It used to be installing an LS motor in a ’55-’57 Chevy required some serious custom fabrication, wiring, and other intense work. Today, that is no longer the case. Thanks to companies like Classic Performance Products (CPP), installing any Gen III or IV small-block (car, truck, or crate variant) is as easy as retrofitting a Gen I Mouse or Rat. In fact, it might be even easier.
Our subject ’55 210 sedan left the factory with the solid lifter 235 I-6 variant and three-speed overdrive transmission. While the car was fun to cruise around in, the inline six’s lack of power was genuinely dangerous when it came to keeping up with or merging into traffic. The owner simply wanted more power—a lot more. When cooling issues with the 235 cropped up that pointed towards a cracked head, the owner knew it was time to do something.
With the plan being to drive the car from Tampa to the Holley LS Fest in Bowling Green, Kentucky, going with an LS engine seemed the logical choice. And it just so happened the owner recently came by a salvaged 5.3L/4L60E combo out of an ’02 Tahoe that would be perfect for the 210. So, we called up CPP and ordered its Tri-Five LS conversion kit, PN 5557LS1-CIK. It has everything, including headers, motor mounts, and transmission crossmember, for the basic installation of an LS engine in a Tri-Five.
For the full install, other parts are necessary. So, we’ll be splitting the install across two stories so we can better cover everything. We’ve got parts from CPP, Be Cool, Flowmaster, Lokar, Painless Performance, Chevrolet Performance Parts, ACCEL, and more to fully install the 5.3L, and we’ll highlight those parts along with part numbers, to give you the best guide possible for this swap. And along the way, we’ll show you a few tricks to make things easier.
You are right, do not know how to make coffee. We will be up, soon.
1. The car’s original 235 six cylinder might have put out 123 horsepower (gross) when new (our ’55 had a three-speed with OD trans), but in 2014 we’re doubtful it put out even 100. Realistically, 123 gross ponies is probably only 80-90 at the wheels, maybe less. Sorry, not in 2014. The owner wanted this car to be a trouble-free, drive anytime cruiser, with power to melt the tires on demand.
2. After pulling the engine and trans, we removed the factory motor mounts to make way for the new mounts in our CPP kit. The first step is to grind the heads off these rivets in the factory frame. The mounting bolts for the new motor mounts will utilize these holes.
3. With the rivets punched out, we used the included hardware to set the new motor mount in place, so we could mark and drill the new holes we’d need in the top of the frame. A strong drill and good, sharp drill bits make this part of the job a lot easier.
4. When installing the driver-side mount, you’ll need to unbolt and move the front brake line out of the way. Once the mount is in place, you can easily secure the line to the frame.
5. For tightening the nuts that hold new mounts in place, you’ll need hands small enough to fit in the factory access holes.
6. And here’s how it looks with everything installed. Even though our CPP kit was specific to an LS engine, these mounts also work for mounting a small-block or big-block Chevy in between your Tri-Five’s framerails.
7. Because we’re going to be running fuel injection, we wanted to upgrade the fuel system in our ’55. CPP offers a stock size and shape tank already modified for an in-tank fuel pump, but we decided to go with CPP’s 25-gallon EFI tank kit, PN 5557AGT-L25, to get more cruise range. After pulling the old tank, we wire brushed the underside of the trunk floor, then hit it with some of Eastwood’s Rust Encapsulator, to seal up the metal and neutralize any corrosion.
8. To make way for the CPP tank, the factory mounting tabs for the gas tank straps have to be cut off the floor.
9. Another modification needed for the bigger tank is the removal of the spare tire well. To cover this hole easily, we used Classic Industries spare tire well delete panel, PN TF400792. Once the well was removed, we set the front mounting bracket for the new tank in place and secured it to the frame with some clamps.
10. The rear mounting flange on the tank is secured to the rearmost frame crossover. These brackets form the top part of the mounting sandwich.
11. With the tank bolted to the front bracket and clamped in place rearward, we marked the frame and drilled the necessary holes for the mounting bolts to go through. Then we bolted it in place.
12. With the rear of the tank secured, we moved back to the front bracket, removed the clamps, and welded the bracket’s mounting tabs to the framerails. There are also provisions to bolt it in place if you so desire.
13. Here’s how the new tank looks once fully in place. An advantage of the CPP tank is it mounts right in the center of the car, instead of being offset in the frame (because of the spare tire well). These means with a full fuel load, the car will have better balance in the rear, equating to better handling, especially for when we eventually hit the autocross course with our 210. After we mocked up the fuel neck, we pulled the tank back out and did some frame clean up and painting.
14. The final step in the tank install is modifying the factory filler neck. The first step is to cut the neck down in length.
15. Using the stainless steel adapter included with the tank kit and a piece of the factory filler neck rubber hose, you make this adapter that easily connects to the new tank’s filler hose. If you don’t want to use this method, you can also weld the adapter to the factory filler neck pipe.
16. With the filler neck modified and given a shot of Eastwood Rust Encapsulator, it’s bolted back in place, and the CPP flex hose connected from it to the new tank.
17. For a fuel filter that would let us keep the factory fuel return line, we grabbed this factory filter (WIX PN 33733), along with Russell fuel adapters 640853 (2), 640863, and 640940, to adapt the filter into the fuel lines we’ll be running.
18. After some trial and error fitment, we decided this was going to be the best place for our fuel pump and filter.
19. Back up front, we temporarily set the engine in place so we could get our Be Cool radiator installed. The first step is cutting these ears off the factory core support. Be Cool’s Extreme Tri Five cooling assembly (radiator, fans, A/C condenser all together) comes with a new core support that bolts right in, and is capable of supporting 1,000 hp.
20. For this application, we went with Be Cool’s Classic 700hp unit. It comes with dual 11-inch electric fans; natural finish recovery tank; and billet radiator cap; all necessary mounting hardware, brackets, and the wiring harness for the electric fans. Since we’re converting to an LS-series engine, the Be Cool unit’s design with both the inlet and outlet necks on the passenger side mean the cooling hoses will be in the same location as a factory LS-equipped vehicle.
21. The Be Cool unit features full aluminum construction, with a cross-flow, dual one-inch core heat exchanger assembly. Combined with the dual electric fans and capacity of the radiator, even on the hottest summer day our ’55 won’t come close to overheating. And when we add air conditioning later on, we can get a matching condenser unit from Be Cool. The unit also features an integrated high-efficiency transmission cooler that we can hook our 4L60E transmission. Because Be Cool radiators feature epoxy free construction, they can be repaired in the case of unforeseen circumstances. Be Cool radiators are guaranteed to lower your coolant temps a minimum of 20 degrees.
22. To clear the inlet and outlet necks of the new radiator, the core support filer panel has to be modified. The first step was marking exactly how big and where the necessary holes need to be.
23. Using a special punch tool, we made these two holes in the passenger side filler panel. Instead of a ragged opening made by a hole saw or other imprecise method, we have two, precise, factory looking holes.
24. With our holes made, the radiator easily slips into place, and there’s enough clearance around the necks that we don’t have to worry about the filler panel rubbing through the aluminum and creating a coolant leak.
25. With the radiator properly located, we could drill the holes in the core support and filler panels for the mounting brackets.
26. Bolted in place, here’s how it looks. Not only will we have plenty of cooling capacity for a wide range of horsepower levels (supporting future engine upgrades) but we can easily add a Be Cool A/C condenser for when we eventually add air conditioning to the ’55. That’s it for part one of this conversion. In part two, we’ll cover installing our new transmission mounts, running fuel lines, and installing the new wiring harness that will control our LS engine. We’ll also cover shifter and throttle control installation. Stay tuned!