Rattling Dominator

I have a model 99 600 Dominator. Just been rebuilt and it rattles much more than it used to. It has new pistons and cast rings. The noise really sounds like the top end but it may be piston slap. The rockers are gapped correctly and oil is being delivered ok. The bore was given one extra thou based on recommendation of boring engineer. It also vibrates lots, more than I remember. The crank, and pistons were balanced but I suspect when you do balancing you should include everything attached to the crank, ie alternator, primary sprocket etc. is this right?
Regards
Kwraith

One thou more than what?

Kwraith said:

The crank, and pistons were balanced but I suspect when you do balancing you should include everything attached to the crank, ie alternator, primary sprocket etc. is this right?

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Only if doing dynamic balancing and then the alternator rotor and engine sprocket are pushing the quest too far.

Who did the balancing, are they are experienced in balancing 360 twin cranks and what balance factor did you specify.

First off go for basics, are all the mounting hardware still present and torqued up plus have you fitted the head steady.

Ok thanks. Yes all the mountings are present snd tight. I am not sure but the guy had some documentation on the balance requirement. The business did only balancing but mostly cars

Kwraith said:

but mostly cars

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That is likely your issue.

Thanks. If I have to pull it all apart again should I get it rebalanced with rotor, sprocket etc?

When I had my 650ss crank dynamically balanced the only bob-weights added were the weights of the big-ends of the conrods plus the notional value of the oil in the crankshaft (can't remember what that was)
I weighed the big-ends myself using piano wire, suspending them horizontally.

Seems to have worked a treat.
Cheers

Thanks Rob.

Kwraith said:

Thanks. If I have to pull it all apart again should I get it rebalanced with rotor, sprocket etc?

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No. You don’t want them forming part of the balance factor.

If you're being really fastidious you can balance those individual components as you would a wheel, ie so there is no imbalance whatsoever on them.

Some specialist can / will do this. I’ve had rotors balanced before and holes were drilled, so some imbalance was there. But I don’t do this anymore on the basis that it makes bugger all difference as far as I can tell !

At the end of the day, these are low revving motors. Even the thrashers are only gonna be doing 6-7000rpm. It’s really not high rpm when you look at it objectively.

So, do get the crank balanced by someone who knows what they’re doing, and choose your factor carefully, but don’t worry about the rest IMO.

what pistons , are the pins free when pistons heated, are pins free in con rods. block the oil return for a few seconds to oil the rockers.

Fast Eddie said:

So, do get the crank balanced by someone who knows what they’re doing, and choose your factor carefully, but don’t worry about the rest IMO.

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For static balancing, the balancing factor has been published. It's approx. 80%. Make sure the oil content inside the crankshaft is accounted for, and that the sludge trap has been cleaned prior to balancing.

Due to weights of reciprocating parts and the hard mounting of the engine, dynamic balancing is strongly recommended. You need to hand over the crankshaft, complete conrods, bearing shells and complete pistons.

- Knut

If the pistons are not free to float on the pins when hot ( a problem i have seen before ) ,it will be very noisy and rough . If you can be bothered to reply with more information you might learn a thing or two.