NiklasFalk

iTrader: (1)

I'm a procrastinator that have not even started to fix my shortened NB (wall encounter 18 months ago). But thinking out loud is always a possibility.

I love the sound of my ITBs on the built BP6D but why not think of something more extreme.

Starting with available tires (locally in Europe, no US) the 18" slick tires used in GT classes always pops up (not cheap, but you would not be the only one using them).
Engine wise I have been more and more interested in the modern days 327, a LS3 with 4.8 crank and narrowed ports (or custom heads). About twice the cost of a built BP6D, but three times the power. A short stroke built engine would hopefully give a wider dynamic range if max power is set at about 7kprm.

So about 500+ whp on 300 wide 650 tall slick tyres...

First I'm hesitant that the front wheels will turn unless moved a little forward, and in the rear they might need moving backwards to stay clear of the more complex metal.
If the subframes are to be moved, why not swap to something that is built for loads like this, Corvette C5 (complete subframes (maybe custom), arms, hubs, steering rack)?
The added width may make it easier to fit tires, and covering them up would be needed anyway. Playing with numbers makes me think narrowing the C5 by 2" would be just right but that can be done with wheels if the (lack of/negative) scrub does not feel very odd.

Since this will never happen, give it the attention it deserves. But a wide range revving LS at medium cost would be interesting (reduced low end grunt and ability to swing the gears). If anyone ever have used such an engine on road course, it would be nice to hear if it worked better than a standard LS7?

Joe Perez

iTrader: (8)

Serious question:

If you're contemplating swapping out the whole dirvetrain for that of a Corvette, and also replace the subframes with those of a Corvette, why not just drive a Corvette? It would probably be cheaper, and certainly easier.

Full_Tilt_Boogie

iTrader: (1)

The idea of a short stroke/high rod ratio makes sense for a road racing engine, a flat torque curve and high redline is definitely the "ideal", but converting an engine like that doesnt make a lot of sense to me. The LS engines are great in many ways, but surviving at high RPM for long periods is not its strong suit. Even the LS7 with its "dry sump" have been known to fail on the track from oiling issues.

Its going to be easier and more reliable to go with the bigger displacement and keep the revs down. The torque curve just wont be as flat.

emilio700

iTrader: (3)

Adding 7cm to the height of the tires will require fully tubbing front and rear. The extra ride height (CG) gained won't do handling any favors so custom drop spindles would make sense. I say custom because OTS spindles available now would not even get you back to OEM instant centers. Such one off spindles would require custom shocks that are longer than OEM. Andy Hollis (build thread) squeezed 18's under is OLOA build for similar reasons. Rules require certain tires which limited his choice to 18's to get the compound and desired contact patch to weight ratio.

NiklasFalk

iTrader: (1)

Corvettes are too big, too heavy and too easy.

Locally the races are not that long and stock LS7 seems to do fine for some years.
Stock LS3 seems to need help with draining the heads. This only from our local series though.

The gears that are easilly available also plays in favor for a higher rev range, I think . Not to forget the sound...

HarryB

Not sure if serious or trolling. At that level of madness, I would not bother with a Miata at all. Buy the components you like, build the rest (including frame). Far more compromises to be had when starting with an actual car.

NiklasFalk

iTrader: (1)

The rational madness would be four tires and an engine in an empty workshop.
The rest is just fitting the wireframe to a body style.

But the level of madness will also mean that any small team will never be able to do everything right, so choose your favorite poisions (e.g. without proper aero you don't need that engine).

Not completely trolling, since part of this is related to figure out if there are any outrageous ways to get proper slicks on a Miata tub (besides 580 tall Hoosiers).
Oh well, better get back to (thinking about) pull my wreck apart, the spring and light is here.

Davidss

A miata prepped to the level you are talking about wouldn't be much lighter than a stripped C5.

j_man

Why not just use 295 wide Hoosiers on 15x12 wheels? Stock diameter tire and fit just fine front and rear of the Miata.
Unless you're racing in a specific class which binds you to a particular tire or shipping Hoosiers to Europe is that much more expensive?
No way you're going to fit wide and 650mm tall tires unless you tub the front and rear.

k24madness

iTrader: (6)

I agree a long rod short stoke engine is ideal for a track car build. Starting with a pushrod engine that is known to have oiling issues at high G’s would not be my first choice though. I’d pick something else like a ford cammer engine to start with. Better yet a BMW 4 liter V8 from a e90. That thing revs to the moon and is known to last well between rebuilds.

You mention starting with C5 subframes and drivetrain. If going that route keep wheel base long, build tube chassis and wrap in whatever’s available to fit. It would be cool to build a supersize Miata! Carry the look over but re-scale 125%.

I think a better option option would be to start with Miata drivetrain and build a light tube chassis and bolt on panel skins. You’ll fit 15X12/15x11 easy and if you target 300whp it’ll be a monster.

NiklasFalk

iTrader: (1)

E90 V8 is a very nice engine. Higher initial cost (no cheap version to "learn" on.
The LS used in our series seem to cope with the oiling besides smoking a little in brake zones after a couple of laps (assumed valve guide due to less perfect drain from head).

Tubbing the front and rear was my assumption, but how much can you tub the rest before you end up in vial sheet metal?

Starting with 580 tall Hoosiers and improved hubs is a natural start. Whatever drivetrain you use the rest have bigger influence (aero, dampers and training). 200 extra whp will make it harder to stay away from the walls...

Thanks for sharing some brain power