By: Larrowe & Ronnie Cox

One of the simplest methods of improving the overall performance of 1937-51 Chevrolet passenger and trucks is with the installation of a 55-63 Chevy 235-261 six. Not only does the increased displacement enhance performance, but the later engines are a far better design! The 235-cubic-inch inliner made its debut in trucks in 1941 and in passenger cars in 1950 (available only in Powerglide automatic-equipped DeLuxe model cars). The 235 offered improved performance over its 216-cubic inch predecessor, but it still had a number of shortcomings; namely the splash oiling system used to lubricate the rod bearings.

For 1953, Chevrolet introduced an improved version of its venerable six again in Powerglide-equipped cars and featured pressure-lubricated rod bearings. Beginning in 1954, all Chevrolets featured full pressure oiling; this significant change improved the inline engine dramatically. Obviously, swapping one of these engines into an earlier car is a desirable retrofit. But '53 Powerglide and '54 full pressure aren't as easy to come by as they once were, making the more plentiful '55-'63 engines an excellent choice for such swaps. With the same dimensions as the splash system the later engine is a simple and effective up date.

A simple swap for '37-51's

The '37-51 cars all used the same basic engine mounts, which are the rubber biscuit type. Two are used, one on each side of the motor plate. These mounts are also used on the 1935 Master, '36 Master and Standard, as well as all 1937-51 passenger cars and sedan deliveries.

The first step toward improving performance and reliability for these early cars is yanking the original 216 or 15 bolt-head 235 out of the engine compartment.

Once the engine is out ( a process made much easier by removing the sheetmetal from the firewall forward), remove the motor mount plate from the block. To do this, the vibration damper must first be taken off the end of the crankshaft.

Next, remove the oil pan and the two screws from behind the front main cap that secure the timing cover from the inside. Now remove the four bolts and two studs from the rocker assembly and lift it off as a unit. Older models have the oiling tube attached with a screw-on fitting, so loosen it. Later models fit the tubing into a hole in the head. Set the assembly into an overturned valve cover so the springs don't push the rocker arms off the shaft. Punch 12 holes into a cardboard box and number them 1-12. Remove the pushrods and put them in the cardboard in order. Use an egg carton to hold the lifters in the same manner.

The crankshaft can now be turned, either by prying against the teeth on the flywheel or turning it with a special socket that fits over the end of the crankshaft, until the two holes in the camshaft timing gear line up with the two screws in the retainer. These screws are best removed by an impact driver. Pull the cam gear forward and remove the shaft. With the camshaft out, three flathead screws will be visible . Remove the screws and the remaining hex-head screws that retain the plate with the impact driver used earlier. (If the engine is a 37-41, the crankshaft gear must also be removed to get the plate off.) Tap the plate lightly to separate it from the block.

Use the identical procedure to remove the motor plate from the 235/261 to be installed. Install the mounting plate from the old engine on the new one. For high performance application (ease of changing the cam) we suggest you at this time drill the tapped 5/16-inch holes in the timing cover all the way through and tap thread to 3/8 coarse, then install studs. Now you can get the timing cover off without removing the pan!

Install a new seal in the timing cover and slide into place, using the crankshaft socket to center the seal on the shaft then tighten the attaching screws and nuts on the new studs. If you plan to use the wide V- belt the 216 vibration damper and pulley may be used. Remove the pulley from the 216 water pump and press it on the late pump until the belt groove lines up with those in the vibration damper and generator (this operation requires a 10 ton press), then cut off the excess shaft. To make things easy, the Stovebolt Engine Company has these modified pumps in stock. Install the original generator or the wide groove pulley on an alternator. Cast and polished alternator brackets are also available from the Stovebolt Engine Company.

If the late narrow belt is desired, use the vibration damper off the later engine with the water pump pulley from the 53-54 Chevy, Stovebolt also has pumps available for this combination. Use an adapter in the late model head's temperature sender so the early temperature gauge capillary tube can be installed. Install the flywheel and bellhousing from the old engine, along with the original starter and clutch. Now the engine is ready to go back in the car. If a 261 is being installed, make sure a oil filter is used. The 261 is a full flow system on the later models, and no oil pressure will be the result if the oil line to the filter is disconnected.

Jimmies for early Chevys

Interestingly, the procedure outlined can be used to install a GMC 228-248-270-302 in a '36 Master or Standard passenger car by using a '37-51 passenger car motor mount plate. Use the water pump and the vibration damper from a '37-40 Chevrolet, along with the bellhousing, transmission and starter from a '37-39 Chevy car. When using a GMC with a 4 bolt crankshaft flange, use a '37-39 Chjevy truck flywheel for the 9 bolt heavy duty clutch. For the late GMC's with a 6 bolt crank flanges, use the GMC flywheel with a heavy duty passenger car clutch. NOTE: The '37-39 bellhousings will only accommodate a 10-inch clutch.

Late Sixes for '52-54 Chevys

To install a late 235-261 in a '52-54 Chevrolet passenger car, there are two methods to consider. The first is to locate the holes for the late front motor mount in the IFS crossmember (still called knee action by Chevrolet until 1954 ). The holes have to be drilled in the correct places. On the 1952 models, there are flat stops in the right place, but on the 53-54 models there are no indications of where they should be, so you will have to get the measurements from a 49-51 and copy them. Then install a 37-51 passenger car front plate on the late 235-261 engine.

The second way to accomplish this swap is to buy custom mounts from Stovebolt Engine Company The kits come with frame and engine mounts and are a bolt on. The stock '52-54 motor mount towers are riveted to the frame and have to be cut off, as they will obstruct our frame brackets. Once engine mounts are attached lower engine into position, bolt down the transmission rear mount. Then locate the frame brackets. Drill frame holes at this time and bolt in place. The Stovebolt Engine Company motor mount kit is also of value when installing a Stovebolt automatic transmission adapter behind a 235-261 because it shortens the spread to the tail shaft of the transmission.