6-Pack Rods on 1969???

Did the 1969 A-12 6-pack cars have the 6-Pack rods? Or they came out in 70?

From what I understand the 69 440 six packs have the smaller LY rods, just like rs23u1g says. I believe the larger "6-pack" rods came on 70-71 six pack AND 70-73 HP 4bbl. 440's

The 69 A12’s came with LY Rods. (The A12’s also had standard 440 nylon cam timing gears in case you were wondering). You can use the heavier 70 sixpack rods but you have to add a lot of weight to balance the crank and reciprocating mass. The LY rods are fine unless you are building a monster motor. You would be better off buying lighter and stronger aftermarket rods than going with the heavier 70 rods.

You know, I've had "big rod" & "small rod" cranks side by side & they sure look the same. I "thought" all the extra weight for balancing the big rods was in the harmonic balancer + flywheel/torque converter???

It is. The big rod motors are "externally" balanced

If you are working on a 1969 A12, I assume you would not want to externally balance it.

How does one explain the 440 motor home engines that have the big rods (6 pack?) and a normal small steel crank type balancer? I have at least 2 of them.

http://www.440source.com/dampers.htm

OK, thanks for the link, lots of good info there
But, if I understand it correctly, it states:



So, I still don't understand, UNLESS maybe the reduced weight of the pistons ( due to a shorter distance from pin cl to top to reduce compression ?) offset the weight of the rod?

jess

WOW!....JT & 6pack this is new information for me. What I'm getting from all this is confusing me.

1. I have a '73 big-rod motor in my car right now with modified TRW pistons.
a. I remember buying the short block without a balancer
b. I bought a balancer WITH the offset weight and put it on this motor
c. I recall "something" about crank pulley bolt holes not lining up
d. I balanced the motor, so regardless I should be OK
e. My engine is a hodge-podge of various years....so who knows what any of this means.

2. I don't know squat about balancer part numbers, just weight, no weight and thick cast crank (with weight)

3. I wish I had a little bit more info from "above" in JT's quote.

4. If I'm interpreting this correctly (?) then...
a. 3614371 (72-75) + 3830183 (76-79, likely truck/industrial) balancers are symmetrical (no weight) and are for internally balanced, forged crank engines.
b. 3512017 "six pack" dampener must have only been used in '70-'71 big rod 440's (either 6-pack or 4bbl. HD)
c. 3614371 (73-75 HD) steel crank/truck with big OR small rods must be symmetrical (no weight) and:
c1) This pistons must be so much lighter vs. the older pistons that you achieve "balance" without the dampener weight (? -this doesn't make sense)
c2)big rod vs. small rod 73-75 HD 440's got VERY different pistons so the big rod motors had much lighter pistons (total piston + rod weight = same for big rod & small rod)
c3) MORE LIKELY - the torque converters must have more weight on them for big rod motors in 73-75 (or flywheels? - did they make big-rod '73 440 4spd's?)

This hurts my head.... what am I missing?

For a definitive answer, forward this manifesto to Bob K...

AKA 'Mr. SixPack'...

Bingo.

73-up 440s with big rods have a large notch cut out of one crank throws to achieve balance.

I cannot argue with this.....comparison pics?

You know, I do seem to recall a big notch out of the one of the crank throws on my 73 big rod motor. So I didn't need to buy that offset weight balancer after all, huh? I just had the oil pan off, but unfortunately I didn't take any pictures

I've used the heavy rods and .030 over TRW replacement slugs without the offset balancer numerous times...The machine shop didn't have any issues balancing the assembly and there's never been any harmonic vibrations...