How to Build a Street/Strip 350

Last month, we tossed a cam, an intake, and an NOS Cheater nitrous kit at a Goodwrench 350 crate engine from Scoggin-Dickey and made 524 hp with a 200hp shot (“Saturday Night Special,” May ’12). On the normally aspirated side of the ledger, Mr. Goodwrench managed to squeak out 330 hp and 350 lb-ft of torque. These numbers were OK, but we had greater expectations. The goal this month was to bolt the motor in our ’66 Orange Peel Chevelle, run a normally aspirated 12-second pass, possibly squeeze an 11, and not break anything. But before we dropped the 350 into the engine compartment, the original short-block needed enhancing.

While we successfully mixed nitrous with cast pistons, we know all it takes is one minor detonation demerit or tuning miscue for the results to be catastrophic. We’ve grenaded our share of cast-piston engines in the past, so we elected to serve up a set of very affordable Federal-Mogul flat-tops for less than $300, which also bumped compression. We added further insurance with a set of ARP rod bolts, which required rebuilding the big end of the stock powdered-metal rods. That was ably handled by our friends at Jim Grubbs Motorsports. We reused the main bearings because they were virtually new and added a new set of rod bearings with clearances hovering around 0.0025 inch. New Sealed Power rings were also cheap, and for the record, we checked the top and second ring-end gaps, since we planned to hit this package with nitrous. We needn’t have worried about the top ring-end gap, as it measured 0.032 inch, with the second rings slightly tighter. The top ring-end gap on a normally aspirated performance gasoline engine would be closer to 0.018 inch. If we’d used file-fit rings that would have allowed us to custom-set the gaps, we would have chosen a spec more like 0.026 inch for the top rings and 0.030 for the second rings.

After bolting the pieces together, we measured the deck height on all eight holes and were rewarded with eight different heights. It became apparent that the block becomes taller at the rear, adding 0.010 inch of deck height compared with those on the front cylinders. The cure would be to mill the block square to the crankshaft, but we elected to skip this step to minimize expenses. With a Fel-Pro composition head gasket, the front cylinders came in at 9.66:1 compression ratio while the back cylinders measured 9.51:1.

Because our Summit camshaft pushes the lift well over 0.450 inch, we wanted to use the iron Vortec heads but knew that in stock conditions, lift exceeding 0.450 tends to kill the valve-stem seals. Scoggin-Dickey came to the rescue with a modified set of heads that include taller, Z28 valve- springs and enough clearance to handle up to 0.525 inch of valve lift. So if we add a set of 1.6:1 roller rockers at a later time, we will still have plenty of clearance. The price increase for these modded heads is about $170 more for the pair over the stock L-31 Vortec heads, but it’s easily worth the investment. We reused the HEI ignition, the wires, the carb, and the air cleaner from last month’s dyno test, so we were ready to drop the small-block into our Orange Peel Chevelle.

Cam Specs

Test Day

We had a few details to attend to before we could get to the track. The previous engine in the car had been our Lester Scruggs LS 404 ci, which required a resistor in the charging signal wire to the alternator. That tripped us up for several hours before we realized the oversight. After we achieved charging-system success, the next snafu was that our 63-amp alternator was unable to maintain system voltage with the electric fans, the fuel pump, and the headlights all working with the engine idling. We let this slide, but it caused grief later, as you’ll see.