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Old 12-03-2011, 02:57 PM
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427 Tall Deck

Does anyone know the measured deck hieght of the 427 tall deck? Preferably, is there a basic engine dimensions chart for Chevy engines that I can refer too? All I need to know is deck hieghts and bores.

Pls advise
any help would be great tks

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Old 12-03-2011, 03:13 PM
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10.2 deck height. Bore size is 4.250 and stroke is 3.760. The tall deck and the short deck 427`s share the same bore and stroke.
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Old 12-03-2011, 03:43 PM
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Thanks a bunch. Its just 10.200" thats simple thank ya much
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Old 12-04-2011, 06:04 AM
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10.200" is the published "spec". Be sure to actually measure it if you're using it for serious performance or racing. We've found MANY specs to be "nominal" and not necessarily "on the money". Chevy's blocks are among the worst offenders.

The big advantage of the "tall deck" is the ability to create a longer-stroke engine with a good rod/stroke ratio, a known "sore spot" in BBC. We use Eagle H-beams for most of these builds. I REALLY like the 496 combo with the 427 "tall" block. With the 6.8" rod, it can safely rev "to the moon"! You can get "more" with more stroke, but this combo falls into the most desired "parametric range".

Jim
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Old 12-04-2011, 03:15 PM
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Easy to ID buy Water Pump mounting bolt location. Short Deck holes are right next to Deck surface, Tall Decks are +.400" down.
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Old 12-05-2011, 11:32 AM
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Thank you for that. The main reason I want the tall deck is to optimize the rod ratio. I disagree with rod ratios that fall short of 1.6:1. Also, I would like to obtain a square or slightly under square engine in order to lengthen the torque curve.

Do you have any recommendations on where to go for custom rods and pistons? I know Arias sells BBC pistons 4.375 bore and 1.12 comp dist. I'm looking for .020" over, 4.27", and 1" comp dist. Granted that will comprise piston stability within the bore but because of the long rod ratio the piston can retain long skirts for stability. This will allow room for a 7.0525" rod all the while shaving .010" off the deck (if the deck comes out to 10.200). Additionally the 4.25" crank, which I will likely purchase from Eagle, can be offset ground to 4.275" stroke using .060" undersized bearings. Yielding desirable numbers: almost 1.65 rod ratio, sqaure engine(.998 B/S ratio), and 490 CI.

Not only a truly unique engine but I think a very efficient power plant and if pulled off correctly its goin in an F-body. whatda ya think?
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Old 12-05-2011, 03:02 PM
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Only good reason for a smaller bore is physical limitations on the block. Smaller or "square" engine doesn't help broaden the power band.
Done tall deck in some cars and the headers are a real headache. Some manufacturers do make tall deck headers now because of the crate 572 so be sure to get dedicated headers or build some. Short deck headers will not work.
Ohio Crankshaft has some really nice stuff for not much money.
If you have to go custom length rods and/or custom pistons, you could almost buy a 572 complete for what you will spend on the "special" parts and not have nearly the engine the 572 is.
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Old 12-05-2011, 03:22 PM
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I aplaud your creative attempt but fear you'll spend lots for special rods, crank, pistons and bearings(.060 under?) and show an almost negligible HP increase. You can do a tall deck 4.25 stroke with a 1.12 piston and a 6.8 rod and get a 1.6 rod ratio and if you do it with a 4.350 bore you get 505 CID. That's using all off the shelf parts so you can build it on the small budget. You would have to compare your HP numbers with those of guys building this popular version and I'm afraid you will fall even or short in HP and spend way more money. If you're determined to spend money, spend it on killer cylinder heads. That's where the power is.
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Old 12-05-2011, 03:45 PM
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Cheapo BBC 505 tall deck grunt motor
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Old 12-05-2011, 04:08 PM
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Techinspector! I don't know who you are, but I am very close to you!! PM if you like and we'll talk!!!
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Old 12-06-2011, 08:20 AM
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Quote:
Originally Posted by techinspector1
Along those same lines, I'm doing a strictly drag car build but it could be toned down for other uses.
+.100 pistons (JE in my case) 4.5 stroke crank, 6.535 rods and it comes out to be a 535.
With the JE's and this combo, I come up with a 10.180 stack height, leaving about .020" to take off the block if desired.
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Old 12-06-2011, 08:35 AM
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Doing virtually the same drag build with 4 1/4 crank. I'd be curious to know how much, if any, you have to relieve the bottom of the block bores/pan rails for that crank. Could depend some on the rod. I'm using K-1 H beams, 6.8".
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Old 12-06-2011, 08:47 AM
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Quote:
Originally Posted by speedbump
Doing virtually the same drag build with 4 1/4 crank. I'd be curious to know how much, if any, you have to relieve the bottom of the block bores/pan rails for that crank. Could depend some on the rod. I'm using K-1 H beams, 6.8".
It depends on the rod to some extent. I use stroker clearanced scats, but that really only helps in the cam area. The casting variances will determine how much, from nearly none, to extensive if your block has lots of core shift.
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Old 12-06-2011, 12:24 PM
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Smokey always recommended "as much rod as you can get in there!" He even "championed" some with a R/S ratio of 2:1... For an engine revving extremely high for extended periods, this is correct. We've found, for a good combination of durability and available parts, 1.7:1 is about perfect. A "shorter" rod may offer more response and better low-end.

We build mostly Pontiacs, but they're very close to the tall deck in geometry. With the 4.25" stroke, a 6.8 rod yields a good ratio, just over 1.6:1. When they have good heads and the right cam, they rev to 7,500 without any issues. Our 475 CID Pontiac (4" stroke) used 6.8 rods (1.7:1) and revved 9,200 every time it went down the track. Zero issues with the bottom end. Actually, only an occasional head gasket was needed. That's a bown/alcohol 475 making about 2,200 HP.

Personally, I "like" the 496 setup using the tall deck. If you choose a "small base circle" cam, the rod gets much more clearance to the lobe. Use the Pontiac lifter to correct the oil band placement. Eagle makes an excellent kit with a forged crank, H-beams and light weight pistons. No "custom" needed.

FWIW

Jim
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