ASK THE EX­PERT

Our tech ex­pert Keith Calver answers all your Mini tech­ni­cal queries.

Mini Magazine - - Contents -

“If there is no ded­i­cated earth strap pro­vid­ing an easy route to earth, the en­gine will use some­thing else... ”

CAM­BER AD­JUST­MENT Is it pos­si­ble to mod­ify the rear cam­ber on a Mini with­out buy­ing ex­pen­sive new ad­justable brack­ets? I’ve got too much pos­i­tive cam­ber on the off­side, which I’m led to be­lieve is com­mon on Minis. I just want to level it up to zero de­grees. Rick Sim­ple one this – you just re­move the brack­ets and file the hole that the ra­dius arm pin comes through up­wards. I would sug­gest scor­ing some guide­lines into the plate faces by us­ing a ruler or en­gi­neer’s square. You need to only move the hole up­wards. Angling it fore or aft would al­ter the track­ing at the same time – al­though that’s not a dis­as­ter in it­self as long as it is for­wards. That in­creases toe-in and can be ad­justed out by plac­ing shim steel be­tween the bracket and sub­frame. If rear­wards, that in­creases toe-out and is very dif­fi­cult to re­solve. The eas­i­est way is to file the hole in the outer bracket to move the pin end for­wards, then weld a large washer to the bracket to hold the pin end in the for­ward po­si­tion. As for how far up­wards the hole needs fil­ing, that will de­pend on how much you want to change the rear cam­ber an­gle by. Typ­i­cally one de­gree of cam­ber change at the bracket is around 0.170-inch/4.3mm. So if your Mini has one de­gree pos­i­tive cam­ber and you want to make it one de­gree neg­a­tive cam­ber you will need to file the pin hole up by around 0.340-inch/8.6mm. NO EARTH I’ve dis­cov­ered that I’ve been run­ning with­out an earth strap from the body to the en­gine for at least the last two years. Now that I’ve fit­ted one, the starter mo­tor spins much faster and the car is eas­ier to start. Other than the slug­gish start­ing, what other ef­fects on run­ning will there be from not hav­ing the en­gine earthed? Edd The en­gine needs to earth to op­er­ate. The electrics as­so­ci­ated with the start­ing and run­ning of the en­gine, such as the ig­ni­tion sys­tem and starter mo­tor, would not work oth­er­wise. If there is no ded­i­cated earth strap pro­vid­ing an easy route to earth, the en­gine will use some­thing else. Typ­i­cally th­ese end up be­ing the con­trol ca­bles – throt­tle ca­ble, choke ca­ble and/or heater tap ca­ble. The is­sue there is it gen­er­ally doesn’t take too long RED GREASE I’m fit­ting new wheel bear­ings to my Mini, and at £50 each for the gen­uine ones I want them to last. I’ve seen that lots of Mini rac­ers rec­om­mend us­ing a red grease for the bear­ings as op­posed to the nor­mal LM grease. Where can I get red grease from, and is it worth us­ing it for a road car driven in all weath­ers? Toby Top qual­ity grease is al­ways worth the in­vest­ment con­sid­er­ing the hos­tile en­vi­ron­ment the wheel bear­ings have to cope with. The only red coloured grease I am fa­mil­iar with is Red Line Syn­thetic Oils CV2 grease. I have used this for decades on all highly stressed bear­ings – wheel bear­ings, CV joints, in­board CV (Pot) joints and so on. It is less vis­cous (thin­ner) than tra­di­tion wheel bear­ing (‘LM’) greases so causes less drag, and has a much higher sheer strength. All in all, it’s an ex­cel­lent grease.

UP­RAT­ING BRAKES I’ve bought a 1992 Mini Cooper, which I’m de­lighted with. How­ever, I’d like to im­prove the brakes, while keep­ing the stan­dard cal­lipers, as I have bought new AP ones. What would you rec­om­mend to up­grade the 8.4-inch brake set-up for fast road use? I’d like to fit some Min­tex 1144 pads but I’m told they say ‘not for road use’ on the box. So what’s a good al­ter­na­tive? And should I go for grooved discs? Bar­tosz Grooved discs help in two ways. When the discs and pads are in their cool phase, they wipe the pad sur­face clean, re­mov­ing be­fore th­ese over­heat from the cur­rent they are hav­ing to deal with, act­ing a bit like a gi­ant fuse. The re­sult be­ing smok­ing ca­bles, very stiff op­er­a­tion (typ­i­cally on the throt­tle ca­ble, hav­ing it stick with the carb but­ter­fly open), and in some cases a pre­ma­ture ve­hi­cle bar­be­cue. Con­se­quently, to have got­ten away with seem­ingly no main earth strap, some­thing else of a ma­jor size must have been tak­ing the cur­rent, which leads me to sus­pect there may well be an earth ca­ble some­where hid­den from view. You don’t say the year of your Mini, but older Minis had an earth strap from the clutch cover down be­low the starter mo­tor bendix cover to the in­ner wing or front panel. This is eas­ily missed as it was very hard to see – as many an en­thu­si­ast of such

“Hav­ing it stick with the throt­tle open will be a real at­ten­tion-get­ter, es­pe­cially on a mo­tor­way!”

hard­ened de­posits on the pad face caused by high tem­per­a­tures. And at th­ese higher tem­per­a­tures, they also break down the gaseous layer that forms be­tween the hot pad and disc sur­faces. Both im­prove brak­ing per­for­mance, so are def­i­nitely worth it. But don’t go for discs with loads of grooves. AP Rac­ing did a huge test on this some while back now, and found that in the ma­jor­ity of cases, four grooves were enough – typ­i­cally ar­ranged straight across the disc sur­faces, but at 90 de­grees to each other on the re­verse side. This is to main­tain disc strength by pre­vent­ing crack­ing/ break­age from fa­tigue cracks de­vel­op­ing be­tween the slots.

I have not used Min­tex 1144s Minis will at­test to. It of­ten gets missed when en­gines are be­ing re­moved, its pres­ence only be re­alised when the en­gine also picks up the front of the car when be­ing craned out!

I would ad­vise care­fully check­ing the con­trol ca­bles men­tioned pre­vi­ously to make sure they are in per­fect work­ing or­der, es­pe­cially the throt­tle ca­ble. Hav­ing it stick with the throt­tle open will be a real at­ten­tion-get­ter, es­pe­cially at proper speed on a mo­tor­way! And while you’re look­ing it over, see if there is in­deed that sneaky earth strap down un­der the starter mo­tor cover. for a very long time so can not per­son­ally com­ment on their per­for­mance. I quit us­ing them many years ago be­cause when the reg­u­la­tions out­lawed as­bestos from brake pad use, the once ter­rific 1144s (then M171s) re­ally suf­fered. I have been told they are far, far bet­ter now, but have yet to try them. I BRAKE BAL­ANCE I’ve bought a set of Cooper S disc brakes to go on my 1991 Mini May­fair project, and have been ad­vised I need to switch the rear cylin­ders to re­store brake bal­ance? I have com­plete new built-up back­plates with 0.75-inch bore cylin­ders from Mini Spares to go on, so won­der if this is nec­es­sary? have been us­ing EBC pads for all my road Minis for quite some time. UK man­u­fac­tured with ex­cel­lent per­for­mance, and at a very sen­si­ble price, they have proven pretty dif­fi­cult to beat. For nor­mal road use go for the Black­stuff pads. For sportier driving, go for the Green­stuff pads. What cylin­ders should be fit­ted if mine aren’t right? Mel The orig­i­nal Cooper S brak­ing sys­tem fit­ted with the MkI-type servo used the 0.750-inch bore rear wheel cylin­ders. The later S us­ing the Mk3 type servo used 0.625-inch bore rear wheel cylin­ders. Both

HIGH-LIFT ROCK­ERS I’ve got some 1.5:1-ra­tio roller-tip rock­ers I’d like to fit to my Mini. It’s a mildly tuned 998cc mo­tor with a 266 cam and a Stage 3 head, but I’m told not to fit th­ese rock­ers and go for 1.3s in­stead. Ev­ery­one seems to say this, but can you ex­plain why? Is there a way the en­gine could be tuned so that they work? Akos I have never seen worth­while im­prove­ment in per­for­mance when fit­ting 1.5:1-ra­tio rock­ers to small­bore en­gines for road use us­ing rel­a­tively mild cams, par­tic­u­larly when con­sid­er­ing the cost to do so prop­erly. I say prop­erly be­cause not too many small-bore cylin­der heads are con­fig­ured to take the ex­tra lift given by the 1.5:1ra­tio rock­ers. That means stay­ing away from valve spring coil-bind­ing. On race en­gines used the same rear sub­frame mounted reg­u­la­tor valve, so patently there is some­thing in the ef­fec­tive­ness of the servo that has an in­flu­enc­ing fac­tor. I do not know how the lat­est spec mas­ter cylin­der-mounted type ser­vos com­pare with the S Mk3 type, but I would haz­ard a guess that they are very sim­i­lar. Con­se­quently you could prob­a­bly get away with us­ing the same 0.625-inch bore rear wheel cylin­ders (part num­ber GWC1129). But, the S sys­tem did have a rea­son­ably ef­fec­tive rear brake reg­u­la­tor. The later brak­ing sys­tems did not use this type. Reg­u­la­tion was done partly by the mas­ter cylin­der and partly by the PDWA valve. Orig­i­nally I did not think the PDWA valve ef­fected any reg­u­la­tion at all, but a short while back I was as­sured by a renowned brake sys­tems spe­cial­ist that they did pro­vide it to some de­gree. I did not dis­cover how this worked; he re­tired very soon af­ter and dis­ap­peared abroad to en­joy him­self for a few years! Hav­ing messed about with this some years ago now, I found that the 0.5625-inch bore cylin­ders worked well with the set-up as you are go­ing to run it. I’d try that first, sim­ply be­cause you do not they give a few more BHP at the top end, but tend to lose a bit at the bot­tom end. That’s not an is­sue in an en­gine that spends all its time north of 4000rpm, but for road use, mild or fast, low en­gine speed per­for­mance is very im­por­tant. But then again it also de­pends on what cam spec you use. Some cams are de­signed to work specif­i­cally with high ra­tio rock­ers. David Vizard had this very much in mind when he was de­vel­op­ing the MD266 and MD286 cam specs. But then this was for the large­bore based (1275cc plus) en­gines. The small-bore based (850, 998 and 1098cc) en­gines didn’t get much con­sid­er­a­tion.

Hav­ing said that, this is a sub­ject I have dis­cussed at length with a great many folk, en­thu­si­ast and ex­pe­ri­enced spe­cial­ist alike. I would cer­tainly will­ingly ac­cept a sin­gle pound coin for ev­ery en­thu­si­ast that has said that need or want a heap of rear brak­ing go­ing on in a Mini. Lock­ing up the rear wheels is an ab­so­lute no-no, par­tic­u­larly on wet roads. Hav­ing the rear end snap around side­ways is not what you want to be hap­pen­ing. SMOK­ING START My 1996 Mini SPi smokes heav­ily on start-up, but then clears af­ter the ini­tial cloud and won’t smoke again for the rest of the day. It’s a low-mileage car, runs well and never uses oil. What could be caus­ing this ex­ces­sive smoke on start-up? I’m wor­ried about the head gas­ket. Char­lie It de­pends on what colour the smoke is as to where the prob­lem might be. But even then that may not help as the fact the prob­lem dis­ap­pears com­pletely for the rest of the day and it doesn’t use oil throws most sce­nar­ios out the win­dow.

If the smoke is mostly black, that sug­gests over-fu­elling. A weird one if it is, as the fu­elling is their cho­sen cam spec fit­ted with 1.5:1-ra­tio rock­ers in their 998 gave tan­gi­bly bet­ter per­for­mance than when fit­ted with the stan­dard rock­ers. The prob­lem here is al­most no ex­ist­ing back-up data to try and fathom as to why. There are so many fac­tors that can af­fect the per­for­mance of any given en­gine spec; it could be that the rock­ers are mak­ing up for a deficiency in the cam spec, or the mod­i­fied head spec. The over­rid­ing ex­pla­na­tion, then, be­ing that it is just a com­bi­na­tion that works. Not at all sci­en­tific!

A spe­cific ex­pla­na­tion on why very high ra­tio rock­ers do not gen­er­ally work on small bore en­gines would take chap­ters, es­pe­cially as there has been lit­tle in­ves­ti­ga­tion into ex­actly why the phe­nom­ena oc­curs. The fact is, spe­cial­ists worth their salt de­ter­mined by the ECU. Even on the get-you-home safe mode it should not be over-fu­elling enough to cre­ate clouds of black smoke at start up. It could be a leaky in­jec­tor that is dripping fuel in to the plenum that is then in­gested at start up. Once the en­gine is run­ning the leak is not caus­ing an is­sue as the in­jec­tor is squirt­ing fuel as de­manded, who ad­vise one way or the other will have tried var­i­ous com­bi­na­tions and tested them thor­oughly, and thus come up with their own con­clu­sions. I am no dif­fer­ent. In all the small-bore en­gines I have built over the years and have prop­erly dyno or rolling road tested, only a few have given sur­pris­ingly bet­ter per­for­mance over what has been seen be­fore on sim­i­lar builds when a set of 1.5:1-ra­tio rock­ers have been strapped on in place of a set of good 1.3:1 or even 1.4:1-ra­tio rock­ers. And of most of those, I sus­pect the cylin­der head per­for­mance had a sig­nif­i­cant part in that, where the head has been a par­tic­u­larly ef­fec­tive one. con­trolled by the ECU. I doubt it’s any­thing to do with the fuel pres­sure reg­u­la­tor as that would cause over-fu­elling all the time.

If the smoke is mostly blue­grey, that sug­gests ex­ces­sive oil en­ter­ing the com­bus­tion cham­ber. As the prob­lem only hap­pens at start-up, the most likely cause is valve stem seals. With the en­gine not run­ning, oil

“Hav­ing the rear end snap around side­ways is not what you want to be hap­pen­ing...”

pooled around the top of the seal leaks past it, runs down the valves and drips off into the com­bus­tion cham­ber on to the pis­ton crown, or col­lects on the back of the valve if shut, caus­ing a burst of ex­cess oil at start-up. The ele­phant in the room here is that there is no oil con­sump­tion.

If the smoke is white, that tends to be coolant. The prob­lem here is, if there is a coolant leak in to the com­bus­tion cham­ber, it tends to get worse as the leak point gets larger as the en­gine heats up. I have not come across such a leak that goes away as the en­gine gets warmer. With­out know­ing what colour the smoke is, it is hard to know where best to start in­ves­ti­gat­ing the prob­lem. AU­TO­MATIC ECU I’ve just picked up a Mini Sprite au­to­matic, which I’d like to change to man­ual. I have the com­plete en­gine and gear­box from a Mini Side­walk, which is also a 1995 model. What else would I need? Can I use the same ECU for the auto? And is there any other wiring I have to do? I only have the en­gine and gear­box unit, so I’m hop­ing to re­tain as many bits from the Sprite donor car as I can to save on costs. Mal­colm This is not some­thing I have done, or know any­body that has ei­ther. I do know that the ECUs are dif­fer­ent for the au­to­matic and man­ual ap­pli­ca­tions, the main dif­fer­ence be­ing that the auto ECU raises the idle speed when se­lect­ing re­verse. So you can use the auto ECU for the man­ual ap­pli­ca­tion. The auto uses a kick­down sys­tem to boost ac­cel­er­a­tion when the go-pedal is buried, but as the sen­sor for this won’t be plugged in, it sim­ply won’t ac­ti­vate any­thing. And as you are swap­ping a like-for like spec en­gine there shouldn’t be any other is­sues. Th­ese units are the 53bhp-spec en­gines. The Cooper spec en­gine uses a dif­fer­ent camshaft and has a dif­fer­ent ECU to go with it, giv­ing the higher 63bhp out­put. WHAT COAT­ING? I read with in­ter­est your piece on the pit­falls of power-coat­ing in the Oc­to­ber is­sue. I’ve just stripped my sub­frames and hubs back to bare metal and am look­ing for a resilient coat­ing that wont strip off or flake. What ap­proach would you rec­om­mend? Mar­tyn I have been us­ing POR-15 prod­ucts as sold by Frost Auto Restora­tions (www.frost.co. uk). For many years I have been us­ing their chas­sis black top coat sup­ported by the rel­e­vant sur­face prepa­ra­tion prod­ucts. This has given fan­tas­tic per­for­mance in all weath­ers and con­di­tions, giv­ing a hard, chip-re­sis­tant gloss fin­ish that is eas­ily cleaned and looks great. More re­cently they have in­tro­duced sup­pos­edly an even tougher chas­sis black. I am cur­rently us­ing it to re-fin­ish all the front sub­frame and sus­pen­sion com­po­nents for my Clubby Es­tate. I have yet to do the top coat, but so far the ini­tial sur­face prep looks very good.

“If the smoke is mostly blue-grey, that sug­gests ex­ces­sive oil en­ter­ing the com­bus­tion cham­ber...”

Red Line CV2 is highly rec­om­mended by Keith.

Rear cam­ber can be al­tered by mod­i­fy­ing the stock brack­ets.

Grooved discs and de­cent pads can re­ally im­prove your brakes.

Sev­eral types of rear wheel cylin­der are avail­able.

An ex­tra earth strap on a Mini is never a bad idea.

Ex­haust smoke can have a plethora of causes.

1.5-ra­tio rock­ers are gen­er­ally best suited to big-bore en­gines.

POR-15 prod­ucts are ideal for coat­ing bare sub­frames.

An auto ECU should work OK on a man­ual en­gine.

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