On my new motor. 377 LS3 from Texas-Speed (motor is actually built by same company that does Scoggin Dickey's motors). Neutral balanced, talked with TSP today to confirm that.

Powerbond underdrive pulley, zero balanced, reused from my stock motor, no issues noted.

Tex OZ700 clutch/flywheel, zero balanced, reused from my stock motor (~4K miles on it), no prior issues noted. Clutch in or out, makes no difference.

New pilot bearing

Problem is that sitting in the car at idle you can feel a noticable vibration, that moves linearly with RPM's. At about 1800 RPM it feels like the car is wobbling slightly on the jackstands. Talked with the guys who did the motor install and they said vibe was present from 1st start up. The motor starts fine, revs fine, just feels "off." Waiting for my order of VR1 10w30 to come in to I can do a change and fill before taking for a drive myself (tomorrow).

The tune is out to lunch, I know that much. It's misfiring some at idle (heard through exhaust) due to the oil that got into the backside of the turbo's, but not terribly. No pertinant codes showing.

I'm stumped, and looking for some inputs and ideas. Could it be tune related?

 

Vibes could be from a crappy tune. I'd certainly start with getting the tune right before lookng for mechanical reasons for the vibes.

Does the crank pulley look true as it spins?

 

I'm hoping you're right. I didn't get a chance to fire it tonight, but I'm going to change plugs tomorrow and take a good look. The pulley is a single piece powerbond and was fine when it was on the original motor so it shouldn't be an issue unless it's backing off for some reason.

 

Just a thought, but couldnt torque tube bushings cause vibration??

 

I was actually pondering that initially, but then I figured why would they cause such a pronounced vibration with the car just sitting on jackstands?

 

Driveshaft turning at idle?

 

Is the vibration there with both clutch engaged and disengaged? If you rev the engine and take your foot off the throttle does it still have the vibration on the deceleration back to idle?

Clutch engage / disengage will identify if it is torque tube related or not.

Vibration on deceleration will identify if it is engine relayed imbalance or combustion issue cause by cal, bad injector, spark plug, etc…

 

Doesn't matter, clutch in or out. I'd have to double check if it was still there on decel from the rev, I want to say it is but I can't remember exactly. Will be test driving tonight and report back for sure.

 

Check each exhaust port with infra-red temp gun. If you have a cold one, then you know you have a dead cylinder.

I had a terrible engine balance issue with a big-block Chevy. It was incorrectly balanced two times! I had to keep R&R'ing the engine and then finally on the third attempt, they got the balance correct. The vibration was pronounced and most noticeable between 1800 and 2200 rpm on mine.

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If I had an infra-red gun. Good excuse to get one though. Not sure how effective it would be on a cast iron turbo manifold though.......

 

Sunset Racecraft did the build, if SDPC and TSP still use the same source

I have zero info on your car/motor/build

Who is Chicagolands's finest LS tuner?

 

more then likely not, but just thought I'd throw it out, bad motor mounts?

 

Mounts might be suspect, but with only 66K on the clock doubtful.

Steve, motor is a 377 shortblock, GT2-3 camshaft, Patriot stage 2.5 317's, same clutch as you put in, same accessories and pulleys that came off the old motor. Nothing in the driveline was replaced or came out of the car. I have a good tuner here in St. Louis who I should be seeing on Saturday for him to take a look.

Ok, here's the update: Got fresh oil and filter on it, pulled all the plugs and put them right back in because they were brand new, got it out and the vibration is still there. No crossed plug wires.....wait.....not an LT1 like my Trans Am.......nevermind there.

Vibration is present at idle. Upside AND downside of revving, accelerating, decelerating as the engine idles down, engine braking. It's 100% RPM based. More pronounced with higher RPM's. I took it to 4K today easing into it and it got continually more pronounced almost to the point of being a constant buzz. I can feel it in the steering wheel, in the shifter, in the chassis, everywhere. I doubt it's in the clutch because it felt absolutely fine. Smooth as it used to be engaging. It's noticeable enough that at idle if I was to set a glass of water on the car I might be able to capture the water movement.

Pulley were all tracking straight and true, no wobbling or anything. I talked with Nate and he had marked and reinstalled the clutch exactly as it came off the car. I queried about the possibility of the input shaft for the torque tube possibly bumping the pilot bearing out of place during the motor install, and he said they had ZERO trouble getting the engine in and bolted up.

I am going to call it a 99% fact that it's NOT the tune based on what I felt in the car today. I'm a little bummed at it because it's not the silky smooth car I had before. Not looking forward to having to pull the driveline to get to the clutch if it goes that route because the entire damn turbo system's got to come out first.

So.......anyone experienced a pilot bearing failure?? If so, what did it feel like?

Another thought: I'm going to call TSP tomorrow and talk to them about the crankshaft they used. I'm searching on a long shot here, but wondering if they use a LS3 crankshaft and put a 24 tooth reluctor ring on it, or if they used a stock LS1 crankshaft. Just thinking there might be an ever so slight difference between the two (if that's what the builder does) and the LS1 flywheel/clutch coupled to the LS3 crank has something to do with it.

 

Sean,

From the information you provided it is time to talk with the builder. A once per rev imbalance will increase in level with rpm. A two per rev imbalance can mean something is wobbling like the flywheel or harmonic balancer. I would ask the builder if the crankshaft balance was checked, if yes, ask to see the data. Did they check the weighs of the connecting rods and pistons? Do you have a copy of this data?

It doesn't take much imbalance to cause a vibration that can be felt. The most noticeable part for engine imbalance in my opinion is the shifter.

With balancing equipment and the car in a lift it normally only takes about 30 minutes to and hour to balance the engine.

 

I'm going to call Jon @ Texas Speed tomorrow and get him to fax or email me the balancing sheets.

Are you hinting that this can be corrected without removing the motor from the car, talking about balancing equipment and the car in a lift? I would be ELATED if that was the case.

 

holy crap buddy, sounds like a pain it the ***. Good luck with it.

 

Yes, if it is a once per rev imbalance it is very likely it can be balanced in the car. I get the pain....I'm mean pleasure to balance about 6 a year where I work. Some of them you would swear the engine was ready to jump out of the car before balancing and as smooth as silk after word. The trick will be finding someone locally that has the equipment to do it.

 

What places would you recommend checking with?? If it comes down to it, I don't care who does it because I won't be paying. Want a side job??

Pete, believe it or not I'm not up in arms about it. I'm surprisingly quite subdued. Guess I'm used to hardship when I try to do anything. ANYTHING I try to do or have done to one of my cars ends up being a battle.

 

Sean,

In your first posting you mentioned that you used the flywheel and harmonic balancer from the old engine. Do you know the history of that original engine? If not you might be able to fix the vibration issue yourself. If you haven’t already checked and if you don’t know the history of the flywheel and harmonic balancer then there is a chance that one or both have some weights added that were needed on the original engine, but not good for your current new engine. Check to see if ether has weights. If you find some, removing them might fix the issue you are having. Even if you know the history of these parts, I would still look them over for weights. You might already know this, but the flywheel has a series of holes just in from the starter ring gear that are there for adding balance weights. The harmonic balancer can have the same type of holes but could be different depending on manufacture.

I really don’t know anyone in the Illinois that does engine balancing. When I retire from my current job I will probably get into doing engine balancing among other Corvette related things.

 

The motor was an unmolested short block, the Clutch/Flywheel went on the car with the APS TT kit in 07 and are a zero balanced Textralia OZ-700, and the crank pulley I put on the car myself back in 06, it's a Powerbond underdrive pulley. I'm going to get the hand trigger out and get as much of a view of the flywheel as I can and see if there's a weight or something on there this weekend I think. One can only wish.......