Milodon Small Block Main Caps - Buff Bottom End

If you're serious about building power, especially power that lasts beyond one dyno pull, you know that a two-bolt main block just doesn't cut it. High-horsepower motors throw the crank harder, and with a measly two bolts holding your guts in, eventually something is going to fly out, crack, stretch, or flex.

When it comes to strength and bottom-end survival, four-bolt mains are a necessity. The only problem is that most of the four-bolt main blocks are either still in use or are already in someone else's hot rod. But here comes the good news: There are plenty of two-bolt main small-block Chevy 350s and 400s just waiting in your local junkyard, and Milodon makes a two-bolt to four-bolt main conversion kit, so you can play hardball with less hassle and less money. The kit will actually make your engine stronger than a factory four-bolt.

Milodon's kit comes with much bigger and stronger main caps. The splayed outside bolts connect to the block in a much meatier area than a stock four-bolt main cap, decreasing the likelihood of cracking (which four-bolt 400s are notorious for). PAW in Chatsworth, California, sells the kit and offers to install it as an extra when you buy one of the company's engines (that way you don't have to make an extra trip to the machine shop). We went to PAW to take photos of the conversion on a two-bolt main small-block Chevy.

If you're putting together a small-block 350 or 400, Milodon's conversion kit is a great idea. It's not the type of install that you can do at home (unless you've turned your guest house into a machine shop), but with the right tools and gauges, your local machinist can do the conversion for you very easily.

The three center main caps...        read full caption The three center main caps were torqued down to spec, and the air gap was measured with a feeler gauge. Clearances of 0.001- to 0.003-inch are necessary.	The caps were cut until the...        read full caption The caps were cut until the desired clearance was achieved. The caps were then re-torqued and double-checked with the feeler gauge.	With the sleeve in place,...        read full caption With the sleeve in place, a handheld drill was used to bore out the block material.
The new caps were bolted back...        read full caption The new caps were bolted back on and torqued to spec. They were then align-bored and chamfered.	Milodon's kit comes with a...        read full caption Milodon's kit comes with a special sleeve that's inserted into the new cap. The main cap actually serves as a guide for the drill.	After the block was drilled,...        read full caption After the block was drilled, a tap was used to create the threads for the bolts.
The caps were finished off...        read full caption The caps were finished off with an align hone.	A dial bore indicator was...        read full caption A dial bore indicator was used to make sure that each cap was the proper size and was perfectly round in shape.	Much better.
Here you can see how wimpy...        read full caption Here you can see how wimpy the two-bolt main caps look in comparison to Milodon's four-bolt mains. Milodon's four-bolt conversion kit is worth its weight in gold.	Because the new caps are so...        read full caption Because the new caps are so beefy, a notch had to be machined out to clear the dipstick hole on this particular engine.