Hi guys

So i have my bottom end in the shop getting hot tanked and the crank crack tested etc, I'm told this had all been done by the previous owner but as the engine was in pieces any way I thought it better to make sure i knew what i was putting back together..

The machine shop thats doing the work has indicated that it is not worth lightening the rods / fly wheel etc and that as long as it is all balanced correctly it will offer as much performance and I'm better of spending the money elsewhere.

The head is going to GR for some of his attention.

Whats peoples thoughts around lightening the bottom end components? I was of the thought that light = better.. but now I'm not sure. Is it worth the ROI for a fast road / occasional track van?

As a side not the machine shop builds a lot of high end racing motors here in SA and does work for a mini shop..

Darcy

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196# Morris VAN
2013 JGC 5.7 Hemi
2012 Civic Type R

flywheel is worth doing - has the most bang for buck impact

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did I tell you that I won a trophy?

There is a pretty simple formula to work out whether its worth lightening the bottom end.

Multiply the amount to be removed from the crank/flywheel - and not forgetting the backplate - (rods have different rules) by the effective gear ratio (gearbox ratio X final drive) and this will equal the effective weight reduction in vehicle mass.

ie lose 10 lbs and the car will appear to be some 120 odd pounds lighter .. in first gear.... The effect will be commensurately less in second and higher gears. I use an 8 lb flywheel and fabricated backplate so the effect on acceleration is quite worth while.

$$ per m/sec is of course an entirely different calculation

Cheers, Ian

OK so for safety Id be looking to buy a lightened fly wheel from somewhere like minispares. I noticed it says "not recommended for road use " will it still be ok? Also whats the difference between grey/orange and race/competition diaphragms??

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196# Morris VAN
2013 JGC 5.7 Hemi
2012 Civic Type R

Minispares has 2 lightened flywheels, one for road and one for race.
I'd buy the road one. IMO their race one is flimsy, some folks here had problems in the past.
Matt Read (TheMiniMan on here) does lightened std ones, for road use they are fine. Cheaper too.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Love lightened flywheels on minis. They have bags of torque so feel great for the little money you've spent.

Faster on acceleration, faster on deceleration. Win win!

The effects on modern cars leaves a little to be desired, especially in heavy traffic when you just want to creep forward. You nearly stall every time without a stab of the accelerator being added. It can be really noticeable.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I have never driven one but my new 1360 engine build will have a 4.15kg steel flywheel. When I bought it it was one of the lighter ones available that weren't specifically sold as a race item.
I believe lighter flywheels are more likely to stall when you first try to take off if you don't use enough accelerator but the revs will climb much easier so quicker acceleration which will be good fun.

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Respect mine and I'll respect yours.

Who is doing your machining?

McLaren Race Engineering

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196# Morris VAN
2013 JGC 5.7 Hemi
2012 Civic Type R