Stub Pipes, Fitment issues Options

[ChrisFoley]

Instead of continuing to hijack Rick's topic I decided to start another regarding the European Racing Stub Pipes.

I had so much trouble removing the one stub pipe from the engine I haven't seen the other three yet. Are all 4 stubbies identical in a set from European Racing?
#2&3 exhaust ports are different from #1&4 on Type IV heads. The studs on 1&4 are at a 5 degree angle relative to the axis of the port. The studs on 2&3 are in line with the axis of the oval port. If all 4 stub pipes are identical this exacerbates fitment issues when the stub is a tight fit. A stub made of 1 5/8"x.065 tube, swaged to the port shape is a very tight fit - to the point of being an interference fit.
After ovalizing the 1 5/8"" tube it is very close to the studs, leaving no room for a 12mm socket to fit onto the nuts that hold the stub in place. Only a thin socket, or one that has the OD ground way down will work.
Using a 1 5/8"" tube creates a huge step at the port face. Since the stub is squeezed excessively where it goes past the pushrod tubes there will be a small expansion chamber formed in between. Match porting the head to the stub doesn't help because the shape doesn't create a smooth transition to the header.


People wonder why my systems are so expensive. NONE of these issues exist with my stub pipes. A set of my stubbies has two different shapes - straight and 5 degree offset. This takes the port differences into account. All the stub tubes pass through the flange so a better seal is formed with the header, even without any gasket. All three sizes I make are formed from 1 1/2" OD tube:

The Stock stubbies are .095wall DOM steel. The ID after swaging is still larger than the stock port, allowing a small amount of match porting if desired. 2 small steps are much better for exhaust flow than one large step. The 1 1/2" tube doesn't have to be squeezed at the pushrod tubes at all, therefore the smooth shape is much better for flow. The heavy wall tube is better for resistance to cracking and overall longevity. It won't cut into the copper gasket, which would cause the stub to loosen up over time.
My Improved Stubbies are 1 1/2"x.065wall stainless. They are smoothly tapered to match the 1 5/8" header at the flange end so if match porting is done there is no step at all. No dimples in the stub are required to get past the pushrod tubes, although I do dimple the pushrod tubes to make sure no contact exists between them. If the pushrod tube is in hard contact with the stub it will cause premature failure of the o-rings. The header flange is step cut so the end of the stub tube mates tightly inside the flange. The flanges do not create the seal surface.

My Modified stubbies are made to match the 1 3/4" header. In addition to the features of the Improved stubs they are slightly offset towards the outside edge of the port. It is possible to match port to a straighter shape which further improves the exhaust flow as it exits the head. Creating a smooth taper from 1 1/2" tube up to 1 3/4" OD is a difficult feat. When the mandrel is released from inside the tube it makes quite a BANG. The stubs are so close to the outer stud that I include a special flanged nut with a 10mm head so a socket can still be used. A small dimple is required to clear two of the pushrod tubes. I do this with a mandrel inside the tube so the dimple is precise and smooth. It causes no restriction to exhaust flow.

I realize that many people won't spend the money for these features, especially since most headers are an improvement over a stock exhaust. But if you want to get everything possible from your engine it is well worth the expense. I put a great deal of effort into making sure my parts are easy to install, last a long time and perform as expected.

A properly built exhaust system is as important as a properly tuned induction system. My header systems actually help an engine run more smoothly than any other exhaust, even improving fuel economy. I stand by this statement 100%.

[Brad Roberts]

Yes Mike I marked them. I have fought and fought to make sure they all stay marked.. When the coater gets them.. I have to make sure he marks them also.. otherwise you sit there doing the trial/and error method.

B