Changed the plugs and the points on the PR91 yesterday with fantastic results. These were long over due. More bang, less fuel, and a small adjustment to the idle screws, now idling stable and not erratically. Also blowing vapour out the exhaust, not sooty unburnt fuel. But I've got this feeling it could go even better if the timing had some attention.

Although I have a timing gun, I haven't altered the timing. Can anyone tell me what the specs are for timing the G161 and how to do it ? Also, would the degrees btdc be different from the original specs if the engine has oversize pistons and the cam has been ground up a little ?

I know you can "shine some light" on this topic Brett, would be much appreciated.

B.

can do B, just give me a day or 2 to pull the specs out and write up a "how to" for u.
i just wish life would slow down a bit so i can catch up sometimes!

Thanks dude, I can appreciate that. Sometimes we are sucked down the "100 mph vortex of existance" and even the brakes seem to fail temporarily.

p.s. Just from observation and what I recall, unlike some cars, the Bellett has a series of dots or notches on the fly wheel and a pointer "fin" built onto the face of the timing case ? Am I on the right track ??

Any time you can pass on info greatly appreciated. As for now, I've set the new points in the position of the originals and it must be near correct 'cause it ain't too bad when you go for the throttle.

B.

Here we go…. spark plugs, points, and ignition timing - 101.

You’ll need:
21mm spark plug socket, extension bar and ratchet.
Wire brush.
Feeler gauges.
Flat blade screwdriver.
12mm spanner (prefer. a ring spanner).
Small screwdriver or similar (that will fit inside the rubber vacuum hose on the distributor).
Timing light.

I’d suggest checking your spark plugs gaps first, and making sure they are correct, as they can effect how it runs too.
Using the spark plug socket, pull them out (making sure you’re carefull with the white porcelain on them, as a crack in it will ruin the plug), clean them up with a wire brush, and re-gap them.
Check the gaps with the feeler gauges. Originally they had a 0.8mm (32 thou) gap, but if you use electronic ignition like me, you’ll need to open they up to about 1.1mm (42 thou) as the bigger spark it will make needs a bigger gap to jump so it doesn’t burn plug electrodes away.
To close the gap, very, very gently tap the electrode on the bench and keep checking it. To open it, again, very, very gently use a small screwdriver to open the gap, and check.
Bung them back in, making sure you put the plug leads on in the right places! (I’d suggest doing 1 plug at a time so you don’t mix up the leads and which plug was from which cylinder).
Take the distributor cap off by flipping the 2 side clips off. Pull the rotor button off. Turn the engine over (by hand if possible) to get the points to open fully. You’ll see that the points open and close as the square “cam” on the distributor rotor shaft spins past the points, so get 1 of the “cam lobes” to sit in the middle of the block the points use to rub on the “cam”. Check the gap with the feeler gauges. Originally they had between 0.45 and 0.55mm (18-21 thou). If it’s wrong, use the flat blade screwdriver to undo the point’s locking screws and adjust them. This may take some fiddling as they can be a bit tricky to get the gap just right, but perseverance pays off.
When you’re happy with the gap, put the rotor button and cap back on.
Disconnect the rubber vacuum hose from the round diaphragm body on the side of the distributor (this is vital as it controls the vacuum advance mechanism inside the distributor, and leaving it connected while you check the timing might give a false reading). Plug the hose with the small screwdriver (or similar to seal it).
Connect the timing light by putting the 12V (usually red) lead to a good 12V supply. The “+” side of the coil is a good spot. Connect the earth (usually black) lead to earth. Somewhere a bolt is screwed into the car’s body is good. Connect the “trigger” lead to number 1 cylinder’s spark plug lead (number 1 is nearest the front of the engine). Look closely at the connector for the trigger lead…. If it has a little picture of a spark plug and an arrow pointing in 1 direction, connect the trigger lead with the arrow pointing at the spark plug. And yes, it does make a difference!
When standing on the driver’s side of the car, look closely at the crank pulley and the timing cover at the front of the engine. Turning the engine over will show the crank pulley has 3 raised “tabs” in 1 section, spaced equally apart. These are the timing marks. They indicate, in order, 20 degrees Before Top Dead Centre, 10 deg BTDC, and 0 deg BTDC (or Top Dead Centre when the piston is at the top of it’s stroke). As you turn the engine over (it turns clockwise when looking straight at the front of the engine), the 20 deg mark comes around first, then 10, then 0.
On the front of the timing cover (the cover at the front of the engine that the crank pulley bolts thru), you’ll see a small “fin” that sticks out towards the pulley. This is the timing indicator. Keep this “fin” in mind.
With everything ready, start the engine. Ideally, have the engine warmed up so you don’t use the choke and it idles correctly.
Point the timing light at the timing “fin” and press the light’s switch/trigger. It will now flash every time number 1 cylinder fires, and when you look at the timing “fin” and the crank pulley, you’ll notice that the “fin” lines up with a location on the pulley (hopefully somewhere around the 10 deg mark). Obviously, if it’s right in line with the 10 deg mark, the timing is set at 10 deg. If it’s between the 10 and 20 deg marks, then it’s in that range, same for if it’s between the 0 and 10 deg marks.
Turn the engine off and remember approx where the timing was.
OK…. Isuzu set the GT at 12 deg originally (and 14 deg for the sedan). Personally, I think this is too much for use today, as things like fuel octane ratings are different now than in the 60’s, we now have unleaded versus super (leaded), etc, and too much advance in an engine will make it “ping”, or “pre-ignition”, and this KILLS engines by burning out pistons………. Hence, I now set my cars at about 10 deg.
Now, as the rotor in the distributor spins in an anti-clockwise direction, that means that turn the distributor body in a CLOCKWISE direction will give the engine MORE advance, and turning it ANTI-CLOCKWISE will give less advance.
If the timing is not where you want, use the 12mm spanner to loosen…. Slightly!.... the bolt that holds the distributor to the engine.
Re-start the engine, and while watching the timing marks with the timing light going, slowly turn the distributor in the direction it needs to go until the timing is set where you want.
Turn the engine off.
Re-tighten the distributor bolt.
Re-start the engine to make sure the timing is still correct after everything is tight.
Re-connect the rubber vacuum hose.
Disconnect the timing light, and awwwwwaaaaaaaayyyyyyy we go!!

Ohh, and as a side subject, if you’re going to the trouble of replacing the plugs and points, don’t forget to replace the condensor from time to time. It’s the little round “barrel” that is fitted to the outside of the distributor body and has a wire coming out of 1 end, and is held there by a screw. I know of cars that have had all sorts of running issues that have been caused by faulty condensors, so don’t ignore the humble little guy forever!

Hope this helps.

ohh, and B.... oversize pistons won't effect ignition timing.
a bigger cam will, but it'd need to be a far bit bigger than original to do so, not a little bit.

and yes mate, you're on the right track with the notches/dots (actually raised tabs on a Bellett, but near enuf!) and the fin!

happy tuning dude!

A lot of effort went into that well done.
tip. mark the timing notch on the pulley with a dob of liquid paper it will be a little easier to see.

That's brilliant, PR91. You're advice is always so detailed and you go to great efforts. I've already rehearsed it in my head and if it wasn't midnight, I'd want to rush out into the shed and go for it !! 10 degrees btdc should be fairly easy to pick up as it would be the middle notch on the pulley, Right ?

Oh yeah, it did have a habit of pre igniting a little, but this seems to have also improved just by replacing the plugs and points. I'll need to check the gaps though, as you have mentioned their importance !! The only tool I don't have is feeler guages, so it's off to Autopro again. The condenser is also on the shopping list.

Can't wait for a free day to do it, 'cause they tell me gap settings and timing are crucial to how much "goey" an engine developes under acceleration. I guess it also increases the efficiency at which fuel is ignited.

I'll post the verdict when it's done.

Thanks again dudes, Cheers, B

good tip there from gt orphan too.

and yep, the middle tab/notch, so it's easy to pick.

an engine is simply an air pump.... nothing more, but to make it turn, it needs 3 things.
air (well, oxygen), fuel, and ignition.
the more air you can cram in means the more fuel it needs, and the more performance it will give. that's easy, but....
if you don't ignite that air/fuel mix correctly, then it all means 0, because all the air and fuel in world is useless if it doesn't go BANG, which can only done by the ignition....
and yep, fuel ecomony is effected as much, if not more than, the performance of an engine if it's ignition doesn't work properly, meaning (in most cases) that fuel is wasted by not being burnt properly.

and no worries for the write up duuuuuuuuuuuuuuuuddddddddddddddddeeeeeeeeeeeeeeeeee!

Well, I did put a detailed post up of the verdict a week ago, but call me blond, must have forgotten to press "SUBMIT", damn. Heres the shortened version.

New spakies and points, gaps set. Also new condenser "little barrel thingy". Then follow PR91's instructions. Warm up engine (already seems better). Then the timing light shows it's original setting at 12 degrees. This is where it gets interesting. As soon as you shift the setting down you need to idle the engine up a little. Getting it to sit exactly on 10 didn't seem to want to happen no matter how patient I was !? So it's just on about 9 degrees. Then you need to fiddle the idle again. Then test run....awaaaaaayyyy we go!!

Verdict: Idles quietly at around 850 rpm, with out going "lumpedy lump pink..." Then, pick up is smooth and more agressive, in fact it seems to have got rid of that "brick" under the accelerator. Even free revving in neutral seems to be more responsive and alot more free. Now it doesn't grumble baddly as you back off or coast downhill. Also seems to have more hoot through every gear and going up hills. And finally, when you swicth off she compresses to a halt quietlty without preigniting madly. I also ran it hard for a couple of runs with what seems like improved ecconomy. The big question is, is 9ish degrees ok, or is this going to lead to something sinister ??

Thanks for all the good oil again, guys.

B.

B.
9-ish will be fine, but i would never go lower than 8 myself.
in fact, gemini's were set at 6 from new, by memory, but i feel even this is a bit low.
as u've proven, making sure these simple things are set correctly has a huge difference on how the whole car drives, and your results show that some persistance in getting it right pays off. well done!
also, as u've u've seen, having 9-ish now has made the car better, certainly not worse, so it'll be better for it in the long run too.

as a footnote, if u go too low, ie: 2,3,4, etc, or worse, u go under 0 advance and go into "retard" (which is making the engine fire after top dead centre, or ATDC), u'll cause a whole new set of problems, least of which will be that the engine now runs hot, and obviously that causes probs in itself.

enjoy the new found grunt B!
cheers.

Thanks for putting my fears to rest, PR91. I can confidently "fang" next time without thinking the worst.....frizzled valvue, a hole in the head, or worse a shattered piston.

btw, lost the handbrake the other day, went limp If I can't rig up a temporary fix on it, might end up on the help forum as well !

B

That write up must have taken ages PR91

I'm renewing an old thread here and forgive me if the following has already been discussed in the distant past:

Does the Gt have the fine adjustment on the side of the distributor which moves the vacuum advance in and out a bit to enable fine tuning of the timing? That could help when you have things in the "ball park".

I am running the yellowperil with 15 degrees advance which is "set and forget" because the weber doesn't have a vacuum advance port in it and i don't get any pinging at all, even at very low speed in 4th. I guess I 'm tempted to put more advance on but it seems to run well at that and my cam has slightly lowered my compression I'd say because I can now run premium whereas before I could only run the BP Ultimate.

I know the Belletts have very hard valve seats in tha aluminium heads but I've found that adding the Valvoline Flash Lube valve saver fluid tends to raise the octane rating and can help get rid of pinging when you have high compression/advance. Keep a few squeezy bottles in the glove box, buy it by the litre and you'll halve the cost compared with buying the 50ml squeezy bottles.

That was amazing
It never ceases to amaze me the knowledge that is is available to us...and all we have to do is ask.
Next time i need some help, I know who to ask. My bellett family

Most people are always willing to help if appraoched, this goes back to the original car club days of the 60's - 70' and has been brought through by people like Brett, Greg and others that know the meaning of assist your friends in a way you would like to be assisted .
ALL POWER to Bellett.net
cheers Ken