1 5/8 Primary Headers
Registered User
Joined: Sep 2002
Posts: 464
From: Orlando, FL
Let me quote a more reputable source:
from: http://www.grapeaperacing.com/GrapeA...ustheaders.cfm
First site I found on google about header primary tech. Draw your own conclusions.
The first thing to consider is the size of the primary tubes. Bigger tubes will give better breathing for top-end power, but the low velocity at lower rpm will make for more reversion to contaminate the next charge, so larger tubes will usually cost some low-end power. It is a common mistake to port the heads to match the headers primary pipes, but this does more harm than good. The primary tubes should be larger than the exhaust ports, this makes a reversion dam to limit reverse flow.
The shorter the primary tubes are the higher in the rpm range they will help power. Each exhaust pulse causes a high pressure wave to travel toward the collector. When it reaches the collector it is inverted and travels back toward the cylinder as a low pressure wave. It is this low pressure area that helps scavenge exhaust out of the cylinder during the overlap period. This happens when the low pressure area reaches the exhaust valve during the overlap period. The low pressure area helps draw out the exhaust and draw in more fresh intake charge. All the pressure waves travel at the speed of sound (1200-1300 ft/sec in the hot exhaust). With all the pressure waves traveling at a constant speed, you can see that the header can be only be tuned to a narrow rpm range. On a street car that needs low-end, the tubes should be longer, in a high rpm drag car they will need to be much shorter. To get you close to the optimum primary tube length, use this formula:
Length (in inches) = (CID x 1900) ÷ (rpm x pri.OD2)
Length (in inches) = (CID x 1900) ÷ (rpm x pri.OD2)
First site I found on google about header primary tech. Draw your own conclusions.
Registered User
Joined: Mar 2002
Posts: 3,634
From: Newark, Delaware
Originally posted by ibanez6rg
You can get all the emission BS with JetHot longtubes. If you're building up a car, LTs will do best. Otherwise, stock motor... not really sure. Losing HP at top-end with LTs?? Defiantly not! Losing torque on the bottom-end, more like.
You can get all the emission BS with JetHot longtubes. If you're building up a car, LTs will do best. Otherwise, stock motor... not really sure. Losing HP at top-end with LTs?? Defiantly not! Losing torque on the bottom-end, more like.
Check out any dyno tests comparing the 2 headers. Car Craft just did yet another one last month. The mid length headers blew the longtubes away in the top end HP department.
I really don't think my car is too close to stock, either.
Frank
Registered User
Joined: Mar 2002
Posts: 3,634
From: Newark, Delaware
Originally posted by ibanez6rg
You can get all the emission BS with JetHot longtubes. If you're building up a car, LTs will do best. Otherwise, stock motor... not really sure. Losing HP at top-end with LTs?? Defiantly not! Losing torque on the bottom-end, more like.
You can get all the emission BS with JetHot longtubes. If you're building up a car, LTs will do best. Otherwise, stock motor... not really sure. Losing HP at top-end with LTs?? Defiantly not! Losing torque on the bottom-end, more like.
Frank
Registered User
Joined: Jun 2001
Posts: 872
From: "Shoulda Gotton An LS1 Racin"
Originally posted by 12SCNDZ
I see you've got more cam than I do + longtubes...Mind if I ask what your car runs?
Frank
I see you've got more cam than I do + longtubes...Mind if I ask what your car runs?
Frank
Nice times. What stall is your converter?
Registered User
Joined: May 2002
Posts: 4,579
From: Cincinnati, OH
Originally posted by 12SCNDZ
I see you've got more cam than I do + longtubes...Mind if I ask what your car runs?
Frank
I see you've got more cam than I do + longtubes...Mind if I ask what your car runs?
Frank
I'll still have to disagree with you though - LTs shine on top-end, my car pulled so much harder after the install. With the exhaust I'm running I have very little backpressure. The reason I say this is, LTs will flow much better at higher RPMs. They allow the engine to breath more. I'm not going for anything more than a high 11 second car.
Thread Starter
Registered User
Joined: Jul 2003
Posts: 1,668
From: Cliffside Park, NJ
Yo
If LT increase top end, than shorties/mid lengths are useless? Well, not useless but not as effective as Long Tube because LT's add high end power while Firebirds already have a tremendous amount of torque?
I'm still curious about the difference in hp and torque gains from 1 5/8 primaries to a set of long tubes... if its a big difference or not.
Chris
If LT increase top end, than shorties/mid lengths are useless? Well, not useless but not as effective as Long Tube because LT's add high end power while Firebirds already have a tremendous amount of torque?
I'm still curious about the difference in hp and torque gains from 1 5/8 primaries to a set of long tubes... if its a big difference or not.
Chris
Registered User
Joined: Sep 2002
Posts: 464
From: Orlando, FL
Originally posted by ibanez6rg
No times, I will in the spring after my head swap.
I'll still have to disagree with you though - LTs shine on top-end, my car pulled so much harder after the install. With the exhaust I'm running I have very little backpressure. The reason I say this is, LTs will flow much better at higher RPMs. They allow the engine to breath more. I'm not going for anything more than a high 11 second car.
No times, I will in the spring after my head swap.
I'll still have to disagree with you though - LTs shine on top-end, my car pulled so much harder after the install. With the exhaust I'm running I have very little backpressure. The reason I say this is, LTs will flow much better at higher RPMs. They allow the engine to breath more. I'm not going for anything more than a high 11 second car.
Seriously, LONG TUBE HEADERS will generally make more top end HP than a 1 5/8" shorty/mid PROVIDING they have 1 3/4" primaries. The larger primaries make up for the loss of top end from the longer tubes.
Registered User
Joined: Sep 2000
Posts: 3,223
From: Browns Mills, New Jersey
Originally posted by 12SCNDZ
Why does everyone push longtubes? Do you all like the idea of LOSING top end HP?
Frank
Why does everyone push longtubes? Do you all like the idea of LOSING top end HP?
Frank
Registered User
Joined: Mar 2003
Posts: 1,623
From: Fairfield, ca
Yeah 12SCNDZ your car does have some great times for what it has but you would honestly gain some more power with some better flowing headers, like AS&M's mid-lengths, or long tubes. The Macs are very nice headers but they are better when used on a bolt on car.
Administrator
Joined: Nov 1998
Posts: 71,094
From: Hell was full so they sent me to NJ
To answer the original question, the JBA's are 1-5/8" "shorties". On top of that, they are a "step" header design. The first couple inches of each primary is only about 1-1/2". The theory is that the higher primary tube velocities aid scavengeing at low RPM. This works.... the JBA's provide excellent low end torque on a basically stock engine, but if you make any sort of breathing improvements at all, the stepped, small diameter primaries are going to kill you. I had them when my car was a "bolt on"... and they strangled the top end. The JBA's also seem to have added a weld bead to the flange port, as an "anti-reversion" measure. That further choked the flow at high RPM.
If you are serious about long term improvements for major power, invest in either a good set of Hooker LT's, or the AS&M mid-lengths. I have seen both support LT1 engines in the 800-1,100HP range.
If you are serious about long term improvements for major power, invest in either a good set of Hooker LT's, or the AS&M mid-lengths. I have seen both support LT1 engines in the 800-1,100HP range.
Thread Starter
Registered User
Joined: Jul 2003
Posts: 1,668
From: Cliffside Park, NJ
Yo
Hey thanks... about time someone answered it... haha j/k
Nah, I just want to be in the 320-350 range. I was told the car dynoed at 319hp but it seems shaky to me, I don't know why... A stock Formula with the JBA Headers, tri-flow exhaust, random tech cat converter, lingenfelter cold airtake charger, and... I think thats it. Doesn't 319 sound high?
Chris
Hey thanks... about time someone answered it... haha j/k
Nah, I just want to be in the 320-350 range. I was told the car dynoed at 319hp but it seems shaky to me, I don't know why... A stock Formula with the JBA Headers, tri-flow exhaust, random tech cat converter, lingenfelter cold airtake charger, and... I think thats it. Doesn't 319 sound high?
Chris
Registered User
Joined: Mar 2002
Posts: 3,634
From: Newark, Delaware
Originally posted by Smokn '94 Z
Dam. I was just looking at your sig. Your race wt is only 3448 with you in it? And with your seats? That is nice. I wieghed in at 3595 with no seats or spare with me in it. I weigh 200 lbs. Nice times. What stall is your converter?
Dam. I was just looking at your sig. Your race wt is only 3448 with you in it? And with your seats? That is nice. I wieghed in at 3595 with no seats or spare with me in it. I weigh 200 lbs.
Nice times. What stall is your converter?
My car is a very little optioned car...standard windows, locks, and no t-tops...About the only options mine had were factory 3.23's and cruise control. Yes, I still have all the seats, A/C, P/S, and bumper supports...I weigh 190#.
Frank
Registered User
Joined: Sep 2003
Posts: 1,327
From: Hartford, CT
Originally posted by ChrisUlrich
Yo
Hey thanks... about time someone answered it... haha j/k
Nah, I just want to be in the 320-350 range. I was told the car dynoed at 319hp but it seems shaky to me, I don't know why... A stock Formula with the JBA Headers, tri-flow exhaust, random tech cat converter, lingenfelter cold airtake charger, and... I think thats it. Doesn't 319 sound high?
Chris
Yo
Hey thanks... about time someone answered it... haha j/k
Nah, I just want to be in the 320-350 range. I was told the car dynoed at 319hp but it seems shaky to me, I don't know why... A stock Formula with the JBA Headers, tri-flow exhaust, random tech cat converter, lingenfelter cold airtake charger, and... I think thats it. Doesn't 319 sound high?
Chris