Documented forum build · 996 · water-cooled

2004 996 Carrera 4S 3.8 DIY rebuild

A scored M96/03 from a 2004 Carrera 4S was rebuilt at home from 3.6 to 3.8 litres with LN Engineering Nickies and Hoffman-prepared heads, documented through assembly, first road use and a forum-author-reported 25,000-mile follow-up.

Evidence: Opening thread page — diagnosis, rebuild choices, goals and work split · Page 2 — teardown, cylinder findings and retained connecting rods · Page 6 — piston, cylinder-head and cam-timing assembly · Page 7 posts 92–95 — driveline, installation and initial road result · Page 8 posts 107, 113 and 118 — 500-, 3,000- and 10,000-mile reports · Page 9 post 122 — 25,000-mile update

Vehicle: 2004 Porsche 996 Carrera 4S
Engine: M96/03 3.6-litre flat six with scored cylinders → 3.8-litre M96/03-based flat six with LN Engineering Nickies and rebuilt, ported cylinder heads
Forum: Rennlist
Thread author: OutNSpace · 5 July 2018

Vehicle and engine evidence: Opening thread page — diagnosis, rebuild choices, goals and work split · Page 2 — teardown, cylinder findings and retained connecting rods · Page 6 — piston, cylinder-head and cam-timing assembly · Page 8 posts 107, 113 and 118 — 500-, 3,000- and 10,000-mile reports

Why it came apart

A warm ticking noise and oil expelled from one exhaust led to borescope inspection, which showed severe cylinder scoring; teardown later showed the worst scoring in cylinder four and additional damage in cylinder six.

Source: Opening thread page — diagnosis, rebuild choices, goals and work split · Page 2 — teardown, cylinder findings and retained connecting rods

What the project aimed to do

Repair the underlying cylinder problem for long-term ownership, increase displacement to 3.8 litres and control cost by completing the removal, teardown and assembly as a documented DIY project.

Source: Opening thread page — diagnosis, rebuild choices, goals and work split

Who did what

The owner performed and documented the DIY teardown and assembly; LN Engineering supplied the 3.8 Nickies work, Hoffman Automotive cleaned, pressure-tested, ported and rebuilt the heads, and a local specialist balanced the rotating assembly.

Source: Opening thread page — diagnosis, rebuild choices, goals and work split · Page 2 — teardown, cylinder findings and retained connecting rods

The author identified an M96/03 3.6-litre engine and elected to rebuild it after borescope evidence of scoring, with the intention of keeping the car long term.

Vehicle context: Opening thread page — diagnosis, rebuild choices, goals and work split

Documented sequence

Diagnosis and option selection
The author documented the borescope finding, compared replacement and rebuild routes, selected a 3.8-litre LN Nickies approach and recorded the expected parts and tooling costs.
Source: Opening thread page — diagnosis, rebuild choices, goals and work split
Teardown and specialist preparation
The engine was removed and stripped, cylinders four and six were inspected, the original rods were retained for street use, and the block, heads and rotating parts went to their respective specialists.
Source: Page 2 — teardown, cylinder findings and retained connecting rods
Bottom end, heads and timing
The thread follows piston and circlip installation, endoscope verification, cylinder-head fitting with ARP fasteners, chain-guide assembly and M96/03 VarioCam Plus timing.
Source: Page 6 — piston, cylinder-head and cam-timing assembly
Driveline, installation and first road use
A new dual-mass flywheel, clutch and pressure plate were fitted before the engine returned to the car; after correcting an oxygen-sensor connection issue, the author reported an initial road run of about 150 miles.
Source: Page 7 posts 92–95 — driveline, installation and initial road result
Break-in and long-term follow-up
The author posted results at 500, 3,000 and 10,000 miles, then returned in June 2023 with a 25,000-mile post-build update.
Source: Page 8 posts 107, 113 and 118 — 500-, 3,000- and 10,000-mile reports · Page 9 post 122 — 25,000-mile update

Named components and work

Cylinders, pistons and rods

LN Engineering 3.8 Nickies and matching replacement pistons were combined with the cleaned original connecting rods and new bearings for the street-focused build.

Source: Opening thread page — diagnosis, rebuild choices, goals and work split · Page 2 — teardown, cylinder findings and retained connecting rods · Page 6 — piston, cylinder-head and cam-timing assembly

Cylinder heads and valve train

Hoffman Automotive cleaned, pressure-tested, ported and rebuilt the heads; the thread then documents their installation and the VarioCam Plus timing sequence.

Source: Opening thread page — diagnosis, rebuild choices, goals and work split · Page 6 — piston, cylinder-head and cam-timing assembly · Page 8 posts 107, 113 and 118 — 500-, 3,000- and 10,000-mile reports

Fasteners, timing and driveline

The project records renewed chains and guides, selected ARP fasteners, a new dual-mass flywheel and an EPS clutch with increased friction area.

Source: Opening thread page — diagnosis, rebuild choices, goals and work split · Page 6 — piston, cylinder-head and cam-timing assembly · Page 7 posts 92–95 — driveline, installation and initial road result

Reported outcomes

Forum-author-reported initial road result

About 150 miles without a CEL or reported running issue

After correcting an oxygen-sensor connection, the author described smooth operation and strong torque during the first varied-load break-in drive.

Source: Page 7 posts 92–95 — driveline, installation and initial road result

Forum-author-reported 10,000-mile follow-up

No engine issues reported

The author reported reaching 10,000 miles, using full power and remaining very satisfied with the rebuild; no independent test accompanied the statement.

Source: Page 8 posts 107, 113 and 118 — 500-, 3,000- and 10,000-mile reports

Forum-author-reported 25,000-mile follow-up

Engine described as strong and trouble-free

The June 2023 update reports 25,000 post-build miles and smooth running; it is a same-author durability statement rather than an inspection result.

Source: Page 9 post 122 — 25,000-mile update

Evidence limits

Mileage, reliability and driving impressions are forum-author reports and were not independently verified.
No before-and-after dyno graph or measured power and torque result was published in the reviewed posts.
The reported torque improvement is subjective and combines the displacement change with head and exhaust work.
Fresh automated requests to the main thread returned HTTP 403 from the forum's bot protection; the cited material was reviewed through public browser-indexed pages without authentication.

Access note: The detailed thread pages and mileage follow-ups were publicly readable in browser-indexed forum pages without account authentication. Raw automated requests to the main thread met the forum's HTTP 403 bot protection when rechecked.

Reviewed source trail

Opening thread page — diagnosis, rebuild choices, goals and work split · reviewed 2026-08-25
Page 2 — teardown, cylinder findings and retained connecting rods · reviewed 2026-08-25
Page 6 — piston, cylinder-head and cam-timing assembly · reviewed 2026-08-25
Page 7 posts 92–95 — driveline, installation and initial road result · reviewed 2026-08-25
Page 8 posts 107, 113 and 118 — 500-, 3,000- and 10,000-mile reports · reviewed 2026-08-25
Page 9 post 122 — 25,000-mile update · reviewed 2026-08-25