70mm TB & 1 5/8 shorties too big for stock motor?

9

90LX5spd

New Member

Aug 13, 2005

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Feb 26, 2006

#1

• Feb 26, 2006

• #1

A buddy of mine with a '91 GT is getting ready to order a TB and unequal length shorty headers. His ride has all the usual bolt-ons (pulleys, cat-back, off-road h-pipe, MSD, Edelbrock Performer, 3.55s) but doesn't plan on installing heads anytime soon (he just installed a new stock long-block). He wants a 70mm TB and 1 5/8 headers but I caution him it might hurt his mid-range torque output. Would a 65mm TB and 1 1/2 headers better suit him? If he does get heads (the stockers being true major restriction in the package) will these smaller pieces still support descent power or would they become a restriction at that point? Thanks.

 

Tonys96Cobra

professional deer "mounter"

Oct 28, 2005

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Syracuse

Feb 26, 2006

#2

• Feb 26, 2006

• #2

Get the 70, it wont hurt much if any now, and he will definitely need it when he gets heads. A 75 would be even better with heads, but too much now.

 

T

Topdowncruise

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Apr 7, 2005

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Feb 26, 2006

#3

• Feb 26, 2006

• #3

65mm is lots esp. since you say he has no plans to get upgraded heads.Even then the 65 mm is fine for most combos.

 

Bad92GT

The 5 Minute Plan Man

Jun 10, 2004

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Feb 26, 2006

#4

• Feb 26, 2006

• #4

no it wont.. go for it.. your improving flow.. you want to stuff those E7's with as much air as possible for now

 

Grn92LX

Fidanza Man!

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#5

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No, those parts are FAR from too big for a bolt on car.

 

purple87lx

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Jun 5, 2005

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#6

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• #6

The 1 5/8 headers is a good thing thats a yes all the way,but iv heard mixed reviews on the TB.Some say a 70 is to big for a stock motor but others say go for it

 

legalize420

Active Member

May 21, 2005

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Feb 26, 2006

#7

• Feb 26, 2006

• #7

IMO, stock tb works the best on stock heads n/a. i originally bought a 70 when i bought my cobra intake. i ended up putting the stock on back on beacuse it drove much better. i had the 70 on my current combo and ditched it for the 65. 1 5/8 headers will be fine

 

A

AmMscl

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Feb 14, 2004

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Feb 26, 2006

#8

• Feb 26, 2006

• #8

BIGGER THE BETTER
70mm is way too big for a stock motor (low end will suffer!)

 

9

90LX5spd

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Aug 13, 2005

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#9

• Feb 26, 2006

• #9

So it seems the larger headers are fine but stay conservative with the TB. Good torque is something 5.0s are known for and I'm betting my buddy doesn't want to lose that in favor of a few ponies here and there on the top end.

 

Grn92LX

Fidanza Man!

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#10

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AmMscl said:

BIGGER THE BETTER
70mm is way too big for a stock motor (low end will suffer!)

Click to expand...

No. Low end isn't effected by a tb. 70mm is perfect for his bolt on car. Been there/done that

1 5/8" and 70mm is fine.

 

B

BaXTeR3221

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Jan 12, 2004

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Feb 26, 2006

#11

• Feb 26, 2006

• #11

Agree with the other guys, those parts will work nicely and give him some room to grow.

 

Henceforward

The Avatar Master

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Jul 17, 2001

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#12

• Feb 26, 2006

• #12

I am running that combo, and have yet to go back to the track, but at least it sounds better.

 

5spd GT

"the 5.0 owns all"

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Feb 26, 2006

#13

• Feb 26, 2006

• #13

The parts will be fine.

TB can effect driveability issues like tip-in if you go big...

Don't neccessarily believe in the bigger is better clause...seems like your on your way!

Keep what you got for now

 

ninety15.0

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Mar 10, 2004

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#14

• Feb 26, 2006

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1 5/8 is generally the normal primary tube size...i think 1 3/4 is the next step up for moderate HCI cars and then 1 7/8 for stroked HCI's and up. So the headers will be perfect but i would suggest a 65mm tb. With stock heads i think intake air velocity is more important than intake air volume so going with a bigger TB might actually hurt your performace/driveability. I have heard that a 65mm tb is good up to about 300 rwhp maybe a little more. good luck man