G'day Folks,

I recently ventured 1,000kms North from Canberra toward the Queensland border to collect a mint AU III XR8 347 stroker with a factory 5-speed.

I drove the car back to Sydney for the night before venturing back to Canberra. However, while driving along the M5 to Canberra, I noticed this strange vibration that I did not previously notice. I can't say for sure that it wasn't there to begin with, but I definitely didn't notice it beforehand. Furthermore, I had the car inspected beforehand and they didn't pick up on anything untoward.

Anyways, the vibration occurs while the car is both stationary and driving, and is relative to the engine RPM.

I can't for the life of me figure out what it would be. There doesn't appear to be anything visually obvious. The only things I can possibly think of is the harmonic balancer (which appears new and doesn't show any obvious imbalance while engine is running), the flywheel, clutch or god forbid, the crank.

Does anyone have any similar experiences they have seen or heard of? The driveline literally has all the bells and whistles. Specs are as follows:

Original AU 5.0L roller cam block, bored and stroked to a 347 with an EAGLE crank (http://www.eaglerod.com/index.php?optio ... &Itemid=32), EAGLE H-beam conrods, Clevite77 std B.E. & Main bearings, SRP forged pistons .020” oversize, Trickflow stage 2 cam (TFS-51402001), Trickflow 170cc Twisted Wedge Heads, Edelbrock Victor Series intake manifold, Edelbrock 4" MAF, MSD ignition, SCT flash tuned, lightened flywheel, ceramic button clutch, short-shifter, steel tail shaft, etc.

Most of those details are probably irrelevant, but I understand having more information is certainly better than not enough!

Any help you might be able to provide would be greatly appreciative, as the vehicle is otherwise in immaculate condition within genuine 68,000kms.

Many thanks!

Last edited by Bassfreak55 on Mon Apr 13, 2015 10:34 pm, edited 3 times in total.

check ya balancer

Was it balanced? All Eagle 347 kits are approx 28oz or 0oz. The AU balancer is 50oz. Ditto the flywheel

The balancer is the most likely cause

If the balancer has died (either because it wasn't balanced, or because the balance ring has moved) then the engine needs to be disassembled and the rotating assembly re-balanced with the replacement component. If you can get bob weight measurements from the balancing shop, it makes the process a little easier - just remove crank and front/rear accessories

When I build 347's I always have multiple external accessories balanced for both future flexibility & safety. The 347 I'm building atm is balanced with 2 different balancers, a flex plate and a flywheel

Externally balanced motors are a PITA

I spoke to the engine builder (Ian Richards @ Aitkenvale Auto & Dyno) who built it late 2013 and said it certainly would have been balanced, but couldn't elaborate on particulars. The link for the model Eagle crank used (model number 430234005400, using the link in my first post) suggests the crank is "internally balanced". Now, I don't have any experience whatsoever with regard to engine balancing, so that might be irrelevant.

I guess I'm trying to ascertain what (if anything) can be done to confirm what the likely cause is without having to remove or dismantle the engine.

If it is indeed the harmonic balancer, would there be a tell-tale sign or giveaway?

Appreciate your help, guys. Thanks!

i found by moving the belt by itself [no engine running] on an engine here that had the balancer fail, that the balancer's 'outer' ring would spin on the 'inner' ring

Ask for the balancing record. It will give you all the answers. If it is internally (neutral) balanced, it makes things very easy to replace external rotating parts. They just need to be neutral balanced then installed.

To check your balancer, remove the belt and do a visual inspection on the vehicle. Grab the pulley and try to wiggle it. Then start the engine and put a timing light on it in base timing mode. If any of these tests show movement of the outer pulley portion of the balancer, it is stuffed

Thanks for the reply. I contacted the workshop and asked if they could locate any balancing records, so we'll see how that goes.

In the meantime, can anyone recommend any reputable and trustworthy workshops in either Sydney or Canberra (preferably) where I might be able the take the AU?

Thanks again!

Hey folks,

Just heard back from the workshop however no success. Unfortunately, the engine was originally built by a workshop in Perth (no further details) with further work done when the car (and owner) moved to Queensland with work. Long story short, the balancing records are unavailable.

The workshop in Queensland however, made a suggestion: "I’m unsure if Gentech (or another workshop) can obtain another balancer of the same type (I can’t remember what brand it was off hand) to check its indexing in case it has spun".

Does that makes sense to anyone and if so, is it a worthwhile avenue of enquiry? And if that is the case, can it just be replaced with an identical part?

Thanks again!

Can you take a picture of the balancer? If that crank you've linked to is definitely the one in the engine (as opposed to the Eagle cast crank 103023400) then it will need a neutral balanced balancer and flexplate/flywheel...

There are very few neutral balanced units for an AU V8, and the fact that the engine/car has been through several shops before finally running is a little disconcerting, very easy for information to get lost or not passed on. I'm speculating that a balancer wasn't included with the rotating assembly when it went to the machine shop, and somewhere down the line a standard weight AU V8 unit has gone on.

I'm currently deployed to the Solomon Islands with work but due to return for a short time on the 7th May, so will take/upload the photo then. I know 100% that it isn't a standard harmonic balancer, but unsure as to its details (had to get myself organised myself for this deployment!!)

The part number the workshop quoted for the Eagle crank was definitely 430234005400-C, which appears to be the internally balanced one rather than the alternative part number you queried. I know an absolute fortune was spent on the engine, so have no doubt it would be the more expensive forged variant.

The car was originally in Perth with the first owner, who had the engine built there before moving to Queensland in 2007, where he took the car with him. This is when he started taking it to the Aitkenvale workshop for further modifications (tuning, gearbox, diff and brakes).

These are the only engine photos I have on hand at the moment:

 

 

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First test the balancer like I said above

If it is stuffed and since you are sure the crank is the p/n you quoted, just replace with another neutral balanced balancer.

Easy, thats the beauty of neutral balanced engines