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MG MGB Technical - headers

replacing my exhaust, what is better pacesetter or patriot headers? thanks Doug
dd doug46chief

Doug. When I had to make this modification to my 79, I used a factory exhaust manifold, the early header pipe, and had my local muffler shop adapt the rear section of the factory exhaust to the earlier system. The factory exhaust manifold and header pipe forms a tuned exhaust system.

My only experience with headers is with the Peco and Cannon systems. Neither, in my opinion, are as desirable as the factory system. Of the two, the Cannon seems to be the better made unit with the Peco having flanges of different thickness on the three branches--one wonders if the flanges are made from whatever scrap steel happens to be on hand.

Speaking of flange thickness, the factory exhaust manifold used two different thicknesses of flange, one size on the HS and a different (thinner as I remember it) one on the HIF manifold. The intake manifolds had a flange thickness to match the paired exhaust manifold.

You have some form of aftermarket intake manifold for your Weber DGEV carb and the exhaust manifold and intake manifold will have to have the flanges measured to see which is thicker. Then, use spacers between the large washers and the thinner manifold's flanges to get an exact fit. A very slight difference will not matter, but too much difference in effective flange thickness will cause the manifolds to not seal correctly to the gasket, causing leaks.

Les
Les Bengtson

Les- Thanx for rattling my cage. Recently adapting a new set of SU HIF onto a reused HS stock manifold, I had a fleeting awareness of this nugget somewhere in my remote region. Can you explain the difference and reason for the 2 manifolds please. My rig seems just fine, and I'm now considering slicing the heatshield after reducing the thickness of the phenolic spacers soas to keep lingage freedup. Then I'm planning an induction box, angled to miss the booster, and a remote K&N where the oil cooler used to be. Dyno says the 2 itsy bitsy conicals on the carbs cost 10 BHP!
Also IMHO, although I agree with Les on the peco flange thickness variations over the 5 or 6 I've done over the years, the tuned Peco package: header/tailpipe seems to be an awfully good mousetrap. Peter claims he measured a 5-7 BHP increase midrange using the Peco system. On the last one for the super charger, I just puddle welded the flanges, then ground them to the exact intake manifold thickness. Personally I like the note, not to loud, but no sissy either.

Cheers, Vem
vem myers

This thread was discussed between 29/03/2012 and 12/04/2012

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