Re: Repower needs bigger exhaust ports?
if your going to go diesel, I recommend a Cummins. A nice QSB6.7 would push that along nicely. However back to the big block you already have.
remove it yourself, take it to your local engine builder, and for under $2000 you can have your motor back looking and running like new. if you need new heads you will be in it for about $3000 max. If you updated your profile with your location, many of us could suggest a shop.
now lets discuss big blocks. Mercruiser still uses big blocks. they get the long block from GM performance. the 454 is no longer in production, and neither is the 496 which shared the same block. However the 502 and 572 are. This is the basis of Mercruisers 525hp and 425hp motors (the 425 is a detuned 525)
The new LS motors that are being used in lieu of the big block are nice engines, however in either event your looking at a large number of bills to obtain. they also do not have the torque of your current big block.
your 454 is from the great days of low compression and conservative cams. your motor will make 330 hp all day long and there is not a part that is stressed at all. your same block and heads will support much much more power if you wanted. would require new rotating assembly, cam kit, and a few other changes. you can easily get 450hp and still be under $3000
