My 4.6 V8 Rebuild Thread

[101RRS]

A question to the learnered engine rebuilding peoples.

The engine builder said that as I am using a matched crankshaft, pistons and rods no balancing is required.

Now if I were to put on the 4.0 pistons onto the 4.6 crank and rods I am assuming that balancing would now be required. Yes/No

Researching balancing I see that the whole system needs to be broken down to its individual components (including the flywheel which is still in my 101) and each weighed etc and then reassembled to minimise out of balance and then the crank drilled or weight added to finalise the balance. Yes/No

If this work is required it would seem pretty labour intensive.

Thoughts - comments appreciated.

Garry

[PhilipA]

There are 2 parts to balancing.
Static- where the pistons and rods are individually weighed and equalised.

And Dynamic where the rotating assembly of the crankshaft plus weights to simulate the pistons and rods, plus flywheel, dynamic balancer are spun and weight added or subtracted to the crank to make it dynamically balanced.

If you change any component such as the pistons , you will have to redynamically balance as you have already discovered that the pistons have different bowls and therefore different weight.

BTW, it my understanding that Thor 4.6 has a less accurate balance from new as the Thor injection measures the piston acceleration on each stroke and "balances" the cylinder effort individually. Is yours a Thor?

If so it is probably worth the exercise and moreso if you are using different pistons/ rods. I would.
Regards Philip A

[clubagreenie]

To really dynamically balance it you need to:

Weigh the pistons and rods, then linish to match the weights to the lowest value. Weigh a set of rings, bearings and pin so you establish the total value for the piston/rod assy. This weight is used to be the weight for the bob weights which are attached to the crank, along with the balancer and flywheel/flex plate to simulate the weight of the piston/rod assy without having the things flying around the place. This is spun and balanced dynamically.

Anyone who says even if you change components you don't need to do this. Find another builder. Even if it's a set but been run and getting refitted into a rebuild, it needs to be cleaned, new rings and bearings so there;s enough of a change right there.

I can recommend either Duggan Balancing in Melbourne (absolute gurus) or Wayne Smith Engine Research in North Rocks Sydney. Again A old, crusty but brilliant man who you learn something from just standing next to him.

[101RRS]

Is yours a Thor?
Regards Philip A

Engine would have been originally a Thor 4.0 but I do not have the Thor manifold/computer etc - induction/fuelling system is something to consider in the future.

To really dynamically balance it you need to:

Weigh the pistons and rods, then linish to match the weights to the lowest value. Weigh a set of rings, bearings and pin so you establish the total value for the piston/rod assy. This weight is used to be the weight for the bob weights which are attached to the crank, along with the balancer and flywheel/flex plate to simulate the weight of the piston/rod assy without having the things flying around the place. This is spun and balanced dynamically.

Anyone who says even if you change components you don't need to do this. Find another builder. Even if it's a set but been run and getting refitted into a rebuild, it needs to be cleaned, new rings and bearings so there;s enough of a change right there.

I can recommend either Duggan Balancing in Melbourne (absolute gurus) or Wayne Smith Engine Research in North Rocks Sydney. Again A old, crusty but brilliant man who you learn something from just standing next to him.

Thanks - sounds like too much work so puts a nail in the coffin for using the 4.0 pistons - I will stay with the 4.6 pistons and save a bit of work.

Thanks

garry

[MacMan]

Another plug for Duggan Balancing who saved me a heap of trouble after a series of bad experiences with another Melbourne based "expert workshop". great guys and very helpful.

[PLR]

G`day Gary ,

yes , it would be best to have it balanced no matter which way by people who know and they will use finer tolerances than what the factory did .

As it would be , because you will not be using the factory flywheel/flexplate etc or the front damper/balancer from the original factory 4.6 it is unlikely to be a balanced set anyhow .

These RV8s are weight balanced (as said by others ) , crank dyn at 500rpm then a final balance with both ends of the crank fitted ( flex/balancer ) The final is at 500rpm and assembled .

Athough the flywheel ends are balanced in there own right it`s my understanding that the front end is balanced with the unit by the factory so not matter it will have this discrepency , so as long as the 4.0ltr set is within the +/- 2gms that the factory uses , that should be as good as what the 4.6 pistons will give .

You will have read on here about people pulling engines apart and finding bits missing , like chunks out of pistons etc and they were not usually looking for a balance issue .

Hammil and Hardcastle both suggest that running at or above 6000 revs internal balancing will be a requirement for a RV8 and because of this the suggestion is also if the RV8 does not see 6000 revs it doesn`t .

If it were me i`d get it balanced if it was no great drama but if a drama i`d make it as best as i could myself with a set of scales etc because one reason would be that ours don`t see much better than 4500 i guess not real sure it`s even that and that`s only small doses .

My opinions often differ to others .

Peter

[101RRS]

Thanks for those comments - as the flywheel is supposed to be included how to they balance an engine that is going to have an auto attached given that the torque converter is essentially "flywheel" and its balance depends on the weight of the oil in it.

Likewise when you replace the clutch in a manual nothing is balanced.

While I appreciate a basic balance on the engine is required - is the level of balancing being talked about really for high reving performance race engines rather than what I am developing.

Cheers

Garry

[clubagreenie]

If it's auto then they attach the flex plate. I'd really advise to have it balanced. You're changing the harmonic balancer and the flex/fly wheel. The things at the extreme ends. It means you can use the right pistons and if you have a good set of scales, 0.5gm or better you can do some of the work yourself.

It's not above what you'd do if you were a reputable builder, just the accuracy changes. I usually order 5 sets of rings, bearings, rod bolts/studs select the closest and they are matched to 0.1gm. But i'm building things from 10,000 to 18,000rpm.

[ozscott]

Hi Garry My father has a 4.6 in his county I have a 4.4 terrier in mine with a HC 4.6 sitting in the shed to rebuild and go into mine. If the 4ltr block has a crack in it I wouldn't us it. I haven't read any other replys so I am sorry if I go over something already touched on.

A resleeve with T sleeves on a 4.6 block is around $1000. If you wish to go out back you don't want to slip a liner out there!! cost you alot more than $1000 to recover it. The slipping liners is the main flaw in the 3.9, 4, and 4.6. It is due to the cylinder walls in the block is alot thinner and therefore get alot hotter. The Oil temp gets way too hot in these engines. You will not see it on the water temp gauge until it is too late. Dad's truck got to 105 on the water temp and 135 on the oil temp towing his caravan one hot day in December last year. The oil should be cooler than the water! If you have all the bits for you 101 you will be right as they had an excellent oil cooler on them. The only issue is you have to run the correct oil filter! the Z9 will fit but is not the correct filter as the 101 has a higher capacity, higher pressure system than any other rover. Donalson make the right one which I run and noticed an increase in oil pressure straight away. Since putting an oil cooler on dad's truck no matter how hard you push the engine on a stinking hot day with the AC flat out the water temp wont go over 92 and the oil 80

If you wish to run it on LPG I would suggest going to high compression. If you don't on LPG you will get poor fuel economy, a noticable drop in perfomance, and it will run hot. I run my terrier a 10.5: 1 all you have to do to run it out west on poorer fuels just retard the timing about 3 degrees which is not hard. I have two marks on the dizzy for this reason. Or take some octane booster.

I have the early Hot Wire EFI system on my truck, easy to fit as they had a separate wiring harness to the mian one in the vehicle for it. Carfully pull it out of a Disco or Rangie and fit it. You would need to rechip the computer for the 4.6. You can also get a sandwich plate for the ram tubes making them longer and giving you more torque.

If you stick to the carbies you would have to change the needles and you will find it will run out of air very low in the reves

My Father spent $10000 rebuilding his engine and it is awsome. Heading North up the F3 it pulled 120 up Mooney Mooney in 5th and didn't even look like slowing down.
Tim

My d1 has engine oil pipes that pass through the radiator, as well as it having an auto trans cooler. It's a 3.9. I assume the d2 would be the same? So was that a more recent idea than County?

Cheers

[clubagreenie]

The D2 has external coolers. The fittings of which are notorious for not staying put.