[GThound]

After my intake manifold modifications and explorations, I completed my MODERNIZE Opel Fuel Injection System build.

That EFI system running on the Holley Terminator X ECU platform is installed on my 1971 Opel GT and the car is running great! The current engine is a 2.0 liter CR 1980’s built engine block with the big valve head and autocross CR150 cam. The injection build got so many things right and achieved its goal to unlock the engines potential.

The next phase of my Opel’s journey is to achieve the following;

• Improved seat of pants acceleration
• More torque (target 180 ft lbs)
• More horsepower (target 180 hp)
• Wide power band (2,000-6,500 rpm)
• Snappy throttle response (maintain)
• idles at < 900 RPM (maintain)
• Runs on 93 octane pump gas (maintain)
• Super reliable (maintain)
• Goofier smile when I accelerate

After lots of reading and many discussions it seems to comesdown to fundamentals: air, fuel, spark, and physics.

I believe that I have nearly maximized my fuel and spark on my current engine with optimized electronic delivery of each (I am using a crank position sensor and cam position sensor for sequential injection and spark). That leaves me with opportunities for: better breathing (headwork) more fuel (displacement instead of RPMs), and mechanics to widen the power band.

Also, I am rather committed to the Opel engine, rather than an engine swap. And I want streetability, so higher RPMs are out. That leaves me making a cylinder charge with more fuel and more efficient (better breathing). So more cubic centimeters of displacement, more compression to get more fuel and reworked mechanicals on the bottom for a wider power band. And more headwork, camshaft, exhaust, for better breathing.

I know that there are other 2.4 build threads on this forum. I think that I have read them all. But each one is a bit unique in terms of its goals, components, budget, approach, etc. The aim of this thread is to capture my 2.4 stroker build journey.

 

[GThound]

The first components procured for this build were the connecting rods.

They are Eagle Specialty Products CRS5472N3D 5.472" 4340 Forged H-Beam Connecting Rod Set for Dodge Neon.
——————
Edit…. The rods that were in the box, were different that what I ordered. What showed up were 5.6” long rods. Great for rod ratio, but pin height is too short.
———————
The Eagle rods have been sitting in my basement for almost a year while I was fabricating, installing, and tuning my fuel injection system.

Some reasons these rods are a good choice for my build include:

• Longer than stock rods for a better rod ratio
• Lighter than stock rods
• Forged and shot peened for strength
• Strong H beam design
• Come with ARP bolts
• Should work well with my stroked crank

From a budget build perspective, this seemed like a bargain as picked them up on an Amazon warehouse deal last May for $137. But, the money saved on rods may be more than offset by the price of the likely required custom pistons to get the matching 21 mm pin size and right piston compression height.

Since the rods are the only component I have on hand so far, Rod balancing is where the journey begins.

First I weighed each connecting rod. Then did some research on rod balancing and realized that the best practice is to balance them end to end. Being me, I designed and3D printed components for the rod balancing jig. But, I had a difficult time getting reproducible results, so went through quite a few design iterations. Eventually I was able to reproduce consistent results.

I was actually quite pleased with the tightness of the weight grouping. They were all within a gram of each other. But once I had my equipment and method figured out, it took some work get get the end to end weights to match.

I labeled each rod and laid them all out on a piece of cardboard.

Rod #2 was the lightest and that one remained untouched throughout the process. The other three rods all had weight removed from the big end. In the pic below you can see an untouched rod on the left and a rod with material removed on the right near the lettering by the rod bolt.

Lastly rod 3 was also lightened on the small end which brought all to the same gram weight.

 

[Young Gt Lover]

Cool! I will be following this build. How much are you going to bore out the block?

 

[Autoholic]

What crank do you have? And if you're increasing the stroke, remember to check for skirt clearance. The 2.4 blocks have some material removed so the rods don't hit the block. What other parts do you plan to use in this build? Or are looking for?

 

[GThound]

Cool! I will be following this build. How much are you going to bore out the block?

First I need to get the crank welded and offset ground. Also, I need to see how much I need to machine to get the cylinders round again. All that said, if I can find pistons that have a 21 mm pin and the right compression height, I say let them drive the bore diameter. Else, what is on the larger but still safe side? 96 mm? I believe the Chevy 305 pistons in the original Bob Legere 2.4 build article were 3.766” diameter Chevy 305 pistons = 95.65 mm. i believe I have also seen 96mm, 96.5 mm and al sorts of inch based increments in between.

 

[mark1]

After my intake manifold modifications and explorations, I completed my MODERNIZE Opel Fuel Injection System build.

That EFI system running on the Holley Terminator X ECU platform is installed on my 1971 Opel GT and the car is running great! The current engine is a 2.0 liter CR 1980’s built engine block with the big valve head and autocross CR150 cam. The injection build got so many things right and achieved its goal to unlock the engines potential.

The next phase of my Opel’s journey is to achieve the following;

• more torque (target 180 ft lbs)
• more horsepower (target 180 hp)
• Wide power band
• Snappy throttle response (maintain)
• idles at < 900 RPM (maintain)
• Runs on pump gas (93 octane)
• Super reliable (maintain)
• Makes me smile when I drive it

Sorry, I may have missed where you're at now on HP & Torque, if you're looking to move up to 180/180. Can you tell me where you are now, or point me to the comment/thread?

 

[LynnB]

"All that said, if I can find pistons that have a 21 mm pin and the right compression height, I say let them drive the bore diameter. Else, what is on the larger but still safe side? 96 mm? I believe the Chevy 305 pistons in the original Bob Legere 2.4 build article were 3.766” diameter Chevy 305 pistons = 95.65 mm."

JMHO. If I were going this far with a build (and I have) I would not knock myself out looking for off the shelf pistons. Custom pistons are not that expensive (especially on a 4 banger).
When I built the engine in my 83 745i, I ordered custom pistons, as well as a custom camshaft (not saying you need a custom camshaft). That way you can dial in everything to optimum; pin height, compression height, CR, etc.

 

[GThound]

What crank do you have? And if you're increasing the stroke, remember to check for skirt clearance. The 2.4 blocks have some material removed so the rods don't hit the block. What other parts do you plan to use in this build? Or are looking for?

Great questions. Sounds like you are almost as excited as I am. That said, I am in the planning and procurement phase. Not in a rush. There are lots of interdependencies between design and component decisions along the way. Let me know if you have components available. I have not even sent my crank off for offset welding / machining. I was going to purchase from a member on this forum, but he changed his mind. I am building a material bill of goods list, but it is not yet ready to post. I am still learning as I go.

 

[GThound]

Sorry, I may have missed where you're at now on HP & Torque, if you're looking to move up to 180/180. Can you tell me where you are now, or point me to the comment/thread?

Well, to be quite honest, I am not exactly sure where I am now for horse power and torque and I'm alright with that. Instead of putting my car on the dyno, I would rather take the money and invest in components / fabrication until I stop changing things. Once changes are made (and I am always making changes), in my mind, it sort of resets the need for a dyno test. Don't get me wrong, I am a (mad) scientist. I love experiments, I love the data. In fact, I rarely ever go for a drive without my laptop, because I love the data logs and tuning and learning. I spent a whole summer refining the porting on a downdraft intake manifold while measuring changes in air velocity, pressure drop, etc.

That said, my best approximation that I have for horsepower right now is my fuel consumption rate in lbs / hr that I pull from my data logs. It seems that I tend to max out at just over 70 lb / hr, depending on the day (weather, timing, and target AFR adjustments). Assuming 0.5 lb fuel / hp, 70 lbs fuel / hr puts me at roughly 140 estimated ball park horse power.

It was running really good today and I wanted to see where it maxed out. But, my oil pressure has been a bit high recently, so I have not been hammering it too hard (shifting based on oil pressure, instead of tachometer) until I change the oil and get the oil pressure back in the realm of reasonableness.

So, in a nutshell, I am looking for a step change in acceleration, horsepower, and torque, that are accessible (wide power band) with great drivability (easy start, low idle, great reliability). If the build only got me to 172 horsepower would I be disappointed? Not at all. That said, I will go to great lengths (as in learning to balance rods, lighten my crankshaft, doing crazy Rallybob style porting, scrapping my 2.25 inch exhaust for 2.5" exhaust, etc) to maximize / optimize the results and driving experience.

If I came to the conclusion that I needed independent throttle bodies to get from 170ish to 180+ naturally aspirated horsepower, would I consider another intake manifold build in the future? Quite possibly…

But right now, I am most interested in what that extra 500cc of displacement will do in a stroker configuration with a head optimized for its flow needs.

 

[Young Gt Lover]

Well, to be quite honest, I am not exactly sure where I am now for horse power and torque and I'm alright with that. Instead of putting my car on the dyno, I would rather take the money and invest in components / fabrication until I stop changing things. Once changes are made (and I am always making changes), in my mind, it sort of resets the need for a dyno test. Don't get me wrong, I am a (mad) scientist. I love experiments, I love the data. In fact, I rarely ever go for a drive without my laptop, because I love the data logs and tuning and learning. I spent a whole summer refining the porting on a downdraft intake manifold while measuring changes in air velocity, pressure drop, etc.

That said, my best approximation that I have for horsepower right now is my fuel consumption rate in lbs / hr that I pull from my data logs. It seems that I tend to max out at just over 70 lb / hr, depending on the day (weather, timing, and target AFR adjustments). Assuming 0.5 lb fuel / hp, 70 lbs fuel / hr puts me at roughly 140 estimated ball park horse power.

It was running really good today and I wanted to see where it maxed out. But, my oil pressure has been a bit high recently, so I have not been hammering it too hard (shifting based on oil pressure, instead of tachometer) until I change the oil and get the oil pressure back in the realm of reasonableness.

So, in a nutshell, I am looking for a step change in acceleration, horsepower, and torque, that are accessible (wide power band) with great drivability (easy start, low idle, great reliability). If the build only got me to 172 horsepower would I be disappointed? Not at all. That said, I will go to great lengths (as in learning to balance rods, lighten my crankshaft, doing crazy Rallybob style porting, scrapping my 2.25 inch exhaust for 2.5" exhaust, etc) to maximize / optimize the results and driving experience.

If I came to the conclusion that I needed independent throttle bodies to get from 170ish to 180+ naturally aspirated horsepower, would I consider another intake manifold build in the future? Quite possibly…

But right now, I am most interested in what that extra 500cc of displacement will do in a stroker configuration with a head optimized for its flow needs.

That is pretty good hp if it really is 140 for a 2.0L

It will be cool to see this build!

 

[GThound]

"All that said, if I can find pistons that have a 21 mm pin and the right compression height, I say let them drive the bore diameter. Else, what is on the larger but still safe side? 96 mm? I believe the Chevy 305 pistons in the original Bob Legere 2.4 build article were 3.766” diameter Chevy 305 pistons = 95.65 mm."

JMHO. If I were going this far with a build (and I have) I would not knock myself out looking for off the shelf pistons. Custom pistons are not that expensive (especially on a 4 banger).
When I built the engine in my 83 745i, I ordered custom pistons, as well as a custom camshaft (not saying you need a custom camshaft). That way you can dial in everything to optimum; pin height, compression height, CR, etc.

This seems like good advice based on experience. Rallybob said basically the same thing, that custom pistons take care of many of the constraints. The more I play with the spreadsheet calculations, the more I may just want to get exactly the pistons I want for my specifications.

I will end up with a customized welded and offset ground 1.9 liter crankshaft and I will end up needing a custom camshaft (likely a regrind hydraulic). So that is why I am looking to save a little money where I can, to pay for that which I cannot do on my own.

I called “The Piston Guy” today after a quick google search. He seems to deal with many piston manufactures and can help provide guidance for your application. He seemed to think that there were many good custom forged pistons available today. Entry level pricing if I recall correctly was about $120-$130 each (Wyseco) and up, with JE being on the premium side of things and possibly overkill for a non turbo / non racing application. As for rings, I thought he said about $35 per cylinder. I think he said pins were included with some pistons but keepers Would be extra.

 

[GThound]

That is pretty good hp if it really is 140 for a 2.0L

It will be cool to see this build!

I had an Acura Integra that had somewhere in the same 130-140 horse power and it feels about it the same realm.

That said, there were a lot of factors to get my 2.0 liter Opel engine dialed in. Such as:

1. VOLTS: I got the electrical system right. New grounds, new positive cable, new 1 wire 120 amp alternator, kicks out consistent 14.5 volts at all RP
2. CFM: Removed intake restriction - 1975 fuel injection intake manifold instead of downdraft intake. Running big valve head and 2.25” exhaust.
3. COLD AIR. I could not believe the difference the cold air intake made. It was literally the easiest, cheapest thing I did. I bought a piece of 3” dryer vent and installed it in the Home Depot parking lot. I am not sure if my carbureted engine would have response like this. But my fuel injection system sure did. It reduced combustion air from 120-130F to something like 70-80F.
4. Perfectly tuned AFR: air fuel ratio is dialed in on 2D table and adjusts based on atmospheric pressure, temperature, High pressure fuel, smallest possible injectors, newest injector technology, injectors right at cylinder head
5. SPARK perfectly electronically timed based on 2D table using 4 independent coil near plug coil packs.
6. ENGINE MECHANICS: C&R build with venolia pistons, higher compression, autocross cam.

 

[Commodåren]

Stroke it to 81,5 mm instead of 85, that way you can use 1,56" comp height Chevy 305 pistons or C30SE pistons together with the stock 128 mm rods. The rod ratio will be about the same as with the 134 mm rods and 85 mm stroke.

 

[Autoholic]

Great questions. Sounds like you are almost as excited as I am. That said, I am in the planning and procurement phase. Not in a rush. There are lots of interdependencies between design and component decisions along the way. Let me know if you have components available. I have not even sent my crank off for offset welding / machining. I was going to purchase from a member on this forum, but he changed his mind. I am building a material bill of goods list, but it is not yet ready to post. I am still learning as I go.

I have my own 2.4L (C24NE) build in progress. My 2.4 came from Charles and was shipped from Poland. In my build, I have MaxPeeding C24NE rods, Wiseco C24NE pistons (these are flat tops with valve reliefs cut), Aasco Motorsports aluminum flywheel which uses a S10 clutch, Sachs all metal throughout bearing, Harland Sharp roller rockers, Piper Cams adjustable cam sprocket, Krause Rennsport Technik 47/41mm sport valve kit that comes with valve springs, guides, and seals. I plan to keep the mechanical fuel pump so I have a couple PTZ fuel pumps and I want to use the '75 Manta clutch fan setup so I have a couple GMB water pumps, a couple fan clutches, and a couple NOS 5 blade fans. I have 3 alternators with one of them being 85 amps and a starter. I plan to use a Weber 38 DGAS so I need to still get that. I have an Isky cam blank and I'm figuring out what I want that cam grind to be. I also have an Isky OR-77 cam that I don't plan on using. Too mild for the bigger 2.4L. The last major things I still need to get is a Spec S10 clutch assembly and create my own set of solid lifters. No one produces new solid lifters, so I'm looking into either buying a metal lathe and doing them myself or have them made in China. Either solution would then have heat treatment done here in the US. I also plan to create my own intake manifold and my own oil pan. I've been putting this build together for several years though, that's why I've purchased most of what I need.

If you want a set of Harland Sharp roller rockers, they are still making them but in limited batches like once a year. So you might have a wait a little bit to get a set and the person to talk to is Randy Jr. The Aasco Motorsports aluminum flywheel was a group buy a few years back. If you really wanted one, you would need to put together another group buy. For a cam, you might want to look into ENEM over in Europe, their E11 might fit your build. It's close to what I'm considering for my cam blank.

 

[V6Opel]

With those rods I'm calculating a 139mm rod which is significantly longer than stock. I looked at countless combinations when building my stroker 2.6L and settled on 136 mm rods. With 139 rods, 208 mm CIH deck height, and the stock stroke of 85mm you would need a compression height of 26.5 mm. If you stroke the crank that pin height comes down even shorter. The issue you run into is really short pistons and excess cylinder wall wear. At least that is what I read in all the research I did. Your rod to stroke ratio is also something you need to pay attention to as mentioned above. If too low, you will also accelerate the cylinder wear. I was able to use off the shelf 97mm Buick V6 pistons (cheap!), VW G60 136mm rods and put together a combination that yielded 2.6L displacement. The nice thing about the VW rods was that the big end diameter was smaller than the Opel crank and I was able to offset grind 1.5mm thus adding 3mm to the stroke with no welding required.

Edit: also with really short pin heights the piston rings are shoved up higher above the pin and not much clearance. I'm not the expert here but pictures of really short pistons did not strike my engineering fancy.

 

[mark1]

"All that said, if I can find pistons that have a 21 mm pin and the right compression height, I say let them drive the bore diameter. Else, what is on the larger but still safe side? 96 mm? I believe the Chevy 305 pistons in the original Bob Legere 2.4 build article were 3.766” diameter Chevy 305 pistons = 95.65 mm."

JMHO. If I were going this far with a build (and I have) I would not knock myself out looking for off the shelf pistons. Custom pistons are not that expensive (especially on a 4 banger).
When I built the engine in my 83 745i, I ordered custom pistons, as well as a custom camshaft (not saying you need a custom camshaft). That way you can dial in everything to optimum; pin height, compression height, CR, etc.

When I went from 2.0l to 2.2l I got custom pistons direct from Wiseco; looks like $706 in 2018, with every feature I could want (e.g. slippery coating on the skirt, desired CR...). What impressed me was how well the support guy helped me through the process of spec'ing what I wanted to get; I thought it was going to be nightmare for an Opel, but turned out to be easy. So, I definitely agree with LB.

 

[GThound]

So while trying to figure out which rod bearings to order, I realized that the Eagle connecting rods that Amazon sent last May were a different model number and longer than the rods which I ordered. They owned their mistake and now I am back to square one.

My plan now is the Bob Legere classic “Original Recipe" for converting a 1.9 liter CIH engine into a 2.4 liter stroker. He wrote the original article 30 years ago and should still work today. It is available for download on this site. I tried to save a copy here on this thread for easy reference.

This approach should maximize my torque, which should be great for acceleration in my street car, which is what I am after. I understand that there could be a little extra pistons / cylinder wear with low rod ratio (high angles). But, it is not going to be a high mileage car, and I love torque. I am glad that I got this straight in my head before sending out the crank for welding and offset grinding. Else, I would have had the wrong rod journal size on my crank. That would have been a pricey mistake.

This plan calls for original Opel rods on a 0.25” welded offset ground crank for a 3.25” (82.6 mm stroke). I will hopefully be able to use some budget friendly off the shelf pistons if I don’t have to make many compromises. We shall see.

I received my engine block core from @BQS4 here in Georgia. Thank you Gene!

Also I ordered a set of micrometers in several sizes to help take the proper measurements needed to spec out the crankshaft for grinding.

Today I removed one of the rods and pistons from my core engine block. Then I heated the rod end and drove out the connecting rod in my 12 ton shop press. I will take some pictures of the set up I used while pushing out the wrist pin when I do the next ones.

 

[GThound]

Strike 2!

1. The first Eagle rods were too long
2. Current rods are cast not forged

I started polishing the beams and lightening the rod but could not get it down to the weight of Bob’s original article. It turns out that I have cast rods. So, now I am on the hunt for a set of forged Opel rods for this torque monster build.
Hopefully I can get a set of forged rods from @BQS4

 

[Autoholic]

Are the 2.4L rods forged? I have a set of stock rods and pistons that I won’t be needing.

 

[DavidF1972]

Look. All this stroker talk just needs to stop!!
Every time I start reading about them, out comes the calculator and I start searching the internet for pistons and rods... madness I tell you pure madness..