6 Pack rods

[66_B_Body4ever]

Couple of questions for those in the know, Is it worth while using 6 pack rods over stock rods in a standard bore engine that might push 450+ horse. I realize they are heavier, but how much. I see that Eagle H beams weigh in at approx. 765 grams, what do the 6 pack rods vs. the stock rods weigh in at?

 

[66_B_Body4ever]

Do these appear to be 6 pack rods? They look beefier than std.

 

[69 Runner]

No reason to use the six pack rods. My (ex) Six Pack Challenger made 419 to the rear wheels and didn't run them

 

[BlueThunder]

I thinik you have to have your engine exterally balanced for true 6 pack rods.

 

[66_B_Body4ever]

I have read somewhere that you need a larger than normal balancer...The rods, if purchased would be hung on a forged crank.

 

[Meep-Meep]

I don't know the weight difference between 6 pack rods vs stock but consider this: How many scattered 440's are there as a result of six pack rods? Didn't Sox and Martin (and others) race these engines? Now if you shift at 7500 RPM then you may have a problem, but for a street engine with shift points at 6000 RPM max I'd say use whatever you want. Personally, I think the best production rod to use is the OE 64 Max Wedge type or the early Max/300J rod. Same beam as the 440 but lots more material around the parting line to minimize deflection at high RPM. Seems to be a good balance of weight and strength. Now good luck finding a set. I'd stick to a properly prepared set of OEM's. I just got a set of LY rods resized with new bolts for about $275.00, which is about half price of aftermarket.

Getting 450 HP out of a 440 or a 383 is not that difficult and can be done with properly machined factory parts - even the heads. Pay attention to cam vs compression ratio.

 

[66_B_Body4ever]

Thanks boys, always good info. I was initially going to purchase a 500 ci. stroker kit from either 440 source or the one available through Indy cylinder heads. At this point (budgeting) I will stick with a stock bore configuration and ported/flowed 452's with 2.14/1.81 valves and the MP grind .509 hydraulic cam, Edelbrock performer rpm intake etc. Any input is appreciated.

 

[69 Runner]

My Challenger was certified "factory stock" (yeah I know this will open a big can of worms) and made that 419 to the rear wheels. So obviously it can be done without using a big cam IF you do it right

 

[66_B_Body4ever]

Thats why I am here, knowledge is wealth!

 

[66_B_Body4ever]

Stock 6 pack cam was around .450 lift right?

 

[69 Runner]

NHRA blueprint specs list it as .455/.470

 

[66_B_Body4ever]

I have a digital gram scale, can I balance my own rods...obviously closer to 0+/- grams is ideal, but what is considered tolerable?

 

[Meep-Meep]

That's not the whole story. You can match up the heavy rod with the light piston and get things close but you still have to be in the ball park of the actual spec, which is called out in oz/inches (or gram/inches) at a one inch radius. I'm no expert in balancing engines but I do know the way they are set up is you weigh the rod and piston assy and divide by two to get the bob weight for the crank. Then you add/remove from each end of the crank to get a true dynamic balance. I'm sure the factory tolerance allows for the weight difference for up to .040" overbore pistons but for a really good balance you are probably within a few grams. A well balanced engine is a happy engine :grin:

 

[66_B_Body4ever]

That's not the whole story. You can match up the heavy rod with the light piston and get things close but you still have to be in the ball park of the actual spec, which is called out in oz/inches (or gram/inches) at a one inch radius. I'm no expert in balancing engines but I do know the way they are set up is you weigh the rod and piston assy and divide by two to get the bob weight for the crank. Then you add/remove from each end of the crank to get a true dynamic balance. I'm sure the factory tolerance allows for the weight difference for up to .040" overbore pistons but for a really good balance you are probably within a few grams. A well balanced engine is a happy engine :grin:

Thanks, I will leave it up to my engine guy to tackle that one...I want her to be a well balanced unit!
-J

 

[dantrap]

Hey 66, you can use the the stock YL rod with out any problems. Have them mag-ed or x-ray-ed for stress cracks. There are several aftermarket suppliers selling NEW YL type rods for low cost on ebay or other sites. The big advantage to the standard or YL type or aftermarket rods is low weight allowing internal ballance. If you use reconditioned Rods use new fastners always. you could have the beams polished and the small end bushed dependent on your application. Let your builder ballance the whole assembly out.

 

[66_B_Body4ever]

Thanks dantrap and everyone else. Very helpful.
-Jeff

 

[71gtx]

I have read somewhere that you need a larger than normal balancer...The rods, if purchased would be hung on a forged crank.[/QUOTE


I thinik you have to have your engine exterally balanced for true 6 pack rods. .[/QUOTE



the 70-71 440 hp are externally balanced 6 pack rods

72 up 440 hp are neutral balanced with 6 pack rods

 

[Cranky]

6 pack rods can be used in an internally balanced engine....but you can't just throw them into an engine that's been internally balanced using the smaller rods. Any time you make a weight change, a rebalance is in order. And I balance my rods and pistons before taking the rest of the junk to my machinist. Makes his job easier and a happy machinist is always good 6 pack rods can be made to work well but the LY rods do just as good when using a light weight piston. Heavy pistons is what kills rods....