Tims BAD 44U

bad 44u · Post by **bad 44u** » 17 Jan 2007, 14:35

My gemini has been on hold for a couple years while i was away but im about to get the car prepared now.
The motor is the g200wa with a shaved head o;ringed block copper head gasget standard bottom end except the main bearings where modified and oil filter locater was modified for a oil cooler. the head has had a port and polish. The valves got a 3 angle job.
Induction is a custom inlet manifold made out of 2 90 degree bends approx 15cm long each making a z. with two rebuilt 40mm dellortos and a direct port nitrous system(pre fast n furious movie)50 hp jets. 15psi carter lift pump holley fuel regulator. HEI distributor looks like its off a nissan pulsar with the modular chip removed and a msd 6a wired up. 4 in to 1 extrctors and 2 1'2 inch exhaust. light weght flywheel rpm heavy duty pressure plate & 4 puck clutch. 5 sp gear box with remote gear stick. diesel diff with a welded centre commodore diskd all round and 90-10 shocks up front.
When we put it on the dyno it made 130 hp at 4200 rpm and bucket loads of torque. id like to replace the cam bearings and maybe cams befor we power run it and tune the nitrous. hopefully over 250 hp with 75 hp nos.
does anyone know whats a safe rpm for stock internals?

Post by **IZU069** » 17 Jan 2007, 16:34

Apparently the stock pots handle 180HP.
Try L1 profile cams. With the port job and new pistons (and 45mm Webers) this should give 220HP.
BTW - a standard G200W should be 135HP. I'm curious why yours is less?
My standard G200W but fitted with twin 45DCOE Webers and a 2" exhaust (with around 26" 2-into1 pipes from the standard manifold) produced 135HP. It should have been 150HP, but the engine was worn. But it's torque exceeded 380Nm (from 2000-3000 RPM).
Cheers,
Peter.

bad 44u · Post by **bad 44u** » 17 Jan 2007, 19:57

the dyno curve was just starting to head straight up when the operator shut it down because the cam bearings where not 100% and he wouldn't power run it while i wasn't there but he estimated around the 160-170 with out the gas. what are L1 profile cams & where can i get them & bearings from. I was told standard cams on these motors are better with forced induction or nitrous have you ever heard of this

Post by **IZU069** » 17 Jan 2007, 20:57

Apparently the L1 is a common race profile; normally too lumpy for road use except on Isuzu G-series twincams. I'd assume camshaft regrinders should know of them....
The L1 was recommended for normal aspiration - eg, 2 x 45mm DCOE. I don't know about their suitability for turbos or supers.
Peter.

bad 44u · Post by **bad 44u** » 18 Jan 2007, 13:10

what is the redline for a standard twin cam. the guy that built the engine thought around 6000 with standard rods. ive been chasing cam bearings and the only way i could get them was by buying two sets of piazza bearings which becomes quiet costly.

GeminiCoupe · Post by **GeminiCoupe** » 18 Jan 2007, 13:32

Peak power in standard form on the G180w was 6800rpm, on the G200w its 6400rpm.

Was 130hp at the wheels or flywheel? if its at that low an rpm your doing well..

Nick-

GeminiCoupe · Post by **GeminiCoupe** » 18 Jan 2007, 13:33

PS. put a Petrol diff back in it [3.89 vs 3.5 for the diesel] and youll pick up a few more hp.

bad 44u · Post by **bad 44u** » 19 Jan 2007, 09:55

aren't the petrol diff's alot weaker?
it was 130 at the wheels.
the induction noise was awesome, when you opened it up the intake manifold got cold to the touch.

Post by **elky** » 20 Jan 2007, 08:30

yea petty diff is weaker....

try putting a petty ringgear and pinion on the diesel centre , dunno if it will fit but have been thinkin of this for a while....

cheers

Post by **Poida** » 20 Jan 2007, 11:37

Won't fit elky. Different in too many variables.

I think if you drive sensibly you should be fine with a petrol rear end. Start off by finding one that hasn't got a lot of gear lash (look for an auto car with low km and a sane driver history) With it on a bench, drain all he diff oil, pull the tin hat off and have a visual and fingers check of the diferential gears for looseness and damage. If the gears don't heve chipped teeth, move in and out or slop from side to side then that's a good start. If they are shagged you need to pull the whole centre out to check further but normally the whole diff is past the point of rebuild for a performance car when they get that bad. So lets assume you find a nice set of diff gears, nnext step is to check the pinion/crown lash and the gear contact points and adjust them tiil they are in spec. Once you get that done the diff is as strong as it will ever be and the chances of busting it are reduced. It's worth pulling the axles out to visually inspect them for any signs of twisting or hammering of the splines. I'd also replace the rubber mount at the torque tube if you can get hold of one. They fatigue with time and often are the first thing to fail.

It means having the rear axle assembly out of the car but you can prepare and fit it for really little cost and a decent replacement or spare one is reasonable easy to find.

What kills any diff (including the Jap ones from ZZ or diesel cars) is being brutal. If you want to dump the clucth at every start, do roll backs and belt the car into gutters then it will eventually break. The soft part of the Gemini is the axle ends. They are inly small 23 spline ends so that is what you will tear off if you push it too hard. The same Salisbury centre should be able to manage easily in a 970kg Gemini because it was used in the heavier Commodore with a 142hp engine.

Post by **IZU069** » 09 May 2007, 18:24

Sorry Nick/GeminiCoupe from 18Jan.
The 100kW was at the rear wheels.
Good point! It's at the flywheel for my other discussions (ie 150HP with 45DCOEs, 220HP with L1 & port)

I guess that means then engine wasn't too worn after all.
But it is now - my last comp test was 100psi & 120psi (2 each) - she won't pull the skin off a custard now.

archangel62 · Post by **archangel62** » 10 May 2007, 04:04

bad 44u wrote:Induction is a custom inlet manifold made out of 2 90 degree bends approx 15cm long each making a z. with two rebuilt 40mm dellortos and a direct port nitrous system(pre fast n furious movie)50 hp jets.

LOL @ F&F reference
How hard was it to make the inlet? Got any pics? I've been thinking of making one with mandrell bends for a small internal volume and forward facing TB to suit a responsive turbo application...
Got any pics/vids of the twincam?

bad 44u · Post by **bad 44u** » 11 May 2007, 14:47

i was actually thinking of cutting it and spinning it around for the exact reason you are thinking of,if i do it no intercooler and methanol short path should be really responsive. the inlet's of the throttle bodies would sit at the perfect height. ill get some photo's for you.
yeah thrash it thats what there meant for. after i got mine off the dyno i went to take off at the lights and it free reved to 6000rpm i had to check if it was in gear or the clutch was slipping when i looked back there was smoke everywhere it was just spinning on the spot wasn't even making noise.

Isuzu G-series Twin Cam

Tims BAD 44U

Tims BAD 44U

twin cam

Re: Tims BAD 44U