LA 318: Information Compilation

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LA 318 Cylinder Heads
There is a large list of LA 318 cylinder heads in How To Hot Rod Small Block Mopar Engines, covering 1967-1987.  The W-2 (P3870812) is a cylinder head that was introduced in 1976 for racing purposes, but never used in production; an Econo W-2 (P4120043) exists as well.  The best, and maybe only, aftermarket LA 318 cylinder head is the Edelbrock Performer.  The maximum that LA engine cylinder heads can be milled is 0.060”.

LA 318 Exhaust
The exhaust manifolds are notoriously restrictive.  Switching to headers significantly adds power and noise, but reduces durability and drivability, especially in colder climates.  The LA 318 came almost exclusively with single exhaust.  Street header pipe diameter should be somewhere around 1.75”, and should be used with an H-pipe exhaust, which reduces exhaust noise.  The “H” should be rearward of the transmission mount and forward of the front U-joint.  The collectors of the street headers should be 2 ½”-3” maximum.

LA 318 Firing Order
1-8-4-3-6-5-7-2

LA 318 Flex Plates
From 1967-1977, there was Part Numbers (PN) 2400885 and 2204768, for a 10.75” and 11.75” torque converter, respectively.  I do not have information on flex plates from 1978-1991.

LA 318 Flywheel
The flywheel from 1967-1986 was Part Number (PN) 2264597, with a 10.5” clutch size and neutral balance.  I do not have information on flywheels from 1987-1991.

LA 318 Ignition
The LA engine was the first to convert from a point-based distributor to an electronic ignition in 1971-1973 (sources vary).  In the mid-1970’s, Chrysler introduced the “Lean Burn” system in both its LA and B engines.  This was the first of the computer-controlled ignitions.  Popular aftermarket ignitions have been Mallory and Accel, and these have been displaced largely by MSD.

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LA 318 Intake Manifolds
There is a large list of LA 318 intake manifolds in How To Hot Rod Small Block Mopar Engines, covering 1967-1986.

LA 318 Oil
A rebuilt engine should be broken in with 20W-50 mineral oil, such as Valvoline, and a camshaft additive should be used at first.  Once broken in, it may be argued that it is best to switch to 10W-30 synthetic, such as Royal Purple, as long as engine clearances aren’t too high, which would cause the oil pressure to be too low.  A zinc-based additive should be added to preserve the camshaft, even though it is asserted in How To Rebuild Small-Block Mopar Engines that additives are unnecessary because modern oil has all necessary additives already.  Don’t take that chance with your camshaft.  Numerous articles declare synthetic to be superior oil (less friction is better for the engine, producing more horsepower, etc.), but caution it should be changed at the same frequency as mineral oil.  For example, in the referenced Mopar Muscle magazine article, peak horsepower increased by 9 from 385 to 394 by switching from 20W-50 mineral oil to 10W-30 synthetic Royal Purple oil.

LA 318 Oil Pan
The factory oil pan holds 4-5 quarts, which is adequate for the street, but not large enough for racing.

LA 318 Oil Pressure
As a general rule of thumb, 10 PSI of oil pressure is required for each 1,000 RPM that the engine turns.  This means that 30 PSI is needed to go 3,000 RPM.  These numbers are based on a hot engine with the oil up to the operating temperature.  The LA engine does not need as much oil pressure as some other engines, so it can be slightly under these numbers and still be okay.

LA 318 Oil Pump
The oil pump is located in the oil pan, bolted to the block in the area of the #5 main.  It is popular to change to the high-volume oil pump for higher performance, but the stock relief spring should be changed as well.

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LA 318 Pistons
All LA 318 pistons are cast aluminum.  The stock piston pin diameter is 0.9842” with a length of 2.99”-3.00”, weighing 154.6 grams.  In 1967, there was Part Number (PN) 2808405, weighing approximately 592 grams, and with a pin height of 1.75”.  In 1968-1969, there was PN 3004509, 592 g., and 1.77”.  In 1970-1972, there was PN 3420222, 592 g., and 1.74”.  In 1973-1984, there was PN 3685751, 594 g., and 1.74”.  In 1985-1986, there was PN 4342772, 594 g., and 1.76”.  I do not have information on pistons from 1987-1991.  In 3 articles in different magazines, Steve Dulcich uses Keith Black KB167 hypereutectic pistons for performance 318 builds.  There is also a forged version in the same compression range: KB844.

LA 318 Pushrods
All LA 318 pushrods were 0.28” in diameter and hydraulic in style.  In 1967, there was Part Number (PN) 2532152, which was 7.5” in length.  In 1968-1974, there was PN 2899561 at 7.5”.  In 1975-1977, there was PN 3780148 at 7.5”.  In 1978-1986, there was PN 4095291 at 7.515”.  In 1985-1986, there was PN 4323205 at 6.766”, which was for a roller set-up.

LA 318 Rings
All LA 318 factory rings are 5/64”, and moly rings of this size are most suitable for the street.  1/16” rings are more appropriate for performance engines, and seal well at both low and high engine speeds.

LA 318 Rocker Arms
All LA 318 rocker arms were of the stamped style (as opposed to adjustable).  In 1967, there was Part Number (PN) 2536145-6.  In 1968-1973, there was PN 3004716-7.  In 1974-1978, there was PN 3418424-5.  I do not have information on rocker arms from 1979-1991.

LA 318 Rocker Shafts
From 1967-1986, there was Part Number (PN) 2532149.  I do not have information on rocker shafts from 1987-1991.

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LA 318 Spark Plug Gap
The spark plug gap ranges between 0.035”-0.060”.

LA 318 Valves, Exhaust
In 1967-1974, there was Part Number (PN) 2465339 at 1.5” diameter.  In 1975-1978, there was PN 3830705 at 1.5”.  In 1979-1986, there was PN 4100387 at 1.5”.  In 1978-1986, there was PN 4100632 for a 4-barrel, at 1.6”.  I do not have information on exhaust valves from 1987-1991.

LA 318 Valves, Intake
In 1967-1986, there was Part Number (PN) 2465335 at 1.75” diameter.  In 1978-1986, there was PN 3683801 for a 4-barrel, at 1.88”.  I do not have information on intake valves from 1987-1991.

LA 318 VIN
Each VIN from 1968 to 1980 had 13 digits.  The 5th digit indicates engine displacement.  This may be a “G”, indicating a 318 two-barrel from 1967-1980, or “H”, indicating a 318 four-barrel from 1978-1980.  I do not have information on the more recent 17-digit VIN’s newer than 1980.

LA 318 Vibration Dampers (Harmonic Balancers)
Except for 1967, all LA 318 vibration dampers are cast, as opposed to forged.  In 1967, there was Part Number (PN) 2658459.  In 1968-1969, there was PN 2658458.  In 1970-1971, there was PN 2951673.  In 1972-1974, there was PN 3614369.  In 1975-1977, there was a “Lean Burn” PN 3830481.  In 1976-1977, there was PN 3614369.  In 1978, there was PN 3830481.  In 1979-1980, there was PN 4095633.  In 1981-1986, there was PN 4173443.  I do not have information on vibration dampers from 1987-1991.

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Performance Packages for the LA 318
The following packages (Stage I – VI) have been copied from How To Hot Rod Small Block Mopar Engines.

Stage I
Cylinder Heads: Stock
Valves: Stock 1.74” Intake and 1.50” Exhaust
Compression Ratio: 8.0:1 with unleaded gas
Exhaust System: Stock manifolds, dual exhaust
Carburetion: Big 2-barrel or small 4-barrel
Intake Manifold: Stock cast iron
Ignition: Stock electric
Camshaft: 0.400”-0.420” valve lift, 240-250 adv. duration, 18-24 degree overlap, hydraulic
Special Applications: None.  Too mild.
Estimated Bracket Ό-mile E.T.: 16 seconds

Stage II
Cylinder Heads: Stock
Valves: Stock
Compression Ratio: 8.5:1 with unleaded gas
Exhaust System: Stock manifolds, dual exhaust
Carburetion: Small 4-barrel
Intake Manifold: Stock cast iron
Ignition: Stock electric
Camshaft: 0.420”-0.435” valve lift, 255-260 adv. duration, 30-35 degree overlap, hydraulic
Estimated Bracket Ό-mile E.T.: 15 seconds

Stage III
Cylinder Heads: Stock
Valves: Stock 1.74” and 1.50” back-cut
Compression Ratio: 9.0:1
Exhaust System: 340 manifolds, dual exhaust
Carburetion: Carter TQ or Holley spread-bore
Intake Manifold: Stock 318-340-360, cast iron TQ
Ignition: High-performance electronic ignition with vac. advance
Camshaft: 0.435”-0.455” valve lift, 264-272 adv. duration, 40-50 degree overlap, hydraulic
Estimated Bracket Ό-mile E.T.: 14 seconds

Stage IV
Cylinder Heads: 360
Valves: 1.88” and 1.60” with bracket valve job
Compression Ratio: 9.5:1 with unleaded premium gas
Exhaust System: Street headers
Carburetion: Carter TQ or Holley spread-bore
Intake Manifold: Holley single-plane Dominator
Ignition: High-performance electronic with race coil
Camshaft: 0.470”-0.485” valve lift, 280-285 (285-292 with manual transmission) adv. duration, 60-70 degree overlap, hydraulic
Estimated Bracket Ό-mile E.T.: 13 seconds

Stage V
Cylinder Heads: Ported 360
Valves: 1.88” to 1.60” with bracket valve job
Compression Ratio: 9.5:1 with unleaded premium gas
Exhaust System: Race headers
Carburetion: 750 CFM Holley
Intake Manifold: Holley single-plane
Ignition: High-performance electronic with race coil
Camshaft: 0.500”-0.530” valve lift, 280-290 (290-300 with manual transmission) adv. duration, 55-70 degree overlap, mechanical
Estimated Bracket Ό-mile E.T.: 12 seconds

Stage VI
Cylinder Heads: W-2 Econo
Valves: 2.02” and 1.60”
Compression Ratio: 11:1 with race gas
Exhaust System: Race headers
Carburetion: 750 CFM Holley
Intake Manifold: Holley single-plane
Ignition: Race electronic
Camshaft: 0.575”-0.600” valve lift, 290-300 (300-315 with manual transmission) adv. duration
Estimated Bracket Ό-mile E.T.: 11 seconds

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