There are no sparks flying from a bench grinder here, no blinding blue glare of a welding torch. Picture instead a bunch of tattooed, bearded guys wearing black skullies and T-shirts, blue jeans, and lots of Maltese crosses ... all sitting around your computer poring over your portfolio. Welcome to the premiere of Monster Portfolio Garage, where we construct a tough, hardened array of winning stocks to muscle your way to a comfortable retirement.

Just call me Rich "Jesse James" Duprey.

Starting with a stock frame, so to speak, we're going to add the V-twin engine of equities -- small-cap stocks that will get our motors running. Over at Motley Fool Hidden Gems, wannabe Hell's Angel Tom Gardner straps on some leather chaps and sorts through the universe of 9,000 stocks looking for those ripsnorting small caps that show equal promise of growth and return. To date, Tom has been smoking the competition, laying rubber as he beats the market's returns by 20 percentage points.

Finding our frame of reference
We're going to begin building out our bad-to-the-bone portfolio with the frame. If the frame's not right, it doesn't matter how torqued out the engine is, the bike just won't ride right. For most investors, that solid frame -- the foundation upon which everything else rests -- should include index funds. A broad market index -- such as Vanguard's Total Stock Market Index (FUND:VTSMX), which sports a tiny expense ratio even as it holds thousands of individual stocks -- provides a stable base to begin our project.

Since the fund's inception, it has returned an average of 10.5% a year, similar to the market's averages over the past 80 years. It will have up years as well as down ones, but its broad base helps it serve as our ballast.

Thanks a lot, big guy
With our frame in place, we can hammer our gas tank out of a variety of large-cap stocks, as these will provide the fuel for generating long-term gains. Stalwarts Microsoft (NASDAQ:MSFT) and Dell (NASDAQ:DELL) have provided investors with incredible results, yielding returns of 17% and 44%, respectively, over the past decade. Large caps are the fuel for long-term gains. They won't run up 20% or 30% overnight. They may not even run up 20% or 30% in the span of several months. But over the years, these big players will provide us with a low center of gravity for easy riding.

By anchoring our portfolio with these large companies, we'll avoid a lot of volatility. Sure, even the best-built bikes can have mechanical failure, and portfolios, including those built of big companies, can have an occasional meltdown. Just ask anyone who invested in Oracle (NASDAQ:ORCL) back in 2000, when the stock dropped almost $27 billion off its market cap in just one day. Over the past 10 years, however, it has had a more than 15% total return.

Small caps, big guns
Now, to get our portfolio rumbling, we need a sweet, chromed-out V-twin engine. For that, look no further than small-cap stocks. Imagine you're sitting at the traffic light and your engine's idling. You can hear and feel the vibration of the horses rumbling and chortling inside. Like thunder rolling down from the hilltops, this engine is waiting to rip wide, blue flames out of the slash-cut tailpipes. That's what small caps can do for your portfolio. They're the high-octane nitrous that will juice the returns of our Monster Portfolio.

Here we can turn to Tom's investing prowess to help us find the big guns of the small-cap universe. In the two years that Hidden Gems has been recommending stocks, Tom has uncovered Mine Safety Appliances (NYSE:MSA) for a 160% return; oven maker Middleby (NASDAQ:MIDD) for a 250% return; and, in just a year, Stanley Furniture (NASDAQ:STLY) for a 37% return.

Each month, two stocks receive the official nod, representing the best thinking of Tom and Bill Mann. Two or three more companies are placed on a watch list, where members pore over their financials on dedicated discussion boards. One or two companies too small to be official recommendations are given special status as Tiny Gems, micro-cap companies worthy of further consideration. In all, Hidden Gems subscribers have crafted a special community where investors can turn their "skillz" toward stocks.

While I enjoy investing in small-cap stocks -- I love screening for them and researching them, in part because their financials are usually far simpler and easier to understand -- they shouldn't be the only ingredient in the mix. They're exceptionally volatile, sometimes with a small float or low volume, and they can ricochet around on bad news, good news, or even no news at all. They're exciting, to be sure, but you want to be able to sleep at night, too.

A Foolish ride of your own
A well-balanced portfolio consisting of index funds, large-cap stocks, and a handful of small caps -- figure about 20% of your portfolio's total -- will give you a smooth ride.

You can craft your own Monster Portfolio, and you don't even have to go to the garage to build it. Heck, sit in your living room in your underwear if you choose. (Then again ... maybe you shouldn't.) You don't even need any scary biker dudes looking over your shoulder. Start with your frame of index funds, add a fuel tank of large-cap stocks for long-term performance, and mix in some small-cap stocks like those found in the pages of Hidden Gems. Start your journey down the road to retirement.

If you'd like to see Tom and Bill's best small-cap stock prospects right now, you can view the nearly 50 recommendations with a 30-day free trial to Hidden Gems. Click here to learn more.

Fool contributor Rich Duprey rides Harleys and sports a couple of skull tattoos. Rich does not own shares of any company mentioned in this article. Dell is a Motley Fool Stock Advisor recommendation. The Motley Fool has adisclosure policy.