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Discussion Starter · #1 ·
Here's my Isuzu g200w twincam I intend to fit to the GT.
It sits on a engine trolley that simulates the GT engine cross member so I can work out how to make it fit.
The intake I started 5years ago I am going to run 2x 1 1/2" Fish carburettors. the car is RHD so I will be tidying up the conversion at the same time. The cars been sitting years so forgive its condition.
Next week I am digging the engine out and started it's prep for installation including electronic dizzy and custom winged sump but it may have only one wing for exhaust clearance.
Hope you enjoy my progress but it may be slow.
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Discussion Starter · #2 ·
I just received a valve regrind kit supplying me all the top end gaskets, and while at it I got a set of twincam bearings and bearings for the intermediate shaft (runs in place of the pushrod camshaft)
Also got the electronic dizzy.
Just had a chat to the only person I know has been using these motors for years and he advised against rebuilding the engine unless needed. I had been thinking sports cam and forged pistons, but he had found all Gemini's he has had twin cams in run sub 15sec 1/4miles and have heaps of torque for road use with stock cams and exhaust manifold only change being twin 40 DCOEs or aftermarket ems in place of stock EFI. I am told stock engine pulls like a train to 7000rpm but 8500rpm is safe even in stock form, but pistons don't like over 200 fwhp, I don't think that's an issue even with a rally cam and headers power is normally 135-150 depending on intake setup and my intake is unproven.

I am still thinking cams to give that race car driving experience and beefed up torque tube driveshaft because of my oversize wheel combo. I have the name of a local guy that sleeves them and provides solid rubber torque tube mounts.

What do others think
Forged pistons ?
Cams, header, my twin carb intake. ??
Maybe mill the head to bump compression from 8.3 to 9.5-10.???
 

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Nice to see you posting back on the forum again Alex. Not knowing where you intend to drive, I’ll get it going with my 2¢, I’d stick with the guys advice on leaving it alone IF it’s a pretty solid engine. It looks like you’ll have your hands full squeezing it in. It sounds like a rocket just the way it is. It looks like you may get the rest of the usable drive trane to handle it as is? Not sure what you had planned there.
 

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Discussion Starter · #4 ·
Nice to see you posting back on the forum again Alex. Not knowing where you intend to drive, I’ll get it going with my 2¢, I’d stick with the guys advice on leaving it alone IF it’s a pretty solid engine. It looks like you’ll have your hands full squeezing it in. It sounds like a rocket just the way it is. It looks like you may get the rest of the usable drive trane to handle it as is? Not sure what you had planned there.
Yes, It's hard to know what to do I do want to make a road going fast classic but ultimate performance is not the goal. I really should fight the urge to keep modifying and get it going again. I will beef up the torque tube for sure but if I am honest with myself a lot of the performance stuff is already in place, they just need a tidy up.
But even as I write this I keep thinking Cams, higher compression. But I know in reality it will only mean something to me and slow progress.
 

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Yes, It's hard to know what to do I do want to make a road going fast classic but ultimate performance is not the goal. I really should fight the urge to keep modifying and get it going again. I will beef up the torque tube for sure but if I am honest with myself a lot of the performance stuff is already in place, they just need a tidy up.
But even as I write this I keep thinking Cams, higher compression. But I know in reality it will only mean something to me and slow progress.


I get that, if I had a nickel for each time I think of adding more power I’d be rich as the old saying goes. All I do is tool around town. I wasn’t sure how you intended to drive your GT or couldn’t remember if you like to drive more competitively.
For street driving it seems perfect 135 hp (101 kW) and 123 lb·ft (167 N·m) of torque. Curious choice, really looking forward to seeing how it goes in 🙂 please share your ideas, what transmission, drive shaft & rear end do you have in mind?
 

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Discussion Starter · #6 ·
I get that, if I had a nickel for each time I think of adding more power I’d be rich as the old saying goes. All I do is tool around town. I wasn’t sure how you intended to drive your GT or couldn’t remember if you like to drive more competitively.
For street driving it seems perfect 135 hp (101 kW) and 123 lb·ft (167 N·m) of torque. Curious choice, really looking forward to seeing how it goes in 🙂 please share your ideas, what transmission, drive shaft & rear end do you have in mind?
I bought the motor years ago but the problem was I couldn't find a transmission and only last month was told by a chap racing a Issuzu Bellett GT which had been upgraded from the 1600 twincam to the 2 lt type I have "any Bellett box will fit" and his has raced 3 seasons with over 200hp. So I bought 5x 4 speed Bellett boxes for $50 from a guy in the Bellett club clearing out his stuff.
The reason for the engine choice is I wanted some that looked race/period and was in the "Opel/GM"family.
The Isuzu twincam was perfect but I must admit a bit too rare.
Rear end is 3.9-1 Isuzu/Holden Gemini wagon (already in the car) although needs refinement, and will get a re-enforced torque tube, and combo clutch set up yet to be sorted and custom drive shaft.
 

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Discussion Starter · #7 ·
Just been checking out to intake I started a couple of years ago.
Fist thing I notice is I have the studs wrong, I need to align the throttle shafts along the plenum not across.
Problem being should the throttles open towards the rear wall of the plenum at part throttle or towards the ports?
I'm leaning towards opening towards the back wall which should fill the plenum with a good mist under high vacuum part throttle.
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