed

[Loiner240]

Hoping to get some advice here on a new exhaust manifold for my LHD 240Z. It has a tubular exhaust manifold and a Janspeed exhaust system. I believe the manifold is mild steel, judging by the welds that have been previously done. However, it’s leaking in a few places and beyond repair. So I need some advice on the best option for a replacement manifold. Cast Iron, mild steel, stainless? I have been told that stainless manifolds crack easily and that tubular manifolds aren’t really necessary. These questions might be academic if you can’t actually source these things! The car actually has an L28 engine and has been tuned to Stage 2 with a gas flowed cylinder head and high compression ratio (producing around 190BHP).

 

[Alphabettispaghetti]

Hoping to get some advice here on a new exhaust manifold for my LHD 240Z. It has a tubular exhaust manifold and a Janspeed exhaust system. I believe the manifold is mild steel, judging by the welds that have been previously done. However, it’s leaking in a few places and beyond repair. So I need some advice on the best option for a replacement manifold. Cast Iron, mild steel, stainless? I have been told that stainless manifolds crack easily and that tubular manifolds aren’t really necessary. These questions might be academic if you can’t actually source these things! The car actually has an L28 engine and has been tuned to Stage 2 with a gas flowed cylinder head and high compression ratio (producing around 190BHP).

There's lots of choice in exhausts now days.

Z story
Fujitsubo
Kameari
pace setter
MSA

What do you want out of it? whats your budget?

Whats stage 2? have you had it on a rolling road? what's your cam/carb spec?

 

[Loiner240]

Thanks for the reply. I’ll have a look at the companies you have listed. ‘Stage 2’ is just a term used to mean that the car has had work to raise the power output. I believe the car was put on a rolling road when it was restored in 2011 – I didn’t own it then. It has SU carbs. I’m not after the very maximum possible power but I like what it does at the moment so wouldn’t want to see too much reduction! Therein lies the problem - I’m not clear what differences there are between the performance of tubular/standard and longevity of cast/mild steel/stainless. The price I would be prepared to pay would depend on whether there were significant differences. I was just going to go for stainless tubular, it’s just that a mechanic friend told me that stainless manifolds tend to crack and the power gains where marginal, so what I thought would be straightforward became more complicated.

 

[SeanDezart]

.....it’s just that a mechanic friend told me that stainless manifolds tend to crack and the power gains where marginal..

With respect to your friend, rollocks. I've not had one yet that's cracked after road, rally or track use after nearly 10 years of exposed use.

Power gains from using stainless over mild steel - yes, marginal but one doesn't fit stainless to gain power !

 

[Loiner240]

Re cracking, that's good to know. Re power, I meant that in relation to tubular as opposed to standard log manifolds. He was advising me to go for a log manifold.

 

[SeanDezart]

Sorry - what is a log manifold ?

 

[Albrecht]

Sorry - what is a log manifold ?

The stock - cast iron - exhaust manifold is an example of a 'Log manifold' design.



Advice given sounds rather Millennial, and whilst it may be applicable to more modern turbocharger-equipped cars it is not applicable to 1960s-designed normal aspiration engines. Nissan's L-series engines respond very well to soundly designed tubular exhaust manifolds and their matching exhaust systems.

 

[richiep]

As has been said, L-series engines respond well to tubular manifold designs, particularly of the 6-2 format. They generally all (even the less decent examples like MSA, Pacesetter, etc.) outperform the stock manifold/exhaust system, and are a critical component in any performance build. Bear in mind that Nissan, back in period in Japan, offered tubular manifolds and matching exhausts as upgrades as part of their Sports Option list. Nissan Motorsports USA also offered two sizes of tubular design that have been very successful. Sean's Z Story manifolds owe their DNA to these Japanese and US designs - so they were doing something right!

Your friend's advice is definitely erroneous/misplaced in this case.

 

[Loiner240]

Thanks for the advice everybody, it's very helpful.

 

[Mark N]

The stainless manifold cracking issue is more related to cheap stainless turbo manifolds as they are subjected to more heat and stress (extra weight of the turbo, wastegate, downpipe, etc.).