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I am looking into a few of the different balanced rotating assemblies available for a 377/383 stroker build. need some help here.. :confused:

Eagle sells a BALANCED external balance 383 rotating assembly that comes with a new flexplate and harmonic dampener. Will this pre-balanced kit be good enough to drop into the block and bolt up, or will i need to have my local machine shop check their work and rebalance it???
 

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double checking is always a good thing.. but..
if you has an engine balanced at one local shop would you then bring it to another to check the first shops work?
can't hurt having it rechecked.. other than your wallet..
 

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Does this kit have a cast or forged crank? Are you using I beam or H Beam rods. To be on the safe side I would have it checked out.
 

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Most of the kits that I see are not very close on their balance job. Usually + - 5 gr. or sometimes + - 10 percent. A machine shop will usually use a + - 1/2 gr. balance.
 

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I've also seen cases where the components used to set the bob weight differ from what was sent in the kit. As an example in one case the weight of the rod bearings on the balance card was way off from what I measured. According to the description the kit was supposed to come with Clevite bearings and it actually shipped with Kings which were about 8 grams heavier.
 

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Most of the kits that I see are not very close on their balance job. Usually + - 5 gr. or sometimes + - 10 percent. A machine shop will usually use a + - 1/2 gr. balance.

my 496 kit was very close.. but I bought mine through scott shafiroff racing, and that might be why.. they prob. balanced it.. not eagle..
 

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names like shaffiroff/lukovich/mitchell all have big names,(there are others) usually supply good parts.My friend John Graham races in Calgary and uses Shaffiroff parts,My parts came from Jeff Lukovich,no complaints so far
 

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Most of the kits that I see are not very close on their balance job. Usually + - 5 gr. or sometimes + - 10 percent. A machine shop will usually use a + - 1/2 gr. balance.
Depending on what it is 5 grams is well within the acceptable range for anything on the street. In fact most engines on the street won't be within that spec from the factory. 10% on the other hand can mean a LOT when you're dealing with a 1700 gram bob weight- that would be 170 grams.
 

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Discussion Starter · #9 ·
i just got off the phone with Eagle, and their techincian Tim assured me that the BALANCED 383 kits like they sell on summit or jegs are already balanced +/- 2 grams. He said they undergo the same balance job as their race balanced rotating assemblies and i would be able to open the box and install. (after making clearances on the rods and block of course) :thumbup:
 

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I've also seen cases where the components used to set the bob weight differ from what was sent in the kit. As an example in one case the weight of the rod bearings on the balance card was way off from what I measured. According to the description the kit was supposed to come with Clevite bearings and it actually shipped with Kings which were about 8 grams heavier.
Thanks for weighing in with this info.
As I have said many times on this board.....TRUST NOBODY.
 

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FWIW, I have swapped pistons to something MUCH heavier and ran the engine without balancing. And many others run race engines that way too. I'm not saying balancing isn't a good thing to do, but I've ran engines just fine without it.

The other issue is that when balancing there is actually only a very small window in which any balance job is perfectly dynamically balanced. Something I wonder about when you see race engines going to anywhere 48-55% balance when 50% is believed by many to be the absolute perfect number for a V8.
 

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I think they are about as accurate as a "factory balanced" engine is. It's pretty close, but can be greatly improved on. Here's my story: Many years ago I bought a "balanced kit" to build a 334 CID engine using a 305 block and a cut down 400 crank. Turned out the 305 block I had, the main bearings had spun badly, and it was junk. So, I just hung onto the kit until a good 305 block was given to me years latter. After it was together, and in the truck, something was'nt right. It would idle fine, but start to drive, it was like it was pulling a battleship, and had a "dull" feeling to it. I actually parked the truck for several years rather than mess with it anymore. Then one day, in a magazine, I saw a layout of several Chevrolet flywheels and flexplates. WHAT??? That can't be right. Took off the converter shield and.............FOUR-FIFTY-FOUR flexplate!!! Swapped to a 400 flexplate, and it's been smooth sailing since. California Discount Warehouse must only balance their engines to "known, general specs", without balancing them WITH the dampener and flexplate on the rotating assembly, and put a 454 flexplate in the box. My truck had sat for six years, and I had the kit stored for probaly another six before that, so forget about any kind of warranty or compensation. Now I take MY PARTS to MY MACHINIST, because the others obviously can't be trusted. Butch/junior stocker.
 

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FWIW, I have swapped pistons to something MUCH heavier and ran the engine without balancing. And many others run race engines that way too. I'm not saying balancing isn't a good thing to do, but I've ran engines just fine without it.

The other issue is that when balancing there is actually only a very small window in which any balance job is perfectly dynamically balanced. Something I wonder about when you see race engines going to anywhere 48-55% balance when 50% is believed by many to be the absolute perfect number for a V8.
Engines like cup enignes that spin over 8000 RPM alot of those cranks are over balanced. The blower engines I build I over balance be 2% as they spin 9500 and no problems.

Machined a block for a customer and the pistons were appox. 72 grams lighter and they said it would be fine. Now that they have runn the engine they are going to take back apart and balance the rotator like I said needed to be done.
 

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i just got off the phone with Eagle, and their techincian Tim assured me that the BALANCED 383 kits like they sell on summit or jegs are already balanced +/- 2 grams. He said they undergo the same balance job as their race balanced rotating assemblies and i would be able to open the box and install. (after making clearances on the rods and block of course) :thumbup:
I have seen one of there prebalanced kits and one end of the crank was off 36 grams.

Whats really interesting when you buy a prebalanced kit the pistons are in a sealed box the ring are in a sealed box and rods are still in the plastic sealed wraping HMMMMMMMMM
 

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what cnc just posted
side note,I bought a set of carillo rods for my LS-7 and they were sealed when I got them. They were perfect when the box was opened at the machine shop. They even commented they had never seen perfect rods before
 

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I am looking into a few of the different balanced rotating assemblies available for a 377/383 stroker build. need some help here.. :confused:

Eagle sells a BALANCED external balance 383 rotating assembly that comes with a new flexplate and harmonic dampener. Will this pre-balanced kit be good enough to drop into the block and bolt up, or will i need to have my local machine shop check their work and rebalance it???
Sometimes Yes and sometimes No. We had them both ways and when they aren't right it's a costly fix as the engine has to be torn down, cleaned, the rotating parts sent to a balance shop or worse returned to the source which often became an argument over what was or not done to the parts. So we stopped using kits a looong time ago. They may be convient for engine assemblers but not what an engine builder needs. When you build an engine you check and inspect each part and the assemblies they make. Often, especially with strokers you find adjustments need to be made for fit checking purposes. This is not to mention that some balancers just think that getting the whole thing kind of close is good enough where I want specific balances in particular places along the crankshaft.

So we buy only pieces and build the combinations. This also gives me a chance to select the exact combination of parts from various manufacturers and sources that I prefer and trust or want to experiment with. Balance is one of the last operations we do, however, the engine will be assembled and checked for timing between cam and crank and clearances of bearings and parts at least once for a standard build and several times for custom/competition builds even when using common off the shelf parts as often you get unpleasant dimensional surprises that are a lot easier to deal with before fire is put in the cylinders. Balance quality will vary between street and competition builds with that varience is cost. There is little sense in putting the effort (thus cost) into a mild performance street build up as goes into a high level competition engine and the type of balance between simple straight up versus games with under or over balance as this gets esoteric and costly and is not necessary for engines that don't see RPMs in the 6000 up range. That's not to say that a hot street engine isn't balanced well and correctly but I'll accept a bit wider tolerance in the intrest of cost. That is unless the customer wants it to the knats and is willing to pay for it even if it will never be used nor felt, if the customer want to spend money on an overbuild I'm willing to take it and we have several that do just that.

So the summary is that prebalanced kits may or not be correct and may or not be correctly done. Then there is aways the issue that assembly may require changes that upset the balance requiring it be done again. Lastly, if the balance isn't correct it takes engine removal and disassembly to correct which is a lot of effort and cost that is most likely not going to be covered by the manufacturer or seller.

Bogie
 

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I have seen one of there prebalanced kits and one end of the crank was off 36 grams.

Whats really interesting when you buy a prebalanced kit the pistons are in a sealed box the ring are in a sealed box and rods are still in the plastic sealed wraping HMMMMMMMMM
funny mine was sealed but the pistons where marked with weight and my last name, same with the rods,, sealed in plastic but they had the weight and my last name on the rod in marker, hum how did they mark the rods, maybe just maybe the seal the parts so they don't rust on the shelf..
 

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Balancing

Hey 377 .... Just pay the 180 bucks and have it balanced It is not worth the risk!!!!! My Eagle crank was off and came with the wrong balancer so off to the balance guy it went.He had to remove some from the crank and the flex plate....I learned some things you cant cheese out on.....Balance it!!!!!!
 

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Crank balance

Save a few bucks now cuttin corners and in the long run it will cut deep in your wallet!!!!!!!!!!
 

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funny mine was sealed but the pistons where marked with weight and my last name, same with the rods,, sealed in plastic but they had the weight and my last name on the rod in marker, hum how did they mark the rods, maybe just maybe the seal the parts so they don't rust on the shelf..
Its intersting the seal on the piston box is not even broken but! So how did they get the pistons out of the box with out breaking the seal??

Do a search on problems with prebalanced assemblies
 
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