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Discussion Starter · #1 ·
Weakest Link?

With the following upgrades, which components on my Opel will become the weakest link? Assume the car is a Manta, pretty much bone stock at the moment.

1). Engine will be upgraded with a 2.4L (it just cleared customs!). Planned mods include head work, with Rallye Bob's recommendations for larger valves and a set of Samdog's roller rockers that have been sitting in my basement begging to see the light of day! I don't plan to do much of anything to the bottom end, aside from maybe a cleanup with new bearings and perhaps stronger ARP bolts (if I can find them). I don't want to increase displacement. Exhaust manifold will be the one that came with the 2.4 (pretty much the same as a "Sprint" manifold I believe). I'm open to suggestions on exhaust size.

2). I have a set of dBilas twin intake manifolds (and thermostat housing) for the 2.4L and would like to go with a fuel injection setup via megasquirt. No final decision yet on cam, though I'd like something that let's me keep plenty of low end grunt. I want the car to have a muscle car feel, which is why I went with the "real" 2.4 rather than a higher-reving 1.9 conversion. I realize the 2.4 will never see the high rpms that would really let the roller rockers shine, so I'm torn on whether to use them on this engine...but at least they're available. I have plenty of other projects to use them in! :D

3). Getrag 240 5 speed (I already have it available, hopefully it's strong enough to handle a strong 2.4). I was planning to go with the popular S10 clutch setup.

4). Larger ('75) brakes have already been installed on the front, with Brembo rotors, green stuff pads, and braided stainless hoses. I have the larger 3/4" wheel cylinders for the rear as well.

4). Suspension mods will include a Bob-designed rear panhard rod (thanks again Paul!), and Bob's recommended progressive springs and shocks for 1.5"-2" lowering (if I can ever get out to Duane Foley's to get the parts car!).

Rearend is a major concern I would think. Will a Quaife give it the strength needed to stand up to the new drivetrain, or do I need to consider other options.
How about the torque tube setup?

I'm hoping to generate some discussion on things to look out for when doing these kinds of upgrades to ensure that the car remains safe. I don't really want to radically change the car (no toyota rearends, etc.) since I'd like it to remain fully an Opel.

Cheers to all, and Happy Easter! Not long 'til Carlisle!!!
Todd Kirby
 

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boomerang opeler
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todd the weak point will be the rear end you dont whant to change
you could go to a quaife LSD or change the whole thing but its going to die on the standard one, do the search thing and you will see theres a lot of talk about how to go from a better diff to a full change of axel but with what you said that rear will die
 

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Hey Dude;
If you're going to go the F.I. route, can I just keep these dual side draft intakes? (wink, wink, nudge, nudge ;) ROFLMAO :D )
 

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Discussion Starter · #4 ·
Nope

Nope, they will nicely house throttle bodies!
Todd
 

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just count on every mod you do you will need 2 or 3 others to make it work



i would start planning on an oil cooler and a bigger radiator (just to protect your investment)

Take a look at the torque tube donut and drive shaft.

don't forget the water pump if its a used motor just go ahead and change it out

you get the picture

Davegt27
 

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neuropel said:
With the following upgrades, which components on my Opel will become the weakest link? Assume the car is a Manta, pretty much bone stock at the moment.

1). Engine will be upgraded with a 2.4L (it just cleared customs!). Planned mods include head work, with Rallye Bob's recommendations for larger valves and a set of Samdog's roller rockers that have been sitting in my basement begging to see the light of day! I don't plan to do much of anything to the bottom end, aside from maybe a cleanup with new bearings and perhaps stronger ARP bolts (if I can find them). I don't want to increase displacement. Exhaust manifold will be the one that came with the 2.4 (pretty much the same as a "Sprint" manifold I believe). I'm open to suggestions on exhaust size.
An exhaust of 2.5" diameter will work very well with a modified 2.4. I have a set or two of 2.4 ARP rod bolts left if you need them. Before you throw away those 2.4 bearings, make sure you can get new ones....the mains are interchangeable with other CIH engines, but the rods are specific to the 2.4.

neuropel said:
2). I have a set of dBilas twin intake manifolds (and thermostat housing) for the 2.4L and would like to go with a fuel injection setup via megasquirt. No final decision yet on cam, though I'd like something that let's me keep plenty of low end grunt. I want the car to have a muscle car feel, which is why I went with the "real" 2.4 rather than a higher-reving 1.9 conversion. I realize the 2.4 will never see the high rpms that would really let the roller rockers shine, so I'm torn on whether to use them on this engine...but at least they're available. I have plenty of other projects to use them in! :D
Don't worry about torque. Duane's 2.4 Manta had 125 hp and 150 ft lbs of torque with a healthy cam. Power peak was at 5400-5500 rpms....so you can cam a 2.4 pretty well and still keep the grunt you desire. A stock 2.4 cam is all done making power by 4800 rpms.

neuropel said:
Rearend is a major concern I would think. Will a Quaife give it the strength needed to stand up to the new drivetrain, or do I need to consider other options.
How about the torque tube setup?
This will all depend on your driving style and the tires you use (traction). A limited slip will strengthen the rear axle sufficiently....BUT, with this added strength and traction comes the next weak link, which is the torque tube. Ironically with an open differential the torque tube is not such a stressed component. At the least you should replace the side mounts and bump stops, as well as the TT 'donut'. If you're going to beat on the car real hard then consider having the torque tube shaft itself sleeved for strength. This is just a matter of welding a steel tube over the existing shaft for increased rigidity. It should then be rebalanced.

HTH,
Bob
 

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Discussion Starter · #8 ·
RallyBob said:
I have a set or two of 2.4 ARP rod bolts left if you need them.
Definitely will talk further with you about those. Let me see what I have first.

RallyBob said:
Before you throw away those 2.4 bearings, make sure you can get new ones....the mains are interchangeable with other CIH engines, but the rods are specific to the 2.4.
Any good sources for the 2.4 rod bearings?

RallyBob said:
Don't worry about torque. Duane's 2.4 Manta had 125 hp and 150 ft lbs of torque with a healthy cam. Power peak was at 5400-5500 rpms....so you can cam a 2.4 pretty well and still keep the grunt you desire. A stock 2.4 cam is all done making power by 4800 rpms.
I have a new Isky "combo" cam from OGTS that I bought from another local Opeler. (HP "Combination" .430" lift, 268 duration), hydraulic grind. Would this be a decent choice?

Bob, thanks as always for the excellent, free advice.
Todd K.
 

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neuropel said:
Any good sources for the 2.4 rod bearings?
Try OGTS, if he doesn't have them you'll have to source them from Europe.

I have a new Isky "combo" cam from OGTS that I bought from another local Opeler. (HP "Combination" .430" lift, 268 duration), hydraulic grind. Would this be a decent choice?
You'd barely notice it by idle. Good for about 5000-5200 rpms with a 2.4. I've found that 2.4's like a wider lobe separation angle (112 degree), as well as more lift and duration. I'd personally put a cam with about .475" lift or so in, and duration in the mid-240 @ .050" range. Otherwise you'll give up about 20-25 hp compared to a stock cam.

Bob
 
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Moderators Note: Moved to "Opel Engine Performance Mods" as that seemed to be the main discussion. If it veers back to differential talk, I can split it
 

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Hi Todd,

Great to hear another one of the forum member is going down the 2.4 route, hopefully your mods won't prove too problematic.

I'm in the middle of a 2.4 upgrade myself and am having plenty of fun with it.

Started off with a 2.2 block and have picked up an unusual 2.4 crank as it only has 4 counter-weights rather than 8 counter-weights, the joy of this that the crank weighs in a 38lbs rather than 44lbs.

I'm using a set of Lotus Carlton conrods and Mahle (oversize) 2.4 pistons.

The flywheel and crank have been balanced and hopefully that's the bottom end sorted, but as Rallybob said makes sure you can get the bearings because I've had plenty of fun trying source some over here in the UK.

As for the head, I'm using a 2.2 head with the raised ports. The valves are oversized being 41/46mm and the chambers have been ported and flowed.

I'm also using a set of Samdogs (Gregg's) / Rallybob's roller rockers and like you my engine isn't going to be a screamer, but my thinking is that sometimes you have to just treat yourself :D and hopefully the engine will be a little quieter than the usual clatter associated with the CIH motor.

As for the cam, I'm using a Kent 244 which is 296" duration, but because of this I'm also having to have the valve reliefs in the pistons cut out to ensure we don't have a big bang on the first start up.

In theory the engine should be back together in the next week or so, but then I need to think about fuel / air mixtures as I'm running the car on stock injection. The injectors I have will cope with 200+bhp and as for the air intake I'm modifying a 3litre inlet plenum, which also has the larger throttle body.

I appreciate that I will have to go down the mappable ecu route in the future, but this is fighteningly expensive over here, $1500 + so this will be a couple of months down the line, unless of course someone has a Megasquirt going.

Fingers crossed when it's all back together I'll have a 150bhp + and if anyones got any more advice on the build then feel free to type away.
 

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rearend mods

has anyone taken the entire rear end (axles, housings, spring buckets, etc.) out of a non-opel vehicle and put it under a gt? i'm sure some1 has done a custom ford 9" swap for drag racing, but any stock housings from car to car? Does the Impulse have the same setup as the gt (trailing arms, solid housings,etc)?
 

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Search!

Matt M240Z said:
has anyone taken the entire rear end (axles, housings, spring buckets, etc.) out of a non-opel vehicle and put it under a gt? i'm sure some1 has done a custom ford 9" swap for drag racing, but any stock housings from car to car? Does the Impulse have the same setup as the gt (trailing arms, solid housings,etc)?
Matt - just type "Impulse Diff" into the search box at the top of the page and many questions will be answered.

IMHO the 'killer' stock looking diff for a GT would be a 7.5"/7.625" Camaro or S10 ten bolt centre section with Isuzu Impulse axle tubes grafted into it with custom axles and a steel torque tube with sliding pivot joint a la Dave Jackson's Manta in the UK.

That would give a Torsen LSD with a wide choice of easy to obtain gear ratios and four stud disc brakes with the original Opel stud pattern.

Sorry! The Rats have been loose in my brain again ......... ;)
 

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wonder how much all that'd cost jim, altho the chevy parts are probably laying around my house somewhere, impulses are hard to find.
 

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What would be the strenght with that combo jim? Sounds like a very cool way to adapt LSD, strenght and disc brakes to an Opel!!
 

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Strong!

I have a 7.5"/7.625" 10-bolt Torsen carrier and 3.42 gears here - they are much bigger and stronger than Opel/Isuzu stock stuff. The "advantage" is that such a set up would look standard to the casual observer as the 10-bolt is just a bigger version of the Sailsbury diff. It should hold 250-300 horse power .....
Turbo 2.4 Opel motor ????
 
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