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Discussion Starter · #1 ·
this question might not directly involve itself with chassis building but i figured i would try to put it out to as many ppl as possible. what i have is a normal 10.5 car...3100 LBS. BBC, turbo 400, fogger....car runs consistent 7.70-7.60's 1.14-1.18 60's drives straight ,doesnt wheelie to much.

the problem we are having is the engine keeps taking out the thrust bearing on the crank. we have checked driveshaft play (3/4 is the closest it gets both directions of rearend travel). the engine is mounted double rail with a 3/8 thick mid plate and a halo behind the plate about 1 " from the bellhousing.

the crank is bryant so ill stake that they arent using junk metal. all of our engine builders are top notch and do quality work over the years. there appears to be no rhyme or reason for it 20+ runs sometimes less and all the sudden .30 end play in the crank and shavings in the oil.

my driver likes to let the engine sing from time to time( secret is out, lol) also, the trans case has an ultra bell but the rear mount is still rubber(possibly some kind of tail whip effect tilting the converter and input assembly?), converter is neal chance bolt together too.

im open to any idea off the wall or not at this point so any help would be appreciated. thx guys
 

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I have a customer that is having the same problem.. also a Chance Bolt together converter..

We ended up building a Crank brace.. We have an adjustable bearing support on the front of the balancer to limit the amount the crank can come forward.. this car has a Bruno Liberty in it so it is not anything pushing from the rear causing the problem. the trans is mounted on slides....

In my opinion I think the converter is basically becoming a hydraulic ram... Fluid pressure is pushing the converter forward is the only is thing I can think is happening
 

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Discussion Starter · #7 ·
the trans was coming out this weekend to go through top to bottom, one of the things hutch suggested was some kind of high pressure bypass. it had this problem before we used the 2 piece billet converter also and its hard to believe the billet converter body would balloon that much but its something to look into. any other ideas keep em coming plz thanks for the replies.
 

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this question might not directly involve itself with chassis building but i figured i would try to put it out to as many ppl as possible. what i have is a normal 10.5 car...3100 LBS. BBC, turbo 400, fogger....car runs consistent 7.70-7.60's 1.14-1.18 60's drives straight ,doesnt wheelie to much.

the problem we are having is the engine keeps taking out the thrust bearing on the crank. we have checked driveshaft play (3/4 is the closest it gets both directions of rearend travel). the engine is mounted double rail with a 3/8 thick mid plate and a halo behind the plate about 1 " from the bellhousing.

the crank is bryant so ill stake that they arent using junk metal. all of our engine builders are top notch and do quality work over the years. there appears to be no rhyme or reason for it 20+ runs sometimes less and all the sudden .30 end play in the crank and shavings in the oil.

my driver likes to let the engine sing from time to time( secret is out, lol) also, the trans case has an ultra bell but the rear mount is still rubber(possibly some kind of tail whip effect tilting the converter and input assembly?), converter is neal chance bolt together too.

im open to any idea off the wall or not at this point so any help would be appreciated. thx guys
We had a similar issue using a billet flex plate.Put a cheaper/thinner flex plate in and the problems went away.
 

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first i want to explain the way an automatic trans and torque converter work together, the transmission pump keeps the converter CHARGED not full , the difference is - example a glass of water is FULL but there is no pressure on it , a torque converter is CHARGED meaning it is full and there is pressure on it also . This charge pressure hydraulicly pushes the converter toward the crankshaft (ie this is why ALL automatics have FLEXplate not flywheel) now there is an acceptable amount of pressure the crank shaft can handle before it eats the main thrust ,when we exceed that point you kill the main thrust . (small block cranks somewhere around 125 lbs pressure) some of the most common reasons for main thrust damage are when the converter bottoms out against ANY part of the crank (pilot bore, lip, crank bolts) if this happens you no longer have a "functional flexplate" now the converter is pushing the crankshaft directly . Excessive thrust pressure can also come from restictive exhaust flow out of the converter or having more converter charge than what can flow back out . Restricted exhaust flow can occur any where from the converter all the way back to where it flows through the transmission. (too many areas to list) Of course the ballooning converter theory - this is the most misunderstood concept in drag racing , it started from a widely misunderstood tech bulliton from GM service department in the 1960's , I grew up thinking if you killed a main thrust you have a ballooned converter , until i killed a main thrust in 1987 and when i checked my converter to see how much it ballooned , it had not ballooned at all !!! how could this be? EVERYONE has always said bad main thrust = ballooned converter . OK remember that when you bolted your converter to the flexplate you pulled the converter about .125 (1/8") out of the front pump , so if the converter balloons it will stretch in the directions of least resistance meaning it has to stretch that .125 and bottom out in front pump before it pushes equally on the cranshaft , therefor anyone who killed a main thrust due to "ballooning" would also have the converter buried in the front pump (cheesey example- think of a balloon instead of a converter against your flexplate and you have a metal rod incerted in the balloon so you can push on the crank with 100 lbs of force and air the balloon up at the same time , the balloon will stretch away from the crank ) hopefully this gives you a visual of how a ballooned converter is not capable of killing the main thrust and the evidence is that your converter did not bottom out in the front pump .
Marty Chance
NEAL CHANCE RACING CONVERTERS
note : i will be happy to help anyone with this problem regardless of what brand you use 316-542-9869
 

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Discussion Starter · #11 ·
excellent posts, the car does have one of those "billet" reactor style flexplates...that could very well be the dynamic force we were looking for. i think andy has talked to you before marty ill have him call you today.
 

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Travel limiters are recommended also. If the engine/trans is able to move fwd/backwards at all on the launch after the driveline spine locks , there will be force exerted on the crankshaft.
The reactor flexplate is not the problem.

Hutch
 

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Travel limiters are recommended also. If the engine/trans is able to move fwd/backwards at all on the launch after the driveline spine locks , there will be force exerted on the crankshaft.
The reactor flexplate is not the problem.

Hutch

X2
Highly recommend engine limiters if not already equipped.
One per side.
 
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