conrods 340/318?Ar

[Dodgy Dick]

Do 340 Conrods differ from 318 rods?
TKs
R

 

[C Body Bob]

Do 340 Conrods differ from 318 rods?
TKs
R

Yep

 

[Dodgy Dick]

how????

 

[Bighead440]

Not always. I have torn down 318 LA motors in almost every configuration. SOME early 70's seem to have floating-pin OR pressed pin 340/360 rods, and the early ('67-69) red 318's usually have floating 273-style rods. Never say never, because Ma MoPar will surprise you. On big blocks, you will see internally balanced 6-pack rod, steel crank engines in motorhomes, when the 6-pack engines were externally balanced, etc.

 

[C Body Bob]

how????

In a nutshell the early rods (273-318) where bushed & lighter rods. The 340 was non bushed (better longevity) & about 100 ghrams heavier. The early rod is what I like in my street builds. The 340 rod is what I'd use for 6500 & up track duty. Along about 72 or so ALL LA's came with the heavier non bushed rod & it became widely known as the 360 rod as the 340 went away. Then the Magnum rod came out 92 & is the best of both worlds. About 25 ghrams lighter that the "lite" 318 early rod yet stronger than the 340-360 rod. Bobs choice from here on. Polish, magnaflux & shot pean the darn things & spin to 7500. And there are plenty of aftermarket rods available. Most pistons can be used with either. I like KB hyperutectic in street builds. Google is your friend. Read writings from actual engine builders. Casting numbers are on the rod.

 

[Bighead440]

As far as I know, all 340's were the bushed heavy rod, 360 used the same forging with a pressed pin. LA 318's are a crapshoot some years.

 

[max1196]

72 and on 340 rods were press fit, C Body Bob has it explained above.

 

[moper]

This is how I understand it..
Pre-70 318 rods are all floating pin, and thinner/lighter than 340s. '71 and up 318s are pressed pin but the same weight as the earlier rods. Early 318/273 rods can be used in 340s with rebalancing - this was done a lot by budget racers back in the day.
All 340 rods are heavier beam and floating pin. All 340 years will interchange with no machining or balancing Even with the different cranks and pistons used in them.
All 360 rods are lighter than the 340 rod and but pressed pin. 340 rods and 360 rods cannot interchange without machine work and rebalancing.

 

[Dodgy Dick]

Thanks but it would be good if they had id markings to go by? any clues?

 

[moper]

Nope. Part numbers are cast in, but I've never seen something that lists the features of each number. And some models are identical in features and size, yet carry a different part number (supersessions).