Author Topic: Torque conerter bolts sheered off  (Read 678 times)

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DEANs427

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Torque conerter bolts sheered off
« on: September 04, 2022, 02:05:38 PM »
I've been doing this for a while but can't remember seeing this..
500+hp- Y block and C4 trans
without warning in 3 rd gear at 1000 ft bolts broke and engine ran free into limiter
limiter saved the engine
about 60-70 passes on combo
an ideas on this??
1956 Ford Gasser 427FE
1966 Fairlane
1966 Bronco supercharged

JamesonRacing

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Re: Torque conerter bolts sheered off
« Reply #1 on: September 04, 2022, 05:41:13 PM »
I've have the center of a 428 "wagon wheel" flexplate shear, but never lost a bolt like that.

The tension on the bolt is expected to be much higher than the bending load that the fastener will see, with the friction between the two objects being clamped resisting the movement between the objects.

It seems that to have the fasteners shear, they must have loosened enough to relax the clamping load, then subjecting the fasteners to bending stresses and leading to failure.
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galaxiex

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Re: Torque conerter bolts sheered off
« Reply #2 on: September 04, 2022, 07:15:50 PM »
Those adapter/spacer things don't look very strong...
Any grade markings on them?

Lotta leverage and shear side load with the T/C spaced that far from the flexplate.

Fasteners are strongest in tension and weakest in shear.

I'd try to find something grade 8 or better to replace them.
Every 20 minute job is 1 broken bolt away from becoming a 3 day ordeal.

jayb

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Re: Torque conerter bolts sheered off
« Reply #3 on: September 05, 2022, 04:08:39 PM »
For sure it's those spacers, they should at minimum the diameter of the distance between the flex plate and the converter, and bigger diameter is definitely better.  I think they just started rocking a little at a time and eventually cracked and broke the bolts.  I've used 2" diameter spacers that I cut on a lathe in a case like that, and bolted them in place, then welded them to the converter ears in a few spots. 
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

Stangman

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Re: Torque conerter bolts sheered off
« Reply #4 on: September 05, 2022, 07:20:31 PM »
I don’t understand why it has such a long spacer for a 10 inch converter.

galaxiex

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Re: Torque conerter bolts sheered off
« Reply #5 on: September 05, 2022, 08:09:10 PM »
Probably
I don’t understand why it has such a long spacer for a 10 inch converter.

Probably has an adapter plate to bolt up the C4 to the Y block?
An adapter plate would space the trans farther back.

If that's the case, a spacer on the crank hub to bring the flex plate closer to the trans would help.
Every 20 minute job is 1 broken bolt away from becoming a 3 day ordeal.

Falcon67

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Re: Torque conerter bolts sheered off
« Reply #6 on: September 06, 2022, 09:17:27 AM »
I use spacers on the dragster for the PG to flex plate.  But the spacers are aluminum, 1/4" thick and 1" or so in diameter.  I use 1/2" Grade 8 fasteners to tie it all together.  If you need standoffs that tall, I'd make some thick and wide spacer plates to fill that gap so the bolts can exert full clamp load and it's spread out some.

DEANs427

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Re: Torque conerter bolts sheered off
« Reply #7 on: September 06, 2022, 12:35:41 PM »
it is an adapter kit to mate the C4 to the y block. uses an adapter pilot to mate c4 converter hub to y block crank pilot. an adapter bellhousing is part of the kit. i have used this kit on other projects with no problems but never at this power level. spacer thickness at the flywheel to TQ attaching point is .750". would like to re-engineer this but what to get it back together for the nostalgia race at Rock Falls on Sep. 16-17. I use a torque ring spacer welded on my gasser converter and with probably make one for this too.
Thank you all for your input!!
Dean Markuson

1956 Ford Gasser 427FE
1966 Fairlane
1966 Bronco supercharged