Exhaust Manifolds


A call from another member prompted these tips.

The idea was to make a manifold from steel tubing something like the Bugatti style ‘bunch of bananas’, which is simple, elegant and effective.

The flanges for mounting to the head and exhaust pipe can be water jet cut if you make a drawing, and for the latter a three or four-bolt design is better than the bug two bolt style which blows gaskets regularly.

The gasket faces of the flanges need to be machined smooth and then small circular grooves machined into the face to extend gasket life greatly.

The manifold flange which mates to the exhaust pipe flange should be assembled loosely and bolted up to the exhaust pipe flange and tack welded in situ, removed then welded fully. This will assure excellent alignment.

Tube bending is best left to the experts as it requires proper equipment to do it neatly, hence a drawing is essential. This is NOT pipe bending.

Most manifolds are attached to the block or head with nuts screwed onto studs mounted into the casting, which are a source of problems as they freeze into the casting and snap off easily and are very difficult to remove.

If this happens you could try the Grabit tool mentioned earlier, but give it every chance by soaking the studs to be removed in “Blaster”, available from Blaster Group P/L, 30/8 Victoria Ave in Castle Hill. Tel” 9894 7360.

It is far better than ‘Penetrene’ or WD40.

If replacing the studs, go the whole way and make them from 316 Stainless steel.

Throw away all the manifold nuts and make special ones from hexagon brass longer than usual so they completely cover the stud, which will stop the usual protruding part of the stud growing by rusting and stripping the thread of the nut as it is unscrewed, and if the nut freezes onto the stud the brass threads will strip in preference to the stud.

While you are at it make a few spares and keep them in glove box or car tool kit.

More technical tips