Nothing so scientific I’m afraid. In Australia we don’t have emissions testing for older vehicles, unless they have had engine swaps, then they must comply with the standards applicable to the donor engine.

All I was referring to was the basic smell when you start up in the garage or reverse in. The previous engine wasn’t in bad shape, it had a nos BBD and GM HEI on it. It really stunk, economy was OK and plugs looked good. I pulled it because I wanted to use it in another project and I had a nice core to build for this car. The new engine definately smells less, cold start up or hot. Scientific? Nope! But the owners of the car (my parents) have made similar comment. The old engine had a lower detonation threshold too. Whether that was the dished pistons, Polished chambers or cam selection or a combination of all is open to opinion I guess.
If the OP doesn’t already have long rods then it’s really a financial call in my book. It’s a lot nicer build with the newer piston, those old beer can pistons and low deck height do the job but let’s be honest it’s not exactly state of the art. By the time you get new bolts and reco your original rods your likely getting close to halfway to a set of new long rods anyways.

All of the proceeding is a moot point as soon as you bolt on a turbo. It's almost like Chrysler designed the engine back in 1959 with that thought in mind.

So this is interesting:

If you can make it through this he is against the long rod 225 for reasons that seem more antidotal than factual.

https://www.youtube.com/watch?v=b8Y96xywS-E

What does seem to be true from the video is cliff of torque at about 2500 RPM: This video use real data to show how a property tuned distributor and timing can do. I love this dyno run because it is in the normal driving range of a something you want to drive on the street. It show clearly, especially after the recurve, the cliff is really obvious at just over 2600 RPM, it rises sharply after that RPM. Is this truly due to the very under square nature of the 225? I was reading a book by John Baechetel and he state that in theory there are a few advantages to an under square engine in torque but in practice it is barely noticeable.

https://moparconnectionmagazine.com/mor ... slant-six/

Does anyone here have an understanding as to the sharp rise in torque before 2600 RPM (or in other words the sharp decrease in torque below 2600 RPM) on this dyno?

Thanks,
Jim

My guess is that they did not get on the gas to WOT until that RPM. Most dyno runs I've seen start at around 3000 RPM. Good stuff in the second link about dist recurving.

Uncle Tony has a few nuggets in there, but it is hard to know (for an uninformed newbie) what is fact and what is guesswork/supposition. There is some of both, although he is pretty well on target for the parts of the video I watched. Sitting through 30 min of video is quite inefficient for information gathering, esp if you know what you are trying to learn. It is more fun for most people than reading, as I understand it.

Lou

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Home of Slant6-powered fun machines since 1988

In general engine building terms rod length ratios have been beaten to death in many engine building arenas. There is more power and efficiency by far to be found in piston and ring design and sealing. Basically the rod length is what it needs to be, within reason. It’s job is to connect the crank and the piston , you won’t find any measurable power going to a long rod in a Slant or any other engine. You will lighten recip weight and gain better ring seal and less friction by using a more compact piston and ring package. This is the benefit of the long rod, it’s not it’s mechanical action, it simply allows a far better piston. On the flip side of the coin guys used to shudder at the roughly 1.5/1 ratio in a Ford 347, they make big power and last forever.