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Merican Metal
K&S is a popular machine shop to say the least.
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Merican Metal
Blocks in waiting.
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Merican Metal
Block deburing with a carbide bit is simply not a job you can do at home.
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Merican Metal
Port matching involves making passages, such as the round oil passages in the lower left of the block, match the D-shape of the gasket.
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Merican Metal
After port matching.
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This Rottler S8M is used to machine surfaces completely flat such as block decks and heads.
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Merican Metal
Getting all the rotating mass balanced is ideal for a smooth running engine.
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Crank journal polishing.
Story & photos by Bryan Irons
Merican Metal Menace gets cleaned up for some shiny new bits
It should come as no surprise that we like pulling wrenches; the “Tech Editor” moniker is earned with bloody knuckles and sore hands, not degrees on a wall or spelling bee awards. The terminal affliction of knowing that we created something in metal, or even just improving it is therapeutically satisfying (note to 4WDrive staff: this doesn’t mean you can drop your junk off in Irons’ driveway and expect a polished turd in a timely fashion). There are, however, some tasks that we just don’t have the equipment or skill/brains to do at home; engine machining is one of them.
When it came down to whom we were going to hand off the Merican Metal Menace 401 AMC machine work to, the decision was not taken lightly. This is not a mundane task like deciding quilted or regular TP, think of this as picking out a divorce lawyer. We searched high and low around the Interior of BC looking for someone to look after our needs, and after our visit to K&S Machine, we knew we had found “The One”. The sight of an aluminum big block in the front entrance surrounded by boxes of name brand parts put us instantly at ease, the smell of race fuel feeding the shops 6-second Mustang in the back didn’t hurt either. We got to talk with owner Keith Korecki about our plans for the build and that we wanted to handle the final assembly ourselves as well as supply all the parts. This was not an issue. A tour of the facility ensued, where a staff of highly skilled craftsmen were busily working on a backlog of builds. Good shops normally have a bit of wait time to get into.
High-end machinery with clean work areas is something to watch for on a walkabout while picking out your engines handler. This goes from $100,000 milling machines to simple calipers. Accuracy and precision will pay dividends once the build is complete and sloppy work has no place under the hood of your ride. We asked about our AMC specifically and Keith did not think our harebrained scheme of aiming for monster torque numbers on pump gas and a good idle was unfathomable with the parts we were planning on using. K&S had done many AMC engine builds in the past and knew what to look for.
With our nerves at ease, we asked what was required to start the machining process for our engine. Wanting to bring our own parts was going to add a little time to the build, as we would have to work back and forth while we sourced gear. This may sound like a bummer to some, but it gave us an excuse to drop in and check on progress. Many places won’t allow you to do this, but K&S had no issue.
Before releasing our grip on the motor, we wanted to do a few basic clean up and prep procedures. The first step was to remove any casting flash that remained on the motor from the factory and use a die grinder to smooth down any sharp edges. This is to relieve any heat risers in the block that could lead to future cracking. With the notorious oiling problems inherent with the AMC design, we even went so far as to smooth out the oil drain back passages in the front of the block as well as radius a few sharp corners that the oil has to flow around. Our other trick was to port match the oiling passages for smoother transitions between the front cover to the block, as well as drill out the main oil galley to 9/16-in. This ensures a constant supply to the lifters, main and cam bearings. Most of these tricks can be found online, just remember to take every remedy with a grain of salt as free opinion is worth every penny.
After our at-home antics, we dropped off the stripped and smoothed down 401 block and crank at K&S for cleaning, sizing and inspection. This included the crank mains and ARP main studs we will be using. Hot tanking and magnifluxing were performed to check for cracks; we were told that the cylinder bores were in good shape, but we wanted a little more displacement. Boring the cylinders out .030-in would not only allow us to precisely machine the block squarely to the crank, but bring us to the 407 CI mark. The crank was straight but needed a polish to clean it up. Our task was to source pistons, rings, connecting rods and engine bearings for the next step of machining. A good machine shop will not even contemplate starting to whittle away at a block without the actual bearings and pistons in hand.
Sealed Power has been a trusted name in the engine bearing industry for factory builds and high performance applications. We sourced a set of crank and connecting rod bearings and a fresh set of cam bearings to replace the hashed ones that took the motor out of commission to begin with. The copper-lead alloy surface has a steel backing that will be up to the task of the flogging the M3 will surely get. We are targeting the low 400’s in horsepower before any power enhancers.
For pistons and rings we called a couple heavy hitters in the industry. Total Seal Rings and Diamond Pistons have been working together on anything from lawn mower racers to top fuel drag cars. We’ll get you more details on exactly what we got when we start assembly, but we settled on a 10.75:1 static compression ratio with 1.5mm top and second ring and a 3.0mm oil control ring. The thinner rings are light years ahead of what rolled out of the factory 40 years ago. Custom pistons may seem like a farfetched notion for a street driven rig, but the price is very competitive, and the finished product is far superior.
K&S Machine had our fancy ceramic-coated pistons, high-end sealing rings, and nitrous resistant bearings in hand as soon as we heard the man in brown roll up to our house. Total Seal and Diamond have recommendations for exact bore size and crosshatching angles for the piston walls finish. Machining commenced and we received another request, “Bring in the connecting rods, flywheel and a harmonic damper so that the crank can be balanced. Send the cam in too, please”.
From the beginning, we had planned on running the factory-forged connecting rods, and freshening them up with a new set of ARP studs. We were lead to believe they could handle the punishment we had planned, but after calculating the price of bolts, pressing the old pins out and the new pins in, we felt that for the few extra bucks, we could score a set of 4340 billet H-beam connecting rods from Molnar Technologies that come ready for floating piston pins that we can assemble at home and larger ARP2000 7/16 bolts. Easy choice!
AMC’s of this size are an externally balanced piece, meaning there are counterweights on the harmonic damper and flywheel/flexplate. We could have stuffed the crank with Mallory metal and run a neutrally balance damper and flywheel, but this seemed excessive for the relatively low 6,500 RPM red line we were shooting for. With that decided, the factory flywheel from 1974 got the nod and we ordered a piece of BHJ jewelry to run on the snout of the crank for a damper. Harmonic dampers are used to take the force of the piston blows in the engine and “muffle” them to keep the rotating assembly from falling apart under twisting loads. Most stockers we find, no matter what brand engine, are no longer accurately aligned on the crank, which make the timing marks useless and also see the rubber ring spitting out after years of service. BHJ’s SFI certified units are built to exacting standards and designed for years of hard service. This is money well spent on the future of a motor.
We got a ring from K&S a short while later with instructions to come pick up our pile-o-parts. The block was scrubbed by what we can only describe as Mr. Clean with OCD. The mains were ground, bored to size and line honed to perfection. The piston bores were taken .030-in over to a finished size of 4.195-in. K&S only wanted to shave the top of the block slightly to clean it up. We were going to make our final compression ratio with the pistons, not by whittling away at the heads or block. Other processes include honing of the cylinder walls and lifter bores. The Sealed Power cam bearings were installed and the Comp Cam’s bumpstick was used to measure for oil clearance.
The entire rotating assembly got a proper weigh in and balance from the freshly machined flywheel to spiffy new BHJ damper. All our parts were neatly boxed and tagged waiting for our arrival to scurry home and give Editor Stanley’s beer-can-oil-burner the heave hoe from our shop space. Watch for the next Merican Metal Menace where we assemble the bottom end of our classic tire shredder.
- K&S Machine – www.ksmachine.ca - 250 807 2204
- Sealed Power - aftermarket.federalmogul.com
- Comp Cams - www.compcams.com
- BHJ Dynamics - www.bhjdynamics.com – (510) 797-6780
- Total Seal - www.totalseal.com - (800) 874-2743
- Diamond Pistons - www.diamondracing.net – (877) 552-2112
- ARP – www.arp-bolts.com – (805) 339-2200
- Molnar Technologies - www.molnartechnologies.com - (616) 940-4640
Read last issue's Stinky Jeep Part 2 - 2nd installment of Merican Metal Menace.
Read next issue's Bright Shiny Objects - 4th installment of Merican Metal Menace.