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Old 07-20-2004, 10:49 PM
E.T. divided by $ spent= Speed
 
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Header primaries and Hp/Tq

Well in my good fortune my uncle helped me rig a deal to get all the fab work on "Ye Volvo" done.Steering column/linkage,driveshaft and headers built.
Anyway,I had a set of fenderwell headers that we are using to build from.They are 1 3/4 primaries.Were as I should have 1 5/8 optimaly.
What I'm getting at is I'm trying finger out how much torque I'm gonna loss as compared to how much HP I'll gain in its place.The 1 3/4 are goin on so its not like I got a choice,but I wanna know.All though its a super light car anyway so torque loss aint crutial.
Anyway the motors is:
SBC 350
Cast 1.94s(993s w/ 3angle)
8.7:1 or so(has thin gaskets on stock pistons)
Comp EX 262 cam
Performer intake
600 vac sec holley.

DD2000 came out 315Hp/355Tq w/ 1 5/8 if that helps at all.
Also they have normal 3" collectors.Which cost me $148!!!

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Last edited by 78 monte; 07-20-2004 at 11:01 PM.
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Old 07-21-2004, 11:38 AM
E.T. divided by $ spent= Speed
 
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Anyone care to guess??
I'm just wondering if I'll be lobing off 25ft lbs,and gaining a measaly 3hp.
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Old 07-21-2004, 01:04 PM
GTO 1965's Avatar
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Your torque loss will be minimal between 5 to 7 lbs. nothing to worry about.


Jim
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Old 07-21-2004, 02:47 PM
E.T. divided by $ spent= Speed
 
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Hey thats cool to know.Think theres any chance of seein any HP gain w/ my stock heads??
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Old 07-21-2004, 03:00 PM
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An engine runs on air pulses both in and out. Headers diameter, ID, and length are used as tuning tools to optimize torque or HP. In your case, neither will have a gain. 1.534" is optimum ID for the engine CID factored at 6000 rpm. 1 3/4" primary size would not be needed until around 7800 to 8200 rpm. Your other parts don't support that kind of rpm. So best guess you will loose about 22 to 26#/ft of torque. HP would be around 14 to 16HP loss.

Remember this, HP is calculated, torque is measured. For a street car you should worry about having a broad torque band, not a max rpm HP number. Like you said, the 1 3/4" are what you have so run with them. In the future build a stroker and you will have the headers all ready.

Chris
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Old 07-21-2004, 03:17 PM
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i think almost any street sbc should run 5/8's cause as you already know they are better. even the guys in the small block engine challenge said they would have got more if they used 5/8's instead of 3/4's. but i wouldnt worry about it, and i always worry about something. you gottem already use em. (from a guy with an rpm on a 6000lb truck)
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Old 07-21-2004, 03:52 PM
E.T. divided by $ spent= Speed
 
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Yea I knew the 1 3/4 were too big for my motor but like I said these were the only thing that would evan remotly fit the chassis evan with mods.
I'm not worried about the torque loss cause the car only has a stock curb weight of 1975lbs :evil
and 4.56s in the rear(I know,I know but try finding gears for a Dana 30)I plan on putting 3.55s in when I find some.
I really did think I would gain a lil HP like 5-10 on the top around 5000-5500rpm or so,figuring the motor should make power to 5500.Guess not though.
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