Personally I think that because of the 2.25s diesel heritage you should be
able to pull a fair amount of power out of it without over stressing the
components. I think ARC is advertising 110 hp or more which is nearly a 50%
gain from the mods they use. But as I said the torque curve on the 2.8 they
make is impressively high and very flat well into the cruising speed range.
Supercharging or turbocharging should be feasible due to the robust
construction of the lower end (remember it was originally a diesel.) and the
low compression ratio. Lightening some components such as pistons and valve
gear and strengthening others such as connecting rods and bearings should
allow higher rev limits. Of course then you need to look at more radical cam
grinds with possible degradation of torque output.
An interesting exercise, maybe not too practical.
Bill Lawrence
"C. Marin Faure" wrote:
> When I had the 2.25 engine in my 1973 SIII overhauled after it burned a
> couple of valves at about 125,000 miles in the early 1980s, I had the
> cylinders bored .010 or .020 oversize (I forget which we settled on, but I
> think it was .010) to remove the wear "lip" that had formed at the top of
> the piston stroke. The danger of not doing this is that with the tight,
> overhauled head, the chances of getting blow-by were pretty good. At that
> time Land Rover supplied pistons and rings in several oversize sizes for
> just this purpose. I forget how far up you could go, but I believe the
> choices at that time were .010, .020, .030, and .040 oversize.
>
> The rule of thumb is that if you can catch your fingernail on the underside
> of the wear lip at the upper end of the cylinder (where the upper piston
> ring stops at the top of the stroke), you should have the cylinders bored
> and honed and fit oversize pistons and rings.
>
> This process is to deal with normal wear in the engine. Boring and/or
> stroking the engine for additional performance is something else again, and
> I don't know how far you can go withe 2.25 before you run the risk of
> damage. I suspect you can't bore it out too much before you run the risk
> of getting the cylinder walls too thin. I've heard you can take the stock
> engine out to about .060 in relative safety, although I recall reading back
> in the late 1970s that some folks in northern California took some SIII
> 2.25s out to .080 or thereabouts. However, I remember that the guys that
> did this made cylinder sleeves which I guess helps deal with the thin wall
> problem, and they had to make a bunch of other modifications, too. In the
> end, I recall in the articles, they deemed the performance increase they
> got wasn't worth the effort they'd gone to.
>
> You know what they say, you can only polish a turd so much. I don't
> remember all the details of what the guys in California did in the late
> '70s, and I suppose there are things you can do today that hadn't been
> figured out back then. But the utilitiarian, low-revving design of the
> 2.25 is such that I suspect the effort required to make anything resembling
> a performance engine out of it will far exceed the cost and effort of
> simply replacing it with a more powerful engine, because you're probably
> looking at a custom crank, custom cam, reworked head, different valve train
> to elminate float at higher revs, etc., etc., etc. If you're going to
> throw time and money at trying to get noticeably better performance out of
> the 2.25, it's probably better spent in forgetting that engine entirely and
> thowing the time and money at an engine with more potential.
>
> Land Rover stroked the 3.9 V-8 to get the more powerful 4.2 version (they
> actually licensed the design for this from TVR) but it proved to be a
> not-very-good idea in the Range Rover. In the lightweight TVR I guess the
> 4.2 was fine, but under heavy loads like pulling a trailer, the 4.2 block
> can flex slightly, resulting in head gasket problems and oil leaks. It
> soon became apparent that the 4.2 was a mistake in the Range Rover, and it
> was replaced with the 4.0/4.6 versions, which have redesigned, stronger
> blocks.
>
> It would be interesting to know (I doubt Land Rover themselves ever did
> this) just how much power can potentially be coaxed out of the 2.25 (making
> whatever mods are necessary) before it self-destructs. Of course, there
> are two kinds of maximum power. The absolute maximum you can get, period,
> and the maximum you can get and still have a reliable engine that you can
> drive on a thousand mile-plus trip and still expect it to get you home.
>
> It's been my observation and experience over the years that the stock 2.25
> does a very good job in the thousand mile-plus trip and get home okay
> category. Modified 2.25s, while they can yield more power, also seem to
> lose reliability in direct proportion to the degree to which they've been
> modified. I'm sure there have been exceptions, but as a general rule, the
> more this engine is modified, the more it seems to develop diminished
> reliability. No big deal, I guess, if you ony use the vehicle for hill
> climbs or weekend off-road outings. But for a daily driver, or a vehicle
> you want to take on long trips, poor reliability can become a big factor.
>
> ________________________
> C. Marin Faure
> (original owner)
> 1973 Land Rover Series III-88
> 1991 Range Rover Vogue SE
> Seattle, WA
> marin.faure@boeing.com
> faurecm@earthlink.net
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