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what to do

I've been hearing a lot about modifications and I'm at a point where I should start making some decisions about what to do next. I have a '72 Opel GT all stock, minor rust; for the most part in decent shape. New brakes front and rear, the Pinto Holley carb, stock exhaust, 1.9L motor. Where should I go from here? I'm so tired of the Japanese import racers and how they think their new stuff is so cool; when good old fashioned engineering and know how can do just as good if not better. I want good power with decent gas mileage. I've got several domestic V8's, but I know that I can't crank out the same sort of juice from a four cylinder. How can I get the most bang for my buck? What would you suggest for carb upgrades, engine modifications, and suspension improvements? I would like it to still be street legal when I'm done.

The 2.4L Opel and the 5 speed transmission? Is this the best way instead of modifying the stock motor. I don't think I want to spend time and money on the modifications if I can do just as good or better by dropping the car onto a 2.4, and putting in the 5 speed trans.

Any suggestions? Lost in Utah, Ben. :confused: :D
 

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Ben,

From what I have found out, the only two thing you need to have a really nice Opel is MONEY and TIME, so be prepared to spend alot on both. As far as the Japanese cars, there are thousands of them on the road but only a few Opel, so drive with Pride and enjoy the ride..........

Stanley_P
 

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Just remember too, that ALL cars are essentially money pits. I have a Subaru WRX that's a daily driver. Yes, there is a huge aftermarket for this car, but nothing is cheap. My stainless steel REAR exhaust cost me $585 (I paid cost through a friend's shop), a computer chip (piggyback) upgrade would cost me $700, a big brake kit (front only) costs $2000, etc. By comparison, the Opels are actually quite cheap, remember you didn't pay $25K to begin with! And, as Stanley so wisely said, you don't usually have to worrry about seeing yourself at every stoplight. Enjoy your uniqueness!

Bob
 

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It's all about how much you want to spend...

I was doing the motor math last night to try and get to sleep. A normally aspirated 1.9 liter is capable of 200+ streetable HP; this necessitates extensive modification and careful application of matched components. The cost? Probably about $20/HP once yer done.

The late 2 valve motors are more or less bolt ins. With a little massaging, you can get into the 150-160 HP range. Still, you're in the $20/HP category...

Keep in mind the Opel is a LOT ligher than later model cars; this nets out a good power/weight ratio. A 160 HP Opel will run door-to-door with a stock Mustang GT and suck headlights outta most rice burners.

I've built a lot of small displacement 2 valve motors, and the magic number for a mild motor is 72BHP/liter. Most small motors with a 6500 RPM redline are capable of developing 72BHP/liter with the following:

9.0:1 compression
Mild 'street' cam (sometimes called a torque cam)
Port matched and polished intake manifold
Exhaust header and low-restriction exhaust system
Non-progessive 2 bbl carburetor approx 20% larger than stock
Velocity inlet stack or other inlet airflow management
Cold air intake
Exhaust heat shielding
low temp thermostat or orifice plate.

All these mods have to be matched to the other; when it's done right, the car is a joy to drive. In the case of the Opel, these are good for (this is my thumbnail, mind you) of about 125-130 HP. I'm just guessing, but a good port job with oversize valves (a 2.0 head is better) would get you to 135-140 HP.

After this, you have to go big bucks to pull 180 HP, as the motor has to be increased in displacement. After 180 HP, you'll have to give up some driveability to move the power band up a notch - the motor won't run well around town - no bottom end torque.

It's all about airflow, heat management and your credit line...

Chuck.
 

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You should look up TGSI racing on the web (he's a member here as well), he sells a turbo kit for the Opel. You could probably get this as a supercharger as well. To use this would require a fresh engine, but could provide you with some truely wild power increases. I've read articles that state with the correct engine build up, you can top out at around 200 hp, and get about 150-160 for a stock rebuilt 1.9. A good thing to remember at this point, would be that the stock rear axle and transmission for a GT is only good for about 150 hp (correct me if I'm wrong here guys). Good luck, and let us know how things work out.

David
 

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I don't want to burst yer bubbles, but there's no way you're getting 200 hp out of a 1.9 litre Opel engine that's streetable, unless you go turbo, supercharger, or nitrous. I've topped out at 197 hp for a 1.9 racing engine (fastest road-racing Opel in the US BTW), it cost about 7 G's, and is NOT what I'd call a streetable engine.

You can get around 150-160 from a 2.0 litre (bored) version of the 1.9, but the mods are far from bolt-ons. Remember, Opel's hp numbers were incorrect by today's standards, so the starting point of 102 hp is closer to 85 hp. In fact, a genuine 125 hp is very rare, and requires headwork, a reasonable camshaft, and increased induction, among other things. But, the truth is, a 140-150 hp Opel with the correct gears will show its' tailights to a 5.0 Mustang, not just run close to it. My 139 hp street Opel w/ZF tranny never lost a race to a stock Mustang. My friend's 2.1 litre 192 hp Opel racecar would show its taillights to all but about 4-5 production cars made these days. Power-to-weight......

Bob
 
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Actually, I was talking about turbo or supercharging. 200 hp you'd prolly have to use race fuel though.
 

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Rally Bob-

I'm not disagreeing with you. My small motor experience has been with 2.0 & 2.3 Fords, and 2.0,2.2, & 2.5 Mopars. The Mopar motors have head designs that are a good 15 years after the Opel; I would expect lower port flow rate, and this is the limiting rate on HP production in an Opel.

Has anyone attempted raising port floors? it was pretty easy on the Ford & Mopar motors...

Yah, it's all about power-to-weight. This is why I'm not all that enthused with the idea of a motor swappie in an Opel - some folks want to stuff a big ol' 'Merican V8 in the engine bay. To do it right, there's major surgery and driveline upgrades - the net result is a car that weighs in a good 600 lbs more than a stocker. you've lost the nimble feel and the new motor has to generate 30% more HP to address the added heft.

Put another way - let's say you've got a 125 HP motor on board already -- The V8 better put out at least 175 HP, or you're at par.

Oh and Bob - are you talking crankshaft or rear-wheel HP? BIIG difference...my advertised 150 HP 2.0 Mopar modified to 160HP clocked 117 HP at the drive wheels.

One last thing...The auto manufacturers STILL overstate advertised HP by about 20%. I've seen a LOT of brand-new stocker motors on dyno stands that clock in less HP than stock.

Examples: 275 HP Northstar - 255HP
160 HP GM 2.0 turbo - 128 HP
146 HP Mopar 2.2 - 122 HP

And the really good one: Ford advertised the 5.0 Mustang at 225 HP for years, starting in 1987. Actual HP was closer to 175-180. Therefore, Rally Bob's buddy had a better power-to-weight; that's why he was faster.

I'm sorry - my numbers had been adjusted for street racer fudge factors. It's easier to compare if you start from the same baseline; I was using advertised HP as the base. I did a 2.3 Pinto that ran door-to-door with an advertised 250HP Corvette; working backwards with advertised HP solves for 175 HP in the Pinto. Actual dyno would have been closer to 140.

All depends on the size of the ruler.
 

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Go with the 2.4 you'll be happier you did in the long run ... one thing we all do eventually and that is want more from our engines. One thing to consider though ( actually two main things ) which are a rear end to hold up behind the 2.4 and 5 speed , and ( drum roll please ) BRAKES to stop the damn thing!

RITTER
 

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Chuckspeed, it's true that in stock form the (1.9) Opel heads don't flow that great, but after modding them, I've had no problem smoking the 2.2 Chryslers in terms of airflow, and could just eke past a well-prepped 2.3 Ford head. And if you really tweak a 2.2 or 2.4 Opel head (raised port BTW), you can actually come within 12 cfm of an Esslinger aluminum 2.3 head (148 vs 160 cfm @ 10" water), fully ported. Not merely my opinions, I've had all of these heads on my flowbench over the years.

When my friend's 192 hp Opel used to run in circle track, he was running against 2.3 and 2.5 litre Fords, which cost about $6000 for the (Esslinger) engines, and needed rebuilding twice per year. The Opel went 3 years between rebuilds, and the entire car cost $6700. Also, we were a 4th to 5th place car generally, until one day they started reinforcing the '2000 lb' rule at the track. Suddenly, we were the smallest engine making the most power, as all the other cars had been decidedly underweight. We were 230 lbs overweight (with driver). We apparently had WAY more power than the 2.3 and 2.5 engines, and they were 'claiming' over 200 hp. Needless to say, our car now was a LOT faster than the competition. So yes, there's always discrepancies with dyno figures.

Another instance was an engine I dynoed at 155 hp at the flywheel. But when all the accessories were added (Which the dyno operator originally didn't want to put on), the power dropped to 142. Hey, at least it was 'real world' hp, with the full air filter assembly, pump gas, alternator, and a complete exhaust system with 3 mufflers to keep it quiet. On a chassis dyno, it measured at 113.7 hp. At least the hp and torque rpm peaks corresponded to each dyno's results, but it was interesting to see the losses at the rear wheels. At the same chassis dyno session, a 1985 Monte Carlo SS put down 131 hp to the rear wheels, and a 1990-1992 (?) Corvette put down 164 hp. The Corvette owner was 'insistent' the dyno was broken, since his car came from the factory with 245 hp! Not a happy fellow......

BTW, I'm not trying to start a war with you Chuck, we're just 'bench racing'!

Bob
 

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Ok here's my "clueless Q of the day": What can I expect HP wise from my 72 GT with the Weber Carb and 5 spd getrag with the 1.9? (I know nothing of these things.....):confused:
 

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Well, once again we get into the realm of 'flywheel' horsepower versus 'crankshaft' horsepower. Your 1972 GT, in standard form, ws rated at 75 hp at the flywheel. Depending on the state of tune, I have found this to be closer to 62-65 hp.

A car magazine, Road and Track, once dynoed a 1972 Manta at the rear wheels (exact same engine), and it made 47 hp! Now, this was with the Solex, so with a Weber you can expect about 4 hp more (at the flywheel).

Bob
 

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Ok, so I'm going to be driving a fancy moped. :) Let me ask this follow up question of the day: To get the most bang for my upgrade buck, which would be the best option:

1) the 2.4L conversion
2) header/exhaust kit
3) complete new non-opel engine
4) something else entirely

Anyone? Ideas?
 

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Bob-

Forums are funny places; sometimes you think you're discussing stuff with folks when in reality the other side thinks you're arguing. Therefore - I really do appreciate the comments about bench racing. That's essentially what I thought we we doing, and I *love* doing it!

I find that dynos are funny critters. What the dyno sez is merely an approximation of the real world - it's virtually impossible to replicate the underhood environment in a dyno cell. Dyno'ed motors always seem to be jetted leaner than their fastest ET on the street/strip/track, for example.

My best work occured out at Pop's barn. Pop's got a full machine shop in the barn, and lived far enough out in the country (it's kinda built up now) for us to street test. We had a timing loop and a speed trap set up - the two allowed fine tuning of engine/drivetrain/suspension mods while keeping the vehicle in a real-world environment. it was always fun taking sweepers at triple digits - actually blew a 2.2 Turbo inna left-hander on account of the combination of revs/G's/oil level was enough to starve the oil pump. While I never like grenading a motor, doing it like that kinda eased the pain.

One of my fave motors was a 2.2 inna Shelby Charger I built up for my not-so-little brother. We stopped modifying it when it exceeded the baseline trap speed set by a Porsche 944S. The Shelby was later sold to an SCCA racer and campaigned somewhat successfully out at Waterford Hills.

I agree on the durability aspects of the Opel. I've never liked the Shelby valvetrain (it kept spitting out followers at 125MPH) and the head sealing systems of little Mopars flat suck. One of these days I'm gonna go over to Chrysler Tech Center and have a discussion on differentials of coefficients of thermal expansion along with selecting the correct modulus of elasticity for head bolts. It's not rocket science, but the Mopar boys seem to consistently booger it up.

I've always liked the simplicity and robustness of the Opel motor, and it bums me out when folks start swapping them for Brand 'X' powerplants. Run whatcha brung, dabnabit!

As for Kristi's comment -

If it was me, I'd be pretty happy with a bolt-on solution of:

*Mild cam
*Weber
*Header and low restriction exh.

The trick for the street is to make power down low, as opposed to making lots of power. In a little motor, big HP comes from winding the snot outta it. To wind it up tight, you gotta make sure all the rotating components are up to the task, which usually translates into opening up your pocketbook and emptying the contents into your engine builder's account. This does not mean you've got a fast street motor - I've won races on a lot less HP than my competitors because my combination was better suited to the task.

The combo mentioned above will add approx. 20-25% to your power output while lightening your wallet by about $800-$1000. No need to upgrade the drivetrain, although a better set of front brakes would be well worth it.

The result is a car with a better than average power-to-weight ratio; figure 0-60 times in the high 7 to low 8 second range.
 

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From the peanut gallery

For what it's worth I think Kristi already has most of the key components, that is the Weber and the 5-speed that I would use. The 5 speed for any trip out of town, and the Weber so you won't have to adjust something every other weekend. (Mind you, I kinda like Solex carbs, so feel free to send me yours)

For the next level in the performance area, the exhaust is probably the quickest/ easiest next place to upgrade, followed quickly by:
-the front brakes
-a K&N air filter
-new poly or delrin suspension bushings
-new shocks
-and a good quality alignment at a good shop.

Notice not much for engine mods? The charm of the GT is in the handling and look, not really in it's dragstrip performance. It wasn't too many years ago that a stock VW Rabbit posted better ET's at a famous road course in CA than a Shelby Cobra. The GT was designed with the same thought processes. Fun to drive is only part acceleration.

Again, from the peanut gallery,
Stephen
 

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Don't forget the ignition! What good is eliminating the Solex if you still have to adjust points!! A Pertronix, or Crane XR-700 (or XR-3000), or go for the gusto and get the 'distributorless' system I recently did a writeup about (see the archives, under 'Performance')). But no matter how you do it, it's gonna be better than stock.

Bob
 

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Oops

Forget the last post. The very first thing you should do is replace the points. The pertronics or Compufire drop-in units will be great for almost anything you want to do, but the DIS unit Bob did a write-up on has the cool factor, probably a lot more consistant ignition, and it cleans up the engine bay a bit to boot.

Ignition first, no doubt.
 

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You know, I was just thinking about the Compufire system I did the write up about, and it REALLY is a pretty good deal. I mean, it replaces the distributor cap, the rotor, the points, the condensor, the coil, and the wires all for $175 or so, PLUS you eliminate high voltage arcing and get higher spark energy and no adjustments. If you replaced ALL those components, and switched to a 'regular' electronic system, you still have the shortcomings of the stock components, and you'd probably spend $110 or more for all the parts (cap, rotor, ignition module, hot coil, new wires).
The Compufire is making more sense to me every day. Gonna put it in a few more cars, methinks.....


Bob
 

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Ok so here's the deal... I checked out your archived post and have two questions...

1) I checked out the website you mentioned (doughouserepair.com) and the only thing I could find that sounded similar was $220 - is that it?

2) I also noticed in your archive posting you mention that for a stock engine it may well be overkill. That is exactly what I have.... is this still a good idea for me?
 

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Yup,I just went to their website and sure enough, the price has increased drastically to $220. In my eyes, it's still a bargain, but I realize it's not for everyone. Even the 'list' price was up to $293, up from $249 when I got mine. Looks like the manufacturer hiked it up.

For a stock engine, yes, it's overkill, but as I said, IF you have to replace all those worn stock ignition components anyway, you don't take as hard of a hit with the Compufire. Of course, now with the price increase my words don't ring as true anymore.

Bob
 
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