Volvo had far better resources, even 30 years ago, to design
all the particulars for your car than you will be able to with
some money and the internet and some tools from sears.

Truer words were never spoken...

The thing about old Volvo motors is that they'll run presentably with a lot wrong with them -- they just don't make much power that way, and you end up fussing around trying to tune stuff that's worn out. Been there, done that, for years and years.

So, not having any idea how a stock motor should run (and not knowing that I didn't know), when I did a rebuild I went nuts with the IPD catalog. Big bore kit, street torque cam, Weber conversion, Crane ignition, header (they actually did have an effective header in those days), 2" exhaust, flex fan... I had the motor balanced, to boot. Of course this ran much better than the old worn out motor with worn out carbs, etc., and for some years I thought I had a real hotrod.

Then I put together a basket case of an 1800S. I didn't modify anything, just fixed whatever was wrong. It ran well but felt a lot milder than my hotrod... then one day I finally had the chance to run the 1800 on a racetrack and see what it would do. I was astounded! It easily ran to the redline and just wanted to keep going. My hotrod had trouble hitting 5000 rpm -- the stock motor, with nothing wrong with it, was clearly much faster.

The lesson I learned was not, "don't modify," it was, "engineer first, then modify." A motor begins at the tip of the air intake and ends at the tip of the exhaust. Everything between has to be specifically designed to 1) work together, and 2) produce the exact characteristics you want. It takes a lot of planning and a lot of consulting with one of the handful of experts who actually know what's going to get the results you intend.

Many thousands of $$$ and many hundreds of hours of work later, if all goes well, you'll have succeeded in shuffling the weak points of your car out from under the hood to the brakes, suspension, seats...

(Sure is a heckuva lot of fun, though.)