Hot Stock-Appearing Engine Combo For The Street
I have been reading your mag for about 20 years and I think it's great. Also, I've closely followed the Pure Stock shootouts and I would like to build my 400 engine similarly. I'm not much for the look of aftermarket parts under the hood, as I like it to look stock and go like hell. But, I'm not planning on racing in the Pure Stock series, so my engine just has to look stock and not adhere to any rules. The car is a '68 GTO with a Turbo 400 and 3.55 rear. What I would like is a recipe to make the most power using D-port iron heads, Ram Air manifolds and a factory cast-iron intake, while still maintaining cruiseability. Thanks for the great magazineJim RedyVia Internet
Jim Taylor Responds:
Thanks for the question. Your request is exactly the same as about 60 percent of our customers these days. People want to go fast without a radical, expensive engine, and because of car shows and the value of their Pontiacs, they want a stock look.
Here's what we're doing:
We prepare the '68 No. 16 heads with three-side milling (block, intake, and exhaust). This removes 40-years worth of anti-freeze and rust-etching and trues the surfaces for better gasket sealing.
Then, perform a three-angle valve job on the intake, two on exhaust and use Ferrea 5.200-inch valves (stock size). Valve bowl blending, gasket matching, and a slight massage on the short turn radius are also done. Valvespring seats are trued up and valve guides are cut for positive Teflon seals.
We replace the 400 crankshaft with either an original Pontiac or an Ohio Crankshaft 455 crank. The Ohio crank costs less because it comes ready to drop in. Depending on the customer's budget, we either prepare the stock Pontiac rods or install Crower Sportsman stock-length rods.
Our compression adjustment, which is a must to use 93-octane, is achieved by using Keith Black (KB) No. 371 pistons with a 30.5cc dish. When added to the No. 16 combustion chambers of around 71cc and about 10cc's for head gaskets, it yields a compression area of approximately (you must pour to be sure) 111.5 cc's.
One issue, however, is the KB No. 371 pistons do not come in the standard 455 bore size of 4.150 inches. It comes 0.030-over so we need to bore the 400 block to 4.180 inches or 0.060-inch over. (I've called KB Piston many times and requested the company make the 455 KB No. 371 in a standard 4.150-inch bore, so we would only have to bore the 400 block 0.030-inch over. Even after offering to buy a very large quantity, I've gotten no response.) I wish we had a standard 4.150-inch piston for this application, but don't worry about the 0.060 over on your block. The '68-'72 400 block is known to be beefy.
The 4.180-inch bore and 4.210-inch stroke equal a 462 cubic-inch displacement. One cylinder displacement is 57.74 ci. In cc's that's 946. Now add the compression area of 111.5 cc's, which equals 1,057.5. Then, divide by the compression area of 111.5 cc's. This equals a compression ratio of 9.48:1. With a good fuel and timing curve, the engine will not detonate (ping).
We choose from a variety of cam grinds for this type of buildup. For hydraulic cams, we like the Crane 248/248-deg duration with a 112-deg lobe separation. This will make 14-hg of vacuum at 900 rpm. With Crower rods, we've used the Crower 247/252-deg duration solid lifter cam with great results; it also has a 112-degree LSA and produces 12-hg of vacuum at 900 rpm.
We rebuild and dial in the fuel curve on the Q-jet. Then we rebuild and recurve the original distributor and install a Pertronix unit. This lets the customer use the original wires and looms. The stock intake manifold is an excellent performer and it allows the customer to retain the factory choke.
Original chrome valve covers can be used with the hookups to the factory air filter and don't forget the ram air pan for the '68. Fresh, cooler air makes power.