Any tips on flipping the stock flanges to reverse bolt pattern?

[$upra$rule]

I have a 91 LS400 motor in an 82 Supra, and am considering modifying the stock manifolds for forward facing turbo use. But I want them to run forward and up (to keep the AC & Alt.) instead of forward and down. This means the bolt pattern to the head is the reverse of what I need. Looking at the original manifold, only the #1 & #4 flanges are welded to the manifold, the #2-3 flange is slid over the manifold pipes and then they appear to be flared out.

I'm looking for suggestions (or somebody who has done this) for how best to remove, reverse top-to-bottom, and reinstall this flange. Is there a way to unflare and reflare these pipes, or would it be better just to cut off the flare and have to weld them to the flange after flipping it? I don't want to shorten the distance from the head to the bend in the manifold as I need this clearance for the AC. I'm not a welder, so will be paying somebody to do this.

Thoughts? Suggestions?

 

[Zuffen]

My advice would be make custom headers.

They'll fit better and won't be a mish-mash of chopped up stockers and new bits of pipe.

By the time the welder has mucked around welding & chopping and welding again it will be cheaper to go custom.

 

[zen]

there are even flanges for sale on this site, and cad files if you wish to make your own..(making my own ones, but as a cheap skate am oxy/acc cutting mine out and hole boring the holes, using gasket as template, you dont even have to get flash and cut around the holes ala toyota,just flat bar will do with holes cut in and 2 extra holes for where the steel gaskets are riveted together and slight angle at ends....cost £0/$0) pipe bends are all available on that aution site..(cheap as well)

 

[XR8tt]

Many many high pressure water cutting equipement around these days..
Even in the old country..

 

[edz]

Crown logs

I have a 91 LS400 motor in an 82 Supra, and am considering modifying the stock manifolds for forward facing turbo use. But I want them to run forward and up (to keep the AC & Alt.) instead of forward and down. This means the bolt pattern to the head is the reverse of what I need. Looking at the original manifold, only the #1 & #4 flanges are welded to the manifold, the #2-3 flange is slid over the manifold pipes and then they appear to be flared out.

I'm looking for suggestions (or somebody who has done this) for how best to remove, reverse top-to-bottom, and reinstall this flange. Is there a way to unflare and reflare these pipes, or would it be better just to cut off the flare and have to weld them to the flange after flipping it? I don't want to shorten the distance from the head to the bend in the manifold as I need this clearance for the AC. I'm not a welder, so will be paying somebody to do this.

Thoughts? Suggestions?

If you use the Crown Log manifolds, you can just cut the pair joining plates and reverse the manifolds, pointing them up. The pic below shows this, as I purchased some with the intention of doing this. Note, they are made from stainless steel with cast iron flanges. I ended up making my own from scratch with steampipe bends.

 

[XR8tt]

Yep here's mine for single set up..
All the flanges are from std manifolds.. Even the crossover at the front is Lexus manifold join..
Using 32mm steam bends, pipe.. Std primary exhaust removed and welded to outside of flange..
Getting started..