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Discussion Starter · #1 ·
New Z car owner here with a question.
I am considering replacing the exhaust system on my bone stock '77 280Z with Motorsports 6 into 2 header and twice pipes. Can anyone offer any advice on this mod? While I am sure the header will do good things, I am concerned about the effectiveness of the twice pipes. Would I be better off using mandrel bent pipe and flowmasters from the header back or just use the twice pipes? I have heard that 2.25 in pipe is a better performance/noise tradeoff than the 2.5 in pipe (I think) that the twice pipes are made of . Is this true?
Also, how would this work in conjunction with a larger throttle body?
Thanks in advance for any help and advice.
Thanks to our host for a great site!!
 

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Discussion Starter · #2 ·
RE: here's the skinny

The harsh reality of most headers (except for the NISMO) is that they do SQUAT to increase HP. This is backed up by dyno upon dyno test. I got mine cause it looks cool. on the other hand a bone stock 77 will see good increase in performance from a 2.25 (the 2.5 will resonate in the cabin at cruise speed) coupled with a flowmaster muffler. The larger throttle body is a good idea if can execute its installation properly. You need to match the opening of the intake manifold to the larger TB or it won't help. At the same time you need to get rid of the stock air box and replace it with a k&n filter setup.

Steve G
 

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Just added a Motorsports 6-2-1 header and their 2 1/1" aluminized exhaust system to my '77 a couple of weeks ago. Noticed some improvement in performance yet, I have yet to upgrade the air filter as Steve mentions though I did take the little black tube off. If you go to a larger throttle body, you will need to scribe and port the intake manifold or you will end up with major air turbolence and will take two steps back in your goal to move forward. IMO, go with the motorsport header, use anti-seize on both sides of the gasket, do their performance exhaust 2 1/2", you can add a glass pack later if you don't like the tone, have a muffler shop tack weld your system to get rid of the clamps and upgrade the air filter. Consider the throttle body for later unless you got the cash to drop now. Good luck.
 

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twice pipes

It seems most people use the 2.5" or a 2.25" exhaust system. You'll be surprised at how well the engine revs once it can breath easier. I think in the 1970's the twice pipes were popular, but less so today. Many feel that a "bullet resonator" just after the header will also decrease exhaust resonance on a 2.5" system, and is thus desireable.

Furthermore, if you want to do the throttle body upgrade correctly by grinding out the manifold to "port match" the larger throttle body to the stock intake, you will obviously need to do this with the intake manifold removed from the car (lots of aluminum shavings, dust, etc). So, I would do both at the same time as the exhaust upgrade if the funds allow (& air cleaner too). Let us know what you do.
 

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RE: twice pipes

I've got two 50mm pipes off a 6 into two header. (old Greddy/Trust system from Japan circa 1978)The mufflers really cork the exhaust and keeps it quiet, while the twice pipes let it flow. To get a single system to be that quiet wold be a lot of work. The twice pipes originated from the 432 design work. Look at early differential crosmembers and you will see provisions for a factory twice-pipe system. A single is easier to package with the later diff. crosmember and with less restrictive muffler/resonator should flow as well, and not attract too much attention. The twice pipe packaging on a later car could be a pain--stick with singles. IMHO.
 

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Discussion Starter · #6 ·
<b>RE: what's the best way to port the manifold</b

I installed a webber throttle body recently and did SOME grinding on intake before installation. This was very slow, and tedious. I used a Dremel tool, and a carbide bit. Is there a faster way to remove mass quantities of the manifold, or do I need to designate a whole day of grinding?
 

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RE: Exhausting isn't it... (long)

Steve is right. Repeated dyno tests have shown that unless you have considerably modified your motor you gain very little from headers. In fact you lose quick warmups, often have leaks, eventual rust, high underhood heat. What I did was not cheap in fact about $450.00. I used a stock exhaust manifold Jet-Hot coated inside and out in black. I bought the first pipe (head pipe) from the MSA 2.5" exhaust and cut it and welded on a flange. I then welded on 2.5" mandrel bent pipe from there to a resonator in the transmission tunnel and from there to a Thermal muffler and ended in a Thermal tip. The resonator gets rid of the boominess that the 2.5" system is known for. Now the most important part of the post. This was the most dramatic modification I have done to my car. Bar none. The car revs freer and goes like... well you know. Flowmasters by the way have also been dyno tested and show a drop in HP and torque! I think Thermal or Borla are probably best.
 

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Discussion Starter · #8 ·
Porting intake can be done on the car

I ported my intake to match my new larger throttle body opening last night right on the car. All I did was stuff two oil-soaked rags into the opening, one in the main plenum chamber and the other in the runner to the front cylinder.

Yes, there was a lot of aluminum dust created, but I kept that down to a minimum by keeping the area wet with WD-40. This also helps keep the grind stone from clogging too bad. I used an air-powered die grinder with as large a stone as I could get by with, as this cuts grinding time down. I did mine in about 30-45 minutes. After I was done, I pulled out the rags and gently wiped the dust out using dry, clean rags and spraying more WD-40 to help wash out any remaining dust. I suspect that doing the whole job with a dremel would take a couple of hours, but its certainly doable.

Runs great, but I still have stock exhaust so I'm not getting the full monty yet.
 
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