Auto-parts suppliers may still look like better investments than their Big Three customers these days, but that doesn't necessarily mean it's time to buy all of them. Delphi ( DPH) is one example. Although the company has demonstrated tremendous progress on restructuring relatively high-cost operations and diversifying its sales base, its fate is still heavily tied to General Motors ( GM), which accounts for roughly 60% of Delphi's total sales. And as GM wrestles with market-share losses and historically high levels of inventory, the outlook for GM's production, and consequently Delphi's GM sales, is not encouraging. With the stock down close to 6% so far this year, slightly worse than the 5% decline in the Dow Jones Auto Parts supplier index, many of the company's potential near-term challenges are already reflected in the stock price. On a valuation basis, however, the stock is not very tempting. Although shares trade at an enterprise value-to-EBITDA ratio of 4.5, less than its peer group average of just over 5, the stock should trade at a discount due to its reliance on GM, its leveraged balance sheet (long-term debt to capital ratio of about 50%) and pension obligations (a roughly $4 billion unfunded liability at the end of last year). With its P/E ratio of 11.7 times this year's consensus earnings estimate of 82 cents per share, Delphi is right in line with the auto-parts supplier average of 11.5.