This is the lump we started with, donated by Hot Rod's David Freiburger. This thing was so
If you're a hard-core small-block Chevy guy, the good news about all the attention the LS engines are getting is there's never been a better time to build a budget Gen I small-block. That even applies to the nearly extinct 400 small-block. Vigorously hoarded at one time, a few have appeared at the swap meet, and we even saw one at the junkyard not long ago. This prompted us to consider the ultimate budget tire-smoker when we received a scum-encrusted 400 from Hot Rod's David Freiburger. He swore it was good but abandoned it when he realized its value was declining faster than President Obama's approval rating. Other than the fact that it was a standard-bore block with stock parts, there was little to value in this casting. In fact, our theory is he found the engine at the bottom of a deserted mine shaft under 100 feet of boric-acid-laced water, explaining why our block looked hideous even after a hot tank dunk. The Chevrolet gods demanded an exorcism, but we ignored 'em. Even after an abbreviated séance in which the ghost of Zora Arkus-Duntov threatened to cancel our lifetime membership in the Bow Tie cult, we pressed on. Those were valid warning signs. We decided to build a motor in a way that all good car crafters would understand-by hacking the budget with a blunt instrument. Sure, we took a risk by not boring the block and adding new pistons. The old pistons were in decent shape even after we beat them out of the block with a hammer! We even chose to ignore the serious rust pitting in the cylinder walls. We were not deterred.
We should have been, though, because the mechanical gods got the last laugh.
Our power plan was as simple as it was cheap. We liked the idea of enhancing the 400's strength of torque with a pair of Vortec iron heads and a budget flat-tappet cam to see how much grunt we could make. Then we'd pump the power with a set of large-port Vortec Bow Tie heads. So now that you know the backstory, we'll fast-forward to the assembly effort, dyno testing, and subsequent bloodletting.
Assembling the 400 Short-Block
The smart move would have been to bore and torque-plate-hone the block. But since the push was to hit this short-block cheaply, we decided to stick with the game plan despite evidence of neglect. So this is our worst-case scenario. As you can see from the honing photo, there is power to be gained from doing the correct machine work by boring the block to eliminate the bore wear. We also kept to the bargain-basement plan with Summit's own cast-iron rings and basic bearings. We did have to grind the crank 0.010 inch undersize because there was metal transfer on the rod journals. Add in the cost of hot tanking, resizing the big ends of the rods, and installing cam bearings, and the machine shop cost alone came to roughly $400. Frankly, there's no way to really do this inexpensively. The days of the $1,000 V8 rebuild have gone the way of disco and Pac-Man.
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This is what we had to work with. We had to beat the pistons out of the cylinders with a w
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We took the block to Barrington Engines for the hot tank cleaning, crank grinding, and res
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Even though this same rotating assembly had come out of the block, we started by checking
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Don't forget that press-in plug underneath the rear main cap. It is often removed for clea
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We prefer to take the time to mic each main and rod journal and then measure the actual ma
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We installed the Summit budget rings and then pressed all the pistons back into their bore
Cam Specs
The cam we chose was the least expensive hydraulic flat-tappet cam and lifter set from Summit that also included a dual pattern to better support the Vortec's well-documented weak exhaust-port flow.
| CAMSHAFT |
DURATION AT 0.050 |
LIFT |
LOBE SEPARATION |
| Summit hyd., intake |
234 |
0.488 |
110 |
| Exhaust |
244 |
0.510 |
|