connecting rod and harmonic balancer question

[BubbaCuda]

During the disassembly of my 360 i found two items that brought concern to me.

I pulled the pistons out of my 360 today and found that the number two of the connecting rods was different them the others. Should i be concerned.

The second is the harmonic balancer has cracking to the rubber seal on the back side. Does it need to be replaced. if it does any recommendations.

Any input would be appreciated.

 

[66340SEDAN]

If the engine will be stock and used as a driver I wouldn't worry about the harmonic balancer. Some new balancers are fairly cheap, I have one that has weights that you add to it so you can use it on 3 different style of cranks. You could probably get a stock replacement right from Ma Mopar! Not sure on the rods.....but someone else will!

 

[GTXperience]

Was there any issues with the motor before disassembly? Just out of curiousity, have you had a chance to weigh the oddball rod vs the others & also compare them visually?

Re: the balancer. Do you have a better image of the cracked area?

If need be, I have a set of matching 360 rods and a solid balancer.

 

[BubbaCuda]

I bought the motor complete already pulled out of the car So I really don't know what the condition except they told me i could run it as is..I added the only other picture i have of the Balancer. Sorry about the quality it was getting dark so i snapped some photos with my phone.

 

[lilcuda]

I wouldn't worry about the different forging numbers. They are both 340/360 rod forgings. I WOULD spend the money to have the engine balanced, though just in case there is a weight mismatch. I can't tell from the photos of the balancer how bad the rubber is. Can you try to get a better photo of it? I noticed you're in San Jose. I'm in the SJ area, too. Where are you going to have your machine work done?

As a former machinist, I'm always on the lookout for a good machine shop.

 

[340srule]

The 2899496 rod is a floating pin type,and only came in a '68-'73 340's..the 3418645 is a pressed pin type found in 318/360's...

 

[tobysoldblue]

http://store.summitracing.com/partd...839044+4294908110+4294840106+115&autoview=sku it would be a good idea to replace it if the rubber is cracked already,it can seperate and the 2 parts spin inside each other,causing it to be out of ballance.For $78.00,i wouldnt chance it

 

[BubbaCuda]

Thanks for all the help but i still have a couple of questions.

Im going to take your advice and buy a new harmonic balancer from summit. Should i spend the extra money and get a SFI?

Also do i need to buy a new rod to match the pressed type or buy a new complete set?

 

[Optik]

once the rubber starts to deteriorate in the balancer, it is no good. it is looseing its ability to absorb harmonic vibrations that way and as was also stated, it can spin on itself and throw the motor out of balance and frustrate any attempts to time it, as well. replace it, worth the $ to avoid bigger problems later.
-tim

 

[crackedback]

I'd buy a new balancer. Cheap insurance.

Make sure you index the balancer before buttoning it up. You might be surprised to find out TDC isn't exactly where it's suppose to be... DAMHIK.

 

[BubbaCuda]

A new balancer is on my to buy list for tomorrow. What do you guys think i should do with the rod.
Replace it with a pressed pin type.
Replace all the rods with the floating.
If they weight is right run with it.
Thanks again for all the help

 

[dgc333]

A set of Eagle SIR rods are less expensive than having stock rods reconditioned with with new quality bolts installed. They are extremely close on weight and balance that makes it easier/less expensive to balance the rotating assembly. Plus, they are bushed for floating pins and are rated for up to 500 HP.

A bunch of the competitors in the recent mopar sb dyno challenge thought they were good enough for there 500+ HP 408 strokers.

Better rod for an overall cost savings!

 

[lilcuda]

The 2899496 rod is a floating pin type,and only came in a '68-'73 340's..the 3418645 is a pressed pin type found in 318/360's...

Not necessarily true. I've seen both forging numbers in the floating configuration. I've had multiple sets of each. Could it be that someone converted the 3418645's into floating pin? Yes, but I've seen so many that were floating, I doubt that every single set was converted over. Mopar is famous for using whatever they had laying around.

 

[lilcuda]

A new balancer is on my to buy list for tomorrow. What do you guys think i should do with the rod.
Replace it with a pressed pin type.
Replace all the rods with the floating.
If they weight is right run with it.
Thanks again for all the help

Well, Eagle rods are probably cheaper than having your existing rods properly reconditioned and balanced. You need to clean & magnaflux the rods, install ARP Wav-loc bolts, have them reconditioned and then balanced. If you want the rods converted to floating pins, that's an extra expense. If you do keep the stock rods, don't skimp on the prep! You'll be sorry.