I'm not paying $500 to do anything. That what Morana gets. I'm doing it my self. Shortening the runners on the 3.8 plenum improves mid- range torque and respond something a 3.8 lacks anyway this would be for my 4.2 build anyway.
Again, "but why"?
The reason all of us are confused is because there seems to be a disconnect here. Let's look at the facts
* From all I read, all the singleport modifications were made before splitport heads/intake manifolds emerged on the market. SP heads flow something like 2x better than their singleport ancestors.
* Since it's commonly known that 14# injectors are pretty well maxed out with a singleport 3.8L engine (do the math), you'll need upgraded injectors with the 4.2L. I'm not sure how much viable "carry-over" you are planning in your eventual migration to the 4.2L block.
* If the concern is cost, I know for a fact that splitport heads can be picked up for <$100 a pair along with the matching lower/upper intake manifolds.
* A fancy singleport upper intake will only be compatible with a singleport lower itnake and heads.
If you are planning to go with a 4.2L shortblock, the natural choice would be a splitport heads/intake setup.
The only reason to consider singleport heads would be if you were planning on making a 4.2L SC setup using the stock SC intake manifolds. While that might be the cheapest route to a 4.2L SC setup, the flow capabilities of the SP heads/intake make a vortech SC setup much higher performing (at least, until your block blows up because you didn't start with a SC block). In this scenario, you could reuse your stock singleport heads but your fancy shortened singleport intake will be just a large paperweight.
* If you have the skills and/or determination to cut, shorten, polish, and re-tig a singleport upper intake, you are better off investing the similar effort in a splitport upper intake. You'll get far more performance going that direction.
The only conceivable reason I could see to invest the time/effort in doing a cut and weld job on your existing 3.8L manifold would be for practice. Of course, if you @#[email protected]
#$ up, how are you going to drive to work? Now, if you are planning to buy a spare intake for practice, why not buy a spare splitport upper intake instead of a singleport one?
PS. A good correlary to this situation I've seen recently is with 5.0L heads. Unless you are restricted by some racing series rules, there is no reason to invest significant labor (beyond a simple polish/gasket match job) on iron 5.0 heads anymore now that cheap, high performance aluminum castings are available. It's the march of technology....