Main Bearing Durability Under Boost

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rhyrlik

Founding Member

Jun 15, 2002

125

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Nov 28, 2004

#1

• Nov 28, 2004

• #1

Has anyone here torn down a supercharged GT motor? How do the main bearings hold-up under boost?

I'm debating the purchase of a Cobra crank because I plan on spinning it to 6500 RPM and am concerned about crankshaft flex and bearing failure.

Thanks,

Ralph

 

jstreet0204

Active Member

Jun 26, 2003

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36

Winston Salem, NC

Nov 28, 2004

#2

• Nov 28, 2004

• #2

Just curious, but what is your reasoning for spinning the motor so high?

 

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rhyrlik

Founding Member

Jun 15, 2002

125

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Nov 28, 2004

#3

• Nov 28, 2004

• #3

The my new cams will shift the powerband past 6000 RPM.

 

crew_dawg16

New Member

Apr 25, 2004

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DeKalb, IL

Nov 28, 2004

#4

• Nov 28, 2004

• #4

you should probably get a forged crank if you are going to exceed the stock redline on a regular basis. I know the GT crank is good for 700 hp or so, but rpms are what's hard on cranks/bearings.

 

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rhyrlik

Founding Member

Jun 15, 2002

125

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Nov 28, 2004

#5

• Nov 28, 2004

• #5

I'm just wondering if there is any evidence of flexing or warpage with the GT crank while under boost.

I trust the crank won't snap in two, but I also want my engine to last more than a year.

 

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GinoGT

Founding Member

Aug 11, 2002

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Nov 28, 2004

#6

• Nov 28, 2004

• #6

If the crank is properly prepped, it should hold up. KenB is showing the world what's up with GT cranks in his car: 7000+RPMs and going strong.

The cast GT crank is lighter than the forged Cobra one. Now if you're going to make stupid amounts of power, than the forged would be worth it.

 

03trubluGT

New Member

Nov 19, 2002

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Mansfield, TX

Nov 28, 2004

#7

• Nov 28, 2004

• #7

rhyrlik said:

I'm just wondering if there is any evidence of flexing or warpage with the GT crank while under boost.

I trust the crank won't snap in two, but I also want my engine to last more than a year.

Click to expand...

A friend of mine is putting out about 380 HP in his Vortech-ed Bullitt. He's had it over a year and 20k miles.

I have about 5500 miles on my GT. See sig for power levels. What kind of KB kit do you have? Did you get those numbers from a Mustang Dyno?

Matt

 

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rhyrlik

Founding Member

Jun 15, 2002

125

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0

Nov 29, 2004

#8

• Nov 29, 2004

• #8

I have the 6LB NIC kit.

I want to shift at 6100 RPM, but want that 6500 RPM cushion. I don't want a forged crank because that will require clearancing of the block. I basically want to spend $1000 and drop forged rods and pistons in it, and not have to worry about anything. I don't want mega power, just extra RPM to avoid shifting near the end of the 1/4 mile mark.

 

03trubluGT

New Member

Nov 19, 2002

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Mansfield, TX

Nov 30, 2004

#9

• Nov 30, 2004

• #9

rhyrlik said:

I have the 6LB NIC kit.

I want to shift at 6100 RPM, but want that 6500 RPM cushion. I don't want a forged crank because that will require clearancing of the block. I basically want to spend $1000 and drop forged rods and pistons in it, and not have to worry about anything. I don't want mega power, just extra RPM to avoid shifting near the end of the 1/4 mile mark.

Click to expand...

I'd call Ken B at Modular Depot www.modulardepot.com get the shop's number off the the home page and give him a call or PM.

Matt