Front pulley balance question.

[ihatesissycars]

I've ome to a problem.

In replacing my front pulley to a serp type i'm going to upset my engine balance and without a right old work up real steel can't baalnce it on its own.

They'd need a crank to mount it to, my old pulley and my new pulley and even then they weren't 100% they can.

My old pulley was from a 3.5 sd1 and had no extra added bar, drillings etc (in its original state) on it to affect balance whereas all the 3.9 pullies i've seen have truck loads of bar attatched on one particualr area to help balance the engines. Because the 3.5 cranks and 3.9 cranks are the same but 3.9 pistons weigh more so Rover did a cheap fix by loading up the front pulley to compensate i believe.

Now, my serp pulley has loads of extra weight on it as it should so i was thinking. Remove all its extra wieght so it should in theory be not far from balanced on its own as should the original pulley with weights removed on its own so i was thinking of then putting the weight from the original pulley to the serp pulley in the same position, sound like a plan?

Reals steel tooka ages to do my original balance plus i'll get charged this time for doing something which may not work plus there's travelling there and back again twice which is a pain so the option of cutting a corner is very tempting.

The amount of people running engines using a mix and match of parts that haven't been balanced in any way and have no problems makes me think i'll be at least in the right ball park and ok to use it like that.

Opinions?

[r2d2hp]

Not sure abouut the V8 but on the Essex V6 you balance Flywheel, Crank and front pulley as one item.

Would have thought something similar would happen on the V8

[ihatesissycars]

Yes my engine (everything thats attached to the crank) was balanced as one however i'm not stripping the lot down again just for a different front pulley. There's gotta be a way of getting this serp one in the same ballpark as the original one i had the lot balanced with.

I did think about swapping the balance rings over on the pullies but ones a 6 bolt hole and the other a 4 bolt hole dammit!

[kev_the_mole]

Gav,

two suggestions.

(1) Take the balance weights off both pulleys and go to your nearest engineering dynamic balancer (Yellow Pages) and find out if both pulleys are generally neutrally balanced. If so shift your balance weights on to your serp pulley and it won't be 'too' far out. If they're different ask if they can make the serp pulley balance like the SD1 one and then shift your weights. Not got a clue what it will cost but we pay around £50 for balancing batches of pulleys.

(2) Would a harmonic balancer (torsional damper) do instead?

Cheers,

Ian

[ian.stewart]

I did think about swapping the balance rings over on the pullies but ones a 6 bolt hole and the other a 4 bolt hole dammit!

Dont even think about dismantling the ballencer, they are explosive to say the least when they go bang on the engine, Ive seen one part of a ring come thru a inner and outer wing up the Pod.
Ian

[ihatesissycars]

I did think about swapping the balance rings over on the pullies but ones a 6 bolt hole and the other a 4 bolt hole dammit!

Dont even think about dismantling the ballencer, they are explosive to say the least when they go bang on the engine, Ive seen one part of a ring come thru a inner and outer wing up the Pod.
Ian

I mean the ring that unbolts. I thought i could unbolt one and bolt it to the other pulley but wrong bolt holes.

Ian, i'll have a phone around. It does have the standard rover damper already on it, i don't know if that can take up the slack though!

[ian.stewart]

Yes my engine (everything thats attached to the crank) was balanced as one however i'm not stripping the lot down again just for a different front pulley. There's gotta be a way of getting this serp one in the same ballpark as the original one i had the lot balanced with.

I did think about swapping the balance rings over on the pullies but ones a 6 bolt hole and the other a 4 bolt hole dammit!

what about redrilling the pulley??

[davemgb]

I've been told that early 3.9 cranks needed the large lump of ballast in the pulley but that late 3.9 cranks with larger counterbalance weights don't need the pulley ballast. Can anyone verify that info? Change date is around 94 or 95 and might be associated with the K series introduction.

I presume your putting the serpentine cover on a 3.5, if so I suggest you just discard the balance weight carrier unless it has a belt groove on it you need in which case take out the balance weight.

Dave

[GreenV8S]

I did think about swapping the balance rings over on the pullies but ones a 6 bolt hole and the other a 4 bolt hole dammit!

That's strange, where did the 4 bolt pulley come from?

[ihatesissycars]

An SD1.

My crank is from a 3.5 i think, the ocnrods are recon'd real steel ones and the pistons are new +20" 3.9. The pulley it was originally balanced with was a efi sd1 item and the flywheels was sd1 and the clutch pressure plate is a standard manual trans rover jobbie. Quite a mix and match!

Thas why i had it balanced but now i have this problem to contend with.

Dave, The serp pulley is form a 97 3.9 and has truck loads of balance weight on it so i think its the later 4.0 and 4.6 cranks that have the estra weight on them as 3.5 and 3.9 cranks are supposedly identical other than keyway length. I think.

Ian. I thought about that but i'd end up with 9 or ten holes in it!!!!

I could weld them up i suppose put it'd probably warp it and i don't want to weaken it after what you said about one coming apart.

Does anyone have a spare 6 bolt hole balance ring without any weights on it?

Oopsie! My mistake my sd1 pulley is a 3 bolt one but it still doesn't fit