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Bore score on cylinder 4 confirmed and i’ve decided to go the Slakker/hartech route. Bought my car with 60000 miles and just turned 1790000 so the motor had a hard but great life. Spoke with Brandon about a month ago to start my rebuild on my 3.8 Carrera S motor and he said that he just finished a 4.2 build and that it was for sale. It’s being shipped as we speak and will be arriving this week, so hopefully the car is up and running Very soon. Will report back with my interpretations of the rebuilt motor.
curious about the custom crank. i assume the bore stays the same as the 4.1L builds. additional capacity came from the increased stroke with the new crank? any reason why not just step up the displacement even more like some of the other builders? want to hear some opinions from someone who also tracks these cars, opposeed to the street /C&C builds we typically see on this forum.
Going from an 82.8mm to an 85mm stroke requires reducing the rod journal from 52.8mm to 50.7mm (1.999”), which increases displacement from 4.115L to 4.225L.
Technically, we could go to an 85.5mm stroke (4.25L) and call it as a “4.3,” but that would be more about marketing than meaningful performance gains.
The 1.999” journal size matches the small-block Chevy, making it easy to source race-quality rod bearings.
Since a large portion of our engines see track time, 1.999” is about as small as we’re comfortable going.
__________________
Brandon Clark
Slakker Racing Development - "Hartech UK's exclusive engine machining and rebuilding partner for the US." www.sr.dev
Certified Cylinder Head Machinist - AERA
Certified Hartech Machining and Engine Rebuilding - Hartech UK
Certified High Performance Tuner - EFI Univ
I wish!! 407hp and 357ftlb. Impressive to me as those numbers are on par with a 997.1 gt3rs. Torque numbers especially as that's what accelerated the car and those exceed even a 991.2 gt3rs.
Last edited by snosk8luke; Apr 19, 2025 at 03:09 PM.
It's really hard to see the dyno results in the screenshot. Is that 510ish HP?
0 on the graph is 150, and then it goes 200 250 300 350 and tops at 400, unless they've adjusted the scale from their other screenshots. The screenshot of my 4.1L with the head port tops at 417 with a similar curve.
curious about the custom crank. i assume the bore stays the same as the 4.1L builds. additional capacity came from the increased stroke with the new crank? any reason why not just step up the displacement even more like some of the other builders? want to hear some opinions from someone who also tracks these cars, opposeed to the street /C&C builds we typically see on this forum.
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4.2 incoming
