Header primary sizes [this could get ugly...]

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Apr 20, 2006 | 12:21 AM

#41

Zix

Le Mans Master

Joined: Jul 1999

Posts: 8,683

Likes: 6

From: Phoenix AZ

Quote:

Originally Posted by C4driver99

post *****? Is that why he has all those stars

Ha, look at you posting in the same thread at 10:18...then again at 10:19

Apr 20, 2006 | 12:22 AM

#42

C4driver99

Pro

Joined: Feb 2006

Posts: 688

Likes: 0

From: Concord NC

I know i want stars

Apr 20, 2006 | 12:22 AM

#43

cv67

Team Owner

Joined: Oct 2004

Posts: 81,241

Likes: 3,062

From: altered state

St. Jude Donor '05

stalker

Apr 20, 2006 | 12:23 AM

#44

C4driver99

Pro

Joined: Feb 2006

Posts: 688

Likes: 0

From: Concord NC

HAHA and i just did it again

Apr 20, 2006 | 12:23 AM

#45

C4driver99

Pro

Joined: Feb 2006

Posts: 688

Likes: 0

From: Concord NC

stop following me u crzy people

Apr 20, 2006 | 12:27 AM

#46

Corvette Kid

Large Impressive Member

Joined: Jul 2003

Posts: 65,811

Likes: 71

From: Good health is merely the slowest possible rate at which one can die

St. Jude Donor '04-'05-'06-'07

Quote:

Originally Posted by C4driver99

post *****? Is that why he has all those stars

Damn, talk about the pot calling the kettle black! They gave me all of those stars because I'm special. That's the only reason. It has nothing to do with post count. That's just an urban myth around these parts.

Apr 20, 2006 | 12:29 AM

#47

C4driver99

Pro

Joined: Feb 2006

Posts: 688

Likes: 0

From: Concord NC

i got 495 post is that good enough AND I ACTUALLY TRIED TO HELP PEOPLE most of the time

Apr 20, 2006 | 12:36 AM

#48

cv67

Team Owner

Joined: Oct 2004

Posts: 81,241

Likes: 3,062

From: altered state

St. Jude Donor '05

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Apr 20, 2006 | 02:23 AM

#49

CentralCoaster

Team Owner

Joined: May 2002

Posts: 24,337

Likes: 25

From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed

Quote:

Originally Posted by C4driver99

i got 495 post is that good enough AND I ACTUALLY TRIED TO HELP PEOPLE most of the time

You are annoying. And useless. Shut up or go away please. All this garbage in 20 minutes?

Quote:

Search: Posts Made By: C4driver99

Forum: C4 Tech/Performance Today, 09:36 PM
Replies: 113 Mad As Hell With Em
Views: 2,295 Posted By C4driver99
I cant say anything else. I tried to help gene out and im stopping I think he knows what he wants and that it will work out. BTW no need to be flaming be zix.

Forum: C4 Tech/Performance Today, 09:34 PM
Replies: 113 Mad As Hell With Em
Views: 2,295 Posted By C4driver99

Forum: C4 Tech/Performance Today, 09:33 PM
Replies: 11 LIBERTY BELLhousing
Views: 99 Posted By C4driver99
:leaving

Forum: C4 Tech/Performance Today, 09:32 PM
Replies: 9 CF/EM are unfair
Views: 95 Posted By C4driver99
:leaving

Forum: C4 Tech/Performance Today, 09:30 PM
Replies: 10 What are the best...
Views: 115 Posted By C4driver99
:lurk

Forum: C4 Tech/Performance Today, 09:29 PM
Replies: 47 Header primary sizes [this could get ugly...]
Views: 456 Posted By C4driver99
i got 495 post is that good enough AND I ACTUALLY TRIED TO HELP PEOPLE most of the time:rofl :rofl

Forum: C4 Tech/Performance Today, 09:27 PM
Replies: 113 Mad As Hell With Em
Views: 2,295 Posted By C4driver99
zix is a post ***** COUGH and a stalker COUGH:thumbs

Forum: C4 Tech/Performance Today, 09:27 PM
Replies: 113 Mad As Hell With Em
Views: 2,295 Posted By C4driver99
COUGH your cough wrong COUGGHHHHHH

em is a rip off COOOUUGGHH :cheers

Forum: C4 Tech/Performance Today, 09:25 PM
Replies: 10 What are the best...
Views: 115 Posted By C4driver99
:iagree with the post *****:rofl

Forum: C4 Tech/Performance Today, 09:24 PM
Replies: 5 Need a step-by-step procedure for weatherstrip replacement
Views: 88 Posted By C4driver99
:lurk

Forum: C4 Tech/Performance Today, 09:23 PM
Replies: 47 Header primary sizes [this could get ugly...]
Views: 456 Posted By C4driver99
stop following me u crzy people :toetap

Forum: C4 Tech/Performance Today, 09:23 PM
Replies: 47 Header primary sizes [this could get ugly...]
Views: 456 Posted By C4driver99
HAHA and i just did it again:withstupid

Forum: C4 Tech/Performance Today, 09:22 PM
Replies: 47 Header primary sizes [this could get ugly...]
Views: 456 Posted By C4driver99
:rofl I know i want stars

Forum: C4 Tech/Performance Today, 09:21 PM
Replies: 95 Well how do I put it in words ? " HELP " is a good place to start .
Views: 1,385 Posted By C4driver99
:lurk

Forum: C4 Tech/Performance Today, 09:20 PM
Replies: 13 Bad Thermostat - I think ?
Views: 102 Posted By C4driver99

Forum: C4 Tech/Performance Today, 09:19 PM
Replies: 47 Header primary sizes [this could get ugly...]
Views: 456 Posted By C4driver99
post *****? Is that why he has all those stars

Forum: C4 Tech/Performance Today, 09:18 PM
Replies: 47 Header primary sizes [this could get ugly...]
Views: 456 Posted By C4driver99

withstupid:

Forum: C4 Tech/Performance Today, 09:16 PM
Replies: 7 Replaceing power steering pump pulley on a LT1
Views: 33 Posted By C4driver99
:cheers thanks Pete

Forum: C4 Tech/Performance Today, 09:14 PM
Replies: 113 Mad As Hell With Em
Views: 2,295 Posted By C4driver99
:iagree 100% with jak

Forum: C4 Tech/Performance Today, 09:13 PM
Replies: 113 Mad As Hell With Em
Views: 2,295 Posted By C4driver99

:

Forum: C4 Tech/Performance Today, 09:12 PM
Replies: 9 CF/EM are unfair
Views: 95 Posted By C4driver99
em is full of

Apr 20, 2006 | 09:03 AM

#50

LT4BUD

Safety Car

Joined: Sep 2000

Posts: 3,524

Likes: 4

From: Hinckley Ohio

Quote:

Originally Posted by CFI-EFI

Do you really think it is as simple as some, firm, number? Why don't you give this thread a "POINT" and tells us the "magic" number?
RACE ON!!!

Ok I will, at least per ChevyHigh Performance tests....be sure to look at all pages

http://www.chevyhiperformance.com/te...der/index.html

Crossover RPM's

1-5/8 vs 1-1/2 is 4100rpm
1-3/4 vs 1-5/8 is 4800rpm
1-7/8 vs 1-3/4 is 5500rpm

When I am looking for performance on my LT4, I am in the rpm range of 4500-6500 so this provides some basis to determine what is optimal....if this data is applicable to my engine, which it is not directly, then for sure my choice would be either 1-3/4 or 1-7/8....

Generalized statements are often misleading....too bad we don't have this kind of data for more engine configurations

Apr 20, 2006 | 09:26 AM

#51

VR'92

Team Owner

Joined: Sep 2003

Posts: 25,295

Likes: 4

From: I'm the walkin dude I can see all of the world...

St. Jude Donor '03

We haven't had one of these in a while.

C-yall on page 11.

(Remember CFI is saying you lose extra potential torque with the 1 5/8th not you will lose torque w/ the 1 3/4)

Apr 20, 2006 | 09:58 AM

#52

Ramanstud

Thread Starter

Melting Slicks

Joined: Oct 2002

Posts: 3,193

Likes: 1

From: Cincinnati Oh

Quote:

Originally Posted by LT4BUD

This is with a 383ci carb'd motor putting out around 450HP/370ft-lbs of torque (give or take), so one could then argue that you'd gain more usable power "under the curve" with 1 5/8" on any 383ci or smaller engine that doesn't rev over ~5600 RPM or so... given the DD status of most of our rides, this would then be reinforced due to not only the dailydriver (low RPM) status AND the fact that we're all more than likely running a sub-3000RPM stall and shifting at under 6000RPM (more like 5500 RPM for me). So numerically, these cross-over estimations would be even higher for a 350ci motor with power outputs at or slightly below the levels used in that comparison and would stipulate that the smaller primary size would provide greater acceleration / lower ETs due to more Tq gain vs HP gain. Given I have a much more torquey cam / setup than the test mule here, these differences may been even further enhanced (towards the 1 5/8" primaries).

Interestingly, in the article (with 1 5/8" primaries) I quoted them:

Quote:

With a drop of as much as 29 lb-ft of torque between 3,000 rpm and 4,000 rpm, the 383's in-car acceleration characteristics would suffer dramatically

compared to the 1 1/2" mid-length tubes!

Last edited by Ramanstud; Apr 20, 2006 at 10:05 AM.

Apr 20, 2006 | 10:13 AM

#53

Bruce

Melting Slicks

Joined: Mar 1999

Posts: 2,535

Likes: 2

From: Rochester NY

1 3/4 no less.

Apr 20, 2006 | 10:54 AM

#54

LT4BUD

Safety Car

Joined: Sep 2000

Posts: 3,524

Likes: 4

From: Hinckley Ohio

Quote:

Originally Posted by Ramanstud

???????

4100 is crossover for 1-1/2 vs 1-5/8 and 4800 is crossover for 1-5/8 vs 1-3/4 and 5500 is crossover for 1-3/4 vs 1-7/8

So shouldn't your conclusion be that 1-5/8 is better than 1-3/4 if don't rev above about 4800???

5600 would be the crossover rpm for 1-3/4 vs 1-7/8??

Apr 20, 2006 | 11:55 AM

#55

rocco16

Race Director

Joined: Dec 2002

Posts: 13,345

Likes: 230

From: SCMR Rat Pack'r Charter Member..Great Bend KS

Quote:

Originally Posted by cuisinartvette

I would go 1-5/8 for a street motor.

Best advice you could get.

Larry
code5coupe

Apr 20, 2006 | 01:01 PM

#56

tequilaboy

Melting Slicks

Joined: Aug 2003

Posts: 3,380

Likes: 388

From: Lakeville MI

Based on the data presented in the article 1 3/4" is the clear winner.

Best average power at 375 HP, minimal losses compared to 1 5/8", with some nice gains. Also broadest and flattest torque curve.

Of course we're only talking about 1-4 hp average gains over 3000 rpm, pretty insignificant in the real world.

The gains in the 4000-6000 range however are fairly significant for both 1 5/8" and 1 3/4" with 1 3/4 getting the nod for this 383.

Apr 20, 2006 | 04:30 PM

#57

Ramanstud

Thread Starter

Melting Slicks

Joined: Oct 2002

Posts: 3,193

Likes: 1

From: Cincinnati Oh

Quote:

Originally Posted by LT4BUD

So shouldn't your conclusion be that 1-5/8 is better than 1-3/4 if don't rev above about 4800???

No. It's a curve (or even an average), not single points. You make peak power at, say 5600 rpm - do you shift at 5601 rpm or maybe 6000 so when the rpm's drop down to 5100 rpm you're still in the highest average powerBAND?

My point is, everything is about trade-offs. The "cross over" of advantage may be at a given RPM, but you have to consider the entire range that an engine will operate in. With my SR auto, that will be signifigantly larger than an LT1 manual. So the 1 5/8" may have a greater advantage over a broader powerband than the larger, given my engine's characteristics and intended operating range (5500 max). It's not exact, but hopefully you get my point.

Besides, we're all forgetting how well those short 1 1/2" primaries did on this engine - which most of us would have predicted to really kill power (but didn't).

Last edited by Ramanstud; Apr 20, 2006 at 04:33 PM.

Apr 20, 2006 | 06:02 PM

#58

Davemc1963-87conv

Racer

Joined: Aug 2002

Posts: 386

Likes: 0

From: Lancaster Lancashire

Sounds like the ideal header for a street strip car is a 1.5/8 to 1.3/4 stepped header, maybe the best of both worlds??
I was always led to believe that the main advantage of a smaller header over a larger one was the effect on throttle tip in at part throttle and that the larger headers exagerated or extended the range of any camminess that an engine combination may have. This was probably more noticeable on a carburetted engine than on an injected one though. Modern engine management systems seem to have almost made many of the old school "rule of thumb" theories worthless due to the almost limitless tuneability.
In the seventies/early eighties I and I'm sure others will remember the anti-reversion headers that were available. I remember reading several articles that measured their benefit both on the dyno and on SOTP feel. Some of the major benefits while increasing output from standard manifolds were on economy and part throttle operation due to the anti-reversion effect. My own thoughts are that with a standard/ish size exhaust port both the 1.5/8 and 1.3/4 will offer some anti reversion properties, with the larger size maybe offering more! This may account for many not seeing great reductions in SOTP torque over the 1.5/8 headers. Although this as I have stated only really applies at part throttle.
The comment made about the different size primaries is I think not as daft as it first sounds in broadening a torque curve (again just my thoughts) Going back to theories and looking intake runner length, we all know the differencies in the characteristics that this makes to an engine. (For a carbed street engine look at a Performer RPM manifold and the broad curve it gives using four short/four longer runners) Would it follow then that tuning the exhaust in a similar fashion would provide some benefit in the streetable RPM range we are talking about. It would obviously take someone to develop this to try the theories out. Would it be cost effective? Probably not. The anti-reversion headers I believe did work, but I think they stopped making them because they didn't sell!
Just more food for thought.

Apr 20, 2006 | 06:46 PM

#59

redcorvettedave

Drifting

Joined: Jun 2002

Posts: 1,305

Likes: 11

From: Savannah Ga.

Quote:

Originally Posted by VR'92

We haven't had one of these in a while.

C-yall on page 11.

(Remember CFI is saying you lose extra potential torque with the 1 5/8th not you will lose torque w/ the 1 3/4)

Quite frankly we need and I'v been waiting for one of these

Apr 20, 2006 | 08:00 PM

#60

CFI-EFI

Race Director

Joined: Sep 2000

Posts: 17,298

Likes: 33

From: The Top of Utah

Quote:

Originally Posted by LT4BUD

Ok I will, at least per ChevyHigh Performance tests....be sure to look at all pages

Crossover RPM's

1-5/8 vs 1-1/2 is 4100rpm
1-3/4 vs 1-5/8 is 4800rpm
1-7/8 vs 1-3/4 is 5500rpm

When I am looking for performance on my LT4, I am in the rpm range of 4500-6500 so this provides some basis to determine what is optimal....if this data is applicable to my engine, which it is not directly, then for sure my choice would be either 1-3/4 or 1-7/8....

Generalized statements are often misleading....too bad we don't have this kind of data for more engine configurations

I have the mag. I've looked at all the pages. In an earlier post you suggested the subject of "Crossover" was my idea, from the past. I can't deny that, but it doesn't ring familiar. Like I said, the "crossover point" is a moving target. It varies with cubic inches and with modifications. Remember what engine is being tested here. Based on these crossover points, an L83 or an L98 will NEVER see the advantage of 1 3/4" primaries...pretty much as I've been saying, all along.

Now that you have the "Crossover point" nailed down for a specific engine, how do you make a recommendation on the header size? If you want to shift gears in the quarter at 6000 rpms, are the 1 7/8" headers (with a 5500 rpm crossover) the better choice? Are you going to pull all the way from your 3000 rpm torque converter stall speed, at a disadvantage, to 5500 rpms (a 2500 range) so you can revel in the "fat" part of the curve for the last 500 rpms? What about driving down Main Street and giving it a little kick in the butt to merge on a quick lane change? Do you want to squeeze on the throttle and scoot, or set down your Latte Mocha, while you down shift two gears, and wail on it just to wake it up? That example is a bit of a stretch, but it illustrates my point. There is a lot more to be read than the peaks of the curves. Don't be blinded by the glitz.

RACE ON!!!

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