My 71 340 is being rebuilt. The engine builder is trying to balance it and can't seem to get it to balance. It has the forged crank, forged pistons, stock rods. I bought a brand new vibration damper Mopar Performance P4452816. Anyone think of any reasons why they can't get it to balance? If you need other info to help me diagnose just ask. Thanks!
Engine Balancing Problems
- Thread starter ADHD426
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360duster
Well-Known Member
check your crank again - make sure it´s a forged one. The cast one from later engines needs a specific damper, external balance....i think you can identify it by the parts number.
Michael
Michael
OldmanRick
Well-Known Member
Might be piston weight. If the're heavier then the originals they may have to add weight to the crank? Although it seems a experienced machinist could lead you in the direction of the problem?
Plus what "360" said and also make sure the crank hasn't been lightened previously.
Plus what "360" said and also make sure the crank hasn't been lightened previously.
412 Stroker
Well-Known Member
Personally I would be very suspicous of a machine shop that called me up and said they are trying to balance it and can't seem to get it to balance, never heard of that. is there any place else you can take it??
forged pistons ..which ones? are they heavier then the stock pistons???
to balance the crank...you either add weight or take weight off the crank depending on the weight of the pistons and rods
to balance the crank...you either add weight or take weight off the crank depending on the weight of the pistons and rods
They are sealed power forged and are 30 over. I am going to go over to the shop and double check my crank and make sure it is forged and not cast.
An internally balanced crank should be balanced first with nothing on it but the bob-weights. THEN you either add the balancer and flywheel to each end and re-balance and only taking weight from those parts to get your balance back, or balance the pieces separately.
Russ.
Russ.
Lonewolf3165
Living the Dream!
If you have to turn to the internet (nuthin against FABO) for answers to your problem, I'd say the problem lies with the machine shop. get your stuff outta there & run!
moper
Well-Known Member
What exactly did they tell you why they "can't get it to balance"?
smlveightis
Confused in Confusion
Yup, agree with others. Very suspicious sounding.
70Duster440
Well-Known Member
I had the rotating assembly for a 440 balanced recently. Sealed Power forged (not a weight-matched set) and rods stock rods that apparently came from different motors. He was able to get it all balanced. Make sure you have the right harmonic balancer for the crank.
OwdKasd
Well-Known Member
roughidle
Super Platinum Member
Get your parts outta there!!!
He should be telling you what you need to do, not just that he can't figure it out....
He should be telling you what you need to do, not just that he can't figure it out....
I with everyone else grab your stuff and run like hell. A machine shop sould be able to tell you the problem. If they have to call you to solve this then I don't think your are going to be very happy when there done.
Some forged cranks are for 273 they do not have the 1 inch holes through the journals. The 340's having a heavier rod and piston had this material removed. The 273 cranks are stonger but need to be used with a lighter rod and piston combo. Could be the bob weight they can't get right. They will need to drill the journals or use a lot of mallory. These holes are the weak link on the stock 340 forged cranks. One reason to use a 273 for standard stroke. or a Callies for a stroker. Elliminate the flex under extreme hard launches.
Balancing is not voo doo with chicken feet hanging from the rain stick and **** like that -
you weigh the parts & pieces, get them to be the same weight, or close, depending on what your goals are
you enter the information in the computer, it generates a bobweight taking into consideration the oil that will be attached to the crank, and then you make the weights that swing from the crank to the weight you just calculated.
the crank spins at about 500 rpm for a few seconds and it will show you where to add or remove weight in relation the the 360 degrees of turning the crank - you typically add weight to one side or remove it from another.
them telling you this process cannot be completed is a sure sign they dont know what they are doing.
You should see a scale, weights, and a balancing machine when you get over there.
weights can and should be writtin on each part - magic marker or something to see the heaviest and lightest parts - all parts should be weighed - rings, bearings, pistons, pins, rods, bolts, crank.
you weigh the parts & pieces, get them to be the same weight, or close, depending on what your goals are
you enter the information in the computer, it generates a bobweight taking into consideration the oil that will be attached to the crank, and then you make the weights that swing from the crank to the weight you just calculated.
the crank spins at about 500 rpm for a few seconds and it will show you where to add or remove weight in relation the the 360 degrees of turning the crank - you typically add weight to one side or remove it from another.
them telling you this process cannot be completed is a sure sign they dont know what they are doing.
You should see a scale, weights, and a balancing machine when you get over there.
weights can and should be writtin on each part - magic marker or something to see the heaviest and lightest parts - all parts should be weighed - rings, bearings, pistons, pins, rods, bolts, crank.
Winner winner chicken dinner.
yep, you should see stuff like this:
I worked as an apprentice in a machine shop.My job? Prep stuff for the machinist. First engine I watched balanced was a Arias 11 to 1 ,stock rotator 340.It took him about 2 hours to dial it in.(After all the piston,pin, and end to end matching.) Just to put it in perspective,my 408 sbm stroker drove him nuts,for about 15 hours.
............was it a cast 1973 340 crank or a 318 crank...........318 cranks are already neutral balance...........kim........
Glad to hear you found it.A few shops do Mopar on a daily basis,most don't.At least they didn't try to pass it off as done.
efriedrich
69 383S
so what year 318's are internally balanced.
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