440 Pistons & Rods

[1970FuryConv]

I purchased a set of Keith Black 237 hypereutectic pistons for the 1969 440 street motor that I'm putting together to go into my 1970 Fury Convertible. This is a street motor that will never go racing and will probably never go over 85 miles an hour. I was at my machinist's shop and we measured the weights of the pistons. The stock piston was 1086 g. The 237 pistons ranged from 1002.7 g to 1003.8 g. For a street motor, is it worth shaving metal off of all the pistons to get them down to 1002.7 g?

Just to be clear, I don't do machine work and I have very little knowledge of how it's done. I've assembled 2 440s in the past, along with small block Chrysler's (all of which ran fine when installed), but I just don't have the knowledge to say "this is how you static balance it properly."

Also, what does it mean to recondition the rods if you don't take any weight off the rods?

Thanks for your help in filling in the gaps in what I know. Ben

 

[Big_John]

The best bet is to take everything to a good machine shop and say "balance this, please".

The balancing is more than matching the "static" weights of the bits and pieces. They will weigh everything, then balance the crank to match. It's all done with specialized equipment that will balance the crank to the new weights.

 

[Lefty71]

Within a gram is pretty close. Reconditioning the rods involves checking them for straightness, resizing the big end, and usually new bolts even for a street motor unless the original bolts are newer and unharmed. On the rods, it's important to look at the bearings carefully as you teardown an engine. You'll gain clues about the true condition and history of the crank and rods then.

 

[Big_John]

Here's a decent video of how they recondition rods.



What's really funny is I looked for a video and found this one.... and recognized that it's an old friend of mine that's in the video doing the work.

 

[1970FuryConv]

Within a gram is pretty close. Reconditioning the rods involves checking them for straightness, resizing the big end, and usually new bolts even for a street motor unless the original bolts are newer and unharmed. On the rods, it's important to look at the bearings carefully as you teardown an engine. You'll gain clues about the true condition and history of the crank and rods then.

We are installing new ARP rod bolts. I had a friend who decided against new rod bolts during 440 build for his 70 Challenger. Car wasn't been driven hard. One of the old rod bolts stretched on the way across a bridge. That was the end of the 440.

 

[70bigblockdodge]

Always new bolts. Resizing is good to ensure the bearing is crushed enough to hold it, especially when using parts that have not been together before.
Balancing is a hot topic. I'm not a fan if it is a street car with cast/hypereutectic pistons. Your down about 3 ounces per piston that's pound and a half throughout the engine. You might want to do it. I am 9 grams heavier (72grams total)on the new pistons I put in my Barracuda engine, 2.57 ounces spread over 8, engine was previously balanced with old pistons and they had to take weight out of the flexplate which I lost in order to have a SFI rated one. So gamble it is!
Yours for longevity it is not a bad idea.

 

[71Polara383]

@Xenon

 

[1970FuryConv]

Always new bolts. Resizing is good to ensure the bearing is crushed enough to hold it, especially when using parts that have not been together before.
Balancing is a hot topic. I'm not a fan if it is a street car with cast/hypereutectic pistons. Your down about 3 ounces per piston that's pound and a half throughout the engine. You might want to do it. I am 9 grams heavier (72grams total)on the new pistons I put in my Barracuda engine, 2.57 ounces spread over 8, engine was previously balanced with old pistons and they had to take weight out of the flexplate which I lost in order to have a SFI rated one. So gamble it is!
Yours for longevity it is not a bad idea.

My the machinist agreed with you and advised against dynamic balancing for this motor. He did so for 3 read reasons

1. I took the engine out of a running car that I drove, and the 440 engine had absolutely no balance problems. I drove it up to 65 mph.
   
2. The hypereutectic pistons weigh less than stock.
   
3. The variation across the 8 pistons is only a gram in weight

My machinist called another machinist at NAPA Chamberlayne Avenue in Richmond, which does a lot more engine work than his small shop. The machinist there confirmed that there was no need to balance for the same 3 reasons. Based on both of their advice, I am not going to balance the crankshaft assembly. Thanks! Ben

 

[70bigblockdodge]

My the machinist agreed with you and advised against dynamic balancing for this motor. He did so for 3 read reasons

1. I took the engine out of a running car that I drove, and the 440 engine had absolutely no balance problems. I drove it up to 65 mph.
   
2. The hypereutectic pistons weigh less than stock.
   
3. The variation across the 8 pistons is only a gram in weight

My machinist called another machinist at NAPA Chamberlayne Avenue in Richmond, which does a lot more engine work than his small shop. The machinist there confirmed that there was no need to balance for the same 3 reasons. Based on both of their advice, I am not going to balance the crankshaft assembly. Thanks! Ben

Wow, that's good to know. My bet on mine is hedged.
I have seen plenty that suggest bobweighting heavy to ensure no problems. Now you have that and the $150 in your pocket.

 

[twostick]

My the machinist agreed with you and advised against dynamic balancing for this motor. He did so for 3 read reasons

1. I took the engine out of a running car that I drove, and the 440 engine had absolutely no balance problems. I drove it up to 65 mph.
   
2. The hypereutectic pistons weigh less than stock.
   
3. The variation across the 8 pistons is only a gram in weight

My machinist called another machinist at NAPA Chamberlayne Avenue in Richmond, which does a lot more engine work than his small shop. The machinist there confirmed that there was no need to balance for the same 3 reasons. Based on both of their advice, I am not going to balance the crankshaft assembly. Thanks! Ben

You need a new machinist.

The factory balance job was bad at best and now you're going to make it even worse. Just because you can't feel any vibration doesn't mean all is well. 80+ grams of imbalance at a few thousand RPM turns into a ton of force that can set off a high frequency harmonic that can break a crankshaft.

You would be better off running a Flexhone thru it and just rering your old pistons.

Kevin

 

[70bigblockdodge]

stock piston was 1086 g

Minus

ranged from 1002.7 g to 1003.8 g

Equals 82 grams/per piston
Times 8 = 656grams
Divided by 28g/ oz.
Equal almost 24 ounces, that's a pound and a half. Some math is not right here, that's what I get for not paying attention.
I believe you need to balance that. That seems too much. The variation is only 8grams it has too much from stock piston weight to new piston weight.

 

[1970FuryConv]

Chris, the machinist at NAPA Chamberlayne is a Chrysler guy. He says reduction in weight of 82 grams per piston should not change the balance of the engine. He says that he would be more concerned with increase in piston weight. I've already started putting the block together, so at this point I'm going to gamble and run it.
Lets hope for the best.

 

[Big_John]

With lighter pistons, you now have an "over balance" condition. Some high RPM engine builds are done this way. I don't think it will hurt anything, and I agree that it would be different if the pistons were heavier. The percentages of "over balance" are usually lower than this, and that would push me to have the assembly balanced, but I generally figure on balancing as being part of building a good engine.

Bottom line is that it will work and you probably will never notice a difference.

Static weight is fine... The difference of 1 gram is nothing.


This is one of the better articles I've read on the subject: An in-depth exploration of Engine Balance technology

 

[70bigblockdodge]

Chris, the machinist at NAPA Chamberlayne is a Chrysler guy. He says reduction in weight of 82 grams per piston should not change the balance of the engine. He says that he would be more concerned with increase in piston weight. I've already started putting the block together, so at this point I'm going to gamble and run it.
Lets hope for the best.

Well go with that! Lighter is always better. You mentioned somewhere you do not intend to rev the crap out of it, and again throwing cash at balancing a cast piston engine is good money after bad results, IMO. Rule of thumb is cast pistons are limited to 6000 RPM safely. IMO without gross mismatch using stock replacement type parts, I think balancing is unwarranted. However in my limited knowledge I would have thought your difference was too large from stock to new pistons. I would gamble on it if someone I trust said yes.
The 400 in my Challenger is a 156,000 mile engine. I disassemble cleaned rering/bearing. I knocked the weight off the 12" torque converter welded it to my stock converter 11" converter welded it to another converter to try it out which was worse, back to my stock converter. Then I got smart and bought a B&M flexplate with a piece missing for the external balance, 3 neutral balance converters later I found one that works. Every time there were multiple pulls to 6000 RPM, it is the one thing the engine does well. Point is there is no way I hit that weight 100% right Everytime and on 2 12" and one 11" converters the really loose one is barely 10" across but I switched to unbalanced flex plate. That's a lot of weight movement and removal. Can they all be that right?

 

[1970FuryConv]

Well go with that! Lighter is always better. You mentioned somewhere you do not intend to rev the crap out of it, and again throwing cash at balancing a cast piston engine is good money after bad results, IMO. Rule of thumb is cast pistons are limited to 6000 RPM safely. IMO without gross mismatch using stock replacement type parts, I think balancing is unwarranted. However in my limited knowledge I would have thought your difference was too large from stock to new pistons. I would gamble on it if someone I trust said yes.
The 400 in my Challenger is a 156,000 mile engine. I disassemble cleaned rering/bearing. I knocked the weight off the 12" torque converter welded it to my stock converter 11" converter welded it to another converter to try it out which was worse, back to my stock converter. Then I got smart and bought a B&M flexplate with a piece missing for the external balance, 3 neutral balance converters later I found one that works. Every time there were multiple pulls to 6000 RPM, it is the one thing the engine does well. Point is there is no way I hit that weight 100% right Everytime and on 2 12" and one 11" converters the really loose one is barely 10" across but I switched to unbalanced flex plate. That's a lot of weight movement and removal. Can they all be that right?

True. It also helps that mine is a 440 forged steel crank, LY rod, internal balance motor. And the car is probably never going to go over 85-90mph and that would be once in a blue moon.

 

[oldkimmer]

With lighter pistons, you now have an "over balance" condition. Some high RPM engine builds are done this way. I don't think it will hurt anything, and I agree that it would be different if the pistons were heavier. The percentages of "over balance" are usually lower than this, and that would push me to have the assembly balanced, but I generally figure on balancing as being part of building a good engine.

Bottom line is that it will work and you probably will never notice a difference.

Static weight is fine... The difference of 1 gram is nothing.


This is one of the better articles I've read on the subject: An in-depth exploration of Engine Balance technology

That’s a great read. Thanks. Kim

 

[Kram Edyorloh]

If you get a zero balance, the weight of the oil when running takes that zero away, you check the weight of the piston and rod and if they are within 1 gram carry on, the engine does not even know it.
I've been a mechanic for 45 years, 21 of them self employed and built a lot of these engines and have seen LY rods rev to 7K+ without breaking after reworking with a light piston.....its usually oil starvation that causes it
My 440 64 Valiant saw 6800 on every pass for 4 years and made 600hp n/a
This is a 326 Pontiac I rebuilt from scrap after a clown mechanic left the lifter gallery plugs out behind the cam sprocket and ran it for 15mins...ugh, owner paid $5K for a Pontiac specialist to build this, I rebuilt it for $1500, customer was real happy, block had to be decked, all rods resized, new rings and bearings.
Dont worry if its 1gram, but, if you are pressing new rod bolts in def check the big end dia after, good luck.

 

[Big_John]

If you get a zero balance, the weight of the oil when running takes that zero away,

Many years ago, one of "go to" guys in the business explained to me that a good machine shop allows for oil weight when balancing.

 

[twostick]

Chris, the machinist at NAPA Chamberlayne is a Chrysler guy. He says reduction in weight of 82 grams per piston should not change the balance of the engine. He says that he would be more concerned with increase in piston weight. I've already started putting the block together, so at this point I'm going to gamble and run it.
Lets hope for the best.

Like I said, you need a new machinist.

The one you have and all his buddies apparently either slept through or skipped physics class. He would be concerned about adding 82 grams in piston weight but not concerned about adding 82 grams to the crank counterweight which is what happens when you LIGHTEN the piston by 82 grams. The end result will be the same.

Kevin

 

[PH27L7]

Like I said, you need a new machinist.

The one you have and all his buddies apparently either slept through or skipped physics class. He would be concerned about adding 82 grams in piston weight but not concerned about adding 82 grams to the crank counterweight which is what happens when you LIGHTEN the piston by 82 grams. The end result will be the same.

Kevin

Agree with that. I'd be very worried about main bearing & engine life with that big a difference. Just don't go over 3000RPM & don't expect to put a lot of miles on car. Let us know how it works out!