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So, I have been collecting parts and info for the past few years in anticipation of an engine build. The pistons are in hand after nearly a year and the block is finally at the machine shop. I will take pics and post the progress here (even the inevitable steps backwards) for anyone interested in doing the same. Please be warned this will be a slow process as I only have a few hours a week to dedicate to this and will be teaching my son as we go.
Some early details - Aston Martin 4.7L forged crank, 4.2L block, 87mm forged pistons, forged rods.
Those rods should be mounted to a coffee table so you can sit and look at them when there is nothing on TV. Beautiful.
If you put them in the engine you can't see them anymore.
the car is FI, already pretty modded, biggest being an Avos 2.6 Kenne Bell set up, 15HU rear end with a 3.24 LSD, sport cats, open intake, etc. etc.. I don't have an HP target, building more for strength than overall power. The factory pistons are forged but not the rods or crank.
The last step will be a PVE stand alone ECU so I can properly dial everything in. At the pace of this project I may be dead before that happens!!
Looks like a sick project! How do you know which parts you can do this with? I can follow shop manuals and fix things but to know that the aston crank will work and that someone makes those insane forged rods that will work... whoosh, I'd be lost.
Don’t know about the rods being used, but this is interesting information from Google’s AI “Gemini” :
How are Fractured connecting rods made ?
Fractured connecting rods, also known as fracture-split connecting rods, are manufactured using a specialized process that results in a unique mating surface between the rod and the cap. Here's a breakdown of the process:
1. Forging:
* The connecting rod starts as a single piece, typically made of steel (like carbon steel, micro-alloyed steel, or powder metal).
* It is usually manufactured through forging, a process where the metal is heated and shaped under high pressure using dies. This ensures high strength and durability.
2. Pre-Machining:
* The forged rod is then partially machined to near its final shape, including creating the bore for the crankshaft bearing in the large end.
3. Selective Hardening (Optional):
* In some cases, the area where the fracture will occur might be selectively hardened through induction hardening to ensure a clean and brittle break.
4. Fracturing:
* This is the key step. Instead of machining the cap to separate it from the rod, a controlled fracture is induced.
* Several methods can be used for this:
* Hydraulic or Mechanical Force with a Wedge: A specialized machine clamps the connecting rod. A precisely shaped wedge is then forcefully driven into a split cylinder that fits within the big end bore. This rapid application of strain causes the rod to fracture along a predetermined plane.
* Guillotining: The rod is clamped, and a sharp blade or tool is forced through the designated fracture area, causing it to break.
* The fracture creates two unique, irregular surfaces that perfectly interlock when the cap is reassembled onto the rod.
5. Final Machining:
* After fracturing, the connecting rod and cap are usually further machined. This includes:
* Machining the small end for the piston pin.
* Precision machining the bearing surfaces in both the rod and the cap.
* Drilling bolt holes for reassembly.
Why use fractured connecting rods?
* Improved Alignment and Fit: The fractured surfaces perfectly match each other, providing superior alignment and a more precise fit compared to conventionally machined surfaces. This leads to better bearing contact and potentially increased durability.
* Enhanced Strength: The irregular fractured surface can offer increased resistance to shear forces at the joint.
* Cost Reduction: This method can be more cost-effective for high-volume production as it eliminates the need for separate forging and precision machining of the mating surfaces of the rod and cap.
Important Considerations:
* Fractured connecting rods and caps are a matched set and should not be interchanged with other rods or caps. The fractured surfaces are unique to each pair.
* Traditional resizing methods for connecting rod bearing bores are not applicable to fractured rods. Honing might be an option for slight adjustments, but significant resizing is generally not possible.
In summary, fractured connecting rods are made by forging a single piece, partially machining it, and then using a controlled force to fracture the large end, creating a unique interlocking surface between the rod and the cap. This method offers advantages in terms of alignment, strength, and manufacturing cost for mass-produced engines.
the car is FI, already pretty modded, biggest being an Avos 2.6 Kenne Bell set up, 15HU rear end with a 3.24 LSD, sport cats, open intake, etc. etc.. I don't have an HP target, building more for strength than overall power. The factory pistons are forged but not the rods or crank.
The last step will be a PVE stand alone ECU so I can properly dial everything in. At the pace of this project I may be dead before that happens!!
How has the 2.6 Kenne Bell setup treated you? I have a 2018 AVOS kit waiting to be installed. Is it worth the effort?
absolute best mod for our cars. It transforms the car and is a REALLY well designed kit. AVOS checked all the boxes when he designed them.
Thank you so much! Did you install any supporting mods, bigger fuel injectors, bigger fuel pump? If you did could you please list them out for me. Thank you!
no on the injectors, on my car (4.0) there are no options for bigger injectors. I installed a Kenne Bell Boost-A-Pump but ended up not needing it because the stock system was able to keep up. Other than that I don't recall doing anything more
So, I have been collecting parts and info for the past few years in anticipation of an engine build. The pistons are in hand after nearly a year and the block is finally at the machine shop. I will take pics and post the progress here (even the inevitable steps backwards) for anyone interested in doing the same. Please be warned this will be a slow process as I only have a few hours a week to dedicate to this and will be teaching my son as we go.
Some early details - Aston Martin 4.7L forged crank, 4.2L block, 87mm forged pistons, forged rods.
More to come
id love to know how you got these pistons. I’m doing a aj126 rebuild and want to do e85. Please tap me in
Sadly, these parts are still sitting on a shelf as another project bumped this engine build. Hoping to get back on it this spring, epically now that it looks like the PVR EFI systems are pretty much ready to go.
They were good to deal with but took the better part of a year to make my set so be sure you discuss timing up front. I would imagine subsequent sets would be quicker since all the modeling and design is done if the pistons are similar between the AJ126 and the AJ133S. As far as quality/performance, I cannot comment as mine are still in the box.
Not necessary to upgrade any internals ,the only upgrade is the cooling system, dont waste your money, when you overheat nothing can save you, just upgrade the plastic parts to metal ,change the oil 3-5000 miles, use top tier fuel and your good
Engine Build
