Let It Rev! This ‘Godzilla’ 7.3L V8-Powered Motorhome Gains 120+ HP and Sounds Very Mean Doing It (5 Star Tuned)

This is truly the new 7.3L H.O. (High Output) V8 Motorhome!

2021 thor motorhome 7.3L godzilla v8 tuned 5 star tuning

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You may already know that the new 2021 ‘F53’ Motorhome chassis (built by Ford) has the new 7.3L gas V8 “Godzilla” engine. It replaces the old V10 that was there before. The new V8 should be a good engine for a heavy motorhome, but there is always room for improvement.

Our friends at 5 Star Tuning have decades of experience tuning trucks, SUVs, and Motorhomes for better power delivery, overall drivability, towing, and hauling heavy weights. They got their hands on this new 2021 Thor Hurricane motor home that has a Godzilla under the hood. This is a customer RV that has a couple of thousand miles on it. They immediately put it on the dyno, ran some baseline pulls, added their tuning (via an SCT device), and did much more customized tuning.

I had a unique opportunity to drive the new 2021 Ford F53 and F59 chassis at the Ford Proving Grounds in Arizona this year. I can tell you that the new F53 chassis has a much improved suspension system to go along with the new V8 engine. Here is the video.

Ford has introduced the world to the new 7.3L gas V8 engine months ago. This new push-rod engine made its debut in the 2020 Ford Super Duty pickup trucks. We were so interested in this engine, that we bought one. It’s our F-250 Super Tremor project truck.


I went to the 5 Star Tuning HQ in Florence, South Carolina to see what the new 2020 Super Duty gas and diesel V8s can do on the dyno in the real world. Here is the video.


Motorhome Tuning – 7.3L Gas V8

Let’s switch gears back to the Motorhome. The stock F53 engine rating is making 350 hp @3,900 rpm and 468 lb-ft of torque @3,900 rpm at the crank. This is already not too bad. However, the 2021 Thor motorhome weighs about 19,000 lbs at the curb and has a total GVWR of 22,000 lbs. It can use more power! Here is all the information for this Thor motorhome.

Why tune a Motorhome? A gas-powered motorhomes is more affordable that one with a big turbo-diesel. Why should the diesel guys should have all the fun with big torque. The gas-powered motorhome should also be easy to drive, fast to merge onto the highway, and relaxing to drive up and down any mountain pass.

After some doing, the guys at 5 Star found extra power and torque throughout the engine’s rev range, but there is also a big surprise. The stock engine cuts power after 3,900 rpm, but the engine has more to give. The custom tuning lets the engine rev closer to 4,600 rpm. Wow! The big Thor RV gained 128 hp and 150 lb-ft of torque (at the wheels!). Take a look at the dyno charts below.

You don’t have to rev the big V8 over 4,000 rpm if you don’t want to. However, if you get this tune and you need the extra power to climb that big hill – now you have BIG power there. Maximum tuned power at the wheels was measured at 265.9 hp @4,500 rpm and 335.7 lb-ft of torque @3,950 rpm.

The low and midrange rpm power gains are more modest, but you still get extra oomph. Take a look at the curves.

5 Star Tuning also made the grade shifting of the 6-speed heavy duty transmission a little more aggressive on the way down the mountain. This helps control the downhill speed. I have not been able to test this first hand, but the guys at 5 Star ran this RV up and down the Fancy Gap highway in Virginia. I am looking forward to an opportunity to take this RV on the Ike Gauntletâ„¢ – world’s toughest towing test.

Here are few pictures of the guys on the Fancy Gap.

Take a listen to this new big block RV on the dyno and on the highway.

Also, here is our detailed Ike Gauntlet test of an older V10-powered motorhome.