Isuzu G-series Twin Cam

Got my exhaust fitted today. Im using standard g200w exhaust manifold and apparently it mates up to a sigma pipe. Im not sure if thats a "fits perfectly" or a "2 of 3 bolts line up, fits with minimal work". Either way, something to look at if your fabricating an exhaust to this manifold.






Yeah the tip is poxy. The exhaust shop just put a bit of pipe on there. Will replace it with a real chrome tip.

Looks good!
Similar to my 2L DOHC in a Florian usng a 2" system with about 30" of 2-into-1 section (very torquey) then into a hotdog and over the rear axle into the muffler.

The manifold gasket etc is common to Shuttles and other Isuzus.

I had my system made up years ago for a mere $200! That's everything from the exhaust manifold flange back. Great job too.
It ma be unethical for me to mention who made it. Alas after trying other "local" exhaust centres afterwards, I drove halfway across town and public transported home just so that Clayton Exhausts (Melbourne) could do another exhaust for me. Yet aga I was not dissappointed. (Why is it that some places charge LESS for a job that shts all over more expensive places?)

I think I used brass nuts with flat for the flange. I had some problems with loosening nust for a while (after transplanting into another Florian) and I did not want to use spring washers.

Will a DOHC take a standard manifold? This is something ive never worked out, but if it does it would make things easyer. Get a set of standard extractors and bend them a bit more to fit the bay and make up the rest. I figure since so many other parts are interchangeable its quite likely, but havnt had the bits in front of me to see if it lines up.

You mean SOHC?

Nah, they don't. Cylinders 2 and 3 exhaust outputs are right next to each other on SOHC, and the ports are square. The mounts on the end of the header are the same, BUT the SOHC header extends back a further 5-10cm or so, and is at a different angle, so you'd need to add some length in the exhaust somewhere along the line and give it a bit of a wrenching to make it fit. I was considering doing this temporarily with my crappy 1.75" stock system but I think I'll just stop being pov and either buy Chris' if he wants to sell, or have one made.

Antus, how much did that set you back? And where'd you go? Also when you say it bolts up to a Sigma pipe, where along the line would it fit? After the 2-1 or like, u-bend and tailpipe only? I'm pretty interested. Thanks for the info

P.S. I have comparison pics of SOHC/DOHC exhaust headers I can host if anyone's interested.

archangel62 wrote: Antus, how much did that set you back? And where'd you go? Also when you say it bolts up to a Sigma pipe, where along the line would it fit? After the 2-1 or like, u-bend and tailpipe only? I'm pretty interested. Thanks for the info

I went to Aussie discount mufflers and brakes on port road in hindmarsh. They originally quoted $240, but after it started getting difficult and the extra parts were required it went up to $500. Now I know the shuttle flange fits a trip to u-pull-it could have probably saved me some $, but oh well too late now and happy with what Ive got. The Manifold comes out as 2 pipes, and the sigma part is the gasket, 2 pipes, and down to the 2-1.

So, just what 'wasn't quite right' about the Sigma section of pipe and of you have an invoice, does it list the part number for that section? If not, do you know EXACTLY what model and transmission option it was off? The part number for the gaskets would be good as well.

Knowing exactly what Sigma pipe fits is a handy thing, especially because I have access to wholesale price parts at Humex Exhaust warehouse. Could easily organise some collectors for people at good rates if we can verify what pipe it is.

Nah they didnt say (if they did i'd have posted part numbers). Plus I think they bent it more to clear the edge of the engine bay. (Just by looking). Im not sure its a standard part, but obviously its about the pattern not the part. My invoice just says "exhaust system". So it'd be a case of hunting around the wreckers on sigmas. But if shuttle pipes fit, thats probably a re surer option.

This car should be on the road next week assuming no EFI show stoppers. (totally possible)

Just as easy to have them refabricate from the flange plate.
I supplied the usual "wrecker-oxy'd" section of outlet which were removed and replaced by new 2into1 section shaped as required (about 24-26" is recommended; my 30" is very torquey - ie, over 360Nm above 2000RPM).

early tx headers have the same flange as the twin cam....therefore the flange can b used on the twincam, but not the headers

something i suspected for a while and confirmed it last week

cheers

I'll add to elky's post....

The TX G161Z twin outlet cast headers had two different collector pipes offered. The earliest ones were a pair of pipes that went down under the car and then joined into a single pipe. These are NLA as an after market part and have to be custom fabricated by the exhaust shop. They were the true power pipes. Later series of the twin pipes had a collector pipe that immediately merged into a single pipe and these were far less effective as a power pipe. They still exist as a spare part at exhaust shops. Both types share the same flange plate, gasket and cast header manifold. It's only the collector pipe/s that differ. I have a near new later type collector pipe in my collection of parts. I also have two earlier type collectors. I'll check and see if that flange plate is available as a seperate part through my exhaust wholesaler. If it is, I should be able to get plates and gaskets to suit at pretty cheap prices. You can then get your local exhaust shop to make the twin collectors to suit.

Something else I have that must have at some stage been imported from Japan, is a cast twin header manifold with an O2 sensor in it! Only ever seen this one before,