My black forged Piazza

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Piazza_man
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Post by Piazza_man »

Fingers crossed the head won't give you any more grief.
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archangel62
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Post by archangel62 »

IT LIVES!

Took it for a bit of a drive, everything seems good and the new power is nice! However the gauges are playing up. For some reason, since taking the head off, the temp gauge has fked itself and reads zero. I didn't unplug any of that, I just moved the inlet, so it must have damaged a wire somewhere. The oil light also flashes still - although I've ascertained that it is on solid if there's no oil pressure (happened briefly after changing oil filter of course) - so I have no idea what flashing means.

I drained the oil, put in crappy oil and a flush, drained that and gave it another dash to wash out the flush itself, then changed the oil filter and put some decent 10W40 in it, cleaned up the thermostat and made sure it was working properly and put fresh long-life coolant in it (high glycol, around 360-ish).

Anyway, I want to fix the temp gauge and oil pressure light, but otherwise it's a functional (and faster) car again! It's going to be on daily duties briefly when I replace the Falcon's diff, then very soon I'll be looking at fitting the Falcon front springs to even up ride height, and getting the LSD sorted.
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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Post by IZU069 »

I didn't think 10W40 was the right engine oil but IPTOC here claim 10W30 or 10W40 mineral (or semi-synth), but they also claim 97RON fuel, AND the 10W rating may be for their colder climate. I thought it used normal GTX etc (20W50) and 91-92 RON - not that I ever got to the stage of reoiling and refilling. (I've always used 91/92 RON in my Belletts & Wasp without any additives. I know many Belletts use 95RON (or additives) for reasons I don't understand, though I think additives are warranted for unmodified cast-iron head G150s & G160s.)


You're probably right re the broken wire for the temp sender. Usually a short to earth is a good check for the gauge (goes full scale on most modern vehicles) but that can cause damage on modern electronic dashes. I'm not sure about the Piazza. (I think it's ok, but I don't recall why.)

I've heard of the flashing oil light - maybe in this thread? - but am unaware of its function. I'd have to re-read Piazza Owners Manuals (which I don't think I have) or the piazzamanual.pdf etc.


Elsewhere people use newer oils with different ratings thinking they are better. EG - some use 10W-50 or 5W-50 in Geminis and old Belletts which is definitely not recommended. Nor are synthetic oils. And never heavier 50W (Penzoil, BP Corse+ etc) unless a low revving worn engine - not like my mate that used 50W used in his twincams & seized 3 cranks).

And thermostats should always have an air-bleed hole. I use Stant thermostats and drill my own hole and insert a split pin to act as a jiggler or whatever they are called.
A temp gauge that stays low for an unusually long period before suddenly rising quickly (and usually overshooting before settling back down to normal temp) is usually an indication of vapour or air trapped under the thermostat if the temp sender is located above or soon after. (That was the giveaway to my Wasp's collapsed head gasket several years ago. Compression forced gas into the water jacket which got trapped under the (then) bleed-holeless thermostat.)
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Post by archangel62 »

Yeah, 10W40 is a bit lighter than I'd usually run, but they'd sold out of my usual stuff (I usually go 15W40 on a fresh engine, 20W50 on a slightly older engine). I believe turbos don't like heavier oils, but a replacement T28 is cheaper than a replacement crank, if push came to shove. Regardless, it's been about 5 degrees in the mornings here lately, and the Piazza does of course have an oil cooler. I might go 15W40 or 20W50 next time. I never really understood the synthetic versus non-synthetic debate. I would hope that oil technology has advanced since "mineral only" was specified. Provided it's not left long enough to turn to sludge, I don't see how synthetic could be a bad thing, but then, I'm no expert (and happy to be educated).

Re: octane, I generally run my Geminis on 91RON unless there's a good reason not to, but I'm now having to run the Piazza on 98RON if I intend to give it any boot.

Thermostat - I checked it because the temp gauge wasn't getting a reading, but the radiator and head felt warm. Turns out the thermostat worked fine, albeit somewhat oily from the previous milkshake issue, and it has the air bleed hole with jiggler thing. After getting air pockets in my first Gemini, I'm definitely picky with thermostats, and have drilled holes before! The strange thing about the temp sender is that the wires feel fine. Naturally being a Piazza, you have a snowball's chance in hell of actually seeing under there, but I might have to take photos to locate the issue.

On a sidenote, the wires broke off of my cold air valve during the er, spirited removal of the inlet manifold. My tuner was suspicious of the cold air valve causing issues with the Microtech anyway, but I think this was actually the lift-off dampener which was adjusted wrong. Does the cold air valve on the bottom of the inlet also trigger when the air conditioner is on? I can't test it as it needs a regas following pump replacement, but I'm worred that aircon will essentially stall the car if the cold air valve is gone...
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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Post by IZU069 »

I presume you advance the timing when using 98RON? As I recall, that's the only to extract more power using higher octane. (IE - there is no difference in calorific value of low & hi octane, higher octane merely allows higher compression and hence more torque... er, power; or more advances spark for lower compressions.)

Yet again I don't recall the synth & non-synth reasons, but in a nutshell, our "old" engines can't take advantage of it (so why bother?). Newer engines may not have the byproduct acids & sludges that ours have else their metalurgy is more resistant.
And I have heard of engine damage cause by using synthetics.

Poida should be able to inform better. I know we'd sometimes chuckle over the higher RON stuff along with bigger injectors and resistors etc added to AFM or MAP sensors. (I recently wrote about wankers using an LM317 voltage regulator circuit to boost power else lean mixtures... ah - 'twas on HoldenGemini Open letter to Poida - AFM/TPS signal mods .)
As to fuel additives for unleaded fuel in (non-iron head) Bellett etc engines - LOL!!!!


Good to see you know about thermostats. I'm surprised that Stant has such a respected following yet they are "solid". Gates & Tridon and others usually have holes.
Of course that silly little ~2mm is all that's needed to prevent many a warped or cracked head or scored bore. A valuable lesson to know BEFORE it's found out the hard way!


It's possible the temp gauge sender has failed due to some shock etc. Actually a DMM should confirm some resistance - generally between 7R to 150R (R = Ω) but I'd have to look up the Piazza.

My digidash worked fine except for the voltmeter. One advantage with its "discrete" digital circuitry (as opposed to modern CPU) is that circuits are likely to fail alone - ie, a voltmeter or temp gauge fail will not impact gauges - though there are some common processors involved. Only "master" or common circuits will affect several or all - eg, bad earths, faulty PSU unit,
Of course its disadvantage is its old "discrete" digital circuitry. (Can't get the specialized chips; lots of desoldering etc required.)


Not sure about the aircon. I know it is linked to the starter (the brown(?) "either or" relay) and maybe also the alternator signal (ie, charge light - same as dual-battery isolators; Gemini fuel pumps, etc) and definitely some sort of speed switch to cut out at idle - else increase idle speed (faarst idle?).
And I don't recall anything about the cold air valve.
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Post by archangel62 »

Not sure if this will work, but here's a quick (and not very good) clip of the car on the road! You can hear the difference in sound over a standard car.

https://www.facebook.com/photo.php?v=10 ... =2&theater

----

Essentially, the car is tuned for 98RON. I wanted to get it tuned for 91, but it looooved pinging, so my tuner had to opt for a 98RON tune instead. However, based on it being "safe" (ie backed off a few degrees from the point of knocking) he said that if I drive sensibly, it won't do any damage to run 91RON ie cross country trip, but that if I intend on giving it any right foot, 98RON is required.

Interesting reading about synth/non-synth oils. These days it's nigh-on impossible to buy non-synth. Nearly everything is synthetic! I've seen good results from Valvoline Engine Armour 15W40, and I generally stick to this for general purposes. I believe it's still synth. The laundry rebuild drift Gemini G180Z lived on that stuff, sat on 5000-6000rpm all day under lateral G's, and after two years of such abuse, I checked the rod bearings (generally first point of failure in Isuzu 4's of the era) and they looked almost new. It's hard to really call this accurately, but I reckon they would have survived 10 years of that kind of treatment!

Good info in the temp gauge resistance check. I'll give it a geeze tonight(TM). And by tonight I mean, when I'm at home, the weather is tolerable and I'm neither lazy nor distracted. Although this is somewhat important... lol
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
IZU069
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Post by IZU069 »

I presume you have a much higher than standard compression. 91RON should be good up to 9.5:1 compression. (And that your aren't using the knock sensor.)

Otherwise it's a bad ignition curve. (You're using mapped ignition, not the pathetic recalcitrant Dog knows why GMH ordered that mechanical dizzy?)


I have no troubles getting mineral oils, and I expect they'll be available for many years to come.
I typically buy GTX (formerly GTX-2) on special for ~$13 for 5L; else ~$27. Tho these days I'll buy whatever is cheap due to my oil seal issues and that I'm intending a hone & re-ring and new bearings anyhow. (It's a Florian G161-OHV that's done over 250,000km since I rebuilt it. Still zippy etc but one cyl was dry tested as ~95psi, others were ~145psi.)
I usually use Castrol but I have used Valvoline (which I was advised to drop) and others before the Wasp. I suspect bearings are still ok from the oil light response (my oil gauge sender is faulty) tho one shorted a few months back - I've ow use 2 oil pressure switches in parallel. (That came from having problems finding a higher pressure oil switch. Even after 100,000km it would take 40 secs cold and 20 secs hot for the oil light to come on. It took ages to find faster switches from my stock. I recall the issue well because it coincided with rich dorks arguing in favour of oil-pressure controlled fuel pumps because they like blowing pistons and having engine fires after accidents.)

I see the same reason migrating to synthetic oils as I do a non-pinger migrating from 92RON to 98RON - namely none. Why pay 20% to 100% extra for no else minimal gain?
I change oil & filter every 10,000km (or later) and that's been fine. Note that the orig Bellett/Florian spec was to change oil every 2,000 miles = 3,200km, but with tighter toleranced engine using APC (Gemini) pistons and better oils I figured 10k km was fine. And it's not as if my oil is ever very discoloured - none of the black that I remember (only the occasional grey LOL!).

And even if the longer life of syth were to be economical, I don;t think I'd risk it on my engines. Even if I were to seal them I suspect acids etc would be an issue. (I do use the later sealed "pie-crust" oil cap, but otherwise it's as open as typical Belletts & Florians. And I've always used the later spin-on filters - eg Z9 for my non-twincams.)



Cute faceboob video! Funny how at idle and a bit above it sounds classically like a G-series! Almost the same growl as my DCOE'd 400Nm G200W. Suspension sounds hard though!
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Post by archangel62 »

Howdy - nah, just 8:1 CR, give or take a poofteenth after facing the head and changing to a 1.3mm head gasket. On the raised boost (13psi) the standard intercooler really can't cut the mustard and I believe inlet temps were causing pinging. Any more boost would require super-retarded timing and really rich mixtures, which just weren't worth it. The restrictive exhaust isn't helping matters either. The uTech dictates spark timing, I'm using a locked Piazza dizzy. I was told by the tuner that 91RON simply wouldn't allow any meaningful timing advance - and no timing meant no power, so whilst it "could" be tuned for 91RON, the losses to power and efficiency rendered it pointless. I had assumed that 91RON would produce fairly similar results given an adjusted CR - but it seems that's not the case, and that it's just generally a less usable fuel from a performance standpoint.

The knock controller isn't integrated into the new system - if it turns out it can retard else pass-through a predetermined spark signal I'll run it, but otherwise it won't work with the uTech. I haven't tinkered with that yet - it's definitely not at the top of my priority list! However I'm very interested in finding and purchasing some kind of knock sensor to headphone converter so I can listen myself if need be - or perhaps hook up the knock sensor's output to some kind of warning light.

Speaking of warning lights, I've fixed the temp gauge. Turns out my tiny human brain couldn't comprehend the three temp senders I had to fit to the inlet! Haha. Or, more to the point, I forgot about the one on top, and due to terrible accessibility and vision, I couldn't see what was going on underneath either. A good look at the workshop manual identified the correct wire colour, so I found and followed it to find the end floating loose in "the abyss" under the inlet, and as soon as I saw it I remembered where it was meant to go (on top of the manifold). Easy fixed. It must have come off when I "Hulked" off the inlet manifold during the head gasket change. It wasn't very cooperative.

Now, the oil light. Further tinkering with a multimeter identified that the oil switch at the back of the block is stuffed. I'm assuming that's where it's meant to hook up to, and not the pot at the front (anyone know what that's for? Progressive pressure signal, or temp?)... Resistance check on the rear switch showed no throughput, running or not. A voltage check on the source wire showed a "flashing" 12V which corresponds with the oil/check engine light on dash. Earthing the wire resulted in a solid oil light, which resumed flashing when disconnected. I'll replace the switch on the weekend, all going well, and see if it sorts it out.

Shock absorbers! Keywords - koni adjustable length... (Had trouble finding my previous info last time). Ahem. Turns out Holden Gemini wagon rear shocks will suit lowered Piazzas, as far as I can tell, though the valving may be a little on the soft side. I should start by saying that my previous measurements were wrong - apparently you're meant to measure from the centre of the bottom eyelet, to the top of the shock absorber body, NOT including any of the actual pin. I guess this takes into account stuffed shock bushes. Fair enough.
My measurements with my lowered rear springs called for <500mm* (CRAPPY MEASUREMENT, take maybe 15mm?) extended length to keep the springs captive, or <480mm* (-15mm?) extended length to be on the safe side.
Part number 80-2134 is for Gemini Wagon rear, these are 474 open, 291 compressed, but they are valved softer than the Piazza rear part number (80-2233SP1? which are too long for my application). The Gemini 80-2134 is valved for perhaps a 200lb/in spring, based on the estimates of the person I spoke to.
I mentioned the 45deg layover of the shock, this is crucial when determining valving, as well as springrates and the weight of the car.

All things considered, I will re-measure my shocks, and will most likely opt for a Gemini wagon rear shock, re-valved tougher to suit my application. I've estimated my rear springs at around 4 to 4.5kg/mm, they're fairly tough. I'm quite keen to get these rear shocks sorted. Apparently the Koni Yellow fronts I'll be fitting are about 15-20% tougher than their comparative Reds. And note that Koni's have a pre-valved bump setting, with an adjustable rebound setting. I'd also like to thank Car Torque for their awesome work thus far. One of the other SA distributors I talked to was useless, it's great to talk to someone who really knows her stuff, and can actually consider things like layover angle and shock horizontal placement versus the wheel without blinking an eyelid. On a sidenote, I'm considering a slightly softer spring (or ideally just more progressive), but I'll wait 'til the rear shocks and front springs are done for a fair comparison - and softer springs will not need any shorter shock than I'm already looking at.
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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archangel62
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Post by archangel62 »

Oh - and glad you liked the FB video - it was super basic. I took some lengthier GoPro footage the other night, but yet to see the quality, GoPros don't like night time. Once I get the car properly sorted, I'm planning on doing a drift/grip video using at least one local track, and that'd be edited to my normal standards (a la Pandamonium Drift). It does sound quite mean on noise - when revved out, it sounds a lot like a G series, but with turbo noise. I don't mind it, although I'm also interested to hear it with a bigger and better (though hopefully not much louder) exhaust. The rocker shafts also aren't in the best state, so that could be contributing to the G series noise (lol).

Also, sus this out :)
https://www.facebook.com/media/set/?set ... 117&type=1

Direct links to a couple of my favourites:
https://fbcdn-sphotos-d-a.akamaihd.net/ ... 5607_o.jpg

https://fbcdn-sphotos-e-a.akamaihd.net/ ... 7945_o.jpg

https://fbcdn-sphotos-h-a.akamaihd.net/ ... 6420_o.jpg

https://scontent-b-hkg.xx.fbcdn.net/hph ... 2041_o.jpg

https://scontent-b-hkg.xx.fbcdn.net/hph ... 0450_o.jpg
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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Post by Piazza_man »

I'll be requesting a set of progressive rate rear springs for my car as soon as I can confirm the captured static spring height measurement from you. Haha how's that going btw? I was just thinking we could get 2 sets made at the same time (might be cheaper to do) if you're keen on the PR setup.
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archangel62
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Post by archangel62 »

I'll measure them when I re-measure my shocks. I'm hoping to do it soon (hell, I want my shocks, I've been waiting for them for ages) but I have three cars on the go at the moment! Main efforts have been to getting this running properly :) What kind of springrate were you thinking of going for? And any idea on a rough eyebrow height? I'm not 100% set on replacing the rear springs yet, but I'll wait and see what they're like with decent rear shocks.

Now when you say the captured static spring height, do you mean the spring length where the shocks top out at full droop? Because that will depend on the make and model of shock absorber, and mine aren't factory - hell, there are three lengths of Koni that I've been offered. What are you trying to achieve with the measurements? I only ask so I can answer more accurately.
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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Post by Piazza_man »

I'll be chasing the same rear eyebrow height that was on my car (and now on your car).

Sorry I should have described this better, but yes at full droop when the shocks are at full extension. I need the springs to not fall out to pass rego requirements. Considering 88+ HBL rear spring rate is 2.3 - 4.8kg/mm and your guesstamate that your current rear springs at sitting between 4 - 4.5kg/mm I'll be aiming to keep the stiffness of whatever it really is on your car simply because I quite liked it. HBL give a free spring height of 303.5mm but I wanted to double check if this was enough to capture the springs at full droop. Having said that I know my rear Koni yellows already have a shorter stroke than standard, so that 303.5mm height might not be needed. But if you plan on shortening the stroke even further then that's a different ball game.
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Post by Piazza_man »

Maybe it's easier just to get my mechanic to put my car back on the hoist and do the measurement from there.
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Post by archangel62 »

Good answer, I get what you're saying, I'll be sure to measure it all up when I get my head under there. If we could find a progressive spring with a similar average or maximum springrate and similar height to those ones I bought off of you, we'd be laughing. There's a good chance that Lachlan (Vinnie) would be keen for a pair too. I was actually hoping to test a few different live-axle Commodore and Gemini rear springs, ie aftermarket etc, and see if any could be used without cutting, and therefore with a decent spring seat. Failing that, maybe a Commodore/Gemini progressive spring could be reset or made up to a lower height.

Having said that, if you intend on keeping your shocks, I would strongly recommend the maximum spring length required at full droop for your shocks - or at the very least confirm the full droop length of your shocks directly. If I've learned nothing else, it's that there are a lot of Koni shocks out there that "will fit" - but have different specs. Best not to muck around if you have to satisfy an engineer. And broadly speaking, I think it would be easier to get a spring made with the desired rate and height, and then have your shocks' stroke adjusted if required. I think it's about $100 plus post to have a pair of Koni's height adjusted. At least, I'm pretty sure that's for a pair :s

Re the springrate, I'm pretty sure there are calculators out there to give you a rough spring rate based on spring gauge and effective length (ie diameter and number of coils). Maybe I should measure these up while I'm at it. I'm sure there would be some deviation based on age, material, tempering process etc but it'd give us a better ballpark than "it feels like 4-4.5kg/mm" - because the springs I'm basing that on were all progressive!
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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Post by Piazza_man »

If it helps I know lowered VL wagon turbo springs also work because I had a pair of them on my first blue Piazza. (Lovells springs back then I fink).

Btw the rear eyebrow height was 300mm wasn't it? I could be wrong.
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