Here's my contribution to community service..
If you've got an early A, this is something you're familiar with header options.
But if you are like me, you're frustrated with the lack of spec's on the Big3 of header manufacturers. Mainly on header primary length. Even if it were a ball park..
Of coarse, I'm speaking of Doug's, Hooker, and TTI.
When I began my early A project, the TTI's were on backorder, with no production date in sight and the promise of a price increase. They were the ones I wanted.
Doug's were 'in stock' and only $590. Hookers were available too and a bargain at $544, but there was no way I was cutting my pretty red fenders. Especially for a 1 5/8 tube.
My Dart was coming together quickly and I NEEDED headers. I chose the Doug's.
NOW, since I've upgraded my 360, those Doug's are WAAY TOO SMALL.
So, for the majority of my fellow proud owners of early A's... here's what I've done.
If you are a racer, you will be familiar with the header design software, PipeMax. By Larry Meaux. I simply reversed engineered the headers to find expected RPM ranges for each engine listed.
This is the tuned rpm range for the tube size and collector. this is the 'happy range' for each engine/header combo. There will still be a positive effect on torque below these ranges.
What I've done is laid out 2 possible/typical engine scenario's for the 273, 318, 340, 360, and the 408 to have perspective to what the expected RPM ranges would be for each engine/header combo.
Scenario 1 is: .030 over, cam 220/226 @ .050 x.470 lift 110° LCA and installed on 106° centers, 1.6 Exh valve, and at 100% VE (yes, it's optimistic)
Scenario 2 is: .030 over, cam 230/236 @.050 x .500 lift 110° LCA/106° centers, 1.6 Exh valve, 100% VE.
Note: if your cam is bigger, your header will have to be bigger also.
While some of you may argue, this is too simple, I agree. Other factors contribute. The idea here is to show the trends in engine/header relationships.
Scenario 1 Doug's/Hookers 1 5/8 x 2 1/2 collectors
273 - 5k-7500 rpm (race only, duh) use HP manifolds
318 - 4k -6500 rpm (this does not mean it will be 'dead' under 4k)
340 - 3600-6100 rpm
360 - 3300-5800 rpm
408 - 2600-5100 rpm Unless you're pulling a camper, use the TTI's
Scenario 2 TTI's 1 5/8 x 1 3/4 step (first step is too short, basically straight 1 3/4)
318 - 5k-7500
340 - 4800-7300
360 - 4300-6800
408 - 3500-6000
Feel free to argue some of the data if you wish. I just wanted to provide a perspective for those who've always wondered and could not find the answers online..
If you've got an early A, this is something you're familiar with header options.
But if you are like me, you're frustrated with the lack of spec's on the Big3 of header manufacturers. Mainly on header primary length. Even if it were a ball park..
Of coarse, I'm speaking of Doug's, Hooker, and TTI.
When I began my early A project, the TTI's were on backorder, with no production date in sight and the promise of a price increase. They were the ones I wanted.
Doug's were 'in stock' and only $590. Hookers were available too and a bargain at $544, but there was no way I was cutting my pretty red fenders. Especially for a 1 5/8 tube.
My Dart was coming together quickly and I NEEDED headers. I chose the Doug's.
NOW, since I've upgraded my 360, those Doug's are WAAY TOO SMALL.
So, for the majority of my fellow proud owners of early A's... here's what I've done.
If you are a racer, you will be familiar with the header design software, PipeMax. By Larry Meaux. I simply reversed engineered the headers to find expected RPM ranges for each engine listed.
This is the tuned rpm range for the tube size and collector. this is the 'happy range' for each engine/header combo. There will still be a positive effect on torque below these ranges.
What I've done is laid out 2 possible/typical engine scenario's for the 273, 318, 340, 360, and the 408 to have perspective to what the expected RPM ranges would be for each engine/header combo.
Scenario 1 is: .030 over, cam 220/226 @ .050 x.470 lift 110° LCA and installed on 106° centers, 1.6 Exh valve, and at 100% VE (yes, it's optimistic)
Scenario 2 is: .030 over, cam 230/236 @.050 x .500 lift 110° LCA/106° centers, 1.6 Exh valve, 100% VE.
Note: if your cam is bigger, your header will have to be bigger also.
While some of you may argue, this is too simple, I agree. Other factors contribute. The idea here is to show the trends in engine/header relationships.
Scenario 1 Doug's/Hookers 1 5/8 x 2 1/2 collectors
273 - 5k-7500 rpm (race only, duh) use HP manifolds
318 - 4k -6500 rpm (this does not mean it will be 'dead' under 4k)
340 - 3600-6100 rpm
360 - 3300-5800 rpm
408 - 2600-5100 rpm Unless you're pulling a camper, use the TTI's
Scenario 2 TTI's 1 5/8 x 1 3/4 step (first step is too short, basically straight 1 3/4)
318 - 5k-7500
340 - 4800-7300
360 - 4300-6800
408 - 3500-6000
Feel free to argue some of the data if you wish. I just wanted to provide a perspective for those who've always wondered and could not find the answers online..
