Help With First +T DIY Manifold Attempt - B6304/960

Rudimentary Header Fab.. DIY +t Manifold Attempt B6304/960

I'm back working on my 960 B6304 =T project (Not and ideal +t candidate, I know... but at this point I've committed to it, so let's get that out of the way). I've been making videos during the process, here's a link to the playlist: https://www.youtube.com/playlist?li...1gMDzJ0MhPXjRBx_FxhTh7C3lV0GqpGWlKmu6JY77Ch3E

Initially I tried an el-cheapo e36/M52 cast manifold and drilled to suit in a effort to avoid fab... But the turbo is mounted way too close to the bellshousing to work, also the fresh air intake is obscured by the engine mount...

So I figure I'll fab something, but my fab skills are not fab at all... so the less welding and cutting I have to do, the better.

My thought was to take the original manifolds (Updated below, I'm thinking of looping up from the stock outlets now), scallop them and route them to a divided flange like this one which already has two short 2.5" pipes coming from it: https://www.ebay.com/itm/T4-Divided...let-TAPPED-Mild-Steel-M10-X-1-25/183852329044

The turbo (Cheap ebay jobbie, I think it's a .63) isn't a twin scroll\divided but I figure it's worth doing this on the fab side while I'm making it.

What do you think? Worth a shot using the original headers? Also welcome any general pointers on making manifolds.

Here's a video of the "scalloping" process I came across.
https://www.youtube.com/watch?v=Jxvx6MwsPYk

Mine is just a simple log manifold with a T3 flange on it. I took two 5cyl NA manifolds, since they were tubular and not cast, cut the pipes off, made two 3-cyl sections and got some sch 40 weld-els from the local plumbing supply store. I did most of the welding with my little 110v MIG, and so far no cracks.

Thanks. what turbo did you go with out of curiosity. I do have a 5 cylinder turbo manifold here, but it looks like the flange is cast... maybe.
If you could post a pic of your install under the hood that would be great.

I guess another option would be to loop up and out from the bottom of the stock manifolds where the join the downpipe and run those two pipes to a flange. Hmm.

I am using a big16G (TD05H) with an 8cm T3 internal gate housing. It's...smallish, but it works pretty well. Considering the 5 cyls got a TD04-based unit, I figure a TD05H is a decent start on a 6-cyl. Reasonably quick spool, although feels kinda sluggy down low due to the high stall of the stock converter, but it's a good choice for boost. I used the non-turbo 5cyl manifolds as a base, since they're tubular and the flanges were easy to cut off.

Here's a pic of the turbo/manifold during construction/mockup:

As simple as those log manifolds are to make, they're absolutely woeful for flow.

Shoot a PM to Lankku, who has built many of these manifolds for his 6 cylinder cars. Might even have a supplier for the OP.

This is a budget build, well a budget build if I don't account for my time.
I'm leaning more and more towards using the stock headers in some way.... less welding for me = less opportunities to mess it up. I'm not looking for big power, this is more of an exercise in the process. Plus I figure it would be nice to have a split between 1-3 and 4-6 if I can pull it off.

So now I'm thinking I'll loop around and up from the stock headers using 2x 90deg mandrel bends, at a T3 flange. I'm not worried too much about the stock headers being smaller, I'm not after big power. Sorry about the massive images




One question I have... Am I better to weld the new pipes directly to the manifold outlet (Dissimilar metals), or should I use the donut connections instead, welding the new pipe to one of those and bolting it up?

Sweep said:

As simple as those log manifolds are to make, they're absolutely woeful for flow.

Click to expand...

Sure, if this was an all-out performance vehicle that was looking for every last ounce of power, I might be worried. It's more of a smiles/miles vehicle .

955IsAlive said:

One question I have... Am I better to weld the new pipes directly to the manifold outlet (Dissimilar metals), or should I use the donut connections instead, welding the new pipe to one of those and bolting it up?

Click to expand...

The manifolds are probably cast steel, so they'd end up being fairly easy to weld with the right prep. I'd probably cut the donut flanges off and put some 3-bolt triangular flanges in their place (or V-bands) so you could easily remove the 'J-pipes' going to the turbo for easy maintenance. It does introduce a few more leak points, but if you're diligent, it won't be an issue.

Ok some decisions made one of which was the wrong one it looks like...
I like the idea of using VBand on there so I'm running with that.

I bought 2x 1.75" VBand flanges, but it looks like 1.75" is going to be comically small for any power. Seemingly based on CFM 1.75" is barely good for 110HP... Which puts me at flowing at best 220HP... Of course this is not exact, but it seems to indicate that the outlet is matched for 200 ish HP... ie the stock number. Obvious in retrospect. I had hoped there would be some headroom. Source: https://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/



Just cancelled the order now.. Looks like 2.25 might be the way to go... If I can make it work with the manifold by cutting it back..

So I’m further confused on exhaust sizing. Here’s why... I ordered a divided T3 manifold to practice welding on, and the pipe that seems to work best is a 1.75”

I have one of the stock manifolds cut and it looks like I’ll be coming out of it with a 2.25” flange.

Any thoughts on why I’m looking at 2x 1.75” pipes into the T3 flange? Seems very small, but I guess it’s worked fine for many people? Should I have stuck with 1.75 from the manifold?

2x48mm/1.75" to the turbo sounds good for your application.
I have seen several comparable designs on Savarturbo which made large amounts of power.
1.75" fits perfectly to a twin scroll t3 flange.

Sjeng said:

2x48mm/1.75" to the turbo sounds good for your application.
I have seen several comparable designs on Savarturbo which made large amounts of power.
1.75" fits perfectly to a twin scroll t3 flange.

Click to expand...

Thanks Sjeng. Planning ordering some mandrel bends this week and doing some welding once I've decided what piping size (or combination) I'll be running...
From the exhaust manifolds themselves, should I start with 1.75 and run that all the way to the flange? That said I've already hacked one manifold for 2.25(ish) ha.