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Rb30Det Build(Not Balanced)

texman30det

By texman30det,
in Engines & Forced Induction

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texman30det Rookie

texman30det

Posted
Posted

Hi guys,

Motor is just about ready to be assembled. R32 25de head + 30e bottom end. The nagging misus about time and money has unfortunately made me to decide not get the motor balanced. Secondly im running fully stock bottom end except for ACL race bearings, main and bottom and chromoly piston rings.

Do i need to be worried?..i initially didn't think it wasn't an issue since i was using the same internal components that were from the same block. Crankshaft has been polished and 25de head has been skimmed and cams polished with gtr valve springs etc.

Has anyone done a full build without balancing it?..

thanks for your time.

Cheers in advance.

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https://www.sau.com.au/forums/topic/436346-rb30det-buildnot-balanced/
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Shoota_77 Veteran

Shoota_77

Posted
Posted

I'd say a huge number of engines are built without being balanced. Most non performance builds would never get balanced.

Get the crank balanced then just weight match the rest yourself. Easy to remove weight off the heaviest rods and pistons. With crank balanced and pistons and rods balanced as a pair to within 1 gram of each other it will be perfect. Well worth the effort to protect your oil pump amongst other more obvious benefits.

  • Like 1
GTRPSI Mentor

GTRPSI

Posted
Posted (edited)

Mass produced stock reco rebuilds never get balanced, most rebuilders do this as the engine is considered just a A to B engine and not a revver, its also to keep costs down and to make more money on the engine.

If you are going to give it some stick, its very important to get it balanced, the harmonics and weight thrown around at RPM can want to tear the engine apart.

Having said that, i always balanced all my stock rebuilds as a matter of being fussy, all except 1 that i rebuilt for my father who didnt want to spend, it lasted for over 200,000 Km on a stock rebuild and it was a Corrolla engine that he use to thrash to make the car move as it was only a 1.3L.

Edited by GTRPSI
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KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

My engine is the same as yours... stock bottom end with new rings, bearings but plus new rod bolts. It has not been balanced. The rev limit is 7000 but I usually change up at around 6500 (on the track - on the road its about 2000!) and never sit on the rev limiter. Currently on 314 AWKW. and done about 50,000km over three years.

Having said that if I were to do it again I would prefer to save up for a rebore, high compression forgies and a new harmonic balancer all fully balanced.

  • 2 weeks later...
GOD12A Community Regular

GOD12A

Posted
Posted

Heya TEX,

I balance every engine I touch.

Not only does it allow a higher rev limit and better response, it'll also reduce the harmonic issues associated with an inline six further reducing the chance of cracking the oil pump gear.

A balance should be ~$200 for a 6cyl, so it isn't 'stupid expensive'.

If you disassembled the engine and marked every rod/piston position, you'd have a reasonably good chance of it being OK if you changed none of the rotating assembly.

Otherwise buy/borrow a GOOD digital scale and match the rods/pistons yourself, will be cheaper than paying someone to dynamically balance your engine and better than just guessing.

Hope it helped.

Mark :)

r33_racer Grand Master

r33_racer

Posted
Posted

The only problem most would have doing it themselves is not being able to match the small ends and the big ends of the conrods. Which quite often can be out a fair amount. Without the proper jigging to do that process you are really only matching the overall weight.

Which I guess is better then nothing...

GOD12A Community Regular

GOD12A

Posted
Posted

Heya R33_RACER,

Static balancing of small/big ends is pretty straight forward with a simple jig and a few hours of spare time.

That's going the next step and one I didn't bother discussing as it was beyond the original question regarding simple balancing.

I do agree rod balancing is worthwhile on performance engines, especially high revving examples.

Mark :)

r33_racer Grand Master

r33_racer

Posted
Posted (edited)

Indeed it is. I just wanted to make sure people knew it wasn't just as simple as matching rod/piston weights, especially when it comes to performance/race builds.

However, I get where you are coming from in regards to answering the original question. Quite often its easier to just give a simple answer rather then taking ages to go in depth explaining every facet to a certain process or method. More often then not its not really needed.

Edited by r33_racer
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