Short Deck vs. Tall Deck - Chevelle Tech
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  #1  
Old May 15th, 04, 12:22 AM
jeepster34 jeepster34 is offline
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I found a really good deal on a 427 tall deck (10.2). What is the advantage or disadvantage of a 10.2 over having a 9.8 or vice-versa. Thanks for your time.
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  #2  
Old May 15th, 04, 12:26 AM
LXS LXS is offline
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Quote:
Originally posted by jeepster34:
I found a really good deal on a 427 tall deck (10.2). What is the advantage or disadvantage of a 10.2 over having a 9.8 or vice-versa. Thanks for your time.
Tall decks allow you to use a longer stroke without the worry of having the rods crash into you cam. Along with the taller deck, I believe, you can run a more aggresive cam, again, without worrying about the rods crashing into the cam. That if pretty much the advantage of a tall deck block. The advantage of a short deck block is that it's cheaper.
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  #3  
Old May 15th, 04, 12:39 AM
jeepster34 jeepster34 is offline
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Cheaper for the engine/block or just for parts to supply the engine? Do they still fit under stock hoods or do they require more room?
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  #4  
Old May 15th, 04, 12:44 AM
LXS LXS is offline
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Quote:
Originally posted by jeepster34:
Cheaper for the engine/block or just for parts to supply the engine? Do they still fit under stock hoods or do they require more room?
Well a tall deck block is an aftermarkey block, unless there's some factory tall deck blocks out there that I'm unaware of. Anyways, the block itself will cost more. As for parts, it all depends on what you will be using...usually is someone if using a tall deck block, then that means they'll be using a really long stroke crank, one that will not clear a short deck block. Longer stroke, more cubes. As for fitting under the stock hood, I don't believe you'll see much of a difference, unless you're using a really tall intake and/or with a spacer. If not, then I believe you should be fine. What will the potential motor be gong in?
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Old May 15th, 04, 12:52 AM
jeepster34 jeepster34 is offline
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I have a 68 SS Matching numbers that I want to take the original 396 and set to the side. I am keeping the entire car rearend and tranny and all in tact. Just want to change the engine so I don't mess it up.

I would like to build something with more than 500 + HP, but I am having a hard time finding a 427 or 454 engine/block. I found a 402 and figured I could bore it out .30 over and put a 454 crank which would make it a 434 and that did not sound bad. To add complication I found an original 427 tall deck (My guess is it came out of a truck) complete engine that runs (Needs rebuilt of course) tonight for 1000.00.

The thing is I don't know much about tall decks other than people have urged me to stay with the short decks vs. the tall decks.
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Old May 15th, 04, 1:05 AM
LXS LXS is offline
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O Ok, 427BB tall deck, for whatever reason I was thinking you were talking about a SB tall deck. Well to the best of my knowledge, I've heard people not really recommending 427 tall decks. I'm not totally sure, but for whatever reasons they're not the same as the original 427BBs that we all are familiar with. I'm sure others will chime in and fill in where I left off...good luck with you build up, and keep looking, I'm sure you'll find a good block to build [img]graemlins/thumbsup.gif[/img] ....that 396 stroker doesn't sound like too bad of an idea...I'd do it if I had the $$$ [img]graemlins/beers.gif[/img]
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  #7  
Old May 15th, 04, 1:28 AM
Wolfplace Wolfplace is offline
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The tall 427 truck block was originally made to accommodate a taller piston with 4 rings for heavy duty truck use.
The cam is not raised so cam clearance is the same as a short deck.
Most are quite thick & can be bored .125
Stroking past about 4.125" can be a bit iffy as the water jackets are pretty close to the pan rails.
It takes either intake spacers or a special intake.
It takes a special distributor.
It will sit both taller & wider in your chassis.

You want to measure the bore to be sure it isn't a 366.
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  #8  
Old May 15th, 04, 7:15 AM
Tom's 68 Tom's 68 is offline
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i've heard the reason for using the tall deck is that it has removable cylinder sleeves and for racing you are able to replace the sleeves when all he(( breaks loose
but for every day the shorter one is better because it fits under the stock hood
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  #9  
Old May 15th, 04, 8:32 AM
oman oman is offline
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Yes they do sit taller and wider but if you want cubic inches and torque this might be a way to go. I has to be cheaper than one of those tall deck World or Brodix blocks,,,has to be.

A friend raced circle track cars (dirt) back in the 70's and he used several of the tall deck motors. Everything from the short deck engines EXCEPT pushrods / distrib and intake manifold bolt right on. They are just as tough as the stock height motors and have greater potential for large bore sizes cause they came from trucks and they were meant to get at least one or two over bore rebuilts. (Cememnt mixers run forever and work HARD so they wear out sooner)

The trouble starts when people want to use hedders. Because the head is higher up and further away from the crank centerline all sorts of issues develop. For my money hedders are the biggest PIA in the world (serviceablity / noise / engine compartment heat...all those and more issues) and I will never have them on a car again. That said if you are willing to have the front engine pipes made / custom bent at a shop like Midas or whatever to accomodate the higher and wider exhaust flange position when a tall deck is used I would consider it. If ya just gotta have those damn hedders then better think again.

Also Brodix and I think some other manufacturers make spacers that sit on the intake manifolsd surface of the head and allow use of ANY stock GM intake. Hood clearance will depend on you car and the air filter and ...in other words the total stack height of the engine components. If I were gonna do this I might use the "low riser" aluminum GM manifolds that were on cowel indusction cars. They are cheap at swap meets (not necessarily plentiful) but they are around. I think the torque of a big inch long stroke BBC would offset minor losses in power resulting from the low riser.

Remember the heigh difference is not all that great...wish I could recall the number. A low to mediem riser manifold should fit and who knows perhaps a hi riser will work. My experience is that the dopey hedders are the biggest issue here.
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  #10  
Old May 15th, 04, 10:13 AM
pdq67 pdq67 is offline
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Ditto Mike and Oman!!

An article I've read say's they can go as high as 556" with a 4.625" stroked crank but you will have to be careful grinding on the block!!

I personally wouldn't go over a 4.375" crank in a stock BB...

That makes a 4.375"b x 4.375"s = 526" motor..

And my 496 rotating ass'y dropped right in my '74/'75 P/U block with NO grinding whatsoever!! That's why I figure a 4.375" rotating ass'y should fit fine or with minor hassle after looking mine over...

pdq67
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  #11  
Old May 15th, 04, 11:49 AM
BLK64SS BLK64SS is offline
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As far as production Tall Deck blocks, They Do Not have replaceable sleeves. I dont know of any iron blocks that do.

I have one with a 4.375 bore and 4.250 stroke. I had to do a little bit of grinding on the bottom of each cyl. I used a Team G intake for a TD and a stock type dist.

GM Truck TD Blocks are .200" taller and .400 wider. My headers fit "fairly well " meaning the Driver side fit was great, the pass. side I had to notch the frame. But I also have Brodix Heads which raise the ports .600 also.

Personally 1,000 $ for a TD isnt a deal at all ( if its a stock engine ). I've seen new bare TD blocks going for 600 $ I paid 250 $ for mine with fresh align hone, main girdle, and a good bore.
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  #12  
Old May 15th, 04, 2:51 PM
Schurkey Schurkey is offline
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I've got six GM tall deck Mk IV 427 truck blocks, with two or three casting numbers. The one complete engine has two spun rod bearings, and a mallory unilite conversion in the distributor. I paid $250 by the time I picked it up and drove it home. (300 miles) I consider that a steal of a deal. Most are not that cheap. I've had an offer of a free 366, though.

There are MAJOR differences among these TD 427's in terms of crankshaft clearance "cast in" to the bottom of the cylinders. Three of my blocks have SIGNIFICANTLY more clearance than a 454 passenger car block I compared them to. Others have the same or less clearance.

Crank-to-cam clearance isn't an issue with big blocks. Some of these blocks will swallow a 4 1/4 stroke crank without grinding. (That is according to others, I have not tried this. Looking at the clearance cast into some of my blocks, though, I have NO trouble beliving this.)

The Tall Deck 427 was built with 4-bolt mains, forged crank, and the heavy-duty 3/8 rods. If the price is right, that alone could make it worth buying the TD, if only for parts. The crank will be balanced for HEAVY pistons, though.

I've seen a wide range of heads used on tall-deck blocks. Large oval ports (2.07 valves), round ports (2.07 valves), and round ports with TINY valves, perhaps 1.94 or thereabouts.

In short, inspect the block casting for crank clearance, look at the heads, and see what it's worth to you. The taller and wider block can give you problems with A/C box clearance, brake booster clearance, header fitment, and hood clearance issues. All of these are fixable, depending on what you're willing to do.
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  #13  
Old May 15th, 04, 7:49 PM
Mike Feudo Mike Feudo is offline
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I ran tall decks for years in the old bracket dragster. The MK-1Vs have the same bottom end clearence problems as the std blocks so you really aren't gaining anything there. They are a very tough block with very heavy cylinder walls and don't move the mains around much when heavily stressed but unless you are going to run a very long rod for stroke length I wouldn't bother with the trouble. The manifolds are limited or you have to use spacer plates, the only pushrods they made (when I was using them) were the highest quality. The distributor is no longer a problem but making the whole thing fit in a car with fenders can be.
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  #14  
Old May 15th, 04, 8:17 PM
HPseeker HPseeker is offline
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I am running one in my GMS SPRINT it is a good idea to run 6.535 rods and use the 427 standar deck pistons or 454 crank and 454 pistons ,I am using EAGLE H ,I use the tall motor mounts because of the hamburger 8 quarts oil pan an old set of 1 3/4 headers with a lot of rust was try and it fit but at that time I want to take the car out and really thought that a bigger set will be a better choise . for now running 13.6 e/t with stock exhaust manifolds with 2 1/2 from manifolds thru an X AND flowmasters and 3" tips in front of the rear tires .
I had run with both intakes manifolds a Edelbrock Victor TD-454 ,And now a performance air gap with .400 spacers my hood it a cowl induction hood and got problems with a 14" air cleaner and 3" element but a little grind and 1/8 move to the front no problem ,a 13" will be better
Alot of people stay way from tall decks because they say it is more expensive to built but here in P.R it is a harder to find a good BB at a low price anyway .
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