hey guys got my old extractors back... the ones they took off when i my custom ones made and noticed something interesting... the tool that fitted them originally at midas put them on off centre thus blocking part of each port as you can see in the pic. im hoping this choked my engine severely and when i get it dyno'd tomorrow with my new extractors it will make thousands more horsepower... but im probably just dreaming.

hey guys got my old extractors back... the ones they took off when i my custom ones made and noticed something interesting... the tool that fitted them originally at midas put them on off centre thus blocking part of each port as you can see in the pic. im hoping this choked my engine severely and when i get it dyno'd tomorrow with my new extractors it will make thousands more horsepower... but im probably just dreaming.

How can they be put on "off centre" when they are designed to bolt up to studs which are part of the cylinder head by design.

Don't blame the installer because of dodgy manufacturing.

hmmm if it is dodgy manufacturing i wonder how many ppls extractors are like this... can u see what i mean in the photo its clear that the exhaust ports are partly covered by the extractor flange??

Yeah mate - can definetly see what you mean, the exhaust flange is not even close to being port matched to the exhaust outlet. It would definetly cause "turbulence", if not a slight restriction, but it's impossible to say to what extent it would effect power.

What make / type of extractors are they?

just bout every car from the factory is like this.

you can get this corrected by "port matching" which is where they machine them to match up perfectly.

or make yourself a paper template, and drind the headers yourself, much cheaper than paying for pro port matching and not too difficult :)

ive heard a few claims of port matching stock headers on some cars being nearly as good as getting extractors.

Mass produced items. Close enough is good enough for most manufacturers.

Regards

Its always a good idea to check that the ports match to avoid restriction. Some cars are really bad from the factory although most magnas I've seen the exhaust manifold ports are larger diameter than the head ports.
An easy way is to match up the exhaust gasket to the manifold. The exhaust gasket ports are larger than the cylinder head so if you have enough meat in the manifold, mark it out according to the gasket and port it out using a die grinder. This helps even on stock exhaust manifolds to let the exhaust flow more.

yeah i was speaking to my old man who was a performance mechanic back in the 70's and 80's and he said the same thing that most standard exhaust manifolds are like this too and port matching makes a big difference.... i always wonder why he doesnt tell me this **** until after i realise it myself.... anyways my new extractors were port matched to my head which is ported and polished, the only thing i was worriedd about is the 4 into 1 collector he put on it. it goes 4into1 @2.5" then reduces down to 2" then expands again to 2.5". he said it was to scavenge the gases and speed up the flow. this is alll well and good but it still means at WOT all the gas has to get thru a 2" restriction. meh wish i had the money to test and tune it both ways