The PO put a 454 in my '68 coupe that originally had the 390hp 427. I heard this 454 came from a large fertilizer truck. When I mentioned this the comment was that it's a tall deck motor. I assume this is opposed to a short deck motor. What is the pro/con of this? I figure this motor was setup for more torque. The engine has about 4K on it since the build and runs good and strong. I'm having a hard time deciding if I should pull it during the future frame-off and drop in a 427 again or just keep it (reasonable budget constraints).

I prefer something with some rev to it, but I don't want to go SB.

Thoughts?

 

I'm not aware of any factory tall deck 454s. Not to say they don't exist, but the tall deck blocks were only 366 or 427 as far as I know.

The original purpose of the tall deck blocks was to create room in the cylinder for a taller piston with four rings (an additional compression ring, like a diesel uses). The design unto itself doesn't make any more torque than would a similarly-built standard deck engine. It was just more durable under high, continuous loads.

The advantage of the tall deck block in non-stock applications was for increased displacement since the compression height of the piston could accommodate a longer stroke and longer rod. The tall deck block is where the 500ci Pro Stock engines of the late '70s came from before the advent of aftermarket blocks.

In it's factory displacement -or near factory displacement- there is absolutely no advantage to a tall deck block for a street engine. They present many difficulties since the engine is not only taller, but it is wider as well. You need an intake manifold or intake spacers for a tall deck engine and exhaust systems are slim to none and may require a complete custom installation depending upon the chassis.

Before taking anyone's word you do have a tall deck engine, I'd research it online to see if that is indeed what you have. I kind of doubt it.

 

All HD truck motors are tall deck motors. Its easy to tell a "tall deck" block as the deck of the block is further off the water pump opening, you wont fit one into a C3 with power brakes...massive fail there if you try!

 

Tall deck motors were truck blocks and were 454 blocks. 427 blocks were short deck only but there was a cross over in late 69, early 70 when the same block was used on 427's and 454's. The casting number is 3968512. The 427 was internally balanced and the 454 externally but it was the same block. You can take any 454 and turn it into a 427 but not the truck block.

 

I've never seen a tall deck 454. As mentioned...they are 366's and 427's. Yes there were '69 model 427 short deck car blocks that used the same block as a 454 (had rod notches at bottom of bore) but that has nothing to do with truck blocks. Truck blocks have an additional .400" of deck and are easy to spot. On a short deck the upper water pump hole is very near the deck surface. The truck block has the extra .400".

It is possible to put together a bunch of non standard parts and make a 454 tall deck out of a 427 tall deck block...but no one would go to that much trouble. You used to see stroker cranks in them to get way over 500 cubes...but not very common. And as mentioned...a tall deck makes everything hard to fit...headers...PB etc etc plus the intake needs spacers to make it fit unless you found a tall deck intake.

Post some pics of it with close ups of the upper water pump bolt area.

JIM

 

A 427 and a 454 for cars were the same block. I have a late 69 427 that has a 454 numbers coded block 3968512. It's a 427 that is internally balanced. A 454 isn't. Tall deck is something else and this is the original motor with stamps on the car.

 

I think you just said the same thing I did.

I agree 100% with what you just typed.

In your first post it said: "Tall deck motors were truck blocks and were 454 blocks". Yes they were truck blocks...that what an OEM tall deck is...but tall decks were not built as 454's.

It also said: "427 blocks were short deck only ". This is incorrect.....there were both short deck (car) 427's and tall deck (truck) 427's.

I think we're on the same page...but just a litte confusion on those points.

JIM

 

I believe this is not a tall deck.

 

You sir are correct!!

JIM

 

I thought 454's had " PASS" cast into the rear area of the block ? Or am I thinking about the casting on top of the heads ? I ve seen it stamped somewhere on my motor ..LOL,......

 

That photo says it all. As Jim said, it's not a tall block.

What is "something with more rev to it". What red line are you looking for? With the right parts, you easily can get 7000 out of it. And it wouldn't be slow getting up there either. I limit my 540 to 6000 rpm for longevity reasons, but it's good for 6500.