Do I have to re-balance this 360

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hemichuck

hemichuck

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I was digging through my garage looking to see what I had laying around to build a motor with and I dug up a 360 block I had that is bored .040 and its been align bored and square decked and new cam bearings and freeze plugs are installed. I found a new set of small block rods and a set of Kieth Black 107 pistons to put in it. Stock 360 crank cleaned up standard. I slid one piston and rod in and checked the deck and it will be zero decked when assembled. My question is with the KB 107 pistons that have a weight of 524 grams for piston and 132 for the pin require a re-balance before I assemble it? I looked up a stock 360 piston weight and it said 584 grams and I'm assuming that includes the pin. Getting a motor balanced around here is like pulling teeth, last time I took one to the machine shop I ended up going back 2 and a half years later and picking it up with nothing done. I'd like to have this motor running before April. Any thoughts?
 
I would balance it for sure.
I'm not sure the stock weight you indicate includes the pin... Fairly sure it doesn't but I'd make sure if it was me.
 
The 584 grams is WITHOUT the pin. And the pin is considerably heavier than the KB pin. So you are making a biiiig change in the reciprocating weight..... it's absolutely time to re-balance.

To minimize delays, if you are so inclined and have the tools and capabilities, you can balance the rods yourself but this is some work. You have to balance the total rod weight, and also balance each small end against each other, and each big end against each other. That takes the right setup to weigh big and small ends. Or, since you are in a hurry, drop the $300 or so on a set of SCAT rods I-beam rods which are already balanced 100% as a set and they give you the balance data. The KB piston set should be super close between pistons and pins. (But double check anyway.) With that, all that needs to be done with the rod, piston, pin, ring, and pin lock weights, is to compute the bob-weights, which is just a straight calculation, and give that and just the crank to the shop.

2+ years? That was a serious problem; if it had not been done in a few weeks tops, I would have been back pulling the parts out of that shop. Just manage the situation right and you won't have that issue again. Go to another shop obviously!
 
nm9stheham said:
drop the $300 or so on a set of SCAT rods I-beam rods !
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And they are also a lot stronger and lighter than stock rods plus they come with ARP rod bolts. So factor in that cost too makes these really attractive.
 
I already have a new set of Eagle I beams laying here, Just trying to use up all the parts I have around. When you get up to 40 years worth of building cars you end up with a lot of spare parts around. I really have everything to complete this engine except a good set of heads but I'm heading up to the Indy winter show in a couple of weeks and I will probably get some of the Indy Lax heads to use on it. In addition to what I mentioned I have a Comp cams 305H cam and a set of roller rockers, a Holley Strip Dominator, a 750 Holley double pumper and a set of Headman big tube W2 headers and a Mopar Performance race electronic Distributor and a few other misc. parts. I figured that would empty up a little shelf space. I also found a MP3.58 stroke crank with 340 mains, an Offy Port-o-sonic, A performer RPM for magnum heads, a set of Edelbrock Magnum heads and a set of KB 356 pistons for a 4 inch stroke and a pile of various aftermarket magnum roller cams and other LA performance cams,etc,etc.
 
hemichuck said:
My 70 Dart 340 Swinger is Go Mango similar to the one in your picture
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Well post a Pic, I wanna see I wanna see!

I like the Go Mango color, but Orange is my signature color. I even have the tooling I design at work anodized orange.
 
If you have the weight data from those Eagle I-beams, then you are pretty well all the way there to a balance of just the crankshaft with newly computed bobweights. If that new rod data is complete, then checking weight match of the pistons & pins & locks and rings is all you need to do to be ready to compute new bobweights.
 
if you are OK with the 360 being previously balanced then you could weigh the new pistons/pins/rings/locks (if used) against the old heavier piston/pin/rings then order some heavier pins to get back to the same weight WO (re) balancing & iirc 273 pins were deliberately made very heavy to do this exact same thing at the factory for interchange purposes. HF has an accurate gram scale for cheap. do your homework/Google & see what develops
 
Good thought there RR. I was gonna say that this would require a pin in the range of 210-220 grams.... and the old 273 2 BBL pins were around 220 grams to do exactly what you say.
 
I know I'm gonna have to break down and find a shop to do it but I was just hoping to get away with it like the good old days when we would swap them old TRW forged pistons into a 340 and crank it up and go. I guess back then we didnt know any better or were just too broke to care, I remember doing all kinds of crap back then that I know better than to do now, and getting away with most of it!
 
well swapping in the trw forged pistons worked without a rebalance cuz trw was smart and made the pistons the same weight as stock. and back in the day when I was thinking about a quick 340 rebuild involving changing pistons, I talked to Ed Hamburger the small block mopar guru, he said as long as the weights are within 10% go for it. the new pistons were 11% different so I went for it and with solid engine mounts she ran great for years
 
I wish I could look around my garage and find a complete shortblock to assemble (with new parts, no less)! I'd rebalance to be safe. Why put it together and find it's out of balance?
 
Dude, if you look around in there I believe you could pull out a couple of 408's and a couple of 340's and a few 360's and at least one 440. Like I said Ive been building cars and vending at swap meets for 40 years, My garage is actually a little less "well stocked" than it used to be. I guess i will start looking for someone to balance it. I want to build a 4 inch stroke 340 for my 70 Dart since it was an original 340 car but I think I will just buy a kit thats already balanced for that one.
 
I would not let a few hundred dollars be the reason an engine came apart. I would balance it.
 
hemichuck said:
Dude, if you look around in there I believe you could pull out a couple of 408's and a couple of 340's and a few 360's and at least one 440. Like I said Ive been building cars and vending at swap meets for 40 years, My garage is actually a little less "well stocked" than it used to be.
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Need me to make the 2.5-3 hr drive up there to "relocate" some of your "un-needed" parts? ;) :D
 
RustyRatRod said:
I would not let a few hundred dollars be the reason an engine came apart. I would balance it.
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Believe me, its not a money issue, its a lack of being able to find a shop that will do it in less than a year thing. I dont have any problem paying to get it done.
 
75slant6 said:
Need me to make the 2.5-3 hr drive up there to "relocate" some of your "un-needed" parts? ;) :D
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If it wasnt so much trouble I would take all of it to Indy next month and get rid of it all. Id take the money and buy another Viper, they are infinitely more fun to drive.
 
Psssssss.... Around here you could get that done in like 2 day's... Got to Love So-CAL..
 
racerhog said:
Psssssss.... Around here you could get that done in like 2 day's... Got to Love So-CAL..
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Thats one long *** ride for a balance job, I guess machine shops are like Starbucks out there, one on every corner. Probably 80 percent of the machine shops in Louisville dont even do balancing and the ones that do are covered up. I remember taking a trip to LA in 1984 and I needed parts to build a small block chevy fleet van I was working on so I stopped by PAW and bought the whole kit(dirt cheap) and stuffed it in my suitcase and brought it home.
 
PAW... Was Awesome... Use to buy 392 parts from them....lol
Hope you find someone close to get your stuff balanced... :)
 
hemichuck said:
Believe me, its not a money issue, its a lack of being able to find a shop that will do it in less than a year thing. I dont have any problem paying to get it done.
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Really? The shop I use could have it done in a week. Road trip?
 
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