GM 3.4L DOHC V6 LQ1 Description

[chadz34]

Engine Component Description

 

The cylinder block is made of cast iron and has six cylinders arranged in a v shape with three cylinders in each bank. The cylinder banks are set at a 60° angle for each other. The right bank cylinders (1,3,5) are on the cowl side of the engine compartment, and the left bank cylinders (2,4,6,) are on the front side of the vehicle. Four main bearings support the crankshaft which is retained by bearing caps that are machined with the block for proper alignment and clearances.

 

The aluminum cylinder heads have two intake and two exhaust valves for each cylinder. These heads contain pressed-in valve guides and valve seat inserts.

 

The aluminum camshaft carriers each contain one intake and one exhaust camshaft. The actual aluminum in the carrier serves as the camshaft bearing surface. The camshaft thrust plates, which control the camshaft location, are mounted on the rear of the carriers.

 

The crankshaft is cast nodular iron with deep rolled fillets on all six crankpins and all four main journals. Four steel-backed aluminum bearings are used, with the # 3 bearing being the end-thrust bearing.

 

The camshaft drive is a two-stage system. The first stage transfers power from the crankshaft to an intermediate shaft by means of a chain drive. The second stage uses a belt between the intermediate shaft and the individual camshafts. Special care must be taken during handling and storage of the belt to avoid kinks, cuts, etc. which may cause reduced durability. Both chain and belt tension is set and maintained by fully automatic tensioners. Timing must be reset if sprockets are removed from their shafts. Pins or keys are not used to establish camshaft to crankshaft timing.

 

The pistons are cast aluminum with steel struts using two compression rings and one oil control ring. The piston pin is offset 0.7 mm (0.028 in) towards the major thrust side. This allows a gradual change in the thrust pressure against the cylinder wall as the piston travels its path. Pins are chromium steel and have a floating fit in the pistons. They are retained in the connecting rods by a press fit. Connecting rods are made of forged steel. Full pressure lubrication is directed to the connecting rods by drilled oil passages from the adjacent main bearing journal.

 

The 3.4 Liter engine valve train is a direct-acting double overhead camshaft layout. Motion is transmitted from the camshaft lobe thorough the hydraulic lifter directly to the valve tip. The four valve per cylinder/center spark plug layout optimizes RPM capability, chamber air flow as well as combustion characteristics. The system minimizes valve train reciprocating mass and maximizes speed. The camshafts are driven by the intermediate shaft through a cogged belt drive system. The camshafts are not interchangeable. The right (rear) camshafts are shorter than the left (front) camshafts. The spacing of the camshaft lobes is greater on the intake camshafts. The spacing of the camshaft lobes is shorter on the exhaust camshafts.

 

The intake manifold is a three-piece cast aluminum unit. The lower manifold supports the fuel rail with six fuel injectors. The upper manifold and the throttle body adapter support the throttle body.

 

The exhaust manifolds are high silicon moly cast nodular iron.