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Discussion Starter #1
Back in 1987, a close friend of mine decided to build an Opel for street use and drag racing use. He never finished it. Went gung-ho for a while then abandoned the project. He did manage to start on the engine side of things, doing a lot of stuff that I would have never contemplated for a street engine back then.

One of the things he did was bore the 1.9 block out from 3.66" to 3.875", and fitted some forged, high compression 283 Chevy pistons into it. That equates to an overbore of .215". The pistons were also approximately .030" above the deck! He never figured a way around that part of the problem. Nor did any head gaskets exist back then to accomodate that bore.





He then went on to fit some massive 1.94" and 1.60" Chevy valves into the head. I've done this plenty of times to the 2.2 and 2.4 litre Opel heads, but never to a 1.9 head. Unfortunately in his overzealous attempt at airflow, he broke thru the head casting in a couple of places.



One of the items he spent some money on was a torque converter. He spent $500 (in 1987) on a custom high stall 4500 rpm converter.

So, back this winter while looking for some stuff in my barn I stumbled across the pistons for this engine. When he bailed on the project he gave me everything. I kinda smirked remembering how ambitious his goals were back then, then a whirlwind thought went thru my head...Could the engine be finished knowing what I now know?

I knew I had some copper head gaskets that were the right bore. But I'd have to stack them together to get the required thickness to make the compression height work. I was eventually able to weld two copper gaskets together at the combustion chamber area, and they ended up being .062" thick combined.

As far as the 'thin' bores of the block, I recently chopped up a 1.9 block that had been bored to .106" oversized. The walls were still .240" thick at the thinnest point! So the .215" overbore was not such a big deal after all. I decided I would add some block 'concrete' to stabilize the bores too. Second problem solved.

The cylinder head too, was not such a big deal. The areas that had been broken thru on were the cylinder head bolt holes. I've bored and sleeved them before with stainless tubing. I could also silicon-bronze TIG weld cast iron pretty effectively.

So now we are left with the power adding part of the equation. He never figured out an intake or exhaust system. And also, his cam choice back then was for a reground Chet Herbert cam, hydraulic profile. It would have never lasted with the tiny base circle and the hydraulic lifters...they would have bled down or pumped up solid at the rpms he was contemplating. Also, at roughly .500" lift and 246° .050" duration, the cam was just too small.

Bringing this forward 27 years, I managed to dig out the block and the cylinder head from storage. Kinda rusty, but still useable. I layed out a new set of plans. No street use, just drag race use. And what the heck, let's spray it with nitrous. Either it will go fast or go 'boom'.
 

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Can Opeler
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Now this should be an interesting project. Turning the little 1.9 into a drag engine? Awesome!


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I decided the intake manifold would be the first modern day part I would make. I started with a plenum that would not only help the high rpm power, but would be intrumental in giving the engine equal air/fuel distribution. The stock intake has a lot of shortcomings not only in flow capability, but also distribution.

I used .090" thick 3003 aluminum to fabricate the plenum.





For the carb mounting flange, I got a 1" thick cast aluminum carb spacer from Summit Racing. Even though the spacer had thru-holes rather than threaded holes, for $15 I'm not going to complain! I will just end up fitting helicoils into the spacer to provide for carb mounting studs.



On the back side of the spacer, I used a wood router and a round over bit to ease the airflow into the plenum.



Using one of my recently made 1/2" thick aluminum Opel intake flanges as a starting point. It nests perfectly with the header flanges I had made years ago.

 

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Discussion Starter #4
BTW, the overbore on this engine brings the displacement from 1897 cc's up to 2124 cc's. Pretty big jump for a bore increase alone!

The mock up begins. I'm using my dad's GT for all the checking and fitting, as my GT is at home in my barn. I started by installing new engine mounts to make sure nothing was skewed! As it turns out, one OEM mount was squished down about 1/4".

The intake runners themselves are 2" OD x .125" thick aluminum bends. Plenty strong enough to support the weight of the Holley 450 cfm 4-bbl I would be using. 450 cfm doesn't sound like much, but on a 2.1 litre engine it's huge! A stock Solex carb flows about 190 cfm. A stock Weber 32/36 flows about 270 cfm, and a 38 DGAS flows about 330 cfm. HOWEVER, a 2-bbl and a 4-bbl carb are flowed at different depression levels. So that 450 cfm 4-bbl flows around 636 cfm on a 2-bbl scale!! That's roughly 3.347 Solex's worth of airflow, combined with a plenum volume that's .8 times the engine displacement. It should make some very serious top end power.





Runners #2 and #3 are fitted. Notice I changed the location of the runners from OEM, in order to make them more equal length. The stock runners are not only not equal length, they have distinctly different turn radii. These are roughly 9" to 9.25" in length.



Welded inside and outside at the plenum area. These will be smoothed out afterwards.



Cylinder #1 runner fitted and welded.

 

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Discussion Starter #5
Runner #4 fitted and welded. This took the most time, and required three pieces welded together to make one runner. The plenum warped a bit too, but this was easily corrected later on.



A little more welding, and some plenum smoothing has begun. I did this project over the course of 3 days mostly. I'd estimate 12 hours total into it.



Here you can clearly see the compensation for the engine tilt. On this car anyway, it was 5.5 degree rearward, and 3.5 degrees towards the passenger fender. My new intake plenum is within .1 degree either way.



Another test fit onto the engine, and you can see this is NOT going to fit under the hood! That's okay, I never really intended it to. I'll either just cut a hole in the hood, or more likely make and fit a hood scoop to the OEM hood.





 

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Opel powered drag car

Now this should be an interesting project. Turning the little 1.9 into a drag engine? Awesome!


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It has been done before, with some mild success, I guess the GT would be a buyable project. Rally Bob might have to seek some outside help:lmao: but he will figure it out:yup:
 

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Discussion Starter #7
More plenum work:



Carb flange finally welded into place. I waited until the plenum bottom/runner entries were fully smoothed out.



I matched one intake runner to the port size in the head. Yea, that's a stock intake port dimension on the right!



I fitted the 1/16" NPT nitrous nozzle bungs into the intake runners next. I used a center punch to peen them into place for tack welding, then fitted a nitrous nozzle into each bung to finalize the positioning before welding them in for good.





The nitrous nozzle just protrudes into the port, at the required 90° angle.

 
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Comparison of a stock intake with Weber carb and my new intake with Holley carb.







I made a linkage bracket that fits on the carb studs, and will use an old Lokar throttle cable that was once on a circle track car.



Stock intake bolts are too big to fit! I used the factory 2.4 socket cap screws in this pic, but will probably drill and helicoil the head for 3/8" ARP bolts for even more clearance. The header I'm building will use 1.75" runners stepped up to 1.875" and finally 2". So I need all the clearance I can get!



 

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It has been done before, with some mild success, I guess the GT would be a buyable project. Rally Bob might have to seek some outside help:lmao: but he will figure it out:yup:
If Chuck Norris' car is too slow, he will be calling Rallybob.

Dieter
 

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Can Opeler
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I wish I knew how to do that stuff. Rally bob should make a summer camp for hot rodding Opel engines haha.


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One area of concern for the next step (the header) is the clearance on a GT chassis. Luckily this header will be rather short to work with the high rpms I'll be spinning the engine, but the tube diameters are pretty big. I'll be fitting an auto transmission into my dad's car for mockup purposes, since the transmission pans on those things are pretty big and take up a lot of room. No use guessing here...

The next area that is a tight fit is by the bellhousing itself. Even moreso, the block stabilizer bracket that goes between the engine block and the bellhousing flange. A lot of street GT owners remove this bracket for fitment of an aftermarket header. I want to keep a bracket here since it does aid in stability and I've seen bellhousings crack under racing duress before. Not really a concern with a 100 hp street car mind you...

To make room, I've redesigned the bracket. Not the prettiest thing, but it only needs to be functional and strong.



I will probably grind away the aluminum flange of the auto bellhousing between the bolt mounts too.





Here you can see the header collector I'll be using. It's four 2" OD tubes running into a 3.25" collector diameter. It'll then taper back out to 3.5" main exhaust pipe diameter, and that will taper into a 2.25" tall oval pipe section for more ground clearance.

 

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It has been done before, with some mild success, I guess the GT would be a buyable project. Rally Bob might have to seek some outside help:lmao: but he will figure it out:yup:
You wouldn't happen to have a set of stock length aluminun Opel rods around still, would you? :)
 
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I lost my marbles when I saw the slober-rator



Good thing that this is only at the mock-up stage :)
 

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So today I only spent a little time at my shop. Too hot to do much there. But I dug out some u-bends, attached a header flange to the head, and started laying out the header design. Located the header collector here:



Used a piece of welding rod to lay out the #1 cylinder header tube. 24" long overall, with a step every 8". Starts off at 1.75", then 1.875", and finally 2" into the collector.



Here's the number one tube all welded up and ready to go.



Closeup at the first step.



And finally #1 tube tacked in place at the header flange. That's all I got to do today. Will probably continue on Monday. I did too much this week and my back is paying the price! I need a weekend off...

 
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Discussion Starter #16
Not sure what you have in mind for an automatic, but I have the TH180 from my Bitter.

Kevin
I'm building a fresh TH180, along with some upgrades to the valve body for firmer shifts. I might machine the clutch basket and fit more steels and clutch plates in there too. I got a used ratchet shifter a few weeks back to replace the OEM shifter already. I will be plumbing new 3/8" stainless hard lines and a large cooler too. Might do a deep sump oil pan as well.

Thank you for the offer Kevin!
 
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Discussion Starter #18
I took the weekend off from car stuff.

Yesterday I got in a few hours on this project. I only finished one more tube, but it was a bit tricky getting the required 24" long primary length, fitting it within the confines of a GT chassis, and clearing my new intake. The 2" diameter tubing (3rd step) is not very forgiving when it comes to fitting it under a GT hood! This is cylinder #3, I'm fitting the tubes into the collector in the firing order...running clockwise. So it's 1-3-4-2.













 

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Discussion Starter #19

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Discussion Starter #20 (Edited)
Making steady, if slow, progress still on the header. Last night I got the third primary tube done, cylinder #4 this time.

All the pieces cut and deburred, ready to be tacked together.



Funny thing, when I mocked everything up, I had plenty of clearance between the primary tubes, intake manifold, and the chassis of the car.



Then I welded everything together:



Somewhere along the line, as I welded stuff together, things moved around! So I had to ding a tube here, and ding a tube there....



Eventually, I had to flatten an area of #4 exhaust runner near the heater box. I had clearance when I mocked it up, and after welding I had light contact. As long as I have some air space I'm okay, as I will be running solid engine mounts...:yup:

 
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