Video: Arby’s Marketplace Dodge R5P7 NASCAR mill hits the dyno

Facebook Marketplace is full of treasures, but it is also a hive of scum and villainy. Attempting to purchase a used engine from another country through Marketplace adds an extra level of complexity – organising it all via Messenger, paying via PayPal in a foreign currency – so it’s definitely a roll of the dice. Still, I figured the chance to own one of the most exhilarating and refined small-block engines of all time – the legendary Dodge R5P7 NASCAR V8 – would be worth the risk.

First published in the May 2025 issue of Street Machine

Most R5P7s for sale these days come without pipes, carb or the dry-sump oil tank, but you really want to find one in as complete a state as possible. The original 830cfm carbs are hot property, so you’ll be lucky to come across one of those

These 355 to 358ci mighty-mouse engines have a fearsome reputation, having dominated NASCAR racing from 2001 to 2012. It was the golden age of corporate motorsport sponsorship – a win-at-all-costs, unlimited-budget era never to be seen again – so the Dodge R5P7 was supported by a research and development budget that would blow F1 out of the water. The result was what many believe to be the most highly developed engine in the history of motorsport.

Built to run wide open in race events of up to 500 miles (805km) at a continuous 9000-10,000rpm, R5P7s feature beautifully orchestrated bore (4.175-4.185in) and stroke (3.22-3.26in) combinations, with a phenomenal rod ratio of 1.9:1. Engine horsepower would vary depending on whether the cars they powered competed in long- or short-track events; even the carby float bowls were set up differently depending on the banking angles and circuit design of the tracks

Thousands of these mega-revving small-blocks were produced, and some two decades later, they are still a remarkable engine, highly prized today as replacement mills for ski boats, street cars, drag-and-drive cars, or – thanks to their incredibly refined oiling and cooling systems – world-class burnout builds.

R5P7s are usually numbered or stamped either on the block, the timing cover or the front of the heads. You’ll often find initials like CGR (Chip Ganassi Racing) or ARE (Arrington Race Engines) on the block and heads, and the ARE 107 we stripped down for inspection also has #107 on the crank (below), main caps, pistons and other components, which tells you it hasn’t been rebuilt since it was run by the team

I was keen to snare one of these legendary donks for a street car build I’m hoping to take on Street Machine Drag Challenge, which is how I found myself running the Marketplace gauntlet. Fortunately, the planets aligned for me thanks to the help of Dennis Young, a California-based Aussie who picks up parts in the US to deliver to eager revheads in Australia.

Dennis went to check out the Marketplace R5P7 I’d found, took the valve covers off the motor – which is about as much as you can do in somebody’s driveway – put it on a pallet and got it to the docks in Long Beach, California for its journey Down Under.

The R5P7 name denoted an R5 block with P7 cylinder heads, with the year of manufacture usually engraved inside the head. Early motors ran a roller cam from 2000 through to approximately 2006; flat-tappet cams were used thereafter to reduce the number of potential failure points in the valvetrain. Later engines also ran shimmed valves to eliminate adjustable rockers, and on later versions still, oil was fed through the front of the crank and out through the big ends and mains to further refine the oiling systems

Four months later, the mill finally arrived on our shores, and I decided to take it to the R5P7 gurus at BG Engines in Sydney’s north-west for a thorough going-over.

BG Engines builds mills for all kinds of motorsport pursuits, whether it’s race boats, burnouts, drag racing or drag-and-drive. Owners Damian Baker and Mick Green have long been involved in racing NASCAR mills in the United States, and with their wealth of experience as machinists, engine builders, tuners and racers, I was confident they’d get the best out of my new acquisition.

Running a health check on one of these motors is pretty straightforward. Mine turned over nicely by hand, so Damian grabbed a valve spring tester, and with the rockers on the base circle of the cam, he ran through all the springs. They do vary, as teams ran less and less spring as the motors evolved. In this case, we saw a healthy range of 245-260lb; what you are really looking for is large variances (in the realm of 100-150lb), which may indicate a broken inner spring

After an engine health check that included checking valve spring pressures, running the lash, knocking off the sump and checking big-end and main bearings, the BG crew stripped and cleaned the dry-sump oil pump, made a few new oil lines, threw a kit through the APD 950 E85 carb I’d also bought off Marketplace, and got it all loaded on the dyno with a set of pipes.

At the end of each race, blocks and heads were completely stripped. The blocks were placed in an ultrasonic bath, and the engine internals were binned except for the crankshaft, which was crack-tested

The engine fired easily on the dyno on QM25 race fuel, and Damian then buzzed around the carb – half a turn on mixtures here, a float adjustment there – to get it absolutely perfect.

After a couple of light pulls to 7000rpm, a massive 9000rpm first pull blew our initial predictions of 760-780hp out of the water, with a whopping 825hp result. We were stunned, and even more so when it backed that up with an 828hp second pull! Not bad for a 20-year-old engine!

To ensure parity while testing different fuels, BG Engines set timing at 30 degrees, and three APD 950cfm carburettors were used – one for E85, one for alcohol, and one set up for QM25 race fuel. BG’s resident R5 expert Damian Baker says that back in the day these engines ran on Sunoco race gas, with timing between 24 and 32 degrees

Given that this R5 is destined for a street car build for Drag Challenge, we were keen to try out the E85 carb next. E85 is a lot more affordable than race fuel and no doubt has benefits in the torque department. With my Marketplace APD 950 fitted, we gave the small-block another two dyno runs, and it once again knocked out 9000rpm, with an 818hp best. While that was 10hp down on the race gas, the E85 configuration netted roughly an extra 10lb-ft of torque through the rev range, and that was just with an educated guess on where the carb jetting needed to be.

Once we’d tested the springs and Damian had set the lash at .008in, it was time to inspect all the bearings. The rod bolts have part numbers, but as these are generally not your run-of-the-mill bolt, we called the manufacturer to get the correct torque setting to re-tension them, as specs were not readily available online. We checked the bottom of the oil pan for debris to give us an idea of what shape the motor was in. In this case, the bearings were mint, so it was time to load it on the dyno

Another sweet pull to 9000rpm, this time on alcohol, saw it pick up 11hp over the race gas in the top end, with a staggering 839hp and peak torque of 555lb-ft! Not only did it make more overall power, but it also gave us an extra 20lb-ft of torque in the mid-range, which was a surprise given the increased fuel volume that had to fit in the R5P7’s small combustion chamber, which is typically geared towards race fuel.

While the alcohol fuel was the overall winner in both power and torque, the additional maintenance required to run that fuel, as well as the high cost of the QM25 race fuel, means that E85 would be the fuel of choice for a street car configuration.

Header length on these engines is critical. Even though different teams had their own engine recipes, they essentially all ran an identical header set-up of multi-stepped headers made of Inconel along with a number of merge collectors with expansion tubes. If you are chasing power, you either need to replicate these headers or score an original set!

The incredible thing was how easily the motor did it with all the 20-year-old components; we even gave it a dyno run on both race gas and E85 with the original mechanical lift pump on the motor. The more time you spend around these engines, the more you wish you knew about them years ago!

A big shout-out to the boys at BG Engines; things could not have gone smoother for us, and we thank Damian and Mick for their efforts. Given the whole package came from some randoms on Marketplace, I am more than satisfied with the result.