427 truck tall deck engine mods

Discussion in 'trucks' started by Grumpy, Jul 2, 2018.

  1. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    first....welcome to the web site, and since this is an all too common issue,
    I'm going to move this to the truck section
    if you have pictures of your projects ,
    please, feel free to post those and if you need too ask questions or provide suggestions, start a thread with detailed info, or post related info that may help others,
    btw if you could encourage your friends choose too register,here on this web site, and post pictures of their cars, and add to the conversation, so much the better.
    why not introduce your self,
    why not post some pictures of your car, garage or projects and introduce yourself to the members
    your likely to find other people that live near you with similar projects



    ok Id suggest you take a compression test on all 8 cylinders and post the cylinder head and block ,and ideally the intake, casting numbers ,and several pictures would also be great.
    and please post your oil pressure at idle and at a 3000 rpm crusise, the transmission and rear gear ratio and tire height,and what your intended goals are,,so we have a good idea of the basics were going too be dealing with.
    if the lower block assembly is in good condition you might not have to do too much with that on a basic up-grade.
    we would also want too be sure its not a tall deck 366 BIG BLOCK ENGINE
    the 427 BBC tall deck engine came in several configs, most were designed for long term durability , not brisk performance,
    but they all have the potential to provide that brisk performance if your willing to make the required changes,
    and have the bank balance to purchased the parts required,
    simply because the basic block is a great starting point.
    keep in mind your dealing with a power to weight ratio, you can push a lighter weight truck far easier than a heavy truck, at any given power level.
    while a 427 has potential in stock form the smaller port heads and heavy pistons limit the potential, rpms, and the engines ability to breath well.
    the tall deck height allows you to install a longer stroke, 4.25" stroke crank, and 6.385" rods and lighter weight pistons and as a result building a 550-600 hp 600 ft lb BBC engine is not all that difficult and yeas if you have the time and cash theres other options

    related threads












    Last edited: Jul 6, 2018
  2. William Kopp

    William Kopp Member

    My name is Bill, New to the forum and the world of tall decks. I would love to tear into the motor and build a 900hp tire shredding monster, but alas the pockets are only so deep. So I am thinking maybe find a good set of heads, swap out the pistons and connecting rods, get a nice aluminum intake and cam and settle for a couple of added horses. The motor at idle has about 15 lbs. of oil pressure. 40 when rolling down the road. As far as I can tell the motor has never been opened. I will check the cylinder pressure. 20170704_154715.png
  3. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    I have not done anything with my 427 Tall Deck Engine.
    Its best to leave it stock if your lacking funds.
    A camshaft swap would help power output on a tight budget.

    Went round and round with combos.
    Its best to make it a 496 or 510 ci .
    540 ci is possible many tell me .

    It will cost alot to buid right.
    $15k - 20 k.

    Its the Strongest GM Big Chevy Block ever made. 427 Tall Deck.
  4. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    To get your moneys worth you want 650-700 Hp.
    Shoot for less Hp but likely be sorry later.

    Its an all or nothing type engine.

    Chose to stick to my Pontiac V8s.
    Costs less $$$$.
    Plenty of Fun yet.
    Turbo Boost changes all too.
  5. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    The way GM built a Tall Deck 427 its like a Diesel engine that runs on 87 octane gasoline.
    Pulls a heavy load in a truck effortlessly.
  6. Indycars

    Indycars Administrator Staff Member

    Not everyone on here believes it's all or nothing.

    Wow, is that your car pictured above? Very nice! More pics please!

    Why not start a build thread and give us more details about what you have and what you want
    to do. When you get a preliminary picture of what the build looks like, then we can run some
    computer simulations to help evaluate the selected components.

    We need details like .....

    Budget, how much are you looking t spend?
    Pump Gas? Octane?
    Carburetor or EFI?
    Vehicle drive train, gear ratio.
    Trans, auto or standard?
    Tire size/diameter?
    Is it a daily driver or a weekend fun car or race?

    Most engine builds threads are done here.

    Welcome to the forum Bill!!!

  7. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    congrats the engine picture you posted looks like a clean install, and a great start point.

    yes you can build a very fun to drive combo , using that tall deck, block, as a basis,
    without going bankrupt in the process, let us know the heads, intake and block casting numbers,
    and the result of a compression test
    , it would also help to know the truck weight,
    the rear gear ratio, tire height and transmission your using.
    you might find the the heads you have can be used after a mild port & bowl area rework,
    \as some tall deck heads casting numbers are basically decent, in that they can be ported to flow well.
    and if matched to a well matched cam, intake and headers can provide decent power.
    reading through the previously posted links and sub linked info posted earlier, will prove useful.
  8. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Once you decided to get rid of the stock 4 ring pistons it gets expensive.
    Stock rods no good.
    Tall deck makes only sense to stroke to 496.
    Need good heads.

    Unless you want 300-400 hp.
  9. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Only the Block gets reused.
    That is Reality.
  10. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    427 Tall Deck had just 215-220 Hp.
    Torque about 400 ft/lbs.
    Wheezed down.

  11. Strictly Attitude

    Strictly Attitude solid fixture here in the forum

    Yes to hit the OPs goals in hp larger investment needed NA larger CI needed or power adder. Either way not cheap. 900 hp either your spinning rpm or power adder.
  12. Strictly Attitude

    Strictly Attitude solid fixture here in the forum

    You could grab a nice set of ARP heads nice roller cam and still be an easy 5k envolved lots of options explore them.
    Look for some builds on line and there results. Check youtube for some combos and dyno results.
    Better then guessing on a bunch of bench racing combos ran through some dyno software.
    Dyno software has a place yes and can be used but real world numbers are better base imho.
    Last edited by a moderator: Jul 3, 2018
  13. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    there are lots of very common and well proven combos if you know where to look,
    and theres a great deal of very well documented ways to improve power without spending tons of cash.
    now theres no disputing the fact that, a combo of well matched components,
    better flowing heads, higher compression and a carefully selected cam and intake are going to boost power.
    luckily the cost of some of the options is not astronomical.
    the main issues the stock tall deck engine faces is the heavy 4 ring pistons and mild
    cam, designed for max low rpm durability and long service life ,
    where they did not consider anything much over 4500 rpm useful.

  14. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Thats right Grumpy.
    Its A Truck Engine a 427 Tall Deck.

    No one is going to stock pistons with the right compression height for a 427 3.76 stroke Race Forged for a 1 inch taller deck.
    Ditto for a 454 4.0 stroke and 1 inch taller deck.
    Custom Diamond pistons needed.
    $1,000 right there.

    Only makes sense to build a 496 stroker.
    Need good aftermarket Heads to feed that many cubes.
    400 cfm intake side @ 28 inches water sepression.
    1000 cfm carb. $ 1,000.
    EFI...$2k.- 5 K....
    FULL Roller Valvetrain best in street profile safe zone $2k- 3k.

    Goes on and on...
    $15-20k needed.
    Bullet proof Trans and Diff.
    Figure $5 -10 k more.

    Pontiac 455 wins for me my budget.
  15. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    the standard 9.8" deck height on the BBC requires you to make changes,
    in some components when swapping to the taller truck block with its 10.2" deck height,
    thats .4 inches (a bit under 1/2 an inch) not 1" taller

    ESPECIALLY if your using adapter plates to use a standard deck intake.
    below is the standard intake on tall deck block showing why spacers are required, to allow proper port alignment with the heads spaced further up and out from the crank center line.

    with a tall deck block deck at 10.2" and a 3.76" stroke crank and a 6.535" connecting rod
    remember deck height 10.2"
    minus rod length, 6.535"
    minus 1/2 the crank stroke length 1.88"
    equals the piston compression height. 1.785"

    this is an excellent example of why doing the math before you purchase parts is so important







    Last edited: Jul 28, 2018
  16. William Kopp

    William Kopp Member

  17. William Kopp

    William Kopp Member

    My cash is not "unlimited" but I understand that HP cost money. I love the 427 but I am not sentimental about keeping it if it will cost extra to build. It is already running strong as a stock set up, just wondering the approximate cost of tearing it down and adding a few goodies. I figure connecting rods, pistons, cam, intake. I already have headers, dual exhaust, 750 edlebrock (might need an upgrade there). engine is bolted to a 700r4 and 12 bolt rear with 3.73 gears 29" tall tires. Mostly drive truck on weekends and after work. It is not a show truck (by no means perfect), but everywhere I go people want to look and talk. Everyone had or knew someone who had one of these trucks. As the truck sits now I have 12,000 in it, I purchased from a friend and added A/C (I'm in Florida, I had no choice) I also tinted the windows. I like many of us need to do something (instead of sitting on the couch). I am in the process of restoring a 1978 Blazer, digging out the bondo and rust and replacing with metal and lead. Oh joy, what have I gotten myself into. Thanks again for the info...
  18. William Kopp

    William Kopp Member

  19. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    To build and use a Grumpy 496 BIG BLOCK CHEVY you need a Bullet Proof Transmission and 12-bolt Differential.
    Because 650-700 Ft/lbs of torque will be on Tap.


    OR A 1957-64 PONTIAC 9.3 DIFF.

    It will end up costing $20,000 all together.
    Just no way around.

    I was planning to build and install a Grumpy 496 BBC into my 1987 Corvette Convertible.
    Priced it all out on paper.....
    Just not Feasable for me.

    Pontiac V8 Power is.
    I have Pontiac Muscle cars too.
    1970 & 1963.
  20. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    You essentially reuse the 427 Tall Deck Block.
    Everything else in the drivetrain has to go.
    Not strong enough.

    A Big Racing Fuel system is required too to feed a Thristy 496 BBC.

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