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Installing 427 in my 87 K5

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by blazer_87, Jan 27, 2003.

  1. blazer_87

    blazer_87 Registered Member

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    I finally bought it. A 427 Truck engine. Block# 340220. I am looking for any and all advice about this install. My K5 is currently 350 FI. I hope its easier to go from FI to Carb than visa versa. Any help will be appreciated. Thanks.
     
  2. Bullet

    Bullet 1/2 ton status

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    PM Sparky87K5, he has a 427 in his '87 and it runs on a carb.
     
  3. Z3PR

    Z3PR Banned

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    A fuel injected 427 would be ultrakewl !!!!!!!! Just a though.
     
  4. Sparky87k5

    Sparky87k5 1/2 ton status

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    Putting a 427 truck block in is pretty straight forward. Ypur exhaust manifolds will sit higher because the truck block has a higher deck height then the passenger and pickup blocks. Not really sure if the truck block is a good way to go unless it's in very good shape and cheap. You'll need to swap flex plates so your 700R4 will bolt up. Hope the 700 is in good shape, the 427 will destroy any marginal 700's rather quickly. Engine cooling will need a 4 core 454 radiator if you're in hot climates. Buy new motor mounts! Install external trans cooler, biggest you can buy for the 700. You'll need to get a wire schematic of a 85-86 and rewire under the hood for a carb'd engine. Install a Mallory fuel pressure regulator dropping pressure from 12-15psi of the intank pump to about 5-6psi for the carb. Route remaining pressure in the TBI return fuel line. Other then re-doing the exhaust pipes, possible adding additional springs under the frontend (BBC are a little heavier), it's a pretty easy swap. Verify the bellhousing bolt pattern on the truck blocks accept the 700 trans with the correct flex plate. Good luck, nothing like the looks you'll get when you have it serviced.
     
  5. Lonnie

    Lonnie 1/2 ton status

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    I currently have one of these engines in a 82 pickup. Here's the scoop.

    First it will bolt right in to the small block frame mounts & to the trans.

    You need a flexplate for the trans. Verify that the torque converter bolt pattern matches your flexplate. Most aftermarket flywheels have dual bolt patterns. You can get a standard flexplate for any 396-427 car. Do not use a 454 model.

    The accessory brackets do not line up well due to the higher deck height, but a little slotting of bolt holes on the alternator bracket will let everything fit. 84 brackets for a 1 ton pickup work well.

    If you have a dual thermostat intake, you will have to build an adapter to make the different size hoses fit together.

    The factory distributors in the big trucks has a governor in it along with the carb. Retrofit to a standard distributor & holley 4bbl & you will be set. Some of the truck distributors have hex oil pump shaft instead of the standard slotted shaft. You can drop the pan & substitute the correct shaft to match a regular HEI distributor.

    The oil pan (if a 10qt model may hit the crossmember) My 8qt truck pan clears everything (stock height truck may be near the axle) Truck oil pump matches the deeper pan. Again you can substitute all the car parts (oil pan, pump, pickup & shaft)

    You can swap the intake to a normal variety also, but very few are made for the truck engine (these intakes are for big cube race engines... not good for truck torque. These motors were often used due to their thick cylinder walls for racing.... a .100 overbore is routine & some will go to .125 overbore) Regular big block intakes will work with a spacer kit, but require a special longer distributor.

    The lower crank pulley for the truck has too large of belts to work with normal accessories. To fix this use a 396-427 car balancer. Again do not use a 454 model. (they are counterweighted)

    The truck water pump will also not work as they are offest to reach the taller truck radiators. Again use the car or pickup truck model. Watch as the serpentine belt units often are reverse rotation.

    Hedman has a decent header that fits a 4x4 & will clear with the tall deck motor.

    Also the heads for this motor are very small port/valve combination for great low end torque.... but very low compression (about 7.8:1) If you want to wake it up, swap an early set of closed chamber oval port (rectangle ports are too big for a truck) big block heads from a mid to late 60's car. These will result in 9:1 compression & really make it scream. Mine runs 13's in the qtr on 35" tires with '69 427 heads, crane 278 hydraulic cam & 750 holley DP carb.

    All these truck engines have 4 bolt mains, steel cranks & stronger than normal connecting rods.

    Built properly the 700r4 will live behind it. I did break a few, but they were hard parts.... planetary sets & drums due to having a heavy foot. Hard to resist drag racing Camaro's & Mustangs... especially when you can beat most of them. I have also twisted off 1 front axle & blew 3 built 12 bolt rears. (2 ring & pinions & 1 set of spider gears.) & a few drive shafts. You will find the weak parts just keep buying better stuff.

    Planned to make a quick post, but got carried away. Did I cover everything?
     
  6. blazer_87

    blazer_87 Registered Member

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    What size stall converter are you using? Any input about selecting the right stall would be great!
     
  7. Sparky87k5

    Sparky87k5 1/2 ton status

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    For street/offroad use, stay with the stock stall, higher the stall rating, the higher your trans temp will be on the street due to a higher level of slippage. At most, go about 200-300 over stock. Any BBC built correctly will make more then enough torque to accomplish what a high stall converter would do.
     
  8. Lonnie

    Lonnie 1/2 ton status

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    The stock stall is fine. The higher torque output of a big block will increase the stall speed (brake stall) over what you currently see now with a small block. On a heavy truck, high stall is hard on the trans due to (heat) slippage. Many towing converters are offered with lower than stock stall for this reason. A stock or good rebuilt unit should hold up without problem.
     
  9. 88k5canuck

    88k5canuck Registered Member

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    It's a great swap to do. I am running a 366 big block truck motor in my 71 K10 with 40" tires. Turbo 350 & 205 t-caste. Holley 600 and electric fans.Great torque, down low. I run a slightly higher stall about 1800 or so. The tranny does heat up. I going to install the external tranny cooler.The truck is not fast but for muddin it works great. Even in real thick mud up to the top of the 40's it still spins them great. My alternator is just a 350 one but with pully from truck motor. The water pump is from the truck motor. I would like to see some pics when you get it in there.
     

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