my tuner said NO to lower pulley

DSG03Bolt

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HPP IN TEXAS tuned The Car, I Wanted A #4 Lower To Accent My 2.76 Upper, With A Tune, And Going To Add A Killer Chiller. He Said It Is Proven, Do Not Do Lower Pulley, Bad Fir The Crank, Anyone Care To Enlighten Me?
 

01yellercobra

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As far as it being bad for the crank. ..the stock pulley has a cage that supports the pulley. No belt tension is applied to the crank itself. The aftermarket pullies don't have that cage. So when people start running small pullies and tight belts the crank is pulled against the bearing. This kills the front main bearing.
 

justa03

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I wouldn't worry about it on a Eaton but on the big blowers I would its exactly what slo984now said.
 

95SC

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My car had Metco 4lb lower since 08 , went thru stock pullied Eaton, ported eaton with spray , 2.2 KB and now back to stock Eaton . car still has 4lb Metco lower installed and runs strong to this day without any crank problems
 

Senkak

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I have had a 4lb lower since 2005 with no issues.
This was with a ported Eaton spray combo till 2008.
Been running a VMP TVS 2.3 ever since.
 

oldmodman

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There was quite a long topic on this over on ModFords.

Engines that were running 3.4 Whipples and the big KB were showing front bearing failures, oil pump failures, and even broken off crank snouts.

Only showing up on engines that had the factory pulley bearing cage removed.

This is why the aftermarket bearing cage with fixed larger pulleys was designed and built. It was a very nice product and the first run that the two or three guys doing it sold out quickly. But they had underestimated not only how much time it would take out of their live, but how much it would cost to make.
So they unfortunately cancelled the second run of parts.

But if you are going to continue running the stock Eaton you should be safe with running the bigger crank pulley system. I don't recall any crank or oil pump failures with an Eaton.
 

01yellercobra

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As long as you don't over do it with the belt tension you should be ok. It's the guys that run a belt so small that the tensioner is against the stop and it takes a pry bar to get the belt on that will have issues. I did that early on and it killed my front main bearing.
 

DSG03Bolt

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Im Going To install It. Is There A Belt Chart For Reference? 2.76 Upper, 100Mm Upper Aux Idler,3, 90 Mm Idlers, When I Add 4#, How Much Longer
 

Sethsual

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I found this chart from Metco to be very useful. You'll find the same chart referenced on other sites, too. Don't forget to grab a new pulley for the alternator to slow it down. With your setup, a 3.20" would get ya close, and a 3.50" would be even better (3.50" puts alternator input shaft RPM's at 2,200 at idle, and just below 16K at redline). If you plan on dogging the car even once, this is a very smart investment. Ask me how I know...
 

BlueSnake01

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Great to know this, I was afraid of crank issues with adding a lower pulley. I read also about overspinning the s/c when you add a lower pulley, will it be that serious?
I heard it also heatsoak's quicker, is it that bad compared to upper pulley only?
 

SVTRAT

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Shit loads of cobras running 4lb lower with no issues for years. People that had crank snout break of are people who were running 3.4 whipples and manual tensions since 3.4s are known to have massive amounts of belt slip.
 

Sethsual

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I read also about overspinning the s/c when you add a lower pulley, will it be that serious?
It will overspin the upper as compared to stock, but isn't that the point? So long as you don't take the stock Eaton too high (I'd say above 15#'s), you'll be okay. I have used this chart so many times in the past few months, it's ridiculous. I had the hardest time pinning down what combo to run...
 

X3FBrian

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I think a 2.76 and a 4# lower on a stock unit is overkill. I would stick to a stock lower with a 2.76 until you go port.
 

BlueSnake01

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I think a 2.76 and a 4# lower on a stock unit is overkill. I would stick to a stock lower with a 2.76 until you go port.
That's what I was thinking. Difference from the 2.8 to 2.76 is small, if I would've gone with the 2.9, I would've done it together with a lower 4lb.
 
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