A stronger clutch and a lighter flywheel are bet­ter for cop­ing with ex­tra torque and bet­ter ac­cel­er­a­tion from power up­grades.

Performance Vauxhall - - ASTRA ESTATE - WORDS AND PHO­TOS Mar­tyn Wil­liams

Lighter fly­wheels are guar­an­teed to put some ex­tra zing into any en­gine by re­duc­ing its ro­tat­ing mass. The eas­i­est way to imag­ine the role of this com­po­nent is to think for a mo­ment about the op­po­site ef­fect. What would hap­pen if an Astra flywheel was dou­bled from its stan­dard 9.6kg to nearly 20 kg? The re­sult would be a slug­gish en­gine re­sponse as it drags the flywheel up to speed. In­er­tia on the over­run would also take all the snap out of the down­shifts.

Courte­nay Sport have come up with a pop­u­lar flywheel upgrade for the Zafira GSi Turbo, Astra Mk4 GSi Turbo, SRi Turbo, and Coupe Turbo mod­els (the Astra here is a Stage 4 Triple 8). The re­place­ment flywheel is around 5 kgs lighter at 4.25kg and is ma­chined from bil­let steel and plated for ex­tra dura­bil­ity. It costs £255 and with more power to tame, goes to­gether well with

PER­FOR­MANCE VAUX­HALL a Courte­nay fast road clutch as­sem­bly (cover and plate) at £199.95. This is good for out­puts up to 300 bhp, but be­yond that, an up­rated com­pe­ti­tion type clutch is best at £432. Clutch life un­der nor­mal use tends to be good, so it’s worth mak­ing sure that other com­po­nents will per­form re­li­ably over the same pe­riod of time by splash­ing out on a new hy­draulic slave cylin­der. This is £119.95 from Courte­nay with the clutch.

Re­mov­ing the gear­box and fit­ting a new flywheel and clutch is an ad­vanced DIY task but it’s mainly a nut-and-bolt job that in­cludes dis­con­nect­ing ca­bling, gear link­ages and the drive­shafts. The two im­por­tant tasks are sup­port­ing the en­gine and drop­ping the en­gine bed. Most crit­i­cal is mak­ing sure that this sub­frame – which has about 10 mm of move­ment in the cap­tive nuts – is prop­erly aligned when it goes back.

Align­ing the frame with­out us­ing a jig needs care­ful prepa­ra­tion be­fore re­moval. It will need some ref­er­ence points marked be­tween the body and frame, ideally with a metal scribe and steel ruler for max­i­mum ac­cu­racy. If there are any doubts about how ac­cu­rately it’s been screwed back, it’s al­ways pos­si­ble to have it checked with a jig later. This is worth do­ing any­way, be­cause there is no way of telling if the bed was pre­vi­ously mis­aligned. Keep­ing the en­gine in a raised po­si­tion while the frame is dropped is done pro­fes­sion­ally us­ing a sup­port­ing beam that lo­cates in the wing chan­nels. A DIY so­lu­tion is to use an en­gine crane. Al­ter­na­tively, it’s not rocket sci­ence to cob­ble up a home­made steel beam as­sem­bly us­ing a bolt with chain at­tached to the en­gine to keep it in po­si­tion. If this all sounds like a lot of work, it’s worth know­ing that Courte­nay nor­mally charge about £324 for fit­ting a sup­plied flywheel and clutch pro­vid­ing no other Uni­ver­sal cen­ter­ing tool An­gle gauge Trol­ley jack En­gine crane prob­lems crop up along the way.

Re­assem­bly of the flywheel and clutch in­cludes cen­tring the fric­tion plate with the cover to al­low the gear­box splined in­put shaft to glide into place as it’s re­placed. One way to be sure of an ac­cu­rate re­sult is to use a uni­ver­sal cen­tring tool. A ba­sic tool can be bought for as lit­tle as £15. Cheaper al­ter­na­tives in­clude an old gear­box first mo­tion shaft, or a piece of pipe or even an old jack han­dle that is the right size to fit per­fectly into the fric­tion plate. Then while the cover is only just nipped up – al­low­ing for the fric­tion plate to be moved – the plate can hope­fully be cen­tred by eye, but this can be a bit hit and miss. Once ev­ery­thing is back in its place, one of the fi­nal jobs will be fill­ing the gear­box with oil. It’s not ad­vis­able to re-use the orig­i­nal oil even if the gear­box has only done low mileage be­cause it is prob­a­bly not syn­thetic.

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