Craney

iTrader: (2)

How much taller is a tall deck block then a regular deck block ? And is there any advantage a tall deck block has over a regular block?

dereknkathy

.400 inch. 10.2 as opposed to 9.8. makes motor about .250 wider. means about a quarter inch less between motors. advantages are if you are stroking it. there is a bit more room for crank throws. although most of the extra deck height is for the taller 4 ring truck pistons. since most of these blocks were made as 366's with 396-427 stroke and skinny bores. AND the 366 blocks cannot be bored enough for us to consider them. i am sure aftermarket tall deck blocks approach this differently and provide more crank room.

articfriends

iTrader: (1)

Most of your bigger cubic inch motors use the tall decks, to get any kinda stroke much bigger than 4.25 and still have a decent rod to stroke ratio without having the top of the connecting rod way into the ring package on the piston you need these tall decks, Smitty

tcelano

It's about a quarter inch wider per side. That eats a half inch between the engines. That also makes the exhaust go up by .25 as well. If you use heads that have raised exh ports like a Pro-1, that's another 0.300". On my motors to make e-tops clear the 2-piece Eickert valve covers that have a tall enough base for stud girdles, I have to run an additional 3/8" exh flange spacer and gasket. So in all, I've lost about an inch between exhausts, and gone up about about 0.8" fortunately my transom had never been drilled for any exhausts before. I mounted the engines on 36" centers and ate the 1/2" in the drivelines.

tcelano

As far as advantages, the taller block lets you get, besides more stroke, better rod/stroke ratios and better angles for the same displacement.

Merc used to build the 540 bulldog on a tall deck, but built the 1075 sci to 557 on a short deck. Go figure. 540 is normally considered the practical limit for the short deck. That uses a 4.5 bore, with room to rebore out to 4.6. Once you go to the tall deck you can do 572 or 598 on the 4.5 stroke. Super tall deck blocks can run strokes out to 5" or beyond which is how the big 632 and bigger motors are made. You are still stuck with that max 4.6 bore due to tr 4.84" bore spacing. Only once you do one of those wicked 5" bore spacing custom blocks can the huge 700+ motors work.