Pontiac Long Tube Headers - Full Of Hot Air!

A used air-gauge (optional, see Time Saving and/or Low-Buck Tips sidebar) and a quick-disconnect airline fitting were prepped by putting teflon tape on the threads. They were then screwed into the tapped holes and tightened with a 9/16-inch wrench.

A new Mr. Gasket collector gasket (PN MRG-1204, $3 each) was purchased and a thin layer of Permatex Sensor-Safe Blue RTV Silicone Gasket Maker (PN 80022, retail $4.99) was applied in a light, even coat on both sides. The gasket was then hung up and left to dry overnight.

The collector block-off plate was installed by lining up the gasket with the holes in the header collector, sliding in three 3/8x1-inch long bolts, adding lock washers and nuts, and tightening with a 9/16-inch swivel wrench.

An air line was attached to the fitting on the collector block-off plate, and the air pressure was regulated at the compressor to approximately 15 psi. The entire header was then inspected for any leaks.

A MAPP gas torch is hot enough to sufficiently heat the metal (propane is not) for this repair. Heating began at the top of the dent until it was red hot and worked down. Since nothing was happening with 15 psi of air pressure, it was increased in measured increments until the dent pushed its way out at 50 psi. The header was allowed to cool for a minute before a flapper wheel was used to clean up the repaired area. After paint was applied, it highlighted a small area that still had a ding, so the process was repeated a second time until we were satisfied that the pipe had conformed to the original shape. Here's what it looked like after the second try. Compare it to the second photo in the story.

This dent required 45 psi to make it pop out. Although the original area heated isn't perfect, the metal will be heated from the edges moving slowly inward, and once complete, the entire crease on the front tube should be removed.

For the driver's side repair, even though the MAPP torch would have worked, since MAPP gas ignites at a slightly cooler temperature versus Acetylene (5,301 degrees Fahrenheit versus 5,721 degrees), for this more difficult repair, a traditional acetylene torch was used to heat the area. Although it would be preferable to use a tip designed for heating rather than welding, adjusting the torch itself to provide less heat also works.

Note how the dent and creases are being pushed out as the heat is applied. Rather than apply heat directly to a crease, which may end up creating a rupture, the heat is applied on top or below so the crease can slowly roll its way out.

Work continued until the majority of the creases had been removed, and then as luck would have it, the bottom-most crease had a single area, which was so thin that a tiny bit too much heat combined with the higher air pressure resulted in the metal rupturing. Note that this shot was taken immediately after the metal blew through. The hole will now require a patch weld. If this is beyond your skill set, a local shop should be able to handle the job.

The hole was then welded up with the torch and welding stick. Once satisfied that the weld was good, the extra welding slag around the hole was ground down. Although this looks a bit rough, after the damaged area was dressed with a flapper wheel, the majority of grinding marks came out and the header was ready for paint. From a non-scientific point of view, the header was at least 95-plus percent back to its original shape, though it didn't rate quite that high on the beauty scale. A repaint will improve its cosmetics, but more importantly, the header will once again flow as it should for a fraction of the cost of replacing it.

If you have dents to repair in both headers, another method is to remove them and then bolt them together using a piece of plywood with the vinyl sheets on either side to isolate the headers from each other. It simply saves the effort of moving the primary side block off plate from one header to the other. However, bolting the two headers together took a bit longer than using the single plywood plate, as the bolts on two of the header flanges were very difficult to install nuts on. Ultimately we had to use 2-inch bolts and two 2-inch sections of 3/8-inch threaded rod (all-thread) and grind down a thin nut before both headers could be joined.