Crashz06

So I think I already know the answer to my question but I want a second opinion or maybe 3. I have an 03Z that is stock with the exception of a Haltech intake.. I have 2 sets of ARH headers for it. 1 5/8 non-smog and 1 3/4 smog. The X is catted. Which set do the corvette gods suggest. I'm thinking the 1 3/4 for the cam I plan to do but I'm worried it might be to large of a primary.

FYI, I will be ordering a Vindicator cam and supporting mods next week and all parts will go on at the sametime then followed up by tuning.

Thanks in advance and any help is appreciated.

grantv

1 3/4" is the go-to primary for most people with factory cubes and no blower.

Vetteman Jack

And I think the other size headers you have are 1 7/8" instead of 1 5/8".

grantv

I remember many years back 1 5/8" was pretty common... yes, I'm old. But yes, the other option is probably right.

neutron82

if they are in fact 1 7/8 and not 1 5/8 I would use those, no air pipe provisions will look cleaner and by removing the air pump and pipes it makes plug changes easier as well... either one should make good power regardless though

Crashz06

They are definitely 1 5/8.

vettenuts

Personally, I would go with the largest primary and then have a custom exhaust shop remove the AIR connection. Remove the AIR piping and check valves, which are a source of problems, and tune it out.

I didn't think ARH ever made a 1-5/8" primary for the C5.

Crashz06

Here is the original ad I purchased the "1 5/8" headers from back in January. They were advertised as 1 3/4. I didnt even bother to measure until I received the other set last night when I noticed the size difference. Maybe I've done this wrong but I always thought primaries were advertised and measured by ID. I measured the OD of both sets and come up with 1 3/4 and 1 7/8.

https://www.corvetteforum.com/forums...-for-sale.html

grantv

Always OD, so you have 1 3/4 & 1 7/8 options. I'd go with the smaller, but plenty of people get the 1 7/8 also.

neutron82

measuring OD is the correct way, I'd definitely go with the 1 7/8

Crashz06

Other than the cam swamp I do not plan on any other mods. I dont race the car just my weekend cruiser. Ill be selling the set of headers not being used. I mainly bought the second set because I needed the X pipe. X pipe new from ARH was 600+.

RomanNYC

for that small of an engine I would not suggest running the 1 7/8 unless we are going to be making 550 REAR WHEEL HP or more…or approx 650 at the engine. For that engine, it would mean a supercharger.

The 1 ¾ would be my personal suggestion. Gives you room to grow and there are no down sides to do them now on a stock engine. The 1 7/8 given what you have done, and planning to do with a mild cam you would loose to much low and mid range torque with.

vettenuts

Go with the larger primary. I have yet to see a curve where mid range is sacrificed with the 1-7/8 primary. Since they are off-road, the AIR system can be eliminated as well.

RomanNYC

could be true with other manufacture headers, i know that when comparing the LG 1 3/4 vs LG 1 7/8 the 1 3/4 are superior for engines under 550WHP. the 1 3/4 extractors reduce down a lot more in the collectors than the larger shorter 1 7/8" set

Crashz06

I think Im going to run the 1 7/8 headers. I know I said no more modding after the cam but I know me and this is not the end lol. Thanks all for your help.