3.1EyeCandy

iTrader: (3)

Trying to pick out a set of Hooker headers. Both the 1 7/8 and 1 3/4 stainless are the same price from Hooker directly. My build is going to be on the mild end (LS1, maybe a mild cam, little to no track duty). Bigger isn't always better, but the price being the same I wanted to see what the forum thought.

In what scenarios would you pick a 1 3/4 header for an LS engine vs a 1 7/8?

Thanks,
Jon

3.1EyeCandy

iTrader: (3)

Gosh this is all over the map. Had a link I thought was helpful. Found half a dozen more conflicting....

dmccain

iTrader: (2)

I wouldn't think it would be a huge difference but I myself would go bigger 1 7/8 if had the choice

soloc4

For a mild LS1, 1 3/4 headers are more than enough. You would appreciate the extra clearance that you will have with the smaller headers. I realize that it is only .125”, but everything we do to our cars are measured in fractions of an inch (mine in the thousandths). Just my thoughts on the matter.

ShiftyCapone

iTrader: (7)

1-7/8". You likely won't be able to tell the difference but the larger ones won't leave anything on the table should you add any other mods.

Orr89RocZ

iTrader: (20)

1 7/8

V6canvas

iTrader: (1)

FWIW, I have the Stainless Works swap headers, I think they were the only game in town at the time. 1-5/8" primaries, 2-1/2" collectors. So either way you'll be a step or two bigger than that. Am I leaving power on the table? I don't know, my combo is pretty mild (stock '98 LS1, LS6 intake, headers, 85mm MAF), so I doubt I'd see much difference at the moment. If I ever get the cash to do more, maybe that'll be a bottle neck if I ever get cam/heads slapped on.

Orr89RocZ

iTrader: (20)

Just about everything 4th gen or ls related i have seen come thru the dyno shop has made more with 1 7/8’s. Especially with mods and increased airflow thru cam and or heads. They never seem to lose anything. Im talking ls1 and larger. I dont think i have seen 4.8 or 5.3’s with them

skinny z

As has been demonstrated before, and linked recently to a thread I've subscribed to, is that the header size is tied into the cam spec as well as the rest of engine package. So, if you a given longblock complete with cam, you'll have to see what works for it in particular.
If you're building something from scratch, one of the entries on the cam spec recommendation card will be header sizing. So you can see how this pans out. There's no one correct answer. It may be that a majority of hot rodded LS engine require a 1 7/8" primary hence the bent towards that size, however there's room on either side of that dimension for something outside of that majority.
While I take the bulk of my data as it pertains to the Gen 1 SBC, there are charts and recommendations out there that dictate the size of the primary based on the peak exhaust port flow (in CFM) at the maximum cam lift used. That may very well transfer over into the LS platform as the science doesn't change, Just the inputs.

jbenge

iTrader: (2)

I would go 1 7/8. I've seen some dyno results on LS1tech where even a mild LS1 combo made more power with a 1 7/8 header vs 1 3/4 with no other changes. Not a huge difference but a little. In reality you would probably not even feel the difference especially on a mild combination like you are planning. But you would be better equipped later if you built a more radical combination or larger displacement engine with the 1 7/8 headers.

FYI the hooker headers are very nice and well made. I tried a set on my car LS1 4l60e w/ spohn mounts and I couldn't get the passenger side header on even after taking the motor mounts loose and jacking the engine up as high as I could. I wasn't using the holly motor mounts so that might have been the difference, I had heard they would work but in my case it didn't. I ended up going with Speed Engineering headers and returning the Hooker headers. The quality isn't as good(good for the price though) but they fit extremely well...with my combination anyway.

3.1EyeCandy

iTrader: (3)

Great feedback everyone. Most folks are saying that the 1 7/8 won't lose power down low compared to the 1 3/4 with the LS1. I've found one thread online with the opposite finding, but one data point doesn't reverse a trend. With the price being the same on the two, I'm going to purchase the 1 7/8 on the off chance that one day I have higher end performance parts that can take advantage of them.

I'm planning on running all Holley gear (headers, engine mounts, tranny mount, and exhaust) and selling what I have now. I'm also planning to go back to a stock k-member. Hopefully this translates to good fitment. If any of ya'll are in the Houston area and need some "classic" LS Swap parts, let me know.

vorteciroc

Is this a stock displacement LS1 (346")?

If so... I would definitely go with the smaller diameter primaries in a full-length header set.
Compared to the larger LS2 or LS3... the LS1 is down on torque by a good amount (especially to the LS3 with variable camshaft phasing).

Other than the 1 3/4" headers... a header set with stepped primaries from 1 3/4" stepped to 1 7/8" would be the next best thing.

3.1EyeCandy

iTrader: (3)

Yep. Stock displacement. I've got the 1 7/8" units sitting right here in the box, working on cleaning the garage and getting some better lighting in place as the engine is going to get torn down, inspected, and some parts cleaned/replaced during reassembly. We'll see how it goes. Anecdotal evidence on the internet (LOL) says I won't lose any HP/Torque across the entire RPM band... but if I do at least at that point I'll have a running LS swapped GTA after 10 years of it sitting on jackstands. I'll still be all grins.