Flexplate Tech: Spec’ing A Meziere Billet Flexplate For Street/Strip

Project True SStreet is our 2014 Camaro that we’re aiming to make be a legit 8-second street car, and to make that happen we need to select parts that are capable of surviving in both driving environments. A flexplate is a fairly mundane part to many, however, it’s something that could fail and cause a lot of problems if you don’t have the correct part for your application. To make sure Project True SStreet starts every time the key is turned, we added a True Billet Flexplate from Meziere Enterprises.

The material a flexplate is made of is important, as it has to cope with the stresses of starting the engine when it’s engaged by the starter. Since Project True SStreet is going to be driven to the race track, it was important to select a flexplate that would be strong enough to deal with multiple starter interactions on a regular basis. The True Billet Flexplate is made from 4340 steel and uses a one-piece design, this means it’s ultra-strong and won’t have any issues starting our supercharged LSX engine.

Our techs, Scott and Noah, made sure to follow the instructions to the letter to ensure there were no issues during the installation of the flexplate.

Don Meziere from Meziere Enterprises explains why round bar 4340 material was selected for the True Billet Flexplate.

“First of all, for safety reasons, the 4340 is the very best material we could use. It is an excellent alloy for strength and toughness. It allows us to keep a little of the flex property in the middle of the plate, without much danger of cracking. It also allows us to do some heat treatment on the gear teeth, and get great toughness properties in the area where pinion-to-ring gear loads can be extreme.”

Meziere continues about the material choice: “Why round bar? Our choice of round material is based on the grain structure of the raw material. The final product will have consistent, predictable strength at any point in the plate. If we would have chosen flat material, the final product would be a lot less consistent and would be prone to uneven response to heat treatment processes.”

The True Billet Flexplate is made of 4340 steel, and Meziere put a lot of thought into its design.

A flexplate needs to be created to precise specifications so it holds a true round shape — if it’s not perfectly round, there will be vibrational issues along with problems getting the starter to engage. During the development phase of the flexplate, it was discovered that a one-piece design was the way to go.

“After testing with our preliminary two-piece design, we discovered there was a lot to be gained as far as quality if we also produced the ring gears in-house. That being the case, it made no sense at all to add an unnecessary welding process. It made all the sense in the world to make the one-piece design. The balance with a fully machined design is nearly perfect, as well. That’s one more variable out of the way for the engine builder,” Meziere says.

The flexplate is heat-treated and the teeth are chamfered in a specific way to promote durability and longevity.

The heat-treating process that the flexplate goes through plays a big role in the quality of the final product. The metal that a flexplate is made of needs to have different characteristics based on its function. The portion of the plate that applies the power, versus where the starter gear engages have different strength needs. Meziere’s use of 4340 round bar for the flexplate’s material allows it to use the heat-treating process to optimize each area of the flexplate.

Meziere took the time to chamfer all of the gear teeth on the True Billet Flexplate. This wasn’t done for looks — it plays a big part in how much engagement the starter has with the flexplate.

“The gear teeth are chamfered for a couple of reasons. If you look closely, you will see that one side has a chamfer that is even all around. That is just good machining practice so that sharp edges can’t cause damage to the person working with it. That will be on the side that the starter gear does NOT enter from. Now, flipping the plate over, you will notice the gear is chamfered in a little different fashion. The chamfer on the starter side actually assists the pinion entry at the very beginning of the start cycle. The chamfer is heavier on the side that provides clearance as the pinion spirals and advances. The chamfer is much less pronounced on the side that gets loaded by the pinion,” Meziere explains.

For an application like Project True SStreet an SFI-approved flexplate is a must for safety.

A safe flexplate is important for a high-horsepower street/strip car for many different reasons, and you should look for a flexplate that has an SFI rating. The True Billet Flexplate carries a 29.2 certification from SFI — this means it has survived a spin test at elevated RPM levels, and is a result of the precise machining and tolerances that Meziere uses.

If you’re on the fence about spending the money to get a high-quality flexplate, Meziere has some closing thoughts that you might want to consider, because you can’t make it to the track to win a race if your car won’t start.

“You really need a flexplate that’s reliable, especially in the area of the gear teeth. Making the strongest tooth is definitely a benefit for high horsepower, high compression, and tough-to-start applications. If a tooth fails, it’s a good amount of work to change out the plate, so we want to provide the best chance for success in that area, as well. And finally, the precision of the plate helps the parts around it to work well. If there are balance or runout issues in any direction, they can cause other problems with bearings and bushings, converter and crankshaft connection points,” Meziere says.

Now that we have our True Billet Flexplate installed we’re getting closer to unleashing Project True SStreet on the highways and by-ways of California. You can catch up with the rest of the build right here and follow along as we take care of the final details of the Camaro.

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About the author

Brian Wagner

Spending his childhood at different race tracks around Ohio with his family’s 1967 Nova, Brian developed a true love for drag racing. When Brian is not writing, you can find him at the track as a crew chief, doing freelance photography, or beating on his nitrous-fed 2000 Trans Am.
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