Head Choice

Map63Vette said
Isn't boost pretty much boost no matter how you do it?

Nope. Boost is a function of backpressure/restriction in the intake tract. An engine with lower boost can actually make more power because more air/fuel mixture is passed and burned. Think about a compressor (of any type) spinning at full speed on an engine thats not running. Boost gauge will be at maximum, but no power is created.

2nd consideration is adiabatic efficiency this is related to how much the air gets heated when compressed. More heat means oxygen content does not increase as much and oxygen is necessary to burn fuel.

Of the Roots, centrifugal supercharger, and turbocharger, a roots is typically the least efficient compressor. Centrifugal and turbo have compressors that are similar, but the drive method differs.

Both Roots and centrifugal compressors take hp directly from the crankshaft to drive them. A turbo uses waste exhaust heat energy to drive the turbo, so it is harnessing energy that would be lost out the tailpipe. Its not a free lunch, but a turbo offers the most overall efficiency for the power it creates.

A Roots has the carbs upstream of the compressor, and can only be intercooled via sandwiched cooler, so that adds to overall engine height. Intercooler options for centri and turbo are almost unlimited.

I could go on and on. I *highly* recommend you get Maximum Boost by Corky Bell. :read2:

Map63Vette said
I just think a single turbo system would look lopsided under the hood unless I do twin or run the manifolds together first. And unfortunately I have to speak very hypothetically because I have no money to do anything yet, but if other people have done it and have good advice then I can try my best to spend money smart the first time.

There are a gamut of factors to help decide whether single or twin, each has + and -. Your whole engine compartment is already lopsided with brake MC, steering gearbox and shaft, battery, etc. Plus -- if you get a good-performing system you wont care how it looks. :cheers:

As for your original question on heads:
I would recommend either RHS LA-X or Hughes-Enginequest Magnum heads (Hughes sells them as Iron Rams). The -308 is a good choice for a lower budget, if you can find them in usable condition. Used only on TBI-injected 360s (so from 89-92 IIRC). But if you need to re-work them, might as well spend just a little more and get LA-X or Iron Rams.

I would avoid any effort toward OEM Magnum heads unless they fall from the sky for free for you. They are a good-performing head but they have an Achilles Heel - they are known to crack between the valves, and boosted-HP will probably only exacerbate the issue. The Iron Rams and LA-X use pressed in seats and that prevents the problem (OEM uses induction-hardening of a machined surface to create the valve seats.) Now that I mention it, I think the 308 can have the same cracking problems but that head is not as widely used so the notoriety is less.