Summit City Auto, Diesel And Customs

09/04/2026

CLOSED FOR LABOR DAY WEEKEND! 🔧🪛🧰

We hope everyone has a fantastic and safe labor day. You all deserve some time off for all your hard work!

09/04/2026

09/04/2026

We covered the ZZ632 on this page. 1,004 HP from 632 cubic inches. The most powerful naturally aspirated crate engine ever sold. The ZZ572/720R is its older sibling and its philosophical ancestor: the same big block Chevy family, the same Chevrolet Performance catalog, the same cast iron block with four bolt mains, the same forged everything. But where the ZZ632 represents the absolute ceiling of naturally aspirated displacement, the ZZ572 represents something different. It is the Rat Motor at maximum tune on race fuel. The King of the Rats. And it has been pulling bracket racers into the nine second zone for years while the ZZ632 gets the magazine covers.

The specifications are brutal. Bore 4.560 inches. Stroke 4.375 inches. 572 cubic inches from a tall deck Gen VI big block Chevy casting. Forged 4340 steel crankshaft. Forged 4340 H-beam connecting rods, shot peened. Forged aluminum pistons with full floating wrist pins. Four bolt main caps. 12.0 to 1 compression ratio. That compression number is the detail that separates the ZZ572 from street engines: at 12 to 1, the engine requires 110 octane race fuel. Not 93. Not E85. One hundred ten octane leaded racing gasoline. This engine cannot run on pump gas without detonation destroying the pistons within minutes. The ZZ572/720R is not a street engine disguised as a race engine. It is a race engine sold in a crate with a part number and a factory warranty.

The cylinder heads are where the power lives. Aluminum rectangular port castings with 310cc intake passages. Three hundred ten cubic centimeters of intake port volume is enormous. For comparison, a factory LS3 head has 260cc intake ports. The ZZ632's RS-X spread port heads have even larger ports. The ZZ572's 310cc ports are sized for an engine that makes its power between 4,500 and 6,750 RPM with a mechanical roller camshaft running .714 inches of lift on both intake and exhaust. Duration: 278 degrees intake, 282 degrees exhaust at .050 inch. Those are race cam numbers. The mechanical roller lifters require periodic valve lash adjustment, something hydraulic lifter engines don't need, but they allow the aggressive ramp rates and high lift that the big ports demand. Valve sizes: 2.250 inch intake, 1.880 inch exhaust, stainless steel. A 1,150 CFM Holley Dominator carburetor sits on top. One thousand one hundred fifty CFM. The largest production carburetor Holley makes, feeding 572 cubic inches that consume air at a rate that would starve a smaller carb at 6,000 RPM.

Output: 727 HP at 6,300 RPM and 680 lb-ft at 4,900 RPM. Those numbers are conservative by modern aftermarket standards. The NRE 540 makes 1,100 HP from fewer cubic inches with turbos. Kenny Duttweiler's Bonneville engines make 3,000 HP from 557 cubic inches with twin turbos on methanol. But the ZZ572 makes its 727 HP naturally aspirated, on a single carburetor, with factory components, from a crate engine you can order from a Chevrolet dealer with a credit card and have delivered to your garage on a pallet. No turbo fabrication. No custom fuel system. No engine management tuning. Bolt on the included Dominator carburetor, add a starter and fuel pump, and the engine is ready to run. Chevrolet lists it as capable of pulling bracket racers and heads-up cars into the nine second range. Nine seconds in the quarter mile from a crate engine with a factory part number.

Chevrolet also offers the ZZ572/620 at the same 572 cubic inches but with 9.6 to 1 compression, a hydraulic roller cam (.632 inch lift), an 850 CFM carburetor, and 621 HP. The 620 runs on premium pump gas. The 720R runs on race fuel. Same block. Same bore and stroke. Same displacement. Different cam, different compression, different fuel, different power. The difference between 621 and 727 HP is the difference between a street engine and a race engine. Same architecture. Different commitment.

09/04/2026

😍😍😍

Here’s our 1,000 HP Daily-Driven Supercharged Coyote Package.

This is a killer solution for the Ford guys who want an 8,000 RPM, four-cam, fire-breathing monster that you can literally drive anywhere, every day.

The engine is built with all the good stuff — fully forged bottom end, fully ported cylinder heads, custom camshafts, and a complete supercharger system.

It comes complete with all wiring, Holley electronics, ECU, and a full tune — ready to go.

We can also set you up with a matching 6-speed automatic or 6-speed manual transmission, including the necessary controls, so you can have a complete matched powertrain package.

If you’re looking for an incredible 1,000 HP Ford package that revs to 8,000 RPM and still has real daily-driver manners, give Nelson Racing Engines a call.

09/04/2026

Early engineering marvel!

Every engine builder on this page wants bigger valves. Bigger valves flow more air. More air means more fuel. More fuel means more power. The Boss 429 has 2.28 inch intake valves. The Hemi has 2.25. The L84 Fuelie heads use 2.02. Every serious performance engine uses the largest valves the bore diameter will accommodate because valve size is airflow and airflow is horsepower. The Buick Nailhead had 1.875 inch intake valves in its largest, most powerful 425 cubic inch version. A Chevrolet 283 small block with half the displacement had bigger valves. The Nailhead's valves were so small that when you looked at them from above with stems pointing straight up perpendicular to the deck surface, they looked like nails driven into a board. That is where the name came from. And the engine made 465 lb-ft of torque anyway. From the smallest valves in Detroit. By breaking every rule this page has ever documented about airflow.

The trick was velocity. Small valves restrict total airflow volume. That is a fact. But small valves also accelerate the air that does flow through them to higher velocities. Higher velocity air fills the cylinder more efficiently at low RPM because the air has more momentum as it enters the combustion chamber. At low RPM where cylinder vacuum is relatively weak, a large valve opens a big hole but the air entering through it moves slowly. A small valve opens a smaller hole but the air screams through it. At 2,000 RPM the Nailhead's small valves and tight ports created a column of high velocity air that packed the cylinders more completely than the large lazy ports of competing engines could manage. The Nailhead made its torque where cars actually drive, between 1,500 and 4,000 RPM, by using the small valve limitation as an advantage in the RPM range that mattered.

Buick compensated for the small valves with camshafts that had no business being in a luxury car. The original 322 Nailhead used a cam with 282 degrees intake duration, 292 degrees exhaust, and 67 degrees of overlap. In the 1950s, that was a race cam. The 401 and 425 had even more aggressive profiles, giving those engines a lumpy idle that did not match the image of a banker's Electra 225 leaving the country club. The aggressive cam kept the valves open longer per cycle to compensate for the restricted flow area. Longer duration meant more total airflow per valve event even though the valve opening itself was small. The combination of high port velocity and aggressive cam timing created an engine that made more torque below 4,500 RPM than anything else in the GM lineup and more torque than most engines from Ford and Chrysler. The 401 made 445 lb-ft. The 425 made 465 lb-ft. Buick was so proud of the torque numbers that they printed them on the air cleaner. "Wildcat 445." "Wildcat 465." Customers who didn't know better assumed those were the cubic inches. They weren't. They were the torque.

The architecture was ahead of its time. Big bore, short stroke. Generous 4.75 inch bore spacing that left room for displacement growth from 264 to 425 cubic inches across thirteen years of production. The vertical valve orientation that created the nail appearance also made the engine physically narrower than competing V8s from Cadillac and Oldsmobile because the valve covers didn't splay outward the way angled valve covers on a conventional V8 do. The Nailhead fit in engine bays where wider engines wouldn't. Buick engineers experimented with a turbocharged 425 using three Carter YH sidedraft carburetors feeding a single TRW turbocharger. It produced over 620 lb-ft of torque. It also destroyed every transmission GM tested behind it. The project was shelved. That engine now lives in the GM Heritage Collection in Sterling Heights, Michigan, the most powerful Buick engine ever built and the only one that was too strong for any driveline GM had available.

The Nailhead died after 1966 because the small valves couldn't be fixed. Above 4,500 RPM the airflow restriction became a wall that no camshaft profile could overcome. The replacement Buick big block (400, 430, 455) used larger conventional valves with better high RPM breathing. The Nailhead's limitation killed it. But below 4,500 RPM, in the RPM range where every street car, every luxury sedan, every tow vehicle, and every boulevard cruiser actually operates, the Nailhead was devastating. Four hundred sixty five lb-ft from valves the size of nickels. Printed on the air cleaner. Because Buick knew the torque number was more impressive than the displacement number, and because most customers couldn't tell the difference anyway.

09/04/2026

Whewwwwww. We have been busy. We haven't posted in a while. But here is a few projects we've worked on or are working on. There are so many projects we've worked on recently that we dont have photos of. Like A/C jobs, brakes, alignments, welding fabrication, front end parts, etc.

In not any one particular order:

*Chevy 3500 454 big block getting engine rebuild.
*F150 Ford getting new engine.
*Bronco 2 engine rebuild.
*Ford F350 6 speed transmission.
*Ram 2500 6 speed transmission.
*3.5 liter eco boost timing chain and cam phaser replacement.
*6.0 Powerstroke High Pressure Oil Pump replacement.
*Case tractor wheel hub assembly rebuild
*New Holland tractor wiring short
*Round baler idler pulley replacement
*Tailgate Liftgate installation.

And so so so much more!

Thank you to our customers, community and our staff/team. We couldn't do this without you all. We are blessed to be busy and appreciate the trust and loyalty.

As always we will continue to do our best for you all!

08/31/2026

10% off any front or rear brake service. The maximum discount is $50. Cannot be combined with any other offers or specials.