HOW TO: Port­match heads

Step-by-step DIY guide.

Classic Ford - - CONTENTS -

T he tra­di­tional method for in­creas­ing the horse­power po­ten­tial of your en­gine is to open up the ports al­low­ing more air in; mak­ing it flow much bet­ter and in turn, atom­ise the fuel more ef­fi­ciently; all to gain a strong burn and more of it. You can spend a for­tune with a head spe­cial­ist that’s in­vested acres of time not just in ex­pe­ri­ence but re­search, cou­pled with flow­bench de­vel­op­ment and — in the ex­am­ple of our cho­sen en­gine de­vel­oper, Joe Al­lenby-Byrne of Throb­noz­zle En­gi­neer­ing — com­puter sim­u­la­tion, too. All to get the ul­ti­mate flow for your ap­pli­ca­tion and a mon­ster amount of horse­power and torque. Alas, you can de­stroy a large chunk of that in­vest­ment sim­ply by bolt­ing on your own bits of hard­ware… We all know that, part of the pack­age is the in­duc­tion side, and it’s easy to look at ev­ery­thing as sep­a­rate com­po­nents — you fit your sid­e­draughts, you’ve al­ready got that trick, free-flow­ing ex­haust and in the­ory, they should all work to­gether. But the thing they have to do is match — if they don’t then you could be go­ing back­wards, but in truth you’ve prob­a­bly got a re­stric­tion you don’t need, sim­ply be­cause your ports don’t match up in size and per­haps, ori­en­ta­tion.

The best idea is to give ev­ery­thing to your en­gine builder to match for you, al­though you can do it your­self. Say, for ex­am­ple, you’ve bought a trick en­gine but you’re us­ing your own carbs and ex­haust — you’ll need to match ev­ery­thing to­gether so it works as a pack­age and you get the power you’re en­ti­tled to. With this in mind, Joe showed us how he port matches the man­i­folds — both in­take and ex­haust — along with a few tricks and dodges on the way. All of the ex­am­ples here then are aimed around a Throb­noz­zle Pre-Cross­flow, but they equally ap­ply to any en­gine.


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