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How to Get an Easy 400 HP With a Small-Block Ford

HOT ROD logo HOT ROD 2018-05-15 Hot Rod Network Staff
EDEL-01

Several years ago, we installed an Edelbrock Performer RPM Power Package Top End Kit to a 289 in a '65 Mustang, and while it certainly gave the engine a newfound level of power, it wasn't quite what we were expecting horsepower-wise. Sure enough, a leakdown test proved that the 289's short-block was indeed just flat worn out, with varying percentages of cylinder leakage past the rings. If we wanted the engine to actually run to its potential and take advantage of those nice, shiny, new Edelbrock speed parts, it needed to be rebuilt.

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The question then became whether to keep it at the stock 289 cubic inches (with most likely a 0.030-inch overbore to compensate for the cylinder/piston wear), or go a little bigger with a stroker kit. Upon teardown, it became clear that a 0.030- or 0.040-inch overbore would clean up the cylinder walls, but that would mean new pistons, and the crankshaft wear meant that the crank may need some machine work. And because we were reinstalling the Edelbrock top end kit and wanted to possibly add more power at a later date, we wanted to replace the connecting rods. When you compare the cost of machine work and the need for new rods and pistons anyway, there's really no reason to not go with a stroker kit. Yes, a full stroker kit can be more expensive than re-machining and replacing stock parts, but other than that there are no real downsides to putting a stroker kit in, with the possible exception of a ring seal with short deck-height pistons. This is more commonly an issue with 347ci combos, but we've seen 347s with tons of smoke-free miles on them.

Since we were using Edelbrock parts and the company offered to help us get the most out of them by rebuilding the engine for us, we let them do it. (Okay, in all honesty we begged them to fit us into their schedule!) Edelbrock often uses stroker kits from Scat, so we ordered Scat's 331ci kit that uses a 4340 forged-steel crank with 3.250 inches of stroke (a stock 289 crankshaft has a short 2.87-inch stroke). With a cleanup of the stock 289 block to a finished bore diameter of 4.040 inches, that 3.250-stroke crank provides 334 cubes. Scat also provided the I-beam forged rods (part number 2-ICR5400-927) and Autotec forged pistons with -10.7cc dishes for a streetable compression ratio.

The top end, of course, is Edelbrock's Performer RPM Top End Kit. Available as a single part number, the top end kit's appeal, especially for an engine building novice, is that they've eliminated any guesswork on power levels, including most everything you need to top off a rebuilt short-block including the cylinder heads, camshaft and lifters (lifters not included with a hydraulic roller cam), and intake manifold. The standard RPM kit (part number 2091) comes with a flat tappet cam, but we have experienced camshaft failures recently when using some flat tappet cams, and a roller cam makes more power everywhere anyway, so we went with the more aggressive hydraulic roller in this combination, part number 2043.

This little 334ci thumper was carefully assembled by Edelbrock's main engine builder, Robert Jung, and dyno-tested by Curt Hooker; they have a combined 70-ish years with the company and do these jobs day in and day out. We were guessing the engine would make in the high-300s or low-400s on horsepower based on Edelbrock's extensive dyno-proven combos, and that's right where it came in, with a peak horsepower of 410.5 at 6,000 rpm and 390.6 lb-ft of torque at 4,500. In a relatively lightweight 1965 Mustang, that'll move you down the road just fine and allow burnouts at will.

EDEL-01© Hot Rod Network Staff EDEL-01

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