Lakewood's steel bellhousings are designed to contain a severe clutch explosion. In fact the SFI 6.1 (Sema Foundation, inc.) test to ensure containment is to cut apart a flywheel spinning at high rpm until it shatters. If the bellhousing can contain the pieces, it achieves the SFI certification sticker (below.) Currently only Lakewood bellhousings are SFI certified.
sfi tag
The SFI certification is only good for two years. Technically this means you need to replace the bellhousing every two years. This baffles us since this isn't a component that wears out. Furthermore we've never heard of a tech official checking the date on the tag.

Installing a blowproof steel bellhousing is a pain in the neck, but probably nowhere near as hard as walking without any feet. A while back we had the pleasure of learning first hand the dangers of a clutch explosion. FM staffer Jim Langely and I were out at Sacramento Raceway early last year -Jim was in his '65 coupe and I was in Project 11.99. We had the opportunity to race each other, so naturally we decided to go all out. At the time the project car was running high 12's and Jim's coupe was in the 13's. I remember getting past the 1/8th mile point when a flicker of light caught my attention. I looked in the rear view mirror and saw sparks and smoke under Jim's car. I lifted and coasted off the track and waited for Jim. As his car made it to the return road I notice smoke pouring out from under the hood. Jim's first comment as he got out of the car was "I think I threw a rod." We popped the hood, and tried to find the engine damage in the smoke filled darkness. Like staring at one of those 3D dinosaur posters, it wasn't clear to me at first what had broke, but then it suddenly came into view...the bellhousing was gone! I remember saying "dude, look behind the engine, you can see the input shaft!." It was then that we realized the clutch pressure plate had failed and exploded.

The next day in the light we were able to see the extent of the damage (see side bar). Fortunately Jim wasn't physically injured, but as the pictures show the resulting damage was enough to put the car out of commission for quite a while.

The NHRA requires a blowproof bellhousing be installed in all cars running 11.99 or faster. Yet Jim's coupe was only running in the 13's when the clutch failed, proving that any car with a clutch is subject to this sort of disaster. He had launched the car at around 5000 rpm on Mcreary tires. Like most clutch failures, his pressure plate gave out on the 2-3 shift, not at the launch like you'd expect. What caused it? Ultimately the answer is heat. Pressure plates, clutch disks, and flywheels generate huge amounts of heat, which overtime fatigues the metal and causes stress cracks. A 5000 rpm launch on a slipping, stock clutch was probably the fuse.

The majority of stock bellhousings are aluminum and offer absolutely no containment in the event of a clutch failure. In fact the stock T5 bellhousing fragmented into so many pieces, we were lucky the transmission didn't drop right out!

Needless to say the experience made it very clear to both of us that we needed blowproof bellhousings. NHRA rules require an SFI approved bellhousing. We looked into two brands of bellhousings (Mcleod and Lakewood) and found that only the Lakewood is SFI approved -making the choice very easy.

One look at the Lakewood bellhousing and it's clear that it is built to handle an explosion. Hydro-pressed out of heavy-gauge steel it weighs 40 lbs. or so, and is significantly larger than a stock bellhousing. In addition the block plate is also made from steel, rather than aluminum, and is bolted to the bellhousing with grade-8 fasteners. Continue


In This Article:
The importance of using a Lakewood blowproof bellhousing to contain a clutch or flywheel explosion is apparent in these images. Learn how to install one properly.

The entire aftermath of this clutch explosion can't even be seen in this photo. Shrapnel poked a hole in the hood, pinched a header collector in half, ripped the accelerator pedal right off the firewall, destroyed the shock tower brace, severed the main engine harness, and knocked out a freeze plug in the back of the block. It's amazing the driver wasn't injured.

This is all that was left of the stock bellhousing.

The pressure plate exploded and caused the most damage. This mangled pressure plate cover clearly shows the magnitude of the explosion.

Note the bellhousing is cracked open like an Easter egg.



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