Chrysler / Dodge 1955 engine

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In line L-head engines. This section covers the Chrysler-built L-head in line engines. The information contained in this section is typical for these types.

A section of the 6 cylinder side valve Dodge engine. Some models of De Soto, Plymouth and Chrysler are powered with a similar engine.

Cylinderhead. Always use a new gasket when installing the cylinderhead. The threads of the capscrews should be coated with sealer except the three screws that lead into the intake manifold ports (to prevent sealer to be drawn into the carburetor or valves). Capscrews should be tightened in the sequence shown left to a torque of 35 pound-foot the first time around. Then repeat the procedure and tighten to 65-70 pound-foot. Run engine until all parts are normalized and then re-torque.

Oil pan and gaskets. Left the oil pan with the four gaskets installed. Before installing, clean pan and pan rail of block thoroughly and use new gaskets. Gaskets are fitted into fold over slots of the oil pan to secure a better fit. Right and left side gaskets may be installed with sealing compound applied on both sides. The end gaskets should be installed so that the ends stick above the pan at least 1/8 in. This will form a better seal as gasket is compressed.

Cylinderblock. When the engine is torn down examine the cylinders for wear and scores. Small scuff marks and scratches can be removed with a hone. Rebore cylinderblock if the bores are more than .005 in. out of round or if taper is more than .020 in. A slightly scored or worn block may be honed and .005 in. oversize pistons fitted. After honing, clean cylinder walls with soap and water and a brush, then wipe dry with clean cloth. Lubricate pistons and rings before installing in the cylinderblock.

Core hole plugs. To remove a core hole plug (Welch plug) drive a center punch or chisel in the center of the plug and pry out. Remove rust and dirt and use sealing compound on the plug seat before installing a new plug. Install with convex side out then expand plug by flattening it with a blunt drift and hammer.

Pistons and pins. A cam-ground U slot type piston is used in the Plymouth engine. The piston is also slightly tapered, the largest measurement being at the bottom of the skirt on the thrust sides. The cylinder top ridge must be removed (with a ridge reamer) before the piston and rod assembly can be taken out of the bore. For rebored blocks .005, .020, .030, .040, and .060 in. oversizes are available.

Piston rings. Piston ring end gaps should be .010-020 in. Measure gap with ring about 2 inches from the bottom of cylinder and make sure it is square in the cylinder bore. When a chrome plated upper compression ring is installed it is best to remove cylinder glaze with a hone. This will give quicker ring seating.

Crankshaft. The radius fillets as indicated should be strictly adhered to whenever the crankshaft is being reground. A puller must be used to remove the hub and sprocket. Punch-mark No. 2 and 3 bearing caps so that they may be reinstalled in the same position and location. The caps may break when installed the wrong way around.

When the crankshaft is fitted to the block, use new gaskets and oil seals. Lubricate the bearings before installing crankshaft. Bearing caps should be tightened to 80-85 pound foot torque. Crankshaft end thrust is taken by the rear bearing. End play should be between .003 to.007 in.

Install oil line from pump outlet to cylinder block connection and oil pump suction pipe and screen assembly. Install timing case cover back plate, timing chain and camshaft gear, timing case cover and engine front support. Make sure the seal is properly centered in the timing case cover. Install oil slinger (if so equipped), pulley, clutch cover pressure plate assembly and disc oil pan, clutch housing pan and transmission.

Main bearings. When the main bearings have to be replaced look for a stamped number on the center weight. An M or an R followed by a number indicates that a main or connecting rod bearing has a thicker wall bearing. For example M2 and R1 indicate that .001 in. thicker shells are used on No. 2 main bearing and No. I connecting rod bearing. These bearings are available in the following sizes: .001, .002, .003, .010 in., .012 in., .020 in. for mains and con rods. .030 and .040 in. inserts are available for mains only.

Main bearing clearance is usually between .001 and .0015 in. When the engine is not down a fair indication of the clearance can be obtained by the shim stock method or the plastigage method.

Note: When installing a new rear main bearing in Hy-Drive equipped engines, use a lower insert that does not have the oil drain back groove and hole in the white metal surface.

If inspection indicates that the upper oil seal must be replaced, remove the flywheel.

The upper oil seal is easily removed once the lower seal has been taken out. Push one corner until the other end protrudes after which it can be gripped with pliers and taken out. Before installing a new seal coat the contacting lip with grease, push into place with a rolling motion.

Due to constructional changes in the 1953 model P 24 Plymouth engines the cylinder block, crankshaft, rear main bearing oil seal and cap gaskets are not interchangeable with engines built prior to 1953.

Camshaft and bearing. Removal of the camshaft necessitates removal of the cylinderhead, timing case cover, camshaft sprocket, timing chain and fuel pump. If the valves are not going to be removed hold them up by inserting wooden wedges under each valve head as shown. Lift valve lifters with clothes pins as shown. Remove thrust plate bolts and rotate camshaft while pulling it out. Press off thrust plate and collar in arbor press. Camshaft end play is measured. It should be .002-.006 in. A special tool (C-536) is used to remove and install camshaft bearings. When installing the new bushes make sure the oil hole is in line with the passages in the block.

Valves. The valves can be removed after the cylinderhead and the tappet cover have been taken off. Whenever the valves are serviced, also check the following parts in the valve train: valves, seats, or inserts, guides, springs, tappets, tappet bores. If the old valves and guides are being used again place them in a valve board so that they may be returned to the original positions. Remove all carbon from cylinderhead, piston tops, valves, valve ports. The valve stem clearance in the guide can be measured with a ball or plug gauge or with a dial indicator. Valves that are cracked, burned or warped should be replaced. Reconditioning of valves and seats should be done with accurate equipment. It is important that the valve guides are true and clean and the pilot should be a good snug fit in the guide. Keep seat width between 1/16-1/32 in. A valve should be discarded when less than 1/32 in. is left on the valve head margin after cleaning up on the grinder. The valves and seats should be lightly lapped together. When the lapping is completed make sure that all the compound is removed. Oil valve stem to provide initial lubrication.

Exhaust valve inserts. Inserts that are cracked, burned or pitted should be replaced. Old inserts can be removed with a special tool (C-732). If insert is loose in the block install a .010 in. oversize insert. The counterbore should be bored .002-.004 in. smaller than the insert and the same amount deeper than the height of the insert. The inserts should be chilled in dry ice to obtain maximum contraction.

Valve guides. Replacement guides are available with undersize bores which can be reamed to fit. Stem to guide clearance limits are: .001-.003 in. intake, and .003-005. in. exhaust. The intake valve guides should be installed with the counterbored end down. The exhaust guides should be installed with the counterbored ends up. This provides better heat shielding. The guides should be driven into full depth 7/8 in. below the cylinder block top edge.