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Discussion Starter #1
Here's my set up.
406 sbc
12:1 comp
solid roller .652 .622
duration @ .050 258 268
dart pro1 230 heads
super vic intake
holley 947 cfm
turbo 350 4k conv.
4.56 gears
3k lb car

Here's my question.
How much loss or gain is there between these two headers?
hooker super comps 1 5/8 primary 3" collector
hooker super comps 1 3/4 primary 3" collector

Which one works best for my set up?

thanks
jeff
 

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I can run this through the Dynomation 5 computer model but rather than make me look up all this up I need:

Comp Cams PN
Head flow info from .050"-.700"
Header tube length for each

I'm almost willing to bet the 1-3/4" header will be better.
 

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i agree ^^^^ the 1-5/8s maybe good for torq but could choke it up stairs the 1-3/4 headers would be the better for it upstairs but may sacrifice a tad down low what size exhaust are you going to run if any :yes:
 

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Discussion Starter #4
Comp Cams PN
Head flow info from .050"-.700"
Header tube length for each

I'm almost willing to bet the 1-3/4" header will be better.

cam is a lunati pn 50152
head flow @ .700 is
intake 308cfm/28"
exhuast 207cfm/28"
header primary tubes are equal length 33"
 

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I need the flow for the rest of the lift points, and spark timing...but, I made some educated guesses on all the inputs,

Assuming the headers are identical except for primary ID, they make the same overall average HP (487) but the 1-5/8 makes 1 lb/ft more average torque (482).

If you just take the data from 4,000 stall rpm to 7,000 rpm shift point, the average difference is slightly larger.
552 hp, 533 lb/ft for 1-3/4"
553.6 hp, 535.6 lb/ft for the 1-5/8"

I played around with collector length and other inputs which will make a difference if the headers are not otherwise the same.

With a 10" long collector and open exhaust:

Peak power is predicted as about 615 @ 6,500 with the bigger header and 611 with the smaller.
1-3/4" has 482hp and 574 lb/ft at 4,500 rpm. The 1-5/8" has 497hp and 581 lb/ft @ 4500 rpm

I think the 1-3/4 may be faster if you have traction problems and the 1-5/8" will be quicker if you don't.

Actual real world results will depend your exact configuration
 

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Discussion Starter #6
Thanks for the info. I'm just gonna stick with the 1 5/8 header.
The car hooks great. 28/12.5 et street and caltracs:yes:
i'm also leaving off a trans [email protected] 3500 rpm's.
 

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very good info. I would be curious how a 1 7/8" header would to with the exact set up. do you run mufflers? what is you shift point?
 

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Discussion Starter #10
Run the 1 3/4 but add 18 inches to your collector and that will give your low end torque back and still give you the top end you need with the heads you have. Are you running 2.02 or 2.08 intake valves.

This trick is the poor boys step header. I don't know why it works, but it does.
2.08 valves.
I'm committed to the 1 5/8's right now because I had the #1 primary tube modified to clear the angle plugs.
I am only into these headers for $220. and they are brand new.
Eventualy I will step up the size though.:yes:

Plus, this is good trial and error. I will have a baseline for these headers and will post my times and combonation when the time comes.

jeff
 

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As mentioned above, there is more to header design than just tube ID. the collector length diameter and taper makes a difference. You can fine tune your power delivery with header design changes.

Getting a baseline is a good idea will help see if the header change makes an improvement. Just don't change other variables at the same time you swap headers.
 
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