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Pontiac 400 Poncho Engine Build - A 650HP Hard-Core Pontiac Stroker

If You Own A Pontiac And Were Considering Bolting In A Big-Block Chevy To Make Some Real Horsepower-Shame On You! Repent While There's Still Time And Build...

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There was a time not long ago when if you wanted a really quick street Pontiac, you dropped a Rat motor between the fenderwells. Sure, the purists threw rocks at you, but the simple truth was horsepower was easier and cheaper with the Chevy. Each time this happened, somewhere there was a disturbance in the great cosmic ether of Pontiac karma, and this must have pissed off some rather motivated Pontiac people. They saw each Rat swap as a personal insult and decided to do something about it. The result of this affront is an arsenal of killer Pontiac cylinder heads and cylinder blocks that can lay claim to some serious power numbers. Sure, GM in the fog of forgetting where it came from has scalped the Pontiac logo from the GM family tree, but clearly not everyone intends to forget.

Andy Mitchell, owner of Hardcore Racing, is a low-key engine builder who has constructed a fair number of Pontiac engines that measure up to the company's name. Mitchell has built several big-inch, normally aspirated, real Pontiac engines that have made more than 1,000 hp. There may not be an original GM part to be found in these engines, but they nonetheless pay strict homage to the Pontiac lineage. For this story, we followed along as Mitchell assembled a car-crafty version of a 400 Poncho, block-based, 434ci motor that makes an honest pump gas 650 hp. Here's how he did it.

The Short-Block
The world of Pontiac high performance is rapidly changing. If power is the goal and money is no object, the Indian Adventures II iron block or the Butler aluminum version offer unbelievable strength and large displacement foundations for the born-again Poncho. Mitchell has plenty of experience with these pieces, but this particular customer was looking for a conservative 650 hp, which pointed Mitchell to a stock, '70-vintage, 400 block. It featured a 4.125-inch bore and a 3.750-inch stroke, which is basically a larger-bore version of the 389. Mitchell's combination enlarged the bore to 4.155 inches and stretched the stroke to an even 4.00 inches to produce 434 ci.

According to Mitchell, "In 30 years of building these engines, I've never broken a block, but many other people have. At this power level, we're OK. It's around 750 hp where the stock blocks tend to crack." But this doesn't mean Mitchell didn't inject some beef into this casting. The first upgrade was a full set of Pro-Gram Engineering four-bolt steel main caps. Next, he opened up the main bearing oil feed holes to 3/16 inch and increased the main bearing clearance to 0.003 inch to adjust for the small-journal, 3.00-inch-diameter mains. Rod bearing clearance came in at 0.0028 inch. The only other major requirement for this stock-block buildup was to reinforce the somewhat open lifter bore area on the stock Pontiac blocks. SD Performance makes what it calls the Mega Brace, a series of bolt-in aluminum pieces designed to support the bottom of the lifter bores that tend to crack when subjected to higher engine speeds and greater valvespring pressure. The Mega Brace can even be installed after the short-block is assembled.

Cam Specs
Mitchell custom-spec'd this Comp mechanical roller, so you won't find a part number for this cam in the catalog. Call Mitchell at Hardcore for the details on the lobes.

Intake 266 0.675 111 0.020
Exhaust 272 0.675

Roland Heads
Focus your short attention here. Roland Racing is a small shop that does big things. Casting a cylinder head with the expectation of making a couple of dollars is an achievement unto itself. But doing so for a limited number of Pontiac enthusiasts might well be considered risky. But the results speak for themselves. The Roland CV-1 aluminum cylinder head goes far beyond just replicating a production head by canting the valves to open them into the center of the cylinder and therefore improving flow potential, even on a small-bore engine. This is completely different from typical '60s valve layout technology. This clean-sheet design also demanded changes to the intake port layout to create separation from the pushrods so as not to compromise flow with port intrusions or tunnels. All this equates to some serious flow potential as evidenced by the accompanying flowsheet. While Mitchell did elect to drop extra coin on a T&D shaft rocker system, the Roland CV-1 heads allow the use of more affordable stud-mounted roller rockers. For a made-in-the-USA boutique cylinder head like this, the Roland price of just under $3,000 for a complete pair of heads that flow damn near 350 cfm at 0.700-inch valve lift qualifies for steal-of-the-century status.

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