"Short" deck vs. std. deck vs. "tall" deck. Who, what where, when how etc......? Advantages/disadvantages etc.....?
A tall deck has a taller deck than a short deck motor. Its the height of the head mounting surface. taller deck= longer possible stroke=more cubes.
Oh sorry---i didn't think it mattered; i'm not an engine person as you can probably see. SBC, so 9.025" vs. "8.325-.7" etc.
Ok, i kinda figured that was the reason for the taller deck, but what is the advantage of a short deck?
in the bbc world the low deck is 9.8 from centerline of crank to deck surface, tall deck is 10.2 crank to deck height. Also have .400 longer rods and pushrods. WHY? monster torque builder. We built a 505 bbc using a 427 tall block, with .100 over bore and .250 stroker crank. The lower end of the water jackets were grouted to stiffen them. Used for super/gas super/comp car. Peak Hp of 812 was in under 6200 rpm, really close to the launch and shift points.
You can run a longer rod for a given stroke with a "tall deck" block, if the deck height is the limiting factor then you could run a longer stroke as well like KKP said. Shorter deck should be somewhat lighter and easier to fit into a narrower engine bay (since I expect you are talking about V type engines, the taller the deck the wider the engine). If you are trying to wind the engine tighter, a shorter deck block will have shorter pushrods, which are easier to get "stiff enough" the shorter they are.
Would it also be easier to higher compression out of the shortdeck if everything else is the same---rod length, stroke, etc.?
No, the biggest factor in compression ratio is combustion chamber size (factoring in piston interference). if the stroke is the same the deck height won't matter.
I think whats left out here is rod angle , the shorter the rod, the more it tries to push the rod through the side causing more friction, (MORE friction less HP), the longer rod with a given stroke pushes the rod more up than to the side. In a big block chevy the tall deck block, with a 400 long rod is /was common, when I was raceing. But I gave it up in the early 90's.Roger
I thought all production SBC (Small Chevy) had the same deck hight, unless you are looking at an aftermarket block????
Dont remember the part number, but the GM short deck can take a 3 inch stroke, a bore that breathes well for a 303 with a 6inch rod that will rev to the moon, all in a nice compact, unassuming package. The road less traveled, but it's there if you want. -rick
I think all production small blocks are the same( NOT counting GM PERFORMANCE), but the big block has two deck hights , the 400 tall is a truck block, best place to find one is an old trash truck. They were rare when I was looking. Roger
Tall decks allow longer strokes. There are aftermarket blocks at 11.0 or better for 800 Inch plus motors.Allows long stroke[5 inch] and reasonable rod length and a pin thats not past oil ring. The comment above about rod length and side thrust is correct, but heres an interesting side note. A short rod decreases dwell time of the piston at or near TDC.In other words, the piston moves quicker near TDC. Spends less time there as respects crankshaft rotation. We build our nitrous motors like this, they tend to not detonate as bad since the cylinder pressure isnt held as long near TDC. We eat pistons like a fuel car, so side thrust and wear arent relevant.
The size of your deck always matters, don't by into that size doesn't matter philosophy. And it really doesn't matter to answer the question. The answer is the that a short deck places the head closer to the crank center than a tall deck. If you want to increase the stroke in one and keep longer rods you need a taller deck, or at least you would need a taller deck if you didn't want to end up with your wristpin in the ring lands.
i think the stocker sbcs do have all the same dimensions, but i was looking at the bowtie, GMPP race and "SB 2.2?" and dart blocks because i want 500-800hp and the basic goodwrench and/or junkyard blocks aren't going to cut it. BTW what the hell is an SB 2.2 block?
Resurrecting an old thread in hopes of some clarity. "All production small blocks are the same deck height"...Yes? The salvage yard sent me a 95 truck sbc to replace the 92 car sbc. I put the engine in and now I cannot get the distributor in past the cowl overhang (Did this a few times on the old engine). Blocks look the same. I put the distributors side by side, and the truck unit is 1/8 - 3/16" longer from the gear to the manifold surface. seems like a large number for "Tolerance". I cannot get teh car distributor to clear either. I am about to go measure the motor mounts, but the different heights of the distributors has me scratching my head. Anyone?
I am going to guess that the difference is in the intake and not the engine block. The reason that I believe this is that is that if there was that much difference in the deck height the manifold and the push rods would not interchange. But there is something to consider when mixing and matching parts. if there is a difference of .1875 in distributer shaft length from the late model truck to the early model car there may be a problem mixing and matching distributers.
Beaner, it's the intake. The truck has a much smaller hole. My guess is the intake and distributor on the car are specific to that application to clear the valence/firewall. I'm filing this one away for later engine swaps when firewall clearance/overhang is an issue like in certain small pick-up V-8 applications.
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