Standard Weight of a 440 Piston & Wrist Pin?

[6T8 Charger]

Can anybody confirm the weight of a 1977 Dodge 440 standard piston and wrist pin? I asked Grok and it said 1086 grams. Reason: I'm rebuilding a 440 motor and I need to find a set of pistons with a similar weight so I don't have to rebalance the crankshaft. The scrapper got my stock pistons and wrist pins, so I can't weigh them.

 

[69Bee]

If you are using "Stock Replacement" OEM style pistons, you will be fine; no need to rebalance. If you plan to use forged custom pistons or KB possibly. An aftermarket crank or rods, then you will need rebalancing.

 

[1968rt]

Part# CH Weight Pin Wt CCs Deck Ht TRW / Speedpros are close in weight



L2266F 1.991 876 225 0 flat top .090

L2355F 2.061 872 225 -7cc .020

L2388F 1.926 819 225 0 flat top .155

L2295 2.029 817 250 13.1cc .140 dome .051

7025P 2.050 815 250 13.1cc .140 dome .051

L2286P 2.034 876 225 0 FLAT TOP .048-.051

 

[lewtot184]

1080 is about right. Over bores will be heavier. 8:1 may be lighter. Service manual for a 10:1 states 857.5 for the piston,. Last time I weighed a stock pin it was around 235grms.

 

[6T8 Charger]

I think I've got this figured out. I'm going with the Speed Pro L2355F30 pistons & pins. I called Speed Pro and the tech said the piston weighs 872g and the pin is 220g = 1092g
The factory piston is 858g + the pin weighs 235g = 1093g. I think I can get away without balancing.
Thanks to everybody above for the info.

 

[Geoff 2]

I weighed a stock piston & pin many years back & it was about 1100 grams.

 

[lewtot184]

Balancing an engine is not an exact science.

 

[68-500]

How do you guys feel about over balancing? The crank is weighted for a heavier piston then the piston used. I hear its common on high performance engines. The summit forged piston weights 886g with pin, with the stock piston/pin weighing +\-1080. The over balance would be 200g Im not sure what that percentage that works to be, but I believe 50% is standard balance. And 55% is the overbalance that I have read about.

 

[69Bee]

Balancing an engine is not an exact science.

I disagree, it is actually and accurate and precise sceince when done properly. Here are just a few examples out of my machining manual. I have seen some really scary **** come from other shops that had absolutely NO clue what they were doing.

 

[RemCharger]

Why you would want to run something 200grams out is beyond me. But I'm always open to info based on testing.

 

[68-500]

Im not saying I want to run it 200g out of balance. Im saying I have heard of performance engines being over balanced. And I am curious if anyone has experience with this concept and what would the over balance percentage be with the numbers in the post. 200g may be 51% or 100% over balance I don’t know.

 

[69Bee]

As I read, racing engines operate at the high end of the RPM range so they are out of the normal balance scenario. When the engine is over balanced, it is balanced to run smoother at the higher RPM level. The idea is that the engine may sacrifice smooth operation at a lower RPM in order to have it where it needs it, at high RPM.

 

[68-500]

Yes I have been doing a little reading. I am currently getting some weights together and reverse engineer the factory balance and then figure it with the aftermarket pistons

 

[69Bee]

Why? The weights of the components you have now are used to establish the balance. The rod big ends are matched to the lowest weight, then the total rod weight is matched to the lowest overall weight. The pistons are matched to the lightest piston and pins are moved around to help. Add to that one set of rings, any lock clips for floating pistons, one set of rod bearings, and an assumed residual oil weight (4-6 grams). Then you double this for the bob weights and the crank is drilled, welded, or gets Mallory metal to match the crank to the bobweights which is spun at a specific RPM. I send it out as the equipment is expensive and I am too close to retirement to invest in it. Same goes for crank grinders, too GD expensive and no room for one anyway. My last machine I bought was a CNC Cylinder hone to speed the process up as it mostly works on its own with just some monitoring allowing me to do other things. It used to take me about 3-4 hours standing in front of the hone for a Cummins 6cyl. The new hone finished it in about 30 minutes while I ate lunch!!

 

[68-500]

You obviously have more experience and practice at engine machining than I do or ever will have. Please understand that I am just trying to learn and understand the dynamics at play here. Just pulling some very crude weights together from the ole inter web. It seems like the bob weight for a stock forged crank, LY con rod, factory cast piston the bobweight would be around 2500g. A +\- 2% over/under balance would be around 50g. If you think Im barking up the right or wrong tree please say as much.

 

[69Bee]

Forget about OE, the balance will be dependent on what the new parts. Plus, shops usually balance to about 0.5g tolerance. A +/- 2g is for usually aftermarket piston sets. Custom forged set are much closer than that. With the exception of the crank and rods if OE are used, the other new parts will not be the same, and the balance required will be different. Doesn't mean 50g, 100g, or 200g, it is going to rely on the replacement parts. Bearings and rings will vwey similar, but the likely difference will be the pistons. If you use OE Silvolite, Sealed Power, Egge, etc.. and the vehicle is just a regular car, nothing special, it isn't really necessary to balance. But if you are using aftermarket crank/rods, lighter pistons, or a high-performance engine, then yes, I highly recommend balancing. Also if you get an OE crank from here, OE rods from there, balancer over yonder, and a flywheel/flexplate from CL, then I would also recommend balancing just in case. Better to do the first time, instead of the second time. You do have to sift thru the yahoos on yucktube, but there are some really neat videos on machining processes and cool to watch too.

 

[BSB67]

……If you use OE Silvolite, Sealed Power, Egge, etc.. and the vehicle is just a regular car, nothing special, it isn't really necessary to balance.

This. 10s of thousands of motors have been put together with these replacement piston/pins without balancing without a second thought.

 

[PROSTOCKTOM]

What are you intending to do with this engine in the first place?

If performance, or improved longevity is your goal then the cost of balancing is really low compared to most anything you do with an engine.

Having aftermarket pistons and pins is a great way to save weight and increase the rate that the engine can accelerate (rpms per second)

Choosing a heavy piston/ pin just because you don't want to rebalance the crankshaft is really leaving a lot of good on the table.

However, this depends on your end use and budget.

Tom

 

[68-500]

I think maybe my question was worded wrongly and being misunderstood. I was speaking of engine builders over or under balancing to match a more specific rpm. I really don’t care what balance is at idle a street engine spends most of its time in 2500-3000 range. And race engine maybe more like 4500-8000 build and use dictating. I was just saying if the different weight piston falls within that +\- 2% of bob weight. What would it hurt to use? Just looking at some simple stuff found on line .02x2500g=50g. It seems as if stock dod weight is around 2500-3000g depending on con rod and piston. So 50g different piston/pin weight falls within 2% of neutral balance weight.
I have no intention of using a piston/pin combo 200g lighter than factory without rebalancing. But 50g? Let it rip!

 

[PROSTOCKTOM]

I think maybe my question was worded wrongly and being misunderstood. I was speaking of engine builders over or under balancing to match a more specific rpm. I really don’t care what balance is at idle a street engine spends most of its time in 2500-3000 range. And race engine maybe more like 4500-8000 build and use dictating. I was just saying if the different weight piston falls within that +\- 2% of bob weight. What would it hurt to use? Just looking at some simple stuff found on line .02x2500g=50g. It seems as if stock dod weight is around 2500-3000g depending on con rod and piston. So 50g different piston/pin weight falls within 2% of neutral balance weight.
I have no intention of using a piston/pin combo 200g lighter than factory without rebalancing. But 50g? Let it rip!

Something going around at 1500 rpms out of balance is the same out of balance at any rpms.

You probably don't know this, but commercial laundries have the drums in their washers and driers balanced.

Balancing of any rotating mass regardless of size, weight, or rpms matters in the longevity of a given assembly.

50 grams is almost 2 ozs. x 8. Now your talking almost a 16 ozs. out of balance. You're will feel this and the engine will not like it.

Tom