sr2

If everything is in good condition and working as it should all you can do is progressively reduce the master cylinder diameter until you reach the compromise of a useable pedal height vs. enough mechanical leverage to apply enough pressure to the brakes. As a side note just be aware that your Wildwood "proportioning valve" is simply an adjustable pressure limiting valve that sets a max pressure limit for your rear wheels - i.e. it hasn't a clue as to the % of proportion pressure the front wheels are receiving.

LOL. Opinions are just opinions where as facts are facts and "never the twain shall meet". 😇

You make a valid point mate, nothing more dangerous than someone who thinks they know everything. (I never got past the NZCE stage - they hadn't even invented calculators when I scraped through!). The point I'm making is that an engineering degree is not a prerequisite to becoming a LVVTA certifier.

I'm of the opinion that certification and compliance is well within the realm of what a competent, qualified mechanic is capable of. (With the proviso that excludes the VTNZ WOF "technicians")!

If any competent automotive mechanical engineer couldn't do all three thing you wouldn't want them near your car!

no offence intended Clint you have my respect for both your knowledge and the work you do but if anything your reply supports my case. Our current system it reeks of overlapping layers of complicated bureaucracies all trying trying to justify their own existence?

Quick update…… Loaded the DeTomaso back on to the transporter for a quick trip the North Shore Compliance Centre to have the Vin tag attached. Next stop was to our favourite mechanic for a check of all the mechanicals while we complete the paperwork side for the low volume cert - it has already passed inspection by the certifier. Once that’s done we’ll have to take it for a compliance inspection because apparently the clowns at NZ Transport/Waka Karitane know something the clowns at LVVTA don’t know and they don’t talk to each other! I’m no new-comer to coping with bumbling bureaucracy but this whole process leaves me gob struck.

Sorry mate, probably sounded like a bit of a tosser with that off hand comment. No objection at all with Willwood for street or track day cars, in their defence they are one of the few manufactures out there who are brave enough to market budget aftermarket brake components, (give them full credit it's a bloody minefield). At the sharp end they will never match the likes of Brembo or AP but price wise, in the right application are great value for money.

Hey, great post mate – you make good practical sense. We ran an Evo IV for a while and I have to say I was so impressed with the ABS, it coped with 6 Pot AP’s on huge floating disc’s without blinking. The only ABS I’ve been in contact with that was significantly better was on our GT3 but to be honest Porsche shit is so out of the square I never managed to get my simple, bald old head fully around it! Pads selection has more options today than 30 plus years ago when DS11’s simply didn’t work without heat in them (nothing less than terrifying on a touring stage!). I don’t think the science has changed; softer pads = better bite from cold, less disc wear, but more fade whereas the harder compounds give you the opposite. What has changed however is the modern compounds that bridge the gap – have to say Padgid is my current pad of choice.

As you’ve gathered, our joint, blindingly accurate mathematical guesstimates have confirmed the 4 pots on the front will considerably increase the front bias. Be aware that (presumably) the “bias” valve you’re looking at (i.e. one that is plumbed into the rear line) is actually a pressure limiting valve and will only be able to set a maximum limit to the psi the rears receive. The larger Holden Drums are cool, I’m a fan of Holden drums – PBR nailed it in the day, (I was original trained by PBR in the 80’s in AU) but please at the risk of repeating myself – change only one thing at a time. I have on a number of occasions been asked to diagnose brake issues on both street and competition cars where many components were changed or modified at one time because the builder or more usually the owner thought it would work!

Which cars were ABS? (I'm presuming all were boosted).

May I start with correcting smokin’joe – I have been regularly fucked over by race/rally car brakes for a long time! You’re close with the maths. With a single (i.e. floating) calliper you double the swept area in your calculation. Your standard single piston Toyota calliper has a swept area of 4412 sq/mm. Your proposed 4 pot has a swept area of 5808 sq/mm. You’re looking at a 31% increase on swept area. Your 7/8” m/cyl has a swept area of 387 sq/mm and an additional 31% takes you to 507 sq/mm which is close to 1”. If the 4 pots are of good quality (preferably not Willwood) you may get away with the original 7/8 master cyl – it’s well worth a try. Remember there is minimum fluid displacement with disk brakes; conventionally boosted (i.e. Mastervac) systems normally have a larger master cylinder than you would run with a non-boosted balance bar setup. Potentially the bigger issue could be the increase in front bias. It’s always harder to predict with a disc/drum setup as the inherent self-energising property of leading shoe throws the numbers out a bit. Once again my advice would be to fit the larger front callipers and do a road test paying attention to pedal travel and bias. The Golden rule with modifying brakes is to only change one thing at once. Hope this makes sense.

I found these Jag injection conversion pictures on an Aussie site from 2002.

That was my original idea but with the Holden 6 not being crossflow the exhaust/headers would be in the way of the fuel rail.

Yes I’ve seen their website – scary spendy! I always thought you had to have the injector after the throttle butterfly, obviously you don’t. Opens up some interesting options.