Slant 6 Turbo 68Dart Project
I've been putting off new engine time for too long. I have the money and in a few days I'll have a break from working. Thinking it may be the time.
I need to mind my own business...
BUT, if I am to survive the wars that rage, constantly, inside my head, I need to say something, however irrelevant, now and then...
This may be one of those times...
You see, I am aware of the constant pull toward excellence in performance that goes on with these engine (turbocharged slant sixes.)
They start out as cannon-fodder for every Honda Civic, Toyota Camry V-6 and Honda Accord at every stoplight in the country, with quarter-mile times that would be better, measured with an hourglass; a slant six (stock) that will run in the seventeen-second bracket in the quarter-mile is a rarity. Most run about 19-seconds, or slightly better.
Enter forced-induction technology. This method of going faster works wonders for slant sixes, which happen to be blessed with one of the strongest crank/block/head infrastructures ever put in an American engine.
There are documented results of slant sixes that have survived 37 (no typo, thirty-seven) pounds of boost, without damage.
That protocol, stopping at about 28 pounds of boost, can make for an engine that has 500+ horsepower capability. That kind of power can put an A-Body well into the tens at almost 130mph (quarter-mile times.)
But, not everybody wants to go that fast... so, building a 350-horsepower engine that will push your 3000-pound A Body 12 seconds flat (with only 15 pounds of boost) becomes a "Plan B" and is probably more practical.
A car that runs 12-seconds flat will outrun, probably, 90-percent of the cars on the road, and (this 15-pound, boosted slant,) will run on pump gas, idle like a stocker, get decent mileage, and have impeccable road manners, to boot. Icing on the cake, is, that it really LIKES a 2.76:1 rear axle ratio, so hiway driving is something that this gearing lends itself to with no overdriven, top-gear, being necessary. Yes, that ratio works best on the quarter-mile drag strip, too. It also makes it possible to use the cheaper, more-plentiful, 8.25" ring gear, rear end (rather than a drop-out center-sectiion, 8.75" unit, which has become prohibitively-expensive, in recent times.)
The important part of my tirade, is, that it is not-necessarily CRITICAL that the pistons in this motor be forged, (in this 15-pound-boost, engine,) but, realistically, anybody who recognizes that "boost is addictive" will know that, once you get a taste of a 12-flat car... at some point, and, probably SOON, you're gonna want more.
The sad fact is, 15 pounds is probably pushing the limits of the stock, cast-pistons and rings already, and if you want more performance, there's nowhere to go... You can't raise the boost to 20 pounds without running the risk of breaking something... probably, something that's going to be expensive, or create a problem that is expensive.
What to do????
If you build this engine with forged pistons
to begin with, you are taking a large percentage of the reciprocating assembly out of harm's way, when you (inevitably,) crank up the boost, later on.
Now, there's a catch to this...and, it is this: Wiseco makes the (forged) pistons that work well in this engine, (045"-over) and they come with "dedicated, new-style " rings.
UNFORTUNATELY, they also come with the pin-boss hole drilled for a raised location that fits the 198 rod (rod-length 7.005") and Wiseco teams-up with K-1 Rods to make the appropriate sized rod for this application. The rods ain't cheap!
I believe the rods and pistons, together, cost just a little over $1,000.00.
Now, I understand that stock 198 rods will work OK in this application, the problem being, that they are somewhat hard to find.
I think the pistons, themselves, are "only" $443.00, or, thereabouts.
The crank is usually fine with only a polishing, or a .010"-cleanup.
I have no experience with cast iron cranks, but I THINK a cast crank would work fine and last a long time in this low-boost application.
The point of all this is just this: Do whatever you CAN to get the money to build the engine with forged internals; later, on down the line, when the urge strikes you (and, it WILL) to raise the boost-level from 15 pounds to 20, you can do it and feel good about it; not live in constant fear of ruining the whole thing with boost that is beyond the capability of the pistons/rings, to live.
My car, at 3,000-pounds, total weight with driver, ran a (Wallace calculated, off its eighth-mile times,) 12 seconds, flat in the quarter, at 112mph. That's with 15 pounds of boost and a 2.76:1 gear.
I can, at a later date, raise the boost-level to 20 pounds, and then, to 25 pounds, if nothing egregious happensns. Talk's cheap; we'll see...:banghead:
