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Chris89gta
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Discussion Starter · #1 ·
This will start a big debate. Been doing a little research and thought I would get everyone elses opinion. Which one do you choose? Been quite a few tests lately that show that on a minimal modded motor, you don't lose as much as guys think actually don't lose very much at all w/ the 1/4" bigger primaries, also you pick up just a little more uptop in the powerband, and when you go w/ more mods, you pick up more with them b/c of the already had exhaust flow. Yes you lose a little backpressure... but IMO not enough to justify a problem. I know the standard is the 1 3/4 b/c its enough for the bolt ons, and mild h/c swaps... but if you want to get a little more wild... Would YOU step up to the 1 7/8? I would... and probably will when it comes time for the headers... :D
 

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if i was planning when i bought my headers to do what im planning now(H/C and a 125shot), i would of gotten 1 7/8s or stepped headers. Stepped seem to be a nice compromise.
 

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Funny how things change, because I remember back when the L98 was the hot thing the argument was 1.5" vs 1.75" ...many thought 1.75's were too big for the stock cubes and would kill all your torque.

A lot of that thinking carried over to the LT1 but I've yet to see an LT1 that was actually better off with the smaller primary.

I think the LS1 flows well enough that the 1 7/8ths should be the choice. Even a slightly too big primary is still going to produce more low/mid tq than the stock manifold, which has bacially zero scavenging ability.
 

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Chris89gta
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Discussion Starter · #4 ·
Agreed Chris. The benefit the LS1 has is the great exhaust port they have. I need to find the tests I saw where the dyno graphs showed little to no loss going to the 1 7/8' over the 1 3/4' and even w/ a mildly stock motor they picked up gains up top. Not HUGE numbers, but enough to justify and not block out that option if you plan on more mods later IMO.
 

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Looking back I should have gone 1 7/8 if that means anything to you
 

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either one make sure you get stepped headers. it will net gains more then size differance;)
 
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