FAQ |
Members List |
Social Groups |
Calendar |
Search |
Today's Posts |
|
#1
|
||||
|
||||
Balanced rotating assemblies
I didn't want to mess up another gentleman's thread so I started this one.
Please tell me your expectations when you purchase a "balanced" rotating assembly. Are you thinking they will be balanced within a certain tolerance, as good as the factory job or just hoping it doesn't shake or vibrate. Also would you expect the same quality of job if it was purchased from a large Pontiac vendor as you would say from Scat or Eagle or your favorite machine shop. Anyone have any past issues with the balance job on their rotating assembly. |
The Following User Says Thank You to PAUL K For This Useful Post: | ||
#2
|
||||
|
||||
I would not trust any balance assembly. My machine shop has gotten balanced assemblies from Pontiac vendors, with issues. Everything is checked rods, pistons..crank. Its well worth the bucks you pay to have everything checked. To prevent a nightmare down the road.
|
The Following User Says Thank You to Gach For This Useful Post: | ||
#3
|
|||
|
|||
For me, if I was doing this and purchased a balanced assembly from Butler, my expectation would be that I could take that assembly, and the block to my machine shop for the block machining and assembly and end up with an engine that would live for 50K+ miles. I wouldn't necessarily expect it to be a pristine piece that's 100% perfect in every facet, but I'd also not expect to get a much higher bill because the machine shop had to redo everything.
Or, if I was assembling myself and don't have the ability to even check balance, I should be reasonably certain that I have a product in hand that isn't going to vibrate itself to pieces a year after I assembled it. That's my threshold anyway. If those can't be met with a kit, I'd prefer to work directly with a machine shop and buy the parts needed individually and have them balance and assemble everything. In this case I'd certainly pay a premium for that type of service, but then I want to know the engine is right. In my case that would be what is necessary to have a smooth functioning and reliable engine that would be seen as a moderate street build, not a racing engine.
__________________
-Jason 1969 Pontiac Firebird |
The Following User Says Thank You to JLMounce For This Useful Post: | ||
#4
|
||||
|
||||
I don't trust them Paul and I know you've seen this too. And this isn't meant to bash anyone, but there are balancers out there and then there are balancers. Some are just pickier than others. Some get it close enough and you'll likely never see a problem, while others care about their work and will get them down to the 9th degree.
Just as an example, here are some pictures that show why I go to Paul C. This assembly was already balanced, sent out the door because I guess they felt it was good enough, I then had Paul check it (first picture) So Paul rebalanced it (second picture) |
The Following User Says Thank You to Formulajones For This Useful Post: | ||
#5
|
||||
|
||||
Here is more of the balance job that was supposed to be "perfect"
First pic is the before, second pic is after Paul was done with it. I think this was the flexplate. |
#6
|
||||
|
||||
YouTube videos, of three different Pontiac guys who bought rotating assemblies from Butler that have checked put good. It’s a pretty good record I’m sure there’s more videos.
|
#7
|
|||
|
|||
Wow, that's a nice balance. Our balancer can't get that close. It is a 1998 Sunnen DCB750. It can balance a heavy crank like a Pontiac to a 3 gram tolerance overall in high speed mode. +-1.5G. That's the best the software will allow. For reference, a 5/16" little stainless washer from ARP weighs right at 1 gram. The software give a fudge factor of 2 to 4 grams for 10W-30 vs 20W-50 oil sticking to the crankshaft and being flung around in the crankcase. Yes, a balance of 0-0 would be best and perfect. But a commercially rotating assembly kit within 8 grams left and right would be considered pretty darn good IMO.
|
The Following User Says Thank You to mgarblik For This Useful Post: | ||
#8
|
||||
|
||||
Quote:
|
#9
|
||||
|
||||
Quote:
How did the force values look moving up the rpm scale?
__________________
71 GTO, 463, KRE 295 cfm heads ported by SD Performance, RPM intake, Qjet, Dougs Headers, Comp cams HR 246/252 ...11 to 1 , 3.55 cogs, 3985lbs.....day three- 11.04 at 120mph ....1.53 60', 6.98 1/8 mile |
#10
|
||||
|
||||
I don't know the answer to that mchell but I'll ask when I talk to him.
|
#11
|
||||
|
||||
Quote:
I'm on the fence about that very thing with my next engine build waiting in the wings. A brand new 502 GM crate engine that I want to turn into a 540. Rotating assemblies make the most sense and are about $3000 from Scat. However I'd be giving all that to Paul to sort out, rebalance, go through the rods etc... I'll have to sit down with Paul when this project gets closer and see if he just wants to piece meal the parts, picking certain brands that he knows will work that may be a better product to start with, or if he doesn't mind working with a complete rotating assembly from any one brand. I'd like Paul to make that decision. Either way in the end it will likely cost nearly the same anyway. |
The Following User Says Thank You to Formulajones For This Useful Post: | ||
#12
|
||||
|
||||
When I have had engines balanced the work often varies in price because some engines took more work to balance, more lightening on the rotating assembly, more expensive Mallory metal added to balance it. I balance the assemblies to save money and time to get it done quicker at the shop.
I looked it up out of curiosity, and Butler’s charge $200 to balance a rotating assembly. Which isn’t high, and not really low. When I see a “fixed” cheaper price in a rotating assembly with balancing, I automatically assume: 1. They assumed the rods came in a matched batch, and are close, but not exact. 2. The crank was balanced to the lightest Bob weight, measured from the lightest rod and piston assembly. 3. Nothing was done on ANY of the rod or pistons to get the weights to match. If something was done, it was very minimal. 4. Depending engine platform it is, the total crank out of balance should be close to a factory balance job. Kind of sounds to me like it will be with in that 20 to 40 range the Mike just mentioned in the last post. One of my friends favorite movie quotes when something seems cheap is from the 1980 movie USED CARS. When taxi’s are painted blue with water base paint to be sold as used cars….water base paint? “Sure, we don’t get much rain around here, what do you expect for $200, metal flake? Lol Last edited by Jay S; 10-14-2023 at 10:45 AM. |
The Following User Says Thank You to Jay S For This Useful Post: | ||
#13
|
||||
|
||||
I bought a complete assembly from Butler for my engine. My engine builder said despite all the other horrors I have endured it was primo
__________________
468/TKO600 Ford thru bolt equipped 64 Tempest Custom. Custom Nocturne Blue with black interior. |
#14
|
|||
|
|||
I have said it before, Mike Lewis told me not to mix up my pins with the pistons. So he must have balanced it to very close tolerances.
I need to have my other Scat, Ross, Molnar assembly balanced before he retires for good. Thing is, as minute as those differences in the pin weights had to be, then you file fit the rings and you do not get them exactly all the same. |
The Following User Says Thank You to Dragncar For This Useful Post: | ||
#15
|
||||
|
||||
If the block was balanced previously, and then disassembled for inspection, then put back together again does it need to be re-balanced?
__________________
Esquire '74 T/A 455 Y-code SD clone previously on Dawson's Creek: '74 T/A 400 '81 AMC SX/4 '69 FB 350 |
#16
|
||||
|
||||
No Sir
|
The Following User Says Thank You to PAUL K For This Useful Post: | ||
#17
|
||||
|
||||
How much can a Pontiac be off before it shows up as a problem or vibration?
That other thread mentioned an LS being off 14 front and 26 back, and a Ford being off 35 and 55. Mike did not mention what the Ford was. I know of one 4.25” Butler rotating assembly that was off about the same as the Ford mentioned, it was checked then rebalanced. Would Pontiac’s heavy crank maybe be a factor in a good way masking balancing issues? Last edited by Jay S; 10-13-2023 at 12:25 PM. |
The Following User Says Thank You to Jay S For This Useful Post: | ||
#18
|
||||
|
||||
stupid noob question - I understand the concept of the balancing but what did they mean back in the day when they said "blueprinted"?
Does that mean factory tolerances?
__________________
Esquire '74 T/A 455 Y-code SD clone previously on Dawson's Creek: '74 T/A 400 '81 AMC SX/4 '69 FB 350 |
The Following User Says Thank You to kingbuzzo For This Useful Post: | ||
#19
|
||||
|
||||
Quote:
Should also mention that being within factory specs does not mean they are the right specs for all applications. Factory bearing clearances were allowed to be super tight, and you would not want to build a performance engine with .001" of oil clearance.
__________________
Michael 1970 Oshawa built 1 option Judge. 24 year restoration/upgrade project finally finished! 1979 Trans Am - low-buck drag car project for when I retire Last edited by mrennie; 10-13-2023 at 12:53 PM. |
The Following User Says Thank You to mrennie For This Useful Post: | ||
#20
|
||||
|
||||
I think the definition of "blueprint" varies.... Often I order pistons for guys and explain the compression height has to be determined off a "blueprint" dimension. Meaning the height of the deck. The factory used a specified dimension which varies a bit. A blueprinted specification would be a specific number. As you rebuild an engine there are many specific dimensions that have a tolerance. A blue printed engine would be set at a specific dimension. Alteast that's my definition of blueprint .... and "balanced" Back in the day every high performance car in the Auto Traders had a "balanced & blueprinted" engine. Now those guys are ruling the performance pages on FB.
|
Reply |
|
|