SFI flexplate mandatory in all v8s Jan 2024

[Jim Bailey]

Paul, never had one come apart. Had several crack near the convertor bolt holes, but caught it.

[MR DERBY CITY]

Originally Posted by 4543

I’m not sure if it’s the 7000 rpm or the converter hitting at 5800 instead of the 4400 people used to use! I think the converter hit stresses the flex plate more than going down the track but it could crack at the hit and come apart down track. The stock GM flex plate that I saw has the ring gear only welded on one side. The certified appears to be welded on both sides of the ring gear and possibly more welds. Both of mine are certified but have been in my cards for years. I’m thinking I’m going to replace them. Mike McMahan 2543 H/SA

Better be careful Mike, Old Chinese philosopher Confucius sez older flexplates made in USA might be stronger than newer flex plates made in CHINA ….

[Shake & Bake]

Thats why I buy a Meziere flex plate. I go thru between 8200-8300 rpm on the big end..... Not saying I will never have an issue, but I haven't as of yet. Been running one for quite some time now.

Originally Posted by Jim Bailey

Never had any problems with any SFI certified Mopar Flex Plates "UNTIL" I started to two step. We're our own worst enemy. If you two step, the flex plate must become a part of your service routine. Just saying .........

How long ago was that? 90’s ?

Did anyone actually investigate the car that sent the shrapnel into Hildago’s car? Was it a stock flexplate? When is the last time an automatic flexplate has come apart at a race and come out of a car? I’ve seen a trans or 2 explode and send parts out.

For years (before I was born) a steel SFI flywheel has been required for any manual trans combo regardless of manufacturer or performance level.
Now after this they want to employ the rule for automatic cars. The rpm and hp range of these engine have advanced quite a bit in the last 40 years. Probably exceeding the limits of stock parts at this point. There is always exceptions to the rules for combos. If you have to rebalance an SFI flexplate for an external balance I’m sure it can be done legally. Probably splitting hairs at this point with that argument, but that is what we do here.

[Regan Wilson]

Originally Posted by Todd Hoven

Did anyone actually investigate the car that sent the shrapnel into Hildago’s car? Was it a stock flexplate? When is the last time an automatic flexplate has come apart at a race and come out of a car? I’ve seen a trans or 2 explode and send parts out.

For years (before I was born) a steel SFI flywheel has been required for any manual trans combo regardless of manufacturer or performance level.
Now after this they want to employ the rule for automatic cars. The rpm and hp range of these engine have advanced quite a bit in the last 40 years. Probably exceeding the limits of stock parts at this point. There is always exceptions to the rules for combos. If you have to rebalance an SFI flexplate for an external balance I’m sure it can be done legally. Probably splitting hairs at this point with that argument, but that is what we do here.

The Flexplate was inspected and deemed a parts failure by NHRA. No fault by the racer it belonged to as it was within the given rules.

[mike britt]

In this case the flexplate did not break or come out. It was still bolted to the crankshaft. What happened was the ring gear welds came loose and the ring gear started coming apart in pieces. I found one piece about 2 inches long by the accelerator pedal in bills car. It looked like a stock flexplate to me, but the rules did not require the car to have an SFI flexplate.

[Paul Precht]

Originally Posted by mike britt

In this case the flexplate did not break or come out. It was still bolted to the crankshaft. What happened was the ring gear welds came loose and the ring gear started coming apart in pieces. I found one piece about 2 inches long by the accelerator pedal in bills car. It looked like a stock flexplate to me, but the rules did not require the car to have an SFI flexplate.

The ring gear is the issue for sure and yet Mopars that don't have a ring gear or an explosion possibility are forced to be a part of the new rule.

[Mark Yacavone]

Originally Posted by mike britt

In this case the flexplate did not break or come out. It was still bolted to the crankshaft. What happened was the ring gear welds came loose and the ring gear started coming apart in pieces. I found one piece about 2 inches long by the accelerator pedal in bills car. It looked like a stock flexplate to me, but the rules did not require the car to have an SFI flexplate.

Mike was this a stock case 200, by any chance? Did it sustain a lot of damage too?

This just occurred to me .This, being a Chevy II with fenderwell headers, the car didn't have much in the way under it to absorb and block some of the explosion.
With Jimmy Jr. on the right in the waterbox, it sounds like he was caught in a perfect storm, so to speak..Lucky, lucky ,lucky!

Originally Posted by mike britt

In this case the flexplate did not break or come out. It was still bolted to the crankshaft. What happened was the ring gear welds came loose and the ring gear started coming apart in pieces. I found one piece about 2 inches long by the accelerator pedal in bills car. It looked like a stock flexplate to me, but the rules did not require the car to have an SFI flexplate.

So there you go, a 7k plus RPM engine with a stock flexplate. He didn’t do anything wrong, but if he had an ATI or equivalent SFI flexplate there wouldn’t have been an incident. Probably a cast ring gear that wasn’t rated to go that high or for that much power.