Need some help from of you engine experts... 1973 25 Magnum Sport ,fresh water with SS 300 HP Scorpion Crusader #40152 with a Volvo 270 T drive. I have been told this motor is based on a small block LT Corvette,need to know is it worth refreshing and what can I do to up the HP...or is is better to put in a big block which means all new exhaust etc? Bud

If it is a small block chevy then all the regular tricks and goodies apply, there is no limit. but there is no replacement for displacment, a bigger motor wins out in most catagories. there is trade offs for each, the big motor is heavier, the small motor lacks in TQ. and then there is that drive, the biggest motor will have a hard time getting it over 65mph.

you can do a lot with a smallblock, say a nice 400~500 hp 383 all kinds of heads are available..etc...but will the drive be happy?? I don't know volvo's..can you get parts?? or are you willing to redo the transom and go with a different system??

Bud it's a great smallblock forged crank & pistons, and good rods . With new aftermarket heads, cam & Z28 intake you could make a strong running smallblock. That's what I'm building up for my Sedan.

H2O What would you estimate a rebuild would cost with the add on's you describe...what kind of new HP can you develope . I know you should not put more than 400HP at the 270 T. Bud

If you shop wisely [ebay craigslist] the aftermarket parts [heads intake ect] might be around $800.00 to $1000.00 it all depends on what deals you can find. How is the rest of your motor ? If you need to rebuild it than ??? the cost would rise. A new 400hp smallblock cost around $2800.00 so it just a $$$$ game. What kind of speed are you looking for ? I have put 400 hp big block chevys mated to Volvo E drives and had them live for many years, and that Mag was fast. Cast iron used bigblock exhaust manifolds would not cost to much either, and the rest of your parts [motor mounts,, thermostate] will work. How fast do you want to go 55 60, but the stock Volvo drive will hit it's limits around 60 mph in your Mag.

Mark thanks for the info,60 MPH would be fast enough for the 25 Sport,will also consider a big block as you suggested.Have not opened the engine yet to see what it looks like. Bud