Went to look at a rebuilt 454 engine today, the man said it is a tall deck truck engine and the numbers agree, my question is whats the difference between a short deck and a tall deck?

 

Block is taller i.e. tall deck. Corvette uses the standard short deck. The truck tall deck does not fit well like to headers. The truck tall deck are normally very cheap.

 

Rod length, longer on long deck, shorter on short deck. You really want shorter, truck engines have better torque but low HP because of the long deck and length of stroke. Thats just the basic reason or answer.

 

tall deck means just that..they are heavy duty truck units with a deck of .400 taller.....that way chevy could run a fourth ring on the pistons and much thicker piston tops for durability....they are a favorite for big stroke engines but the parts like the intake manifold are different because of the wider spread...you can probably pick one up on the cheap but it would be a hassle to build i think unless you wanted to build a monster........

 

just to clear things up here a tall deck 427T uses the same 3.75 stroke crank as a 427 car motor. The tall deck motors also used the same length rods as all the 396-454 car engines measured at 6.135". The truck engines made more torque because of the head, cam, and intake combo used on these motors. It had nothing to do with the fact that the blocks were .4" taller. The extra compression ring was the main factor for making the block taller. Also the heavier longer piston stabilized the piston in the bore to make the engine last longer.

Tall decks are good for cars if you really want to make a monster motor. Sticking in a 4.5" stroke crank and bore the block out to the max and you get into the 500~550 cuin range and you have plenty of room to squeeze all of that in ther using a longer connecting rod. The long rods help out with many factors...one is get the rod/stroke ratio closer to the magic 1.7:1 range that will help you run rediculous compression ratios and still use pump gas.

But you can fit most of the same stuff in a standard deck block and get a much lighter piston and that makes everything in the engine happy! Lighter is better.

They make spacers for talldeck blocks to adapt short deck block intakes.

Just make sure you want to deal with the oddities cause nothing is going to fit right with a tall deck.

 

Stick with the short deck block..I know only too well..I put my 496 tall deck motor from my previous project into my 75.. will it fit? sure but not hardly worth the hassle and believe me there are lots of issues making it work.The tall deck after market intakes are all way too tall even with the l88 hood (a 5 inch cowl wouldn,t even do the trick..)as for intake spacers..total PIA using 4 gaskets ,2 per side .need i say more.getting 2 inch headers to clear was a big enough hassle 2"1/8 forget about it!!Brake booster clearance another issue..I just recently tore down my 496 that had approx 2000 miles on it just to use the rods and crank i,m now building a standard deck 454.that should say it all right there.. Tall decks certainly have there place..the engine bay of a vette (thats used mostly on the street/not all out racing) just isn,t one of them!

 

Do the same casting numbers come in short and tall deck? How do you tell one apart visually without breaking it down and measuring?

 

GM did use the same casting numbers for short and tall block (pass car/truck). Without doing some measurements I don't believe you can see it visually. Example 454 (pass), 454T (truck), they have the same cast number, but were used in different years of production for cars and trucks.

http://www.ajgeneral.com/sbc_block_casting_numbers/

 

^nope. They did use passenger/short deck blocks in suburbans and trucks up to 1-ton, but no numbers were used both on short and tall deck blocks, the casting numbers are unique.
There are a couple of easy identifiers. First, if the block is fresh out of the donor car/truck, it may still have the thermostat housing on it. If it does, that's a really easy tell if it's a tall deck - it'll have two thermostats with one housing. Can't miss the configuration of that housing, it'll be familiar to all the men. Second, the distance between the top water pump bolt hole and the deck will be a ringer. It's about .250" on the passenger deck block and about .650 on the tall deck. It'll be easy to recognize, that distance will look either like a quarter of an inch or over a half inch, you can't miss.
Leave the tall deck blocks to the guys that have plenty of room and no clearance issues, you're asking for trouble with a tall deck block in a 'vette. Not that it can't be done, but you'll end up with more time and trouble invested than it's worth.

 

Thanks all,