Headers
Been a while since we posted, but work has not stopped. This is a project we completed several months ago.
When we installed the headers the first time and snugged them up everything seemed tight. But when the engine was fired up it sounded like there was an exhaust leak – a bit more backfiring, complete with flames. We discovered slight leaks on almost all the cylinders. We found that the AFR heads are not tapped as deep as the Dart heads used on the previous engine. The exhaust system was dismantled, mating surfaces cleaned, and reassembled. We used copper gaskets and Permatex Copper Coat on both sides of the gasket, letting it set up a bit, installing it, then tightening it down after it set up overnight. And this time we filed down the ends of the ARP header bolts shortening them slightly and added washers (used with ARP header bolts) which solved the problem.
To connect the collectors to the headers on one side and tail pipes on the other, stainless steel socket head bolts and nuts were used. Once in place the bolts were tightened to pull the sections together, then loosened about a turn. A second nut was then added and tightened. Loosening the nut a turn provides room for expansion.
When studying photos of different original GT40s one can see that the exhaust pipes emerge from the square opening in the center of the rear of the clip at different points and varying angles. Which leads the following ‘adjustment.’
Before assembling the exhaust system we did something else. Recall the top most header just kissed the underside of the clip, which led to the addition of a shield to protect the clip detailed in a prior post. That works just fine, but adding a bit of space between the header and the clip was still desired. Before removing the headers from the prior engine a two foot section of exhaust pipe was slid over the end of each of the eight pipes and pushed downward, bending the headers a bit. This would probably be much easier on new pipes that had not been 'heat treated' with a few thousand miles driving. But it did work. This adjustment required that the support bracket mounted on the transmission be modified by lowering the resting point of the mufflers about an inch. The tail pipes emerge from the rear of the clip at the lower end of the opening rather than centered, but we don’t consider that a problem since once can see variations including our location. This helped add a bit of clearance between the clip and the header.
Very nice Chuck, was wondering when you were going to paint.
