Take a look at a balance card

[czimpel]

I had my 4.1 balanced, and I finally got the motor in the car and running. I'm feeling a vibration in the car from about 1500-3500 rpm. This vibration happens in park, neutral, going down the road...I have a PTC 2800 LU converter.

The vibration was not there before the new engine.

I also added the HR mounts, could this possibly be the difference I'm feeling?

Can someone look and see if this balance sheet seems normal for these engines.(Not sure if it's possible)

Thanks, Cory

 

[ek02]

The bob weight looks a lot higher than any of my balance cards. Bob weight is usually 843-875 on my engines balanced at .366 %, depending on the components. Ask the machine shop how they arrived at the bob weight and if they balanced it to .366% or 50%. Could be that the bob weight is 895 and entered in the wrong place on the card. Disconnect the converter and pull it back, then start it to make sure that is not the vibration. Not sure about the mounts, but that is a possibility if the balance is correct. On a 4.1, be sure you have a 4.1 flywheel and damper and that it was balanced with the crank, unless you have a neutral balance forged crank in which case you would need a neutral balance flywheel and damper.

 

[turbodave23101]

That Bob weight can't possibly be correct. Even at 50%

Sent from my XT1254 using Tapatalk

 

[czimpel]

The flywheel and damper were both sent with the crank for balancing.

 

[TurboTdr3.8]

I can tell you 1 thing the HR mounts makes my cars not as smooth as they used to be , so you may be feeling that

 

[czimpel]

I hope it's just the mounts. I don't feel like tearing this thing back down!

 

[A2000RICH]

Something is very wrong with those numbers. They just don't add up any way i can juggle them. At 36.6 I have never done an engine where the bobs were much over 900 gr. With an additional 15 % they would still not be anywhere close. No way that engine can be even close to balanced with math like that. You better take that thing apart before it shakes itself apart.

 

[czimpel]

Thanks Richard, looks like a winter project!

 

[ek02]

I would ask the machine shop to explain the math on that card. Here are photos of two of my 4.1 balance cards. First one is for a RPM stroker crank, molner rods, and JE pistons. The second one is a CAT stroker crank with CAT rods and JE pistons. Both are internal balance. Hope this can help explain why that card makes no sense. Good luck.

 

[czimpel]

I would ask the machine shop to explain the math on that card. Here are photos of two of my 4.1 balance cards. First one is for a RPM stroker crank, molner rods, and JE pistons. The second one is a CAT stroker crank with CAT rods and JE pistons. Both are internal balance. Hope this can help explain why that card makes no sense. Good luck.

View attachment 261014 View attachment 261015

Thanks, seeing those(although internal balanced), helps me understand mine a little better.

 

[czimpel]

Does anyone happen to have a balance card from a 109 or external 4.1 for reference?

 

[ek02]

Here is a card for a 3.8 with hyper pistons, polished stock rods, and a stock crank.

 

[turbodave231]

The math is exactly the same regardless of whether the crank is internally or externally balanced. The difference is all in the parts.

The Formula is: (Reciprocating Weight x Balance Factor) + Rotating Weight= Bob Weight

There are 2 generally accepted Balance Factors for Buick V6's: 36.6% or 50%

Internally balanced engines use flywheels and crankshaft pulleys/harmonic dampners that are neutral balance (perfectly balanced all by themselves)
External balanced engines use flywheels and crank pulleys/harmonic dampners that have a specific engineered imbalance built into the part.

 

[A2000RICH]

Thanks Richard, looks like a winter project!

My computer balancer stores all the jobs that I do .......just for reference I looked up a couple and here are a few bob numbers on typical engines ........patrick,s stroker (slogn) had weights of 837.13 gr .....it was a 109 balanced at 36.6%............an engine I finished yesterday was a 109 done at 36.6% and had bobs of 833.78.......a stage II 4.1 I did several weeks ago at 50% had bobs of 1038.6 gr.........if you don't live too far from my shop I would be glad to help you out with this mess you have ended up with and you can watch it being done and even take part in the fun if it interests you

 

[czimpel]

Thanks Richard, but I'm in Minnesota. I'd love to make the trip just to meet you and see your shop though. I'll get it worked out. The guy that balanced it is a Late Model race car engine builder. He should know how to balance a crank, V6 or Not. Oh well, at least I caught it and didn't just blame the mounts. Thanks for looking into your balance records too, this all helps!

 

[A2000RICH]

Thanks Richard, but I'm in Minnesota. I'd love to make the trip just to meet you and see your shop though. I'll get it worked out. The guy that balanced it is a Late Model race car engine builder. He should know how to balance a crank, V6 or Not. Oh well, at least I caught it and didn't just blame the mounts. Thanks for looking into your balance records too, this all helps!

i agree it seems unlikely that an experienced shop would make such a mistake......after all the basic functions of an internal combustion engine are pretty similar no matter the type or brand........but i have to say these buick v6's seem to throw some people a curve ball sometimes..........i build a lot of GN engines and i can state for a fact that the worst built engine ever brought to me for repair was built by one of the most well known and successful NASCAR shops in North carolina.......this is an outfit that everyone would recognize immediately........i figure that they have forgot more than i know about building engines and have built thousands of succesful fords and chevy racing engines (and maybe even buicks) for every one that i have built............but somehow they really missed the mark on this particular engine.........the problems were excessive and numerous...........if i had to guess perhaps they don't take them seriously??????

 

[czimpel]

When I talked to him on the phone, he says" I didn't balance this crank, one of my other guys did" an immediate red flag for me. He continues to say that they have done numerous Buick jobs for a local guy who has built many TB motors. I emailed him the balance card yesterday, we'll see where it goes.

I know they will rebalance it for me, I just hope the cover the cost of the gaskets and supplies.

 

[charlie547]

Any update on this? Curious to see what the outcome was.

Sent from my SM-G900V using Tapatalk

 

[czimpel]

He said that he couldn't even find the record in their system of my crank and the balancing. He looked at the balance card and agreed that it in no way could be correct. He's going to make it right, but when I talked about him coving the cost of gaskets, he didn't really give me a definitive answer on that.

I know he'll take care of it, they are a good quality well known shop. He is going to let me wait until winter to pull it out and tear it down again.

I'm just still upset that I went a whole summer without being able to drive it.