Bringing an old-school engine up to standard?
 

Just after some discussion here, I have no real plans. But it occurred to me that some engines that used to be king have fallen by the wayside because of new engine designs. For example our own Holden (GM Australia) engines, in 308ci V8 and 202ci straight six were pretty much dropped the moment the LS1 came onto the scene, thanks to the superior block strength, head flow, and engine management of the latter.

But how much is left in old school designs, with the application of the modern bolt-on tech and some detail work that corrects the horrible build quality of the time?

The 'Holden 6' in its final incarnation was a 3.3 litre straight six with an indirect crossflow (bad) closed chambered (good) pushrod (bad) cylinder head with mechanically controlled electronic ignition (bad, even for the times), analogue EFI (better than carby, but super-bad by modern standards), single hole injectors (bad), and tubular headers (good). It was automatic only (3spd non-lockup), got 10km/l on the open road, developed 106kw and was supposedly capable of a 17-flat quarter mile, in 1985. The compression ratio was about 9:1

As you can see, there are *many* avenues for improvement.
I would expect that if the engine was rebuilt to proper tolerances (with minor head porting and flow balancing for the inlet manifold) it would pick up considerable power (I would expect 10-15%, because that's how damn horrible production was back then and piston-head clearance was hardly a thing people considered) along with a slightly smaller gain in efficiency.
The jump to modern, sequential EFI using injectors of, say, a 12 hole design for improved vaporisation would improve power slightly and efficiency a lot.
The ignition system could easily stay with a distributor (there's nothing technically wrong with it) but spark control would be under the computer control.
Because of the now equal cylinder-cylinder airflow, mixtures would be more even cylinder to cylinder, and ignition timing would be closer to correct for all cylinders, allowing a more aggressive tune to be used safely and improving efficiency further.
Because old-school autos suck, a conversion to a 5spd manual would also occur (there was no technical reason for the engine to be auto only, I and countless others have done it without consequence), improving everything except traffic manners.

How much improvement would you expect? What other things do you think would be useful to upgrade? Do you think a detailed old-school engine with modern bolt-ons could match a non-DI factory built engine of the same size for economy? Remember the Ford Ka still had a Kent motor in it...

Any discussion welcome

I like old Chevy 283s for some reason but the grade of cast iron used for the block and heads was mush. The factory was more concerned with tooling life than engine life. Bore wear like that would not be tolerated today. Start with crap, end with crap.

For the cost of all the upgrades it would be cheaper to just replace the engine with a moden motor.
A 2ltr NA or turbo motor would be a good choice, maybe a Nissan SR20 as it comes in rear wheel drive and auto.

My Flathead (sidevalve) Ford gets 14mpg. There's 4MPG by my reckoning just switching to 12V and going from generator to alternator. A more reliable starting system would mean I could turn it off in traffic so not be idling. I know MPGuino reports that not idling saved me 10% on my old petrol van.

Add alloy heads, modern EFI, more modern gearing and you'd be knocking on the door of what a modern petrol Hilux gets.

But as said above, it's just so much easier to buy an off the shelf modern engine. A Ford Ecoboost 1.0 produces the same power and torque as that 4.2 V8, but with the added benefit of being 100kg lighter, which means you can have a lighter gearbox, smaller brakes, etc.

It might make a bit more sense to update a lateish model engine. The 1.5 SOHC in my 2010 Proton dates back to 1991 or so. It would be a simpler task of adding those multi hole injectors, replacing the cast exhaust, maybe doing some more technical bits like machining lighter valve train parts. This engine doesn't even have EGR!

At the end of the day, even today's production engines are built to a price and therefore there's always room for improvement. Replacing steel with alu, or ti is always an option.

Let's consider a higher-displacement engine with a more undersquare profile, compared to a square or overquare modern downsized one, it would still not surprise me at all if the older one could match or even surpass the efficiency of its more up-to-date counterpart.


Probably. At least here in Brazil, when Volkswagen and Ford set a joint-venture for Brazil and Argentina and shared engines, some cars that resorted to a Renault-derived 1.6L engine from Ford which retained a pushrod valvetrain got better mileage than the ones fitted with the 1.6L VW EA827. But anyway, when it comes to old-school tech, I honestly see no reason for pushrod engines to fall into oblivion, and eventually a flathead could be improved too.

The oversquare bore sizing is purely about revving harder and bigger valves. Unfortunately it has a deleterious effect on fuel economy thanks to flame travel distance.

You'll note how pre-DI Subaru Flat 4's use much, much more fuel than their Mitsubishi counterparts despite being otherwise fundamentally similar cars

My old 454 got about a 20% boost to fuel economy when I got a good lean burn cruise tune going.

It also increases the surface area to dissipate the thermal energy right after the combustion.


I'm not so used to Mitsubishi, only to the 4D56 engine, but anyway, one thing that quite surprised me is the comparatively low compression of the Subaru. My dad had a '10 Impreza with the 2.0L engine and it was quite fuel-efficient despite being AWD.

You might, and I mean might, be able to find later heads for the same block which make a substantial difference. example 2.0/2.2 Douvrin engine (Renault version). You could have 106/108hp (SPFI), 120/123hp (MPFI), 140hp 12v 2.0, 136hp 12v 2.2vi and you might, if you're feeling rich be able to cobble a turbo version out of the 108hp head, some spacers and a supercinq turbo on a custom manifold, which if the 2.2 Chrysler motor was any guide might give you around 150-160ish. If you really like to spend money there was a 16v head for this engine but it's rarer than hens teeth by now..
There's others, the Ford Ka engine is basically a "modern" head bolted onto a Kent block from a 105E/123E Anglia (think flying Rowling-mobile that really dislikes willow trees). Ford are fairly famous for it. Rootes did it with the Audax, 53hp to 107hp in different tunes and displacements, but basically the same engine.
there are also kits available to convert carb cars to SPFI/MPFI, some even with obd2 computers, they're not cheap but they're about. As a guide you'd be looking at 15/20% hp increase, and going from 80hp to 96hp isn't too bad, which is what the 1725cc Humber Sceptre engine would manage.
The problem; would you ever recoupe the money and would you have annoying officials causing you hassle..

If you port and polish completely (head, both manifolds), add scavenger exhaust manifold and bigger valves with double springs you might make 25-30%.. (based on Sceptre II to H120 improvements).
Adding modern injection will gain you some power but will probably help more with smooth running & economy. Done wrong it'll run like a bag of hammers in a cement mixer..
If the manifold is heated, ala Sceptre, then setting up an adjustable version will help economy (bypass when weather hot, heat when cold).
I've been using an octane booster, improved average from 38.6 to 42mpg imperial..
Trouble is to do all that won't be cheap especially the EFI conversion (if it's even possible)..