mpi cylinder head
Turbo Mini Forums

not a turbo question, but hope someone can help

the inlet ports on mpi heads are clover shaped. does this help gain or restrict performance? would i be better off honing what is there as smooth as it will go, or just opening it right up as you would when modifying a carb head? many thanks

I would normally say match the port to the shape and size of the inlet manifold, but someone with more knowledge on the subject may have a different idea.

modd the head as you would do a race head for carb application

the right shape makes power not polished inlet ports

i can do this for you if you wish

Ben. YOu cannot advice him to port it to "race" spec if he's using it on the road :)

What are you using the head for? The horizontal part of the inlet ports are not very restrictive. The guide boss and valve throat area are. These are the same on Mpi as other, and should be adressed first.

slightly modified road use. standard injection/bores. sw5i cam, 1.5 rockers, slightly skimmed head to raise cr, port and polish inlet/exaust ports

If you are using an injecion manifold, either keep the locating rings or, port and dowel the inlet manifold to the head.

what i meant V is... port the ports valve throats guide bosses and fit new 180 pound double springs, guides, and race valves #

the ports need to be modded in a way.... ..... unlike a FULL! RACE HEAD to compliment the rest of the bolt ons and cam choice!

Ok :)

On an SW5 camshaft, use the standard Mpi valves. They are bullitproof compared to anything else on the market concerning guide. Just have them back cut. Use bullet nosed iron guides for best longitivity.

As Ben says. don't polish anything. If you polish the exhaust ports, you won't ruin anything, but it's just time consuming= expensive if someone else does it for you.

Leave the inlet locating rings in as mentioned.

you will get a superb! power gains right throughout the rev range by fitting race valves,

compared to the standard ones even with an SW5 cam Vegard.

but if your on a budget......................

Race valves wear so quickly, that's why. I prefer the A+ valves in anything NA roadgoing.

yes its a budget build. will be doing all work ourselves thanks

yes its a budget build. will be doing all work ourselves thanks

Some basic work can reap big rewards.
3angle the valve seats, back cut the original valve {if on a real budget} remove guide boss, bulletnose guide, smooth short side radius, deshroud the valves & remove the casting marks in the chamber. Then just a general tidy up on the rest of the port making sure it's all smooth & nicely blended.

Edited by Turbo Phil on 30th Jan, 2008.

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Have a look here. Something might be of interest.

http://home.online.no/~lyngset/pictures.cf...t=97&pDispType=

Just remember one thing. Leave the short side radius as BIG as possible.