Sigma-galant.com

So I decided on this nice sunny Adelaide morning I would take the Galant for a run, needed to stop in at work, wanted to check out some new tyres and just have a blast around town.
I get about 10 mins from home accelerating out of a sweeping corner in 3rd and as I get on the throttle it makes this huge noise. My first thought is "Great, the f*cking exhaust ...again". So I turn down a side road and it stalls. Pulled over, opened the bonnet and gave everything a shake, jiggle and poke and all was well, nothing was missing everything that should move did and everything that shouldn't, didn't.
I turned up the idle, started it and it held smooth at about 1200rpm. When I went to the engine bay all was well, no rattles, no knocks, no weird noises. I gave it a rev and heard this massive roar from number two (remember I have twin dual throat carbs) I turned it off and had a dig around. Removed filters, all looked good. Checked all bolts, screws and nuts, all good. Checked butterfly and all good. Pulled the top of the front carb and all looks good.
Started it again and it was the same loud induction noise and very slow to rev.
Pulled out the jets for number two and all good. Swapped leads between cylinders and all good. Adjusted the balance back and forth between the two and made no difference to the noise.
Decided to drive it home, loud, gutless and a little pingy but all good.
Once home I have removed the spark plugs and all good. Checked dizzy cap and leads, all good. Took rocker cover off and cranked(after removing coil lead) and all good. Checked oil and water, all good.
It starts, runs and drives perfectly and is blowing zero smoke, not chewing oil or water and everything under the bonnet seems fine. EXCEPT, it makes this really loud induction noise and is gutless.
Does anyone know what could be wrong or have any idea what to check next? Have I missed something??

HELP!!!!

One of the throttle levers &/or butterflies isn't sticking open ? Almost sounds like one carb / barrel is running wide open ?

On full throttle it is spewing fuel back out threw the carb, I am still thinking valve issues but can't find any
I have had the rocker cover off and the valve train cranks prefectly, all the gaps are correct and the springs are fine.
It has got me more buggered than a small boy at a priest convention.

If fuel is coming back out number 2, then the inlet valve is staying open and allowing the compression of the cylinder to push the fuel out. If that makes any sense?

Sadly Dave, that makes total sense
So..... I am guessing that because the valve operation is correct, the springs are all fine and the valve gap is correct then that leaves a few causes.
Bent valve
Damaged valve or seat
Loose seat

I just dont see how this just happens out of the blue. I drove it to work yesterday and it ran like a clock, better than it ever has and was still the same this morning, until you know what, lol

Okay, last test before I go to UPI and hunt for a replacement head.
It has been suggested that there could be a chunk of grunge on the valve seat. I am going to hold it at some decent revs and fill that port with carbi cleaner and hope it clears what ever it may be. I am not hopeful, I think if it was going to be so easy the 15k drive home would have done that.
I think what has blown me away about this whole thing it the complete lack of mechanical noise to suggest there is a problem, not one single rattle, tick or knock.

To quote the Doors " People are strange, Astrons are stranger. Breakdowns are ugly, especialy in rain. "

The head gasket could have gone between cylinders?
My hatch did that when it went, and it sounded similar to your description of what's happened. But I didn't have the benefit of 4 carb throats to identify it so early.

Do a compression test before you spend any money.

Cheers Dave, put me back on track, lol. I was getting all excited about a new head and it might just need a gasket

Went out and bought a compression tester today and am happy to report that I was sold a hig comp engine like the guy said. Number 1 returned 210, number 4 returned 207 but numbers 2 and 3 were about 45, lol.
Pulled the head off and this is what I found;




Got a new gasket but got to borrow a torque wrench from somewhere.

Glad it's ended up a cheap one for you. This was exactly what my Lancer hatch did. But mine was an old gasket, maybe get the head skimmed to make sure it's flat?

This has only done about 5000k but it is about 3 years old, sat for about 18months between being run in and me getting it. I have put a straight edge on it and all looks fine. I am planning on changing the head for a M6 and going efi before Christmas so should be all good

All cleaned up and new gasket fitted



Head re-fitted. Got to go borrow a torque wrench now and should be running before dinner time

All done, up and running

Don't forget to re-torque it after you have put 100km or so on it and it's been through a few heating/cooling cycles ... you might be suprised how much it takes up !

I hate torquing bolts down, I am always like "nah this is way too tight, it is gunna snap", lol.
But yeah, did about 30k's tonight and I will run it to work and back tomorrow, that should be about 100k's. Give it a re torque and should be all good.

Just a thought. Where did the 'bit' go? Did you check the valves in 2 & 3 for where it may have gotten jammed in there or anything?

Mine went in exactly the same place, must be an Astron thing lol
Anyway, glad to hear it was only a headgasket. Gotta love relatively simple fixes

shuggy wrote:Just a thought. Where did the 'bit' go? Did you check the valves in 2 & 3 for where it may have gotten jammed in there or anything?

Found a tiny bit if flat metal in cylinder 2 and the paper would have burnt up. Gasket metal is super soft and designed to be squashed soul wouldn't have caused any harm.

webby wrote:Mine went in exactly the same place, must be an Astron thing lol
Anyway, glad to hear it was only a headgasket. Gotta love relatively simple fixes

I think it must be hey. Was a simple fix really, time under the bonnet was less than 2 hours but still something I could have done without

Anyway, ran it to work and back today and all is sweet I will do the same on Wednesday and then re torque the head. Then it can sit in the shed awaiting the move

who machined your head jason? I am guessing whoever machined your head used too much rake, which has caused a high spot in the middle of your head. It is a very common practice in machining shops >_<

Don't know to be honest dvsfin, I bought the engine assembled. I am thinking it went because it was never re tentioned. It only had about 1500k's on it when I bought it, then sat for about 18 months before I got it. I put new oil through it, new oil filter, water pump, turned it over by hand and to be honest thats about it.
Hindsight is a wonderful thing

Heart skipped for a sec when I read you were having issues with the coupe!!!
Good to hear it was a simple/straight forward fix!

How much compression are you running?

Cyl 1 - 210, 2 - 207, 3 - 206, 4 - 202

I have been told this is almost avgas territory and could be why I was having issues with it running smoothly in the first place. I only timed it by ear before, after the head gasket went I bought a timing light and it was about 5 BTDC. It is now timed to a running temp of 20 BTDC and is a smooth running weapon. Seat of the pants it is much quicker and I am running 100ron fuel with an additive.
It is an expensive way to go as it is now using about 25l/100k but I am loving it

25 per 100!!!?

My dad's Inter Acco gets the same economy figures, and that's a 10t truck lol. Not as bad as my mate's 12A BP 808 wagon though, it was lucky to get 150km to a tank on the highway. ~27L/100km, provided my assumption of a 40L tank is correct.
That said, it sounds pretty usual for a big-bore carby 4cyl with big carbs, a tonne of compression and a man-sized cam. Can't expect good economy from something like that, lol

webby wrote:That said, it sounds pretty usual for a big-bore carby 4cyl with big carbs, a tonne of compression and a man-sized cam. Can't expect good economy from something like that, lol

Not so.

A High comp engine, in good tune, should be more efficient, especially with highway driving.

My old wagon, loaded up with over a tonne and towing an uncovered 6x4 trailer, was able to average over 9L/100k between Melbourne and Sydney and still sit on 110kph in 5th up most hills.
While it was only 9.6:1 CR, the standard 2.6L is less than 8.4:1CR

Back in the days of leaded fuel I owned a GE sigma, it had a high comp engine, over 11:1, 35/75 long duration cam and motorbike carbs of course.

It would consistently get over 900k on a 60L tank of fuel (highway driving of course) between Sydney and Lismore (had a GF up there and I'd drive up every 2nd weekend). The tailpipe was always a very light grey to white (running lean).

If the engine has to do less to get the air into and out of the cylinders ( carbs, porting, valves, cam, extractors etc...), it should make more power and be more efficient.

The other issue is it takes quite a lot of time and money to correctly tune Weber or Dellorto carbs, and I'd be fairly certain that MOST people would not be bothered spending a lot of either getting them setup properly.

Just my 2c worth.


Cheers.

25/100 was a rough guess, working it out over the 300k's I have done since the new gasket it is maybe closer to 18 or 20 per 100 but it is very rich with a black exhaust.
I think it is the jets but as Superscan said it is hard to get them tuned correctly and I am finding it very hard to get someone interested in tuning them for me.
Decided to wait until after Christmas to give it a make over, it is registered now anyway, lol. But when I do it will be getting a modded M6 head and motorcycle EFi and have the rebuilt LSD fitted

Well there you go, learn something new every day
Probably should have done a tad more research into the subject, rather than going off what the local engine builder told me about more power=worse economy.

I must say I don't have the slightest interest in fuel economy. Climate change is a crock and the oil ain't running out in my life time and this car was never build to out perform a Prius in any fashion other than performance and style, lol
It is running better now than it has with this engine and I don't mind filling up every 200k's
It is doing what it was built to do and that is make me smile