MikeGyver

A reversion lip on the exhaust runner makes sense, but I've never heard of 'intake reversion'. I don't see how that could/would hurt anything.
If it's just for a little misalignment safety margin then that makes sense.

rskrause

Here is Isky's view on intake reversion. Again, it is common practice among engine builders to port as I described. I can't say I have ever independently verified if it helps, does nothing, or is harmful. I will say that the situation of the intake being bigger than the port is DEFINITELY to be avoided. As getting an exact port match is difficult, and having the manifold minutely smaller than the head port is very unlikely to cause a problem, people do it as I described.

http://www.iskycams.com/techtips.php#2002

Rich

96capricemgr

Depending on what intake/head combo you have yes sometimes the intake manifold ports can be bigger than the head. There are several different castings of each. Just because GM made them like that does not make it good though. The stock eliminator guys actually like the small port intakes because they match the heads better as cast.

rskrause

Yes. Definitely easier to make the intake bigger than to make it smaller! I screwed one up once and had to have a buddy weld it (I can't weld worth a damn).

Rich

BCdawg57

So on a normally 300 whp setup how much would that set you back?

rskrause

Depends how bad it is. Do you mean the example shown?

Rich

BCdawg57

Well I hope mine wouldn't be that bad since my heads are also ported but just for conversations sake, let's go with that example..

rskrause

It wouldn't surprise me if that cost 5-10hp.

Rich

BCdawg57

ouch. Oh well I guess I'll have to pull off my intake and see how bad it is.

rskrause

You should be able to get a look with dental mirrors and a flex light. Or, if you can borrow a bore scope, that is much easier.

BCdawg57

Bore scope? That's not something you can rent from autozone is it?

rskrause

Doubt it.

blue 79 Z/28

back in the day bbc guys ran rectangle port intakes on oval port heads and picked up significant power over the oval port manifold......

The_Bishop

Yeah, but it isn't 1970 anymore, it's not a big block, and we are supposed to know better now.

maddog05

MSD gives you multi spark and improves miliage; underdrive pully extends life of alternator and some components on serpentine belt
both together will increase horse power by a small amount.