Once the racing bug got us, we couldn’t help but find out just how fast we could make this box truck run. It was obvious and easily agreed upon that a compound turbo setup had to be fabricated and tested over the winter of 2016 to be ready for summer of 2017. Rather than buying a newer, better turbo we decided an older Volvo semi-truck turbo, a rotomaster tv7701 turbo would have to do. It is a 65x94 compressor wheel and should easily flow enough air for the little 4bt. It has a t6 exhaust flange with a non wastegated housing. After another trip to the local junk yard we acquired all of the intercooler pipes, boots and exhaust pipe we were going to need.
We grabbed the exhaust manifold off of our chicken truck parts tuck in woods, cut the 2 exhaust ports of each end and welded the ends shut to make a makeshift exhaust manifold for the 4bt.
cut exhaust manifold.jpg
We then began to fabricate the down pipe from the high pressure turbo to the atmospheric turbo. We used some scrap ¼ steel we had laying around and a 3in 90 to route the exhaust into the rotomaster. With our limited tooling we had to drill a 3in hole in the plate steel and weld the downpipe into it in order to make a t6 flange that would bolt to the rotomaster. This is of course not ideal for good exhaust flow but would have to do for the time being.
drilling hole for down pipe.jpg
down pipe.jpg
After that we fabricated a bracket to hold the rotomaster in place.
bottom turbo mount.jpg
With the turbos finally mounted we began to fabricate all of the intercooler piping that would be needed.
small turbo mounted on cut 6bt manifold.jpg
turbos mounted on motor.jpg
piped fitted up on motor.jpg
piped fitted up on motor 3.jpg
turbos mounted on motor 2.jpg
front of engine.jpg
We also had to redo the exhaust. We were wanting to run it up through the hood but weren’t able to due to the way the hood comes up. Following that we decided to run it out the side of the truck with some 4in exhaust.
exhaust 2.jpg
For the oiling we picked up a supply hose from pioneer rubber and gasket down in Atlanta and decided to run the turbo drains together and back into the stock turbo drain return. This is of course frowned upon as it is possible for the drains to backup and push back up into the bottom turbo but we went ahead and figured we try it and see what happens. At this point we wired the waste gate on the WH1C shut due to the limited amount of space we had between the 2 turbos. We then got a PDD performer air filter and threw a 6bt harmonic balancer on the motor since we had one laying around.
Once it was all together and running we took it for a quick test drive. Surprisingly it easily boosted over 80 psi and not surprisingly blew the stock head gasket even with the bolts re-torqued to 145 ft/lbs.