Thread: Exhaust system LR to Holden manifold

From what I remember the Landy system is restrictive, you'd be better off getting a custom 2" system installed.
That's what my uncle did back in the 80's with his 186 conversion on his S3.

Actually prior to that he ditched the 2.25 manifold and exhaust, added a set of Perry headers and 2" exhaust and the old Rover engine came alive.
When he installed the Holden he mated the 2" system to the Holden manifold.

That would work, but I’d too just get a new custom system done if it was mine. How much are the pipes you’re looking at delivered?

I did the same. Just get the exhaust shop to run it from the Holden manifold out.

Get a pair of the cast split iron headers as used on 186S, GTR Torana and others. Take it to your muffler shop and get twin 2" straight through independent systems run out to the back. Refer to Phil Irving's writings for the justification for this. Phil reckoned that inline 6 sports engines were best tuned as two x three cylinder engines.

Originally Posted by Bigbjorn

Get a pair of the cast split iron headers as used on 186S, GTR Torana and others. Take it to your muffler shop and get twin 2" straight through independent systems run out to the back. Refer to Phil Irving's writings for the justification for this. Phil reckoned that inline 6 sports engines were best tuned as two x three cylinder engines.

For bottom and mid range torque a single pipe is best on a straight six with a conventional firing order.

I remember HM Headers showing this on a then new G60 Patrol back in the late seventies.
At the time they supplied the race systems to HDT and Ford and they made a twin pipe system for the Patrol, dynoed it, then converted it to a single dump and compared.
The single system made more torque and the same power.
I played the same games with a Jeep system, and timed the climb up Lapstone Hill to compare.

The 186S/XU1 header is better than the stock manifold though, but using equal length secondaries into a single dump.

I would stick with Phil Irving's advice. He has the runs on the board as an engine designer and race car engine builder.

A big difference between a race engine and 4wd engine Brian

Originally Posted by rick130

A big difference between a race engine and 4wd engine Brian

Sports engine as I said. A race inline six is tuned as six single cylinder engines each with its own intake and exhaust tract.