In the ’50s and ’60s the Corvette was a high-performance car. By today’s standards that is a very relative term, but in the ’50s even dual exhaust was considered a performance upgrade. Beyond the appearance, there is very little original equipment on our 1960 Corvette. Under the hood you’ll find a W-head 348, just what Chevrolet would have used had they offered a big-block option in 1960. However, we did port and polish the heads; added a mild, hydraulic performance camshaft and fed the beast with “Dual Quad” FAST EFI. So we’re making north of 300 horsepower and to that end we felt a high-performance exhaust system would be mandatory.
When we say high performance, we wanted it to be factory style HiPo, so exhaust manifolds (also gasket matched and ported) mate to dual exhaust constructed from 2 1/4-inch stainless steel exhaust components. We purchased all required components from Summit Racing and found their exhaust kit (PN SUM-670245) to have more than enough pipe and bends to do the entire car, we actually have several bends and pipe left over for our next project. We were also pleasantly surprised by the affordable price.
The original C1 the head pipe, intermediate pipe and muffler inlet were 2 inch while the muffler outlet and tailpipes were 1 7/8, which essentially means the system was 1 7/8 inches. The smaller tailpipes were used to find clearance over the rear axlehousing and around the spare tire well and up into the bumper exhaust outlets. By today’s standards a 1 7/8-inch exhaust looks more like a peashooter than a tailpipe and with our mighty W-motor under the hood we wanted a full flow exhaust system.
Since this was a frame-up build we rebuilt the engine and fabricated custom motor mounts to place the engine in the frame. We also fabricated a crossover pipe that runs in front of the oil sump and fabricated head pipes off the powdercoated exhaust manifolds. It became abundantly clear that running the exhaust through the chassis would be infinitely easier prior to reuniting the body with the chassis. With that thought in mind we fabricated the 2 1/4-inch stainless steel exhaust system and neatly snaked it through the crossmember. This car had a colorful past, last seeing service as a backyard drag car with a 396 stuffed under the hood, this involved serious modification to the front of the crossmember and the unceremonious enlarging of the exhaust opening in the crossmember with an oxyacetylene torch. We spent some time cleaning up the openings with a grinder, burr and hand file and in the end the added space made things easier.
After the pipes exited the crossmember we mounted a set of stainless steel mufflers from Stainless Specialties. We ended the exhaust work at the mufflers since we would have to wait for the body to be on the frame to route the tailpipes. Actually routing the pipes through the crossmember was not terribly difficult. Yes, it is tight on space but with our custom-made hangers it all fit, albeit some pipes had as little as 1/8-inch clearance from the crossmember. However, we also included a flex-coupler just behind the head pipe. These couplers allow the engine to torque without moving the entire exhaust system. With the flex coupler in place we were able to mount the exhaust going through the crossmember and the tailpipes “almost solid,” meaning, yes, we built the hangers to allow some movement but it is also quite solid to prevent the pipes from hitting the chassis or body. Urethane bushings were used throughout the mounting process to eliminate any chance of vibrations being transmitted through the chassis.
With the body back on the frame we set about fabricating the tailpipes. We decided early on that we would not be running tailpipes out through the bumpers. First, we never really liked the original look of a round pipe protruding through the oval bumper port and second we didn’t want the exhaust rusting our beautiful Advanced Plating chrome. We converted the original bumper ports to backup lights and decided to route the tailpipes in a similar manner to the 1961-’62 Corvette.
We are running a Currie 8-inch Ford rear mounted to the stock-style leaf springs with an original style sway bar. While the intermediate pipes going through the crossmember are full-welded, one-piece units we used Summit TorcTite band clamps to connect the mufflers to the intermediate pipes. This proved to be a wise decision as we ended up rotating the mufflers to near vertical under the car. This did two things, it raised the outlet of the muffler so we could go over the axletube of the rearend housing and it also minimized the amount of muffler directly under the floor. By rotating it near vertical only the edge of the muffler is close to the floor, leaving the larger flat sides to dissipate their heat to the sides.
We also used the same clamps to hold the tailpipes to the mufflers. This allowed us to rotate the tailpipe slightly for needed clearance between both the body and the chassis. We fabricated the tailpipe from three pieces and used an expanded end of the bends to make fabrication easier. By using the expanded ends we could rotate the pieces into perfect alignment, then “double-line mark” the two pipes and take them to the bench for a very light tack-weld. Then a second and even third fitting was tested before we removed the pipe and did the final welding on the bench. The finish welding was done with both our Miller 140 MIG welder and our Miller Synchrowave 200 TIG welder using 304 stainless steel rod or wire. The test fittings included making certain both pipes were exactly the same length and exited on the same angle. This is very important so the pipes look balanced and symmetrical when viewing the car from the rear. A word of caution here, if you decide to use a MIG welder to tack the pipes in place always remember to cover things like brake hoses and brake lines and be very aware of where the fuel line and gas tank vent hose is on the car. Safety first; welding spatter can cause fires and damage hoses and brake lines.
It is very tight fitting the 2 1/4-inch pipe through openings designed for the smaller pipe but with careful, patient fabricating it all clears and the tailpipes exit neatly behind the rear tire, looking very “factory” in the process. The finishing touch was wrapping the mufflers with a DEI Muffler Heat Shield Kit and also using their Reflect-A-Gold reflective heat shield on the floor above the mufflers to help prevent heat from migrating into the passenger compartment.
We were extremely pleased with the final results and the tailpipes are perfectly symmetrical when viewing from the rear. As of this writing we have 600 miles on the car and the pipes still fit perfect with no knocking or frame contact anywhere. We really like knowing the pipes are guiding the exhaust fumes out from under the car and away from the body. It also feels good knowing this is a lifetime exhaust system, no worries about rust or rot with our stainless steel exhaust system.
1. We ordered this 304 SS exhaust kit (PN SUM-670245) from Summit Racing. The 2 1/4-inch pipe size will help our 348 W-motor breathe and the stainless steel means this is the last exhaust system this car will ever need, and it’s all polished.
2. We have come a long way in the tailpipe hanger department. Today there’s a vast array of beautiful custom exhaust hangers fabricated in stainless steel with urethane bushings.
3. Not only are the hangers improved, but the clamps that hold the pipe to the hangers are also much improved. We have seen people use hose clamps as hangers, they simply are not up to the task compared to these modern stainless steel units.
4. Old muffler clamps would tighten down and produce a ridge that made separating the pipes nearly impossible. These heavy-duty muffler clamps are used directly over the seam in a pipe and seal perfectly yet allow you to disassemble the pipes if necessary.
5. We took one of our old stainless steel band clamps and drilled a series of holes in it. This piece can hold two pipes together perfectly while you tack-weld through the holes. Then remove the clamp to finish welding.
6. It’s usually important to cut the tubing with square ends. We used a port-a-band for some cuts but generally this cut-off saw works best. It produces a straight cut every time.
7. We routed our 2 1/4-inch tubing through the crossmember in the original frame with little problems. We opened up a couple of the factory crossmember holes for additional clearance but careful fitting permitted the tubing to fit through the factory openings.
8. We built a crossover pipe that ties the two head pipes together and runs forward in front of the oil pan sump, much like factory crossover pipes. There is also room just behind the crossmember for a crossover pipe. It is often easier to use a smaller tubing size for the crossover pipe.
9. This is our crossover pipe, fabricated from 1 1/4-inch tubing we had on hand. It fits well in front of the sump and we fabricated the flanges joining the two pieces. A piece of thin copper sheet was used to form the flange gasket.
10. With the extremely close tolerances on the exhaust tubing as it passes through the frame it became apparent we would need a flex-coupler on each pipe. This allows the engine to have torque movement and also allows us to mount the tailpipes in the crossmember with less flex.
11. We welded the flex coupler just behind the head pipe. You will also notice the welded-in stainless steel bung for our oxygen sensor that sends signals to the FAST EFI.
12. When we reunited the body with the frame we discovered our mufflers were touching the floor. A simple extension was added to the inlet side, moving the mufflers toward the rear of the car.
13. We used a piece of expanded straight pipe and two 45-degree pieces to fabricate the tailpipe. By using the expanded pieces we could slide the pipe in place and rotate all angles until we had clearance in the very tight confines going over the frame.
14. We used jack stands and blocks of wood and metal to locate the tailpipe precisely where we wanted it to exit. There’s a relief built into the wheelwell and we used that to help locate the pipe.
15. After we had the pipe perfectly located, (tack weld and check again before welding) we TIG welded the seams. Here’s a hot tip; use a fine stainless steel wire brush and brush your welds while hot and all the color comes out. Also, have a dedicated SS brush used only on stainless welds.
16. Here’s the completed pipe; it will be joined to the outlet of the muffler with a band clamp. The use of the clamp gives us some final adjustment, and then brackets are made to hold it perfectly in place.
17. We cut off a short piece of a stainless steel universal hanger and simply bent it in a vice. This gave us a stainless bracket with the large hole to facilitate the urethane bushing.
18. The bracket is bolted to the chassis and a heavy-duty clamp holds the pipe in place. We have seen standard hose clamps used and we can tell you they are weak and will fail over time. Use a clamp designed for exhaust work.
19. Looking up under the Currie rear axlehousing, we can see the tailpipe snaking its way into the wheelwell, once again, it is tight but you can fit a larger pipe (we used 2 1/4-inch) in the space.
20. The driver-side pipe is similar in design and yet different. Because the spare tire well is offset there’s more room on the driver side of the car.
21. And here’s the completed exhaust system. We were very happy with the look of the system and it sounds great, hot rod on the outside, quiet enough to talk in the cabin. Clearance for our Inland Empire aluminum driveshaft is closest where the pipes exit the crossmember.
22. We are determined to keep our cabin cool. Of course, Vintage Air has that handled but keeping heat out is still the best approach to keeping an interior cool. To that end we decided to wrap our Stainless Specialties mufflers with a DEI Muffler Shield Kit. This also seemed to quiet the system a bit.
23. Simple stainless steel straps hold the insulating material around the muffler. While the kit we ordered was for one muffler we found the kit handled both of our mufflers with about 10 inches of material left over. Measure twice … cut once.
24. We also ordered both a roll and a sheet of DEI Reflect-A-Gold heat reflective material. This stuff does an amazing job of reflecting heat away from a panel. We used it on the floor to reflect heat away from the forward end of the mufflers.
25. Cutting the muffler wrap is simple and the material is a pleasure to work with. It conforms to the muffler nicely. We wrapped the muffler and held it in place with masking tape while installing the straps, then simply remove the tape.
26. And here’s the final installation, neat, clean and cool. Keeping the tailpipes as close as possible to the center of our Currie 8-inch rear axlehousing gave us more room and less chance of the axlehousing contacting our pipes on a hard bump.
27. The all-important “view from the rear,” we were very pleased to see the pipes peeking out from behind the tire. The original bumper exhaust ports are now backup lights that we custom fabricated.
Photography by the Author