Step by Step: Machining the Block
Step-1: Clean the Block
Our 289 block is fresh from cleaning, ready for machine work. Jim Grubbs Motorsports has a high-tech cleaning process that is environmentally responsible. Look at the result. It looks like a new old-stock block fresh from its original shipping container.
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Step-2: Ready the Block for Line-Boring
Jim Grubbs has positioned the block in the line-boring machine for close inspection and initial machine work.
Step-3: Remove the Main Caps
The main caps are removed first to set up the line hone. Once set up, they will be reinstalled and torqued for the honing process.
Step-4: Mill the Main Cap Sides (Important!)
Jim Grubbs has decided to resize the line-bore, just to show us how it’s done. Each main cap is dressed with a file and milled as shown. Here, we are milling the sides of the thrust main cap. This gets the sides nice and square.
Step-5: Mill the Main Cap Faces
Once the sides of each main cap are square, the faces are milled as shown. This gets each main cap square with the block.
Step-6: Remove Rough Edges
Each main cap is dressed with a file as shown to remove any rough edges created during the milling process.
Step-7: Countersink the Bolt Holes (Important!)
Bolt holes are countersunk for ease of bolt installation and to reduce the risk of stress cracking.
Step-8: Lubricate the Cap Bolts
Main bearing cap bolts are lubricated with engine oil for smooth, accurate torque readings.
Step-9: Torque the Cap Bolts (Torque Fasteners)
Main caps are torqued to 60 to 70 ft-lbs before the linebore is cut.
Step-10: Check the Main Caps (Precision Measurement)
Main bearing cap dimensions are checked to get a baseline before machine work begins. With a baseline dimension, the machinist has something to work with as a reference. This tells us how much metal has been removed from each of the main caps during the honing process.
Step-11: Hone the Caps
With the main caps torqued into place, Grubbs runs the hone across the main caps. This step gets the main saddles square with the main caps. It also puts a crosshatch pattern in the mains, which keeps the bearings more secure. The line-hone is powered by a large drill, which is hand propelled back and forth to cut the mains and caps.
Step-12: Check the Mains
The main bearing saddles have a nice crosshatch pattern, which will keep the main bearings secure. And because we have main saddles that are true,there will be no unnecessary stress on the crankshaft.
Step-13: Bore the Block
The boring bar is set up to take this block’s standard 4.000-inch bores and cut them .025-inch oversize. Boring the block removes the taper and gets the bores true. Three passes are made to bore each cylinder to 4.025 inches.
Step-14: Mill the Decks
Next, the block’s decks are milled in small steps to ensure we only remove just enough iron to make the decks true. Whenever we mill the block’s decks, we are changing the geometry between the heads and the intake manifold. This is why we need to take it slow and shave only the amount necessary.
Step-15: Inspect the Decks
One pass with the mill nets this result at the block deck. You can see where this block is warped near the coolant passages. One more pass with the mill will get the deck true.
Step-16: Mill as Needed
To get the deck really true, Grubbs goes one more pass with the milling machine.
Step-17: Countersink Bores
Each of the cylinder bores is countersunk for ease of piston installation when the time comes. This takes away sharp edges that can also cause detonation.
Step-18: Chase Bolt Holes
Grubbs believes in chasing and cleaning all bolt holes in the block to ensure smooth assembly. Jim uses WD-40 or cutting oil as a lubricant.
Step-19: Hone Lifter Bores (Professional Mechanic Tip)
Here is something not many of us think about when we’re building an engine. Honing the lifter bores improves oil control and ensures smooth lifter movement. Take a look at this smooth crosshatch pattern.
Step-20: Install the Block Dowels
Install the block dowels and leave them in the block. You’ll have to tap them into place.
Step-21: Get Ready to Hone
We’re going to hone the cylinder bores now. We hone the cylinders to give the walls a super-fine finish in the wake of boring. Grubbs sets up the hone for proper sizing. He also determines how much of the bore needs to be honed.
Step-22: Time to Hone
Grubbs works the hone up and down, checking bore dimensions every so many passes. The objective is a 4.030-inch bore based on piston dimensions for each bore.
Step-23: Inspect the Oil Galley Ports
Here’s a close look at the front oil galley ports. Grubbs will tap these galleys and install screw-in plugs for security. Bolt holes need to be chased and lubricated during the machining process.
Step-24: Tap Oil Galley Passages
Front oil galley passages, which have a press-fit plug from the factory, get tapped for screw-in plugs. This is a wise move for any build-up.
Step-25: Test Fit Plugs
Oil galley plugs are screwed in as a test fit, then removed. We still have to wash the block, which means all freeze and galley plugs must be removed.
Step-26: Ready for Cleaning
Our machined block is ready for a thorough cleaning. Grubbs has it up on the workbench for inspection and any repairs that need to be done.
Step-27: Clean the Block
The block is placed in the washer and thoroughly cleaned. Oil galley passages and cylinder walls are washed using brushes. This gets all of the grit and other debris out from the machining process.
Step-28: Dry the Block
Once out of the washer, the block is dried with compressed air. This removes moisture, which can cause rust. It also clears any debris from cooling system and oil passages.
Step-29: Coat the Cylinder Walls
WD-40 is sprayed on the cylinder walls and decks to prevent rust formation.
Step-30: Prepare the Cam Bearings
Before you install the cam bearings, all five are inspected and dressed as shown. Sharp edges are removed as shown. This prevents scoring the cam journals.
Step-31: Install the Cam Bearings
Cam bearing installation must be approached carefully – gently manipulate them into place without causing bearing damage. Oil holes must line up with the oil galley holes in the block.
Step-32: Line Up the Oil Holes (Important!)
The number-1 cam bearing has two oil holes that must line up with the oil galleys in the block. If you forget this important fact, you will not have oil pressure to any part of the engine beyond the oil filter. You will have oil pressure at the sending unit, which will make it look like you have oil pressure. As the engine runs, void of oil pressure beyond the filter, moving parts are eating each other alive.
Step-33: Paint the Block
The block is painted and readied for assembly. It will be mounted on an engine stand and wrapped in plastic to protect it from dust and debris.
Written by George Reid and Republished with Permission of CarTech Inc
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