Thread: Vortec heads on MKIV

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You will want to read as much as possible on increasing low lift flow and torque,before touchin those heads,vavles ,bowl work,porting,all have specific procedures for low rpms and torque,rather than high hp ,high rpm ,engines.A little info before hand can pay off big time with those heads.As far as the cam goes ,thats a little tricky.3000 ,3500 rpm red line,will need a specific cam if you want to get all the torque possible from the parts you have.I would talk to a cam company or a place that specifically deals in those types of engines(almost always this is free).I have no exsperiance with those engines,but I would imagine that the cam will be 1 of the key components in that engine.The vortecs flow just off the valve seat,what other heads flow.100 lift.The head in stock form slows down at higher lifts and becomes less efficient,but that is ok ,the valve is only at full lift 1 time in the cycle,buy its at low lift 2 times each cycle.If it was me I would not port or bowl work these heads at all!!!All the numbers at low valve lifts(which happens 2 times each cycle) fall off,while the high lift (which only happens 1 time each cycle) go up.IMO you will not be working these heads very hard at all at 3500 rpm(a head runs outa air at higher rpms ,not low)the only increase in air demand will be the cubic inches of the engine.Soo at 3500 rpm and a larger displacement ,the head will only see a (percieved) rpm of 4000 to 4500,right at the rpm these heads start to nose over at and stop making power.That means you are getting the full power potential (not flow potential)of these heads at stock form.I would spend my money on a good low lift type seat in the head(cheap to do) and on a good low lift flow type valve job to help increase the flow at lower lifts,which equals more power where you need it.I would read as much information as I could to help me understand how that setup works.The high flow rates at high valve lifts at high rpm looks impressive and so do the hp numbers to back em up,but that all takes place at 6000 rpms or more ,well above the actual requirements of your engine .You can see where it would be easy to get a set of big aftermarkett heads with huge flow numbers at huge lifts and rpms and end up with a motor that barely runs........Just tryin to help make more informed decisions,I hate to see time and enthusiasm wasted for lack of almost free information..