Future Mods... what to expect

[T0pwater]

I've been reading this forum and the others for 8 months now... This one is my favorite by far. It seems to be the most searchable and cleanest. Best one for learning in my opinion (thanks to the educators - you know who you are).

My question is the following:

I've read about the potential "drawbacks" of early modding stages (the 3.4 setup) - such as a loss in low end torque due to headers eliminating some back pressure (and maybe other reasons). However, I've also read that our cars gain a lot in 0-60 as the mods are added. Does this mean all those gains are in the upper RPM range?

I ask because I am a big fan of the low-mid range torque that my stocker (04 Impala SS) has. It does go anemic... or constipated... or both as the RPMs increase, and I want to fix that, but not at the expense of the low end. This car is my DD. I'm not really into racing and will not be taking this to the track or dyno (except for tuning) any time soon. My goal is to have a really good 0-60 car - hopefully down into the 4's if possible. And a lot of torque on demand in that range.

My tentative long-term plan is gen V + rockers + N* + headers -> pulley -> IC -> pulley (leaving out small mods). What do you guys think I can expect in my 0-60 progression and also in my low-mid torque as I begin to mod? Any suggestions for improvements in my plan to help my goal stated above are much appreciated. Please no 1-line "CAM IT" or "TURBO" responses. I'm not ready/interested right now in either of those paths.

Thanks!

 

[SilvaMan61]

headers are a great investment. now you are right about the loss in low end torque, but its not gone. the pwer band just moves up a little higher. you still get good low end while improving mid-high end. the loss of the low end torque isnt all to much, but it allows for much more aggresive launches because its more managable. now i cant really say what #s youll be seeing 0-60 but headers are a major improvement over stock, and will better your times. plus a gen v is going to be cramming more air in, and much cooler air, you definetly want to be sure that all of it is being exhausted efficiently.

 

[JoRoW99]

Why are you so worried about low end? its not like its gonna be slower. If you arent into racing and dont want to go to a track i dont see why you want to be faster at all, unless you are like me and just like turning wrenches.

 

[Bio248]

if you really want low end, get a smaller cam geared towards that area. if not, go big and move the powerband up where we lack it (the top side). all 3800s fall on their face around 4k unless you do some valvetrain work.

 

[T0pwater]

Why are you so worried about low end? its not like its gonna be slower. If you arent into racing and dont want to go to a track i dont see why you want to be faster at all, unless you are like me and just like turning wrenches.

a) yes I like turning wrenches... to the point that a part of me is glad when my cars break...

b) Why I care about the low end: it's my DD. And yes, maybe it's not the best investment decision to make a car faster that 80% of the time is not pushed hard. But I'm going to, and if my low end (which is where I do my daily driving) sucks, I will hate driving the car for that purpose.

Thanks SilvaMan for the info - I want to do the headers, and if I can still enjoy DD'ing it, I will for sure. Do you think I should go with 1.5 or 1.75 primaries, considering my goals? Also, I'm confused on the primary size of the SD headers. Before they changed their ebay pic to list the 1.5" primary size, I asked them what size primaries they use and was told 1.75". Did they change it or did the person give me bad info?

 

[BillBoost37]

Adding headers may pull down some of the torque until you get the other mods under the hood, however spinning is spinning and you'll still be able to smoke tires if you add headers a bit on the early side.

As far as low end torque. I like it too. There's a resulting problem from it though. The transmission hates it. Our pcm's have programming called torque management to try and keep us from enjoying low end torque in the 0-60 area. The problem is..if you frequently like low end torque, sooner or later your transmission will give you a lesson in walking.

 

[Sinister Drag Designs]

a) yes I like turning wrenches... to the point that a part of me is glad when my cars break...

b) Why I care about the low end: it's my DD. And yes, maybe it's not the best investment decision to make a car faster that 80% of the time is not pushed hard. But I'm going to, and if my low end (which is where I do my daily driving) sucks, I will hate driving the car for that purpose.

Thanks SilvaMan for the info - I want to do the headers, and if I can still enjoy DD'ing it, I will for sure. Do you think I should go with 1.5 or 1.75 primaries, considering my goals? Also, I'm confused on the primary size of the SD headers. Before they changed their ebay pic to list the 1.5" primary size, I asked them what size primaries they use and was told 1.75". Did they change it or did the person give me bad info?

1 5/8th primaries will be fine and will help keep the torque band closer to stock then the larger 1 3/4 models.

 

[footballplaya3k]

I'm not 100% but I'm pretty damn sure they are 1.75. When you hear we lose torque its not like we become Honda status, we still have a lot of torque. And when you pulley down or up your timing you will get at least all that torque back.

 

[dmahlikGT]

As far as i see it basically you make 280ft lbs stock.Adding headers wont drop you to like 267ft lbs, instead youll make your 280ft lbs around 4500rpm instead of 3800rpm.Moving the power band higher.hope that helps

 

[Going Too Phast]

I have a set of Speed Daddy headers. I took my caliper to them and the primaries are 1 5/8" diameter. When talking tubing size the outside diameter is the what is being referred to. The confusion with the SD picture/description is that the 1 1/2" is referring to the inside diameter of the pipes. They are 1 5/8" just like the SLP headers they are copied from.

The 1 5/8" primaries are going to most likely be better for a stock cam. And probably mild cams too. Plogs have 1 5/8" primaries. I'd imagine cams with high rpm power bands (e.g. XPZ) and the necessary ported heads to go with them would be better off with the 1 3/4" primaries. Without dyno/track testing we are all just guessing really. In the OP there was a statement made about back pressure. Just to clarify, back pressure is never desirable. Experts seem to agree what you are shooting for is exhaust gas velocity of 250 ft/sec. Unfortunately I don't think there is an easy way to measure that to see how close you are to that number. Depending on your cam specs, heads, pulley, etc. you will move more air/fuel in which means more exhaust out. In order to hit the 250 ft/sec you would need to increase the primary size. Obviously if your primary size is too big you won't be able to get that ideal exhaust velocity either. It is a balancing act. I also think some headers have fairly large diameter crossover pipes which makes me wonder if that would hurt exhaust velocity for the front cylinders.

Keep in mind that longer primary tubes increase low rpm power though. Headers of course have much longer primaries than stock manifolds/plogs so in that regard they will actually have better low end potential. Of the readily available headers, SD seem to be the best for what you are shooting for. This is mostly theory though. It might not translate to an appreciable difference out in the real world. Just my $0.02.

 

[T0pwater]

The problem is..if you frequently like low end torque, sooner or later your transmission will give you a lesson in walking.

= How I sell my wife on a TEP tranny... "Honey, it just stopped running! And there's this special kind of replacement transmission that you can beat the pis- I mean that is very reliable!"

I have a set of Speed Daddy headers. ... Just my $0.02.

Thanks. This is really good info. This gives some explanation about the exhaust velocity: Exhaust backpressure the myth - ThumperTalk. It def makes sense. It also gives some insight into why equal-length headers are good - the pressure drop in a pipe is proportional to length, so with unequal lengths you have unequal pressures at the collector - and hence some backflow into the longer-length headers. Just a thought. Also, to your point about crossover pipe diameter: the collective area of the front primaries is about 21 in^2. Which is the same area as a 2.6" ID x-over. So anything smaller than that should maintain roughly the same exit velocity.

Also, it's good to know I'll likely get the torque back as I increase my flow with pulleys, gen V, valvetrain, etc. because my exhaust velocity will approach the same as it is today with the mani's.

Does anyone have a link to a decent write-up for fixing the SD header sink trap? That thing is not gonna fly.

 

[matt5112]

i had pacesetters and when switching to SD's my boost levels went down.

Better flow for a mostly stock car.

 

[gtpsleeper]

whats the point in low end torque when all you do is spin?....

 

[T0pwater]

whats the point in low end torque when all you do is spin?....

Low-end torque is more than just low vehicle speed torque. It refers to RPM's - I'm talking 1k-3.5k. You can tap into low-end torque and feel its benefits at 0 MPH and 60 MPH alike. It just means you don't have to rev your engine really high to get peak or near-peak torque (acceleration). It's important to me because of my driving habits.

 

[blueguy]

Low-end torque is more than just low vehicle speed torque. It refers to RPM's - I'm talking 1k-3.5k. You can tap into low-end torque and feel its benefits at 0 MPH and 60 MPH alike. It just means you don't have to rev your engine really high to get peak or near-peak torque (acceleration). It's important to me because of my driving habits.

whats the point in low end torque when all you do is spin?....

It's called teh driver mod. If your spinning the tires...then your car either has...

A) Enough power/torque
B) Not enough tire

i had pacesetters and when switching to SD's my boost levels went down.

Better flow for a mostly stock car.

Also...I don't know how this works...since Pacecrappers have the second largest primaries at 1 7/8"...so if your boost levels DROPPED after getting a more restrictive header/smaller primaried header...then you did something else...example...your different ported blower that "works better".

 

[mechguy]

I say you should worry less about low-end torque with an automatic trans.

Overall torque is increasing greatly with 3.4" pulley & headers.