Vibration at 2100-2500 RPM

[pkbenavidez]

Hello everybody! I'm getting a vibration at 2100 to about 2500 RPM. I'm running a 440 with a 505 stroker kit from 440 source, chrome fluid damper from 440 source, flexplate from 440 source, and a TCI Breakaway TQ with a 2200-2400 stall. I'm also using an electric fan. It vibrates in park and in neutral. Does anyone have an idea what it could?

 

[kiwigtx]

How come you are revving the engine so hard in Neutral and Park? Is this a start-up ritual, or just curiosity? :eusa_think:
I would have been concerned if you were driving at that RPM and had a vibration.

 

[furyus]

These problems can be very difficult to find. If it vibrates sitting still, it's in the engine or trans. Could be the engine balance. Did you get it balanced with the flex plate and balancer in place when the engine was built? I've had new convertor be out of balance internally. Are you using solid mounts?

 

[pkbenavidez]

At first I thought it was the driveshaft, because it vibrated between 60 and 65 mph, at 2100-2500 rpm. then I put it in N and it still did it at that RPM, the same in P. Yes it was balanced with the flexplate and balancer, has rubber mounts. TCI says to torque the bolts to 45-55 ft lbs, but I've always just tightened them up tight with no problems. I still checked them again and they were good, besides I can't get a torque wrench in that little space. What brand TQ did you get that was out of balance?

 

[furyus]

mine was an ATI convertor. Also got a bad trans from them. Won't get any more of my money.

 

[Meep-Meep]

Having a vibration sitting in P is definitely engine and likely the converter. A few questions: Did you have the engine INTERNALLY balanced but got an EXTERNALLY balanced converter or flex plate (with weight)? Or vice-versa? I have that exact same TCI converter as a zero balance application and I liked it so much I got another for a different build. Talk to the folks that balanced the engine and hopefully they can tell you if you require a weighted converter or flex plate. Shops don't typically don't balance converters so I'm betting on a mismatch in that area.

 

[super-bee_ski]

Forged Crank SFI Flexplate Pic 1



Cast Crank Flexplate Pic 2

 

[pkbenavidez]

the shop said they balanced everything internally and no weights on converter. I do have the flex plate in pic #2, but it was balanced on the motor also

 

[Shorthorse]

Something's not right here. Balancing is not really done "on the motor". That picture #2 is a B&M flex plate for an externally balanced motor. The internally balanced flex plate does not have the half moon cutout.

 

[super-bee_ski]

Yeah,
It is hard to diagnose "on-line" but:
1. If you have a Forged Crankshaft you will be running the Flex Plate in picture #1. That means you have an "Internally balanced engine"
Simply put; the reciprocating mass of your Crankshaft/connection rods/pistons are all within a "tolerance" and your Crankshaft will have weights added OR weight removed to help achieve this.

Remember. Physics 101: Harmonic frequencies DO DEVELOP with reciprocating mass.

2. If your Crankshaft is "CAST" then you have to "Balance" the reciprocating mass elsewhere. This CAN be accomplished by adding weight to the Torque Converter as the Factory did OR by using an Externally balanced Flex Plate that I show in Pic #2. Notice it has a "Chunk" taken out of it?

I just ordered 2 of these (Pic 2) from Summit Racing because B&M is not making them anymore.

 

[Meep-Meep]

The reason for external balancing is to add extra weight cheaply and conveniently to the crank counterweights. The balancing procedure for internal balance is to calc the bob weights and only spin the crank until you zero it out. Then add the flexplate or flywheel, damper and zero those out. If during the operation you find you need a ton of mass to balance the crank itself then one can install the weighted flywheel or flex plate to the crank to bring the residual unbalance down to manageable levels. What you don't do is balance the crank, damper and flywheel/FP at once and only remove the mass on the damper and flywheel. Further, if industry standard for external balance on a particular engine says it needs 15g at (x) radius then you work around that. This way you can change the flywheel with another one just going by the specs. Balancing internally usually means adding heavy metal to the crank counterweights and that will allow you to use a non weighted flywheel/FP. If you have the FP in pic 2 and was balanced on your crank then your motor is not internally balanced because that missing mass on the FP at that radius is not balanced by itself. Do you have weights on the converter also? If your crank and FP were balanced as an assembly and became zero together then you don't want weights on the converter.

 

[pkbenavidez]

My bad, the FP is round with no cut out and its a forged crank. The stroker kit comes already balanced. Man its tough having to do things alone. might have to take it to the shop and put it on a lift.

 

[super-bee_ski]

I think "WE" could also look at:
1. Drive line, such as a U-joint being bad and causing the vibration (Is it vibrating in "PARK" with the engine being revved?) or driving?
2. Could it be a Motor Mount?

If you have a Forged/Balanced assembly, then you should HAVE the Flex Plate in PIC #1

 

[mentor70]

personally, i dont think an engine balance issue would manifest itself in that low RPM range... what cam is in this engine?

how are the engine and trans mounts? bolts tight?

 

[747mopar]

A few other things to consider are your ignition, a misfire or stumble at that rpm could cause a vibration and even exhaust drone can easily be mistaken for a driveline vibration? Just saying look even where you wouldn't expect it.

 

[pkbenavidez]

It has a Comp hydraulic roller SN#VO0177-11
Part#23-713-9
Grind#CRB3 XR292HR-10
Can't really feel it from under the hood while at that rpm and don't hear any misfire. In fact the engine runs smooth. Maybe I deed to have someone in the car controlling the RPM's while I check under the car. Does that sound like a good idea? It feels like its coming from under the console.

- - - Updated - - -

I really appreciate everybody trying to help me out.

 

[cdr]

take the belts off & run it , the fan blade and or fan clutch can be bad & make a vibration, dont run it for very long.

 

[pkbenavidez]

take the belts off & run it , the fan blade and or fan clutch can be bad & make a vibration, dont run it for very long.

Thanks! I'll try that.