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Tell me about tall deck big blocks

AJMBLAZER

AJMBLAZER

Better to be lucky than good.
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Howdy all. Been a while since I was on here...years in fact. You might remember me from the turn of the century or so. Lived in San Diego, CA and was a Marine then. Had a '92 Blazer Sport K1500. Anyways...

So who can tell me about tall deck big blocks? Buddy just scored a cheap and running 427 out of a '90 or so GM bus. Starts right up and goes and he's happy. Just spent several hours pulling it...which was fun...big engine, small space, gravel driveway...:crazy:

It's going into his '89 K5. I remember hearing that you can't just bolt on regular car/light truck BBC parts but some will fit. Can anyone give me (and then him) the low down?

Also, it was hooked to a BIG ASS Allison tranny, how does he get the flywheel/tc off?
 
I am in the process of doing a BBC swap on my '90 K5, but I bought a 454 out of a 90's one ton. I don't know alot about the tall deck BBC's except that they were 427's or 366's. I have read that they are "not desireable for installation in cars or light trucks". I don't think the accessory brackets will swap over from a regular BBC, but other than that I don't know why these engines are looked down upon. It doesn't seem that you ever see anyone "build up" a tall deck engine. I'm sure someone with more experience than I will reply.
 
frineds got a TD 427 in his 70-something chevy truck. He rebuilt it but basically a stock build. Has tons of torque. I'm not sure if he really had any probs with accessories really but i remmeber the dual (hooter) thermostat housing converting to his radiator. I think he ended up getting an exhaust flair fitting to go from the big hose to the smaller hose on the radiator. He was heating problems with his stick 7 blade fixed fan but cured that with a set of windstar electric fans
 
This is actually the motor I'm looking at putting in my blazer. It is just a bit under 1/2 taller than a 454 bbc. Plus, the intake is a different size. As far as I know, it bolts up the same as a 454. I guy I talked to about building mine also said you can bore them out quite a bit to make it a 475 or to its max and make it a 482. Also, I think that since it is 1/2 inch taller, the exhaust may not bolt up the same because the pipes that go under the firewall may hit because they are higher than they used to be. I am pretty new with the information on tall decks, so if I'm not totally correct, someone set me straight.:D
 
Ok, basically the engine is the same as any other run of the mill BBC with the exception that the decks are .400" taller which means it uses a different intake manifold and distributor. The advantage to a 427 tall deck is that you can build some pretty big cubes using that block and stroking it. All the accessory holes are the same but the brackets bolted to the heads will sit farther apart from each other from driver and passenger sides since the tall deck makes the heads sit farther apart. Anything else you need to know just ask me.
 
John is running headers on his 427 TD. Not sure if they are spec for a TD or just BBC headers
 
I may be wrong but isn't it difficult to find aftermarket intake manifolds for these engines. If you install a regular BBC manifold, won't there will be a gap b/t the bottom of the manifold and the block?
 
They make spacers so you can run a conventional intake. Here is the Moroso part number for a rectangal port manifold. MOR-65090, you can find this at summit racing.
 
Contact Ringmaster4x4 he has a 427 tall deck in a very Cool first gen blazer and try a search theres been many threads about the tall deck motors there very cool engines tons of tourqe
 
There poeple building these, GM 502 and 572 are both based on tall deck blocks. Some of the cool things about tall deck motors are the fact they all come with forged steel cranks, 4 bolt mains, extra ribing in the block for strenght and 4 ring pistons for a better seal. All the go fast parts from other BBC's are bolt in except the intake (spacers). A set of aftermarket higher flow heads, a good intake, cam and some headers would make on of these scream as they are choked out bad in stock form for duribility
I am currently planning on putting a tall deck crank in a 454 block to make a 427 cube destroke screamer, now all I need to do is win the lotto so I can build it the way I want!:D

P.S. I have heard the belt groove size on these motors is wider than pickup/car accesory systems so watch out for that on that motor swap.
 
yes they are but standard Big block pulleys interchange the 572 engine has a Aftermarket (dart I beleive) High Deck block . But IIRC the 502 is a standard height block with the same stroke,rod length ,and piston pin height as a 454 just the bore is larger. you can take a 502 block and put a new 8.1 crank (496 cid which is a stroked 454) in a 502 block punch it .030 over , and you'll have a 540cid standard deck height BBC.
As far as I know the only real issues with the swapping in of a Highdeck are headers/manifold clearance issues , accesory drive pulleys , and the water necks
As far as building these motors up . As metioned above the Intakes are different, but there are spacers available to use standrad BBC intakes as well as some of the shelf no spacer requied tall deck performance intakes ( but most of these are meant for serious competition use and not very streetable) and of course the distributors are different , But again this stuff is available in the aftermarket.
For the most part the cylinder heads on these motors are junk (from a performance perspective) but they are interchangeable with nearly any BBC head ( with exception to some of the "late model"heads which can be used I'm told but require some trickery)
So in final these Engines have a very real buildup potential . so don't let any one fool you into thinking that they are junk
 
The 502 is indeed a standard deck height (9.8")block. It has siamesed cylinders with 4.47" bores but uses many 454 components. I just finished building one for my truck
 
bayou blazer said:
The 502 is indeed a standard deck height (9.8")block. It has siamesed cylinders with 4.47" bores but uses many 454 components. I just finished building one for my truck
Click to expand...

I stand corrected, heres some info on the 572 http://www.Mortec.com/bbcratemotors.html

Does any one know if stock 427t or 366t manifolds will fit in the framerails on a chevy? It seems by looking at them the would flow better than stock 454 manifolds.
 
I hate to say this but the only way to know for sure would be to actually try them I would think they would fit but I'm not sure
 
Hey thanks guys, I'll pass this on to him. I really know little about it other than what I learned in 4 hours yesterday helping him get it out of the bus. Apparently no one would come out and help and when he called me I was sitting on my butt playing on the computer so eh, the fresh air did me good.

He's planning on just getting the thing into his Blazer and making it run in the short term. How do-able that is I can't say. His Blazer's a rusty beater so I dunno how big drivetrain longevity is on his list of priorities.

He's also planning on using the factory manifolds. I don't know a lot about BBC's but I do remember that GM used some sort of factory manifold/header mutant on the commercial vehicles about when this was made. These manifolds sure look a lot like heavy duty headers...

Thanks guys, I now know 10x more about this than I did before...
 
thats a good plan but a late model 8.1L (aka 8100) chev big block has a crank stroke of 4.37" not 4.25" like a 454 stroker crank. and there are 10.2" deck 454s out there, sure most are 427 or the assratchet 366 but tall deck 454s were made too.


yellowK20 said:
yes they are but standard Big block pulleys interchange the 572 engine has a Aftermarket (dart I beleive) High Deck block . But IIRC the 502 is a standard height block with the same stroke,rod length ,and piston pin height as a 454 just the bore is larger. you can take a 502 block and put a new 8.1 crank (496 cid which is a stroked 454) in a 502 block punch it .030 over , and you'll have a 540cid standard deck height BBC.
As far as I know the only real issues with the swapping in of a Highdeck are headers/manifold clearance issues , accesory drive pulleys , and the water necks
As far as building these motors up . As metioned above the Intakes are different, but there are spacers available to use standrad BBC intakes as well as some of the shelf no spacer requied tall deck performance intakes ( but most of these are meant for serious competition use and not very streetable) and of course the distributors are different , But again this stuff is available in the aftermarket.
For the most part the cylinder heads on these motors are junk (from a performance perspective) but they are interchangeable with nearly any BBC head ( with exception to some of the "late model"heads which can be used I'm told but require some trickery)
So in final these Engines have a very real buildup potential . so don't let any one fool you into thinking that they are junk
Click to expand...
 
and there are 10.2" deck 454s out there, sure most are 427 or the assratchet 366 but tall deck 454s were made too.
Click to expand...
Reeeally?
We're not talking aftermarket or bowtie blocks? A factory production 454 tall deck engine eh? Never heard of that. What did those come in? :crazy:
 
DEMON44 said:
thats a good plan but a late model 8.1L (aka 8100) chev big block has a crank stroke of 4.37" not 4.25" like a 454 stroker crank. and there are 10.2" deck 454s out there, sure most are 427 or the assratchet 366 but tall deck 454s were made too.
Click to expand...
That's what I was saying use the 8.1 crank in a 502 (the 502 and 454 have the same stroke.) punched .030 over will make it a540cid Standard deck height as far as I know thats as big as you can go on production standard deck height Bigblock ( I beleve GM 502 blocks can only be punched .030 over) to get more cubic inches you would have to go to a tall deck block .
As for the 366 I think they can be bored and stroked out pretty far not sure on exact #'s but there not throw away motors as some people say they just don't have the build up potential as a 427TD
 
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