I'm just about to start porting the standard headers off my Sti4 rally car. Having removed all the parts I have the following questions to ask:

There seems to be 5 items that might need porting:
1. LH header
2. RH header
3. Up pipe
4. cross pipe
5. Turbo

I'm not sure exactly which bits it's necessary to port. I can see that the headers themselves seem smaller than the head ports. I have been advised to make the headers BIGGER than the head ports to create a reversion step in the oppsite direction than it seems to be at present.

The joins of the cross pipe and the up pipe look like they are quite well matched to each other (horrible tube inside though!) so maybe it's not necessary to do anything there.

Is it also necessary to port the turbo to make the opening bigger than the end of the up pipe?

I intend to lag the turbo downpipe with exhaust wrap but what about the headers? All those nasty heatshields look dreadful! Is it possible to wrap the headers, crosspipe and up-pipe too?

Any advice would be appreciated,

Martin

 

In the direction of gas flow any join should be as smooth as possible. If you doing any work on a joint not perfectly matched, then add the reversion lip as well. Andy.F described it very well to me in the eraly days; imagine the pipework flowing water instead of air, then add little fishies into the water flow....your porting work should make the fishies path through the pipework as smooth as possible

I also ported turbo inlet to match up-pie, plus porting/polishing compressor cover. Needs a full strip to do it though.

Richard

 

Martin

I got a very professional porting and wrapping job done by "Harvey" (his Scoobynet name), he has an engineering works (I think) near Nortahallerton. The wrap was held on with some very neat wiring and sprayed with high temp paint to stop the water soaking in...top job !!. "Harvey" has also ported turbo's etc

Last time I looked Harvey's Scoob had broken the 500BHP as well !!

Hope this helps

Midlife....

 

Thanks guys..... I understood that the reversion lip was actually better than making the ports perfectly matched as it helps to stop any reflected gasses going back and upsetting the normal direction flow. I notice that on most articles I've found (from doing a search on headers), seem to just go for smooth porting like you have explained.

Martin

 

just make sure you get some decent grinding bits, pays to buy some that last longer than 30mins as i found out

 

I Have a Die grinder and tungsten carbide cutters, they make mincemeat of cast iron!

Martin