NeverSatisfied02

iTrader: (12)

Looking to buy headers for my car. I'm sure y'all have seen my post about the OBX headers. Quick question... Are you guys running 1-3/4 or 1-7/8 headers??

What kind of power is the 1-3/4 good to? I don't want to have to buy headers twice. Sooner or later, it will be a minimum heads/cam bolt-on car so prob in the 450rwhp range. From what I understand, at 500hp, the 1-3/4 become restrictive. Should I run 1-7/8 incase I add nitrous or get mod crazy or should the 1-3/4 be fine?

Darkman

iTrader: (2)

The 1 7/8 should make equal low & mid-range torque and more horsepower even on a stock motor. Assuming the cost is about the same, the only advantage of 1 3/4 headers is they have fewer clearance issues in the engine compartment.

Based on standard engineering gas flow formulas a 1 7/8 piping system will flow 19.5% more than a 1 3/4 piping system of the same design and length. So the difference is not huge.

NeverSatisfied02

iTrader: (12)

Thanks for the info man! Just wonder why majority of guys seem to run the 1-3/4 setup then? Price is almost the exact same (within $30) and if the 1-7/8 flows better and makes the same torque but more horsepower on the high end, it seems foolish to buy the 1-3/4 over the 1-7/8 option.

My thinking is this though...

Even though they both go to a 3" collector, the fact that the rest of the exhaust is only 2.5" means they would both flow the same in the end anyway unless you made the entire exhaust 3"... right? At that point, it seems like the 1-7/8 would actually have a benefit to it but until then, i couldn't see the slightly larger size being an advantage unless the rest of the exhaust could keep up with it.

Maybe im wrong but thats just my thinking.

Darkman

iTrader: (2)

The exhaust gases leave the engine at very high temperatures become cooler the as they travel farther away from the engine. As the gases cool they also contract volumetrically and therefore, take up less space. Because of this, reductions in pipe size become less critical to flow rates farther downstream. Because the exhaust will eventually run into smaller diameter piping it is even more important to maximize the flow closer to the engine.

NeverSatisfied02

iTrader: (12)

Oh I see. Well thanks for breaking it down for me. Makes sense now!

So is 1-3/4 plenty enough up to a certain hp? Like say 500rwhp? I know 1-3/4 is still a big upgrade from factory.

Darkman

iTrader: (2)

There is not a huge different between the two sizes particularly with fewer mods.

The clearance issues with the larger headers can be important if the car is a daily driver since those clearance issues can translate into melted wires, connectors, starters, and engine mounts. You also have do some bending to install the larger size in the V (steering column). Overall in the V, the larger size may not be the best choice unless you are going big (maggies, heads, big cams and such), or building a track oriented car.

Your call.

NeverSatisfied02

iTrader: (12)

I see. Well mine is a daily and I plan to do a nice heads/cam combo and that's about it. Maybe a little laughing gas later but nothing too huge. I think 1-3/4 might be my best bet to avoid clearance issues.

siggyfreud

iTrader: (1)

The smaller pipe size downstream, as the gasses contract, should theoretically help keep exhaust velocity up as well.

RADEoN

iTrader: (12)

I never knew obx made 1 3/4.

NeverSatisfied02

iTrader: (12)

I dont know if they do but kooks does.

babrown18

Yeah I had the same issue. On kooks website they said that the 1-7/8 header is for extreme use... ie heads/cam/maggie etc.. if that's ur plan I think the 1-7/8 will be a good fit. I personally got 1-3/4 kooks headers because I only plan to cam it only.. but like the guys said earlier, its your call.

scatillac

iTrader: (12)

I have 1 7/8" Kooks (coated) and have encountered none of these issues. I did, however fabricate some harness retainers and use DEI's insulating products where the proximity the header tube (and possibility of contact) warranted.

Also, when installing headers of any size, a starter shield/insulator should always be used.

SimplistikTA

So if I planned on doing just a Maggie on the stock heads and cam I'd be good with 1 3/4?

NeverSatisfied02

iTrader: (12)

I hope 1-3/4 will be enough for a nice heads/cam setup. Doubt I'll be supercharging mine.

LS2duc

iTrader: (1)

I was under the impression (not sure why) that 1 3/4 were generally for motors that would not be supercharged, while the wider diamters were more appropriate for forced induction systems. Someone told me, acutually more than one person told me this. Great thing about being newbie, research can be much more anecdotal. When does newbieism cease? When does responsibility commence? I listened to all you forum folks and freaks and a few salesmen and my V runs like the MF'ing space shuttle! Yes-1 7/8 pipes.