Thread: Future Mods... what to expect

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!

Originally Posted by 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.

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?

Originally Posted by T0pwater

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.

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.

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

Better flow for a mostly stock car.

Originally Posted by gtpsleeper

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.

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

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