When >/= 1.75" primaries are concerned I have become dismayed at the lack of header choices available to our cars. For 1.75" primaries I am limited to Dyno Don's shorties or Hooker Long tubes. Both are fairly expensive when you consider the versions that use 1.5 or 1 5/8 are not even half the price. I began looking at some other shorty and mid-length header options for the LS and the prices seem more on par. So my thought was, can I just take a pair of LS headers and:
1. chop off the cylinder head flange with my bandsaw
2. weld the front and back primaries back on the flange
3. Cut the middle primaries back a little and just weld in new pipe to connect to the middle ports?

I've never held an LS header for a thirdgen so I'm not sure how easily achieved this may be. I have a TIG and MIG so welding them myself isn't an issue. I figured this section was probably a better fit than the fabrication section.

 

No reason you can't.
Instead of listing the negatives, make a comprehensive parts list for the project and set a couple thresholds:
% or flat $ amount differential between DIY and just calling Lemons (or whomever makes what you want)
Amount of time you put into it vs. cost differential.

Even still, it's tough to be 100% sure the fitment details of the latter primaries and the collectors will suit your application. IIRC, you're on 93-97 bellhousing and I highly doubt an LS set will be friendly with the slave location.

Which to me says, if you're gonna do the fab, do them your way and start from scratch.

Funny how 1.75" got skipped in the aftermarket on a lot of applications for a long time and " they won't fit" was heard nonstop until the LS products rolled out.

 

I was afraid there would be some odd issue like that.


Looks like I will probably have to now.


So many LS headers are 1.75" while so few sbc headers are. upsetting.

 

Go for it. However, advertised primary diameter is OD not ID.

7/8 OD = 3/4 ID

3/4 OD = 5/8 ID

5/8 OD = 1/2 ID

I have a pair of Speed Engineering 7/8 headers, and a pair or Racing Innovation 3/4 headers and have verified these measurements.

Those headers are $300-$400.

4th gen 3/4 ebay headers are $150 and are an awesome deal, especially if you're going to modify them. Hell you probably couldn't build those for $150 in materials! I have a pair of these too. ($100 craigslist)

http://www.ebay.com/itm/CHEVY-CAMARO...53.m1438.l2649


Check this out:

https://ls1tech.com/forums/conversio...y-headers.html

 

It's because of the stock OEM power shift from the Gen III/IV motors from the SBC. Your average modded SBC 350 would make 300hp and be all in by 5200 rpm, by average I mean the majority of the market that the aftermarket is making product for. Your junk yard GenIII 5.3 LM7 will make that bone stock with 300k miles on it, rev to 6k rpm and move tons more air through the heads. Your new average power rating for a Gen III/IV swap is 400 to 450, necessitating the larger diameter headers. The head flow alone is massive when you compare the two. The factory LS manifolds are pretty much equivalent to SBC 1-5/8" headers, which are adequate for your run of the mill SBC 300hp motor.

 

Started pricing parts to make them from scratch and then I saw that the eBay stainless long tubes are $88.... delivered! So I bought a pair and will cut them apart and buy some more stainless to make a set of mid or shorty length headers from them. Just have to work on my tig skills now.