Isuzu G-series Twin Cam

Hey all,
After photos, advice on fitting a pair of sidedraughts onto my chevette g200w (v. similar to gemini). Most all of the photo's dont provide enough detail as to whats required. The only thing I've worked out for certain is that the resivour needs to be remote (easy fix) . However after a quick look my booster is going to be in the way of #4 cyl... Whats the go on the boosters with sidedraughts? One setup I've seen has the carbs angled to clear it...?

Hey ya mate,
I've been having similar probs with fitting DHLAs, Mainly because i have made my own manifold if you get a Bellett GT-R manifold like most people do you shouldn't have any problem with booster clearance,
my manifold is just a plate of mild steel machined flat then drilled and tapped, so the carbs come straight out from the side of the head (and miss the booster by about 30mm, so i have had to make my own filters with multiple, flat sheets of alloy mesh) eventually I'm going to workout the volumetric efficiency of the engine and make a intake that will resonate at a chosen rpm range and come up over the booster, but thats at least 6 months off so i have my "plate steal" manifold to get me from A to B

oh and your booster is in the way of no1 cyl, first time i went to turn my G200w over it just coughed and farted at me, after about 3 hours of trying to figure out what was wrong i swapped all of the spark leads over and she fired beautifully, so no 1 cyl is at the back of the engine

is the chevette the American hatchback gemi? or the sedan? or the ute? lol

Thanks mate,

My Chevette is the british sedan (although mine is NZ assembled)

Assuming DCOEs, make sure you use F2 emulsion tubes (unless you do have a good info source otherwise).

As per my build thread, have gone for a pair of 40mm IDFs instead, more room for booster & resivour

Alas I'm not certain if emulsions translate, though from my Weber Tuning booklet, they seem to.
And I expect they would....

I am merely going by my advice from last millennium - anything other than an F2 emulsion tube on a DOHC (G200W only?) "won't work".....

This is from the source that gave me "double the torque at half the RPM and 15HP extra" with the 2xDCOE45 F2s & jettings and ~26" 2:1 exhaust.
The dyno reported 300Nm@2k; 383Nm@3k, and 100kW@6k. (atrw figures).

(Then for 220-230HP... forged pistons, cams & slight port)
Later I found its similarity to HDT tuning.

Regarding the clearance problems between brake master cylinder and cylinders number 3 & 4 carburettor...

You don't actually need a brake booster. You can fit one of the master cylinders that were used without a booster. That should solve the clearance issues although it does mean a bit more foot pressure is needed when braking but it isn't a great deal firmer. I have driven boosted Geminis that have felt like the booster isn't working and the owners were not even aware of it. The booster doesn't really do a great deal of work anyway. Geminis are only moderately boosted. The non boosted master cylinder bore diameter is the same as the boosted one! If you have one of the TX-TE style master cylinders (with the two joined at the base type) reservoirs attached to the master cylinder, you can actually remove it from the booster and use it on it's own. The only thing you'll need to do is sort out the actuating rod from the pedal so it's the correct length.

Booster! What's that?

(Except for the Florians, none of my cars have had boosters. Don't need them with G200Ws anyhow - just change down gears.)

I am looking at fabricating a manifold to fit 45mm dellortos to a G200W in a Gemini. I have a complete 117 fuel injection manifold that i dont need. Would it be poor form to cut that up?

IMO no. There are plenty of 117 manifolds and all they are good for is 117s and their original Florian base and hence Chevy LUVs, KBs, Rodeos etc. Even then most would use the more common "over the top" EFI (Piazza, ZZx Gemini etc).

The best manifolds are those that a NSW Bellett-Gemini CC (now ICCA) had made a decade or 2 ago. They were based on the original G161W 117 (similar to Bellett GTR) but extended ~10mm to better suit Webers; had tapered ports; and suited 45mm & 48mm DCOEs.
I think about 45 pairs were manufactured but they are hard to find. (I bought 2 sets one of which soon went to Brett W's G200W Wasp, and the other resold for a "Brock Replica" rally car some years ago.)

Thanks for that. Didn't want to cut it up if it was going to be useful to fellow twin cam lovers.

I have been looking for an alternative for a while but they are hard to find. Take the tip on the tapered runners. Any chance you would now how long the G161W manifolds are face to face?

I don't know the length. But the OEM Weber-types (Hitachi etc) had too high an angle for DCOEs (10 degrees max as I recall, though maybe 12) and the top of the (Weber) float chamber or choke would hit the top of the head - ie, the upper cam-cover gasket webbing.

And note that the taper was on the ports (a trademark of that Gurus inlet manifolds, and afaik, most good manifolds), not the "fuel runners". (Just in case there is some jargon mix up.)


PS - thanks for the "non-butchering" concern. (If only more had that attitude!)