Want to release a few more ponies for nowt but a wee bit time ?
No point in fitting a free flowing new exhaust system if it is being choked prior to getting to the exhaust pipe
Of course this does not apply if you do not have the standard Reliant manifold and have fitted a 4 branch exhaust
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If you have not already ported your manifold to the head It would be worthwhile removing the exhaust manifold and having a measure of the manifold ports .
There are a couple of sizes of exhaust manifolds and all have variable quality regarding consistent port sizes on the same manifold .
I have measured ports as small as 18mm and you can see the difference on the following photos .
Reliant Exhaust Manifold ; Is it choking your power output
Original big size photo link http://i1251.photobucket.com/albums/hh543/fifermanky/EXHAUST%20MANIFOLDS/EXHAUSTMAINIFOLDSSHOWINGDIFFERENCESBETWEENSTANDARDRELIANTEXHAUSTMANIFOLDSBY5mmONTHISPAIR.jpg
Reliant Exhaust Manifold ; Is it choking your power output
Original big size photo link http://i1251.photobucket.com/albums/hh543/fifermanky/EXHAUST%20MANIFOLDS/EXHAUSTMAINIFOLDPORTSHOWING1920mm.jpg
Reliant Exhaust Manifold ; Is it choking your power output
Original big size photo link http://i1251.photobucket.com/albums/hh543/fifermanky/EXHAUST%20MANIFOLDS/EXHAUSTMAINIFOLDPORTSHOWING2308mm.jpg.
If you do modify the ports , remember and match the gasket to the head and to the manifold
The above modification , along with the inlet manifold work to which I would modify the gasket as per
The photo below shows the cylinder head inlet ports prior to being modified
Click on photo to enlarge 
Reliant Exhaust Manifold ; Is it choking your power output
The photo below shows the cylinder head and one set of inlet ports after starting modifying
Click on photo to enlarge 
Reliant Exhaust Manifold ; Is it choking your power output
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Note the metal between the inlet ports has been tapered away so the the inlet gas flow does not come up against the brick wall effect .
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Just be very wary if you attempt to do this modification and if you do not feel confident enough to try it maybe a wee bit practice on a spare old damaged head would give you the skills needed
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