lstvr

Hi Guys,

I'm changing from Mahle to JE because i have got to go from 4.070 to 4.085.
I can get the JE to roughly 3 Grams LIGHTER with a HEAVIER wrist pin, after speaking with JE today, I dont know what the ring pack of the JE pistons weigh, but assuming thats about as close as i get, do you need to re balance?
If so at what point do we say thats close enough 1 gram, 0.5 grams??

KCS

iTrader: (20)

I'd let 3 grams go. The digital balancer I used to use would call anything less than 3 grams good. I've seen cranks go out 40 grams underbalanced with no issues.

ColeGTO

iTrader: (3)

Considering the "typical" oil allowance on a bob weight is 8 grams, I'd say you're good.

If this is an 8,000+RPM combo, then I'd possibly consider rebalancing.

However, if you're that concerned, a balance job is not that expensive.

lstvr

its about $350-400 here in the UK, but if its not necessary then i can think of better things to spend the money on!!

pantera_efi

iTrader: (1)

Hi TVR, LEAVE IT as Overbalance is a GOOD thing.

Your BW is could be 1825-1835 ?

DO the MATH, let us all here KNOW the weights, then we can calculate.

I have ALWAYS heard that a Pound in England is greater in value than if in the states.

You must "match" the rod/piston with pin weights to each other.

As for the GTO "tech" I OVERBALANCE with a GREATER % as RPM is increased.

Lance

ColeGTO

iTrader: (3)

As for the EFI "expert", I'm not going to get into the OVERBALANCE/UNDERBALANCE debate. That's a completely different discussion that not too many people agree on.

Jimbo1367

Is that what the typical balance job costs here stateside?

KCS

iTrader: (20)

Usually $200-300USD range if the crank doesn't need heavy metal slugs pressed in.

pantera_efi

iTrader: (1)

Hi Cole, thanks for kind words, yes with MY ECU, I can measure Crankshaft Acceleration.
This ECU-882C can graph the vibration of the crankshaft.

Now for TVR, I was taught about "overbalance" by the likes of Roger Bailey, Mike Costin, and Brian Hart. (Englishmen)

Lance

lstvr

Thanks guys, I am going to leave alone, hopefully the pistons arrive in spec!