Head Choice

[Map63Vette]

So I've been thinking about doing a blown 390 stroker one of these days, but I'm not sure what heads to go with. It's going to be quite some time before I have the money to do it all, but if I had a good game plan I could try to find some parts on discount or maybe used if they are in good shape, but I'm not sure what to look for. I'd like to go aluminum at least to keep weight down and preferably not something thats going to need a lot of porting (I don't think machine shops around here are the most reasonably priced and I don't have the guts to do it myself). I figure I could drop heads on the engine now and then save up the money and do the blower and stroker kit later. Any suggestions?

 

[bOb shingler]

here's what can be done with used or rebuilt parts. the block, rings and bearings and a few assorted small parts are new.

 

[Map63Vette]

*drool* Yeah, that's about what I was going for, lol. I didn't know if a blown motor really cared much about heads since it was getting force-fed anyway. I figure better flow would make it easier to cram more in, but if the heads don't flow as well you can always crank the boost up some. I figure I would try to find a stock forged crank (if mine isn't already), and then probably new rods and pistons, though I might keep the old rods (I think they're heavy duty 360 pieces from the engine date code). I realize that it's a big block in the photo, but what kind of power does it put down? I'm thinking my build would be in the 500-600+ hp range, do you think stock parts could put up with that? It would probably also need to rev pretty high to get the power, maybe 7000, would that be an issue for stock pieces? What sort of injection system is on that motor? I like the idea of an EFI sway with a blower, but money will probably be an issue...

 

[Prine]

I dont know how many times I am going to have to bring up this Mustang...Stock 5.0L 302ci Internals...and Boost.

[ame="http://www.youtube.com/watch?v=GzsVaGTdW6I"]YouTube- Single Turbo Mustang 5.0 After Install[/ame]

I do not know the guy personally, but THIS video is nearly absolute proof of the capability of just bolting on a Simple Turbo System.


I recommend the best Iron Casting cylinder heads you can find...they offer the best AS CAST combustion chambers, and will resist the HEAT alot better than Aluminum Heads.....and they cost less.

308 castings top my recommendations.

Good Luck.

 

[Map63Vette]

I know that turbos have come along way and that spool and lag isn't really a big deal anymore, but I just don't really care for them. When I hear turbo I always automatically think import. I also don't care for the price tag. Turbo systems, even single ones, run pretty high prices. Granted you need more to make them work (like carb boxes, tubing, manifolds, etc.). The turbo systems I've seen run $5000+, but I've found roots blowers for as low as $3500 for a full setup, though admittedly I would probably need a set of carbs to top it, but I would think I could get a pair for less than $1500.

 

[Prine]

You sound like a know it all....

How about you do it your way....and then tell us all about it? :salute:

Ohh and just wanted to point out...you sure do ask alot of hypothetical questions.

 

[bOb shingler]

map, it's mechanical fuel injection using alcohol.

 

[Map63Vette]

Figured by all of the tubes and wires, lol. That's a monster though, nice looking car.

And I by no means know hardly anything about forced induction other that how the systems work. I've never had a car or even driven one with boost. The closest I've come is being in the back seat of a Subaru WRX a few times. It was a pretty fun ride, I won't deny that, but I was hoping for some old school cool with a blower. Isn't boost pretty much boost no matter how you do it? 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.

 

[GTXperience]

Map, no harm - no foul. Asking questions is the only way you are going to get the answers for when the time is right.

 

[Map63Vette]

Yeah, sorry, may have mis-read that somewhat. I was just thinking from a physics standpoint. If you have a big tube and small tube you can get the same flow from the small one with more pressure than the big one. I didn't see why heads would be any different, though I can imagine it would stress a blower pretty bad if you had to crank boost up all the time.

 

[fury fan]

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 that’s 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. It’s 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:

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 won’t 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.