This photo shows the TA Performance SPX single-plane intake used during most of this month
Did you miss it last month? CC built a very basic Buick 455 and dyno-tested multiple combinations of two camshafts and four intake manifolds. It was entertaining, but the dead spot was in the stock cylinder heads. This month, the resolution: We're going to see how the stock, Stage 1-spec iron heads look when faced with Edelbrock and TA Performance heads in this big comparo of price, features, and power.
As a refresher, the 455 short-block we're beating on is a nearly bone-stock rebuild by JMS Racing Engines, with the only upgrade being Speed-Pro forged pistons (PN L2353F) in a 0.030-inch overbore that are custom-notched for valve clearance by TA Performance. With the 70cc chambers in the baseline iron heads, which TA upgraded to Stage 1 valve sizes, the compression ratio is a measly 8.77:1. All our testing was done with a Holley 750-cfm Street HP carb, an MSD ignition, E3 spark plugs, and a Meziere electric water pump. Thanks to local Buick guy Bruce Kent for loaning us a flywheel.
The variables in last month's testing were the cams and intakes. We found the best horsepower combo to be with a TA Performance SPX single-plane intake and the company's TA-413 cam, a hydraulic flat-tappet grind with 234/244 degrees of duration at 0.050, a lobe separation of 113 degrees, and lift of 0.500/0.500 with the stock rockers. That's the cam and intake used for the first set of head testing, but stay tuned near the end for some info on a combo with a smaller cam and dual-plane intake.
Stock Vs. Edelbrock Heads
The Edelbrock aluminum cylinder heads for Buick V-8s are PN 60049, fully assembled. At press time, the heads sold for $947.95 each through Summit Racing. These heads feature 2.125/1.75-inch valves, the same size as the stock Stage 1 iron heads. The Edelbrock chamber size is 68 cc, so the compression ratio was bumped from 8.77:1 to 8.81:1, which is barely worthy of note.
This graph shows the power difference between the Stage 1 iron heads (blue lines) and the
The Edelbrock heads change the valvetrain arrangement away from the stock-style shaft-rocker setup and are instead designed to use stud-mounted small-block Chevy rocker arms for 3/8-inch studs. If you're doing a swap on an otherwise stock engine, you'll also need to order longer pushrods, though the specific length will depend on the aftermarket rockers you choose. We used Comp Cams PN 1301-16 Pro Magnums in a ratio of 1.52:1. The stock Buick ratio is 1.55:1, but though we did not check to be sure, we felt confident that the stock rockers don't quite add up to the full 1.55:1 ratio. Stockers usually don't. But even if they do, the difference in lift between the 1.55:1 Buick setup and the 1.52:1 Comp roller rockers would be 0.010 inch. If a little bit of lift is worth a horsepower or two, then it's made up for in the roller rockers versus bearingless shaft rockers. We ran the Edelbrock heads with the as-installed valvesprings.
There's a bit of apples and oranges going on with minor differences in compression and valvetrain, but we feel comfortable bench-racing it into irrelevance, especially when you see the huge power gain when going from the stockers to the Edelbrock heads. The Edelbrocks killed the stockers at every point in the rpm range; at the peaks, they were better by 24 lb-ft and 42 hp. Combined with the weight savings of the aluminum Edelbrocks, that's really significant. And if you like the bragging number, the swap took this mild Buick from 459 hp to 501 hp at 5,400 to 5,500 rpm. Peak torque was 519 lb-ft at 3,900 to 4,000.
Costwise, let's assume you're building an engine from scratch. The rebuilt iron heads from TA Performance are $1,395 a pair. Summit charges $1,895.90 for two Edelbrocks. The stock Buick replacement shaft-rocker sets are $155 from TA Performance; the Comp Cams Pro Magnum Chevy rockers required by the Edelbrock heads are $285.95 from Summit. Chances are good you'll need custom pushrods for either combo, so that price is a wash (though technically, the Edelbrocks require hardened pushrods for guideplates and the stockers do not). Therefore, you're into an extra $631.45 for the more powerful heads.