15 replies to this topic

[torry nut]

Depends on what you want to do with your car Fat tony !!!!

If you want horsepower then bomb the eye balls out of a std 2 door not an XU1 !

My opinion anyway !!

[rodomo]

Good topic!
I am interested to learn more too. I have seen and read things about wrapping up extractors to retain heat but am not sure of the reason. I fathom from that that headers would probably do that automatically? Also with the length and size of the engine pipes from the headers to the "Y" piece looks to me to be a gain. The blue/black motor exhaust manifold is effectively headers joined with a couple of extras added for inlet manifold heating. They have better flow characteristics than the old headers as they have less tight corners, but again have big engine pipes to the "Y" section. Having said all that, the EFI black motor had extractors from the factory. Is it cheaper to cast headers than it is to fabricate extractors?

[shanegtr]

My old exhaust consited of extractors (dont know what brand, but they where stuffed hence the replacment) and 2 1/4" system. It was replaced with the 2 piece headers and a 2 1/2" system and its far better. The car seems heaps more drivable at low engine speeds just off idle

[Loui]

keep the originals mate, you could open them up a bit with a die grinder

Also you could get the pipes made up to look factory but with slighty larger pipe and mendrel bends to get a bit of better flow

Plus you may not be able to get historic rego with extractors (ive already asked this question before)


Cheers

Loui

[TerrA LX]

Good topic!
I am interested to learn more too. I have seen and read things about wrapping up extractors to retain heat but am not sure of the reason. I fathom from that that headers would probably do that automatically? Also with the length and size of the engine pipes from the headers to the "Y" piece looks to me to be a gain. The blue/black motor exhaust manifold is effectively headers joined with a couple of extras added for inlet manifold heating. They have better flow characteristics than the old headers as they have less tight corners, but again have big engine pipes to the "Y" section. Having said all that, the EFI black motor had extractors from the factory. Is it cheaper to cast headers than it is to fabricate extractors?

i use rodomo's question here as it has the essence of my answer here.
i have never and probably never will own a hot 6 but speaking theoretically it will apply to any motor.
heat retension aids in the speed of the exhaust, the quicker it cools the slower it goes and yes cast iron retains heat better than 1mm steel.
length (tuned) in Y piece will aid in mid range torque.
tight even radius corners are better than long sweeping curves as they interupt flow more.
casting is cheeper because there is less chance of human error in mass production.

i would ask the builder for some proven gains and if you need that extra (claimed) horsepower then go headers.
or untill you get some hard facts run the casties.

there should be no need to die grind anything bar rough edges etc

ive seen a rail with hot 6 go back to the cast headers for an improvenent.

Edited by ALX76, 30 September 2006 - 11:39 AM.

[rodomo]

I have just changed to a 3.3 Commodore engine and am a little disapointed that the headers don't fit.

The cast blue/black exhaust manifolds are headers. They are just joined together.

[Struggler]

ive seen a rail with hot 6 go back to the cast headers for an improvement.

This is true, the engine spent quite a bit of time on the dyno at Brads Speed Shop years ago. They tried heaps of different extractors and the 2 pce X2 style factory manifolds made the most torque and power. This was covered in Street Machine Magazine years ago, but still applies today.