1966 Isuzu Bellett 1600GT from South Africa - Comments

My con rod for the number 2 piston broke and this caused a major problem,

with the original block.I subsequently

mated a Chevrolet Luv G161 engine block

1975-model with my original cylinder

head.The car still runs beautifully

with the original twin S-U carburettor

configuration.

A g161 engine parts swap such as conrods pistons are a common substitute for bellett gt pr90 and pr91 with bellett gt owners in australia.

I have a 1970 bellett sedan and did the G161 conversion by buying a set of Holden Gemini (Australia) rods and pistons from a wrecker. The original 1471cc block is then bored from 79mm to 82mm with the stroke left the same. This brings it up to 1584cc as in the Isuzu-based Gemini. The Holden Gemini rings, main and big end bearings all fit and are cheap to buy. This conversion, coupled with a set of extractors gives heaps more torque without sacrificing fuel economy. Apart from the usual machining sometimes required, I found there were three main things to be aware of.

1. If you have the deck skimmed, this will give a negative deck height as the Gemini pistons have a small crown - approx 25 thou that rises over the top of the block at TDC. This however is taken up by the head gasket thickness, but it's best not to take too much off either the head or block. I had minimum amounts taken off, but still get a comp ration of 9.3:1 which sometimes causes pinging even on premium fuel.

2. When matching parts from various sources it is well worthwhile to get everything fully balanced. Balancing piston and conrod sets is simple using a good electronic kitchen scale - just find the lightest and grind (carefully) the required amount off the bottom of each of the other 3 rods to get them the same weight as the lightest piston / rod set. I then had all other rotating parts - crank, flywheel, front pulley, clutch pressure plate - balanced at a machine shop.

3. The Gemini big ends required 4 thou to be taken off their sides to get the correct side clearance between the rods and crank cheeks, This was best done by a sheet of glass, some turps as lubricant and some 600 grade grit paper. each rod took about an hour to do, but the correct side clearance is important for oil flow and splash lubrication of other parts.- too little and the oil doesn't flow over the bearing surface quickly enough, too much and the bearing "floats" around.

My only regret now that it is all back together was not increasing valve size as I now find that it is a very driveable car, but it doesn't breathe well at over 90 mph - it gets there quickly, but then just runs out. I've tossed around the idea of a weber carby, but I find that the Nikki in good tune is very serviceable and I'd like to keep as much originality on the outside as possible. Does anyone have any tips? - SUs as on the GT?