In the last month I buildt a couple of turbo manifolds for b16 heads - mostly ramhorn design.
After welding I noticed that the holes for the studs arenīt in the same location than befor welding. So after welding I had to machine the holes to fit correctly.

Yesterday I checked this and noticed that the headflange became smaller while welding.
Befor welding it was 348mm after welding it was 345mm from the left to the right side. So the outer left and the outer right hole also moved roundabout a 1-1.5mm each. Because of this movement the flange doesnīt fit correctly on the studs.

Before welding I mounted the headflange on a very strong and absolutely flat plate(a head dummy) so that it couldnīt warp.

Here is what I uses:
ramhorn design
10mm thick headflange made of 316 stainless
3.2mm thick elbows made of inconel
welds made in 3passes everything mounted on thick "warp prevention plates"
fully backpurged

Anybody with the same experiences?
What do you guys do to make sure that everything fits correctly after welding?

Thanks

 

You are shrinking because you are using a stainless steel flange. Try using mild steel, it does not shrink or warp nearly as much.

Also, try oversizing the bolt holes. If they are a slip fit before welding, they will not fit after welding.

 

how long are you letting it cool down? i leave mine until i can touch them without gloves. i bolt the flange to a 2" thick plate of steel. i'm also using ms and haven't had any problems.

 

I also let it cool down until room temperature. I thought it was a little to thin flange. Maybe I should use a 1/2"thick head flange?

Other thing I thought about was to cnc the flange so much bigger as it will shrinck while welding?

The last thing I thought about was to take mild steele but Iīm a little afraid about corrosion. I know FullRace and some other companys also take mild steel but how does it look after a while?
Does it look rusty? Any pics of a mild steel flange after a year or so?

What do you think?

 

Honestly stainless steel doesn't look too hot after a couple heat cycles. The mild steel will look pretty much the same, unless water actually sits on the flange at times.

I think most people who use stainless do so because of the lower thermal conductivity.

 

if you have exact fit boltholes on stainless flange, when you run it all of your manifold bolts and studs will be sheared off due to stanless steels expansion characteristics.

 

I would try thicker flanges and make an adapter to bolt the flange to while welding.

I use aluminum adapters to try to pull the heat out while welding and faster cool downs