Homemade Turbo Log Manifold

I

InlineUK

Well-known member
Hi Guys, i'd like some opinions please :)

I am planning to make a exhaust manifold for my twin turbo set-up using 90* elbow and tee butt weld fittings (i think in the USA you call them weld-els). I was going to use fittings with a 2" internal dia, but these have a 2.5" outer diameter and won't fit between the flange bolts on the cylinder head.
The biggest that will fit are the 1.5" pipe fittings (1.5"internal, 1.9" external diameter).

The motor is a 250, 8.0:1 CR, 274/274 112* cam, 1.65 rockers, alu head/intake, running up to 10 psi from twin T25 turbos.
The manfold will be split, 1-2-3 and 4-5-6, each 3 feeding one turbo.

So on to my question. Do you think an internal diameter of 1.5" will be too restrictive on the exhaust?

Anothet option would be using 2" fittings and some 1.5 - 2" reducers at the ports. However this will make the manifold quite wide, probably 7" and may cause clearance problems with the shock tower, bodywork etc?

What do people think would be the best option?

Thanks
Nathan
 
1.5" primaries will work fine! Our original header had that size.
I did end up going to 1 5/8" on our latest header.

Will
 
Use schedule 10 stainless steel butt weld pipe and fittings. They are thinner wall than the conventional schedule 40 or schedule 80 fittings but still strong enough for the purpose. Some dimensions for 1-1/2" fittings.

OD 1.900"
Sch 10 wall thickness: .109" ID: 1.682"
Sch 40 wall thickness: .145" ID: 1.610"
Sch 80 wall thickness: .200" ID: 1.500"

If you do need to move any metal around it's much easier to heat and beat sch. 10 and you get the added benefit of the corrosion resistance of Stainless steel.
 
We used 1 5/8" tubing for ours. If I had to do it again, I'd go with 1 1/2" instead. That would make it a lot easier to get to the bolts. If small blocks can turn 6000rpm through 1 5/8" headers with 30" long tubes, I see no reason why 1 1/2" tubes would be a restriction on a turbo manifold.

As far as dimpling around the bolts, we did a lot of that. We just centered the tube around the port and welded everything except where we needed to make dimples. Then we took a hammer and a rounded punch and pushed the tubes in to clear the bolt holes. The rest of the tube stays nice and round that way.
 
I have a 1959 223ci
I used 1.25â€￾ sch.40 pipe which has an ID of 1.38â€￾ and a OD of 1.660â€￾. I would have liked to use 1.5â€￾ pipe but it was too large for the intake and bolt location. I need to finish tig welding the primaries, mount the turbo flange and cap both ends of the collector pipe( which is 2.5â€￾). I will post a finished turbo header in a few weeks.Here are som pics.

http://farm4.static.flickr.com/3077/316 ... 42ffdb.jpg

http://farm4.static.flickr.com/3268/316 ... e6fc80.jpg

http://farm4.static.flickr.com/3123/316 ... 4eb167.jpg
 
Thanks for the replies guys. Some good looking manifolds there! :)

OK, so the 1.5" primaries will be ok, but what about the main logs? Will they be ok in 1.5" too? I was thinking of stepping up to 2" here?
 
No, you gotta increase the log size.
If you're running twins (3 into one turbo, 3 into the other turbo) you can probably use the 2".

If you're running a single then a 2.5" would be better.

Will
 
OK, thanks.
I'll use 1.5" primaries and a 2" log. I've managed to source some butt weld fittings over here in the UK so i'll give it ago!

I shall try and post some pictures as i go :)

Cheers guys
 
I got my parts for the manifold. I went for 1.5" primaries and 2" log. Now all i have to do is weld it up!

DSC00054.jpg
 
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