July 2011 Chevy High Performance Q&A

Kevin McClelland Jun 6, 2011 0 Comment(s)
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First of all, the Eagle rotating assembly (PN 1310200) that you listed above is for increasing the displacement of a 305-cid small-block. It uses a stock 305 bore of 3.736 inches and adds a 3.75 stroke (400 small-block) crankshaft to produce 329 cid. Your 327 comes with a factory bore size of 4 inches and swings a 3-inch stroke. Your 327 Eagle has a complete forged rotating assembly under PN 12040030 that is equipped with SRP flat-top forged pistons. They also offer a kit (PN B12041030) that comes with an SRP forged 7cc dome piston that matches the original 10.25:1 compression ratio for the 327. Unfortunately, these kits are quite a bit more expensive than the cast component equipped assembly that you’ve been looking at. They are great packages that come with all components youwill need with bearings, file-fit moly rings, H-beam forged rods, and a two-piece seal forged crankshaft.

If you’re looking to wring out 400 ponies from your 327 you can get there with some of your stock components. Most of the early 327s came equipped with forged cranks from the factory. You could pick up a set of Eagle 5.7-inch rods and a set of SRP forged pistons for the price of the engine kit you listed. The machine work will be the same with this route or the Eagle assembly.

Since we’re talking about machine work, cutting 0.030 inch off the deck may be a little much. You will need to mock up the rotating assembly after the block has been overbored to your new piston size. Slide in your crank and a rod and piston in the four-corner cylinder numbers 1,2,7, and 8. With these pistons installed, rotate the engine to top dead center on the four corner cylinders and measure down to the piston from the deck. You should see that the pistons are somewhere around 0.015 to 0.022 inch down in the hole. By measuring all four corners you can give the machinist those depths, and they will be able to square up the deck height. We would cut the deck to bring the piston right up to the deck surface. This, with a 0.041-inch-thick head gasket, will give you the best quench.

A camshaft with a really nasty-sounding idle and idle vacuum cannot be used in the same sentence. To give your little Mouse a nasty idle you will kill the idle vacuum down to the point that the power brakes are pointless. Years ago, we did a little test to see how much torque it took to drive all the power accessories on the front of a small-block installed in an ’87 Camaro. It was driving the water pump, alternator, P/S pump, and the A/C pulley that wasn’t engaged. We also had the transmission in drive range sitting still. At 650 rpm the engine had to produce 45 lb-ft of torque to maintain 650 rpm. We measured this with an engine we had installed in the Camaro that had too much camshaft. We measured the idle vacuum at 650 rpm. Then we removed the engine and installed it on an engine dyno. To find the torque required we ran the engine up and applied load to the engine at 650 rpm until we reached the vacuum that we saw in the vehicle. With this amount of load, it required the engine to produce 45 lb-ft of torque. When you think of that amount of load at 650 rpm you can see why a large camshaft can cause havoc.

How about we reach a compromise? Since you’re running a smaller (by today’s standards) engine let’s go with a less aggressive camshaft. The Xtreme Energy 268 (PN 12-242-2) would be a good compromise for your little 327. It will give you a nice chop at idle and just enough idle vacuum for your power accessories. The camshaft specs out at 224/230 duration at 0.050 inch of tappet lift, 0.477/0.480 inch max lift, and is ground on 110 centers. This is the max that I would recommend for your little Apache.


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