has anybody got some ideas on engine missing problem

[EKUTE]

G,day fellow members,I,ve got a curly one regarding the miss I have on number 4 cylinder.Three months back or so I cooked the motor driving along one day.Pulled it apart,the top end that is and found the the head had been repaired and was cracked so I put a reco from the head shed in Morwell.It ran like a champ for a while then it started missing,pulled the plugs out to find number 4 plug wet so I replaced plug leads,dissy cap,plugs and put an electronic pointless ignition unit in.Still the problem persisted so I thought maybe I hadn,t pulled head down properly because a couple of the head studs tightened different to the rest so I pulled the head off again,cleaned and changed head gasket for a second time,ran a tap through all the block threads and oiled head bolts.Put it back together the second time,ran it but problem still exists.Took the car down to the local garage to pressure test cooling system and to check compression.It leaked a couple of psi over a 10 minute period but was unable to find any visible leaks and whilst I had plug out I also checked to see if water was leaking into that cylinder,compression wise I checked number 4 cylinder only,it gave a reading of 110 psi,perhaps a bit low though you,d think that should be enough.One other aspect of this is that it is missing more when cold and seems to improve as it warms so once warm it doesn,t seem to miss at speed though at idle it will run a tab rough.The engine,s got about 130000 miles on it,number 4 cylinder has slightly more wear,bore wear,piston slap than the other cylinders but 110 should be adequate.What am I missing here?Anyone had a problem like this before,it sure has me stumped me,any thoughts?Robert.

[Harv]

How badly did you "cook" the engine? If it is already thin in the jackets, you can do some funky things like cracking the bores. I presume that the block deck looked good, with no evidence of tracking from the jacket holes?

A couple of psi leak over ten minutes doesn't sound like much, but bear in mind that the cooling system only runs on 4psi in a grey. Tempting to pressure the cooling system up to 4psi, and then keep it there by repeatedly topping it up over the course of a few days. Get enough water into it and it should be easier to find where it's going... and more than likely #4.

Normal compression on a grey can be 115psi, depending on what head is fitted and how much has been shaved off it over the years. 110psi is not out of the question - the main thing is to check all the cylinders and make sure they are pretty much even.

Bit of a worry that the head bolts didn't come up evenly. They should be 60-65 lb. ft. on clean dry threads. Lubricated bolts get 15-25% less than this. I'm assuming you didn't try to reuse the head gasket? The monotorque gaskets in particular don't like being reused.

Cheers,
Harv

[Craig Allardyce]

Did you redo the valve clearances after the first run when you fitted the reco head? Re do your compression test with a dry cylinder/s, throttle wide open (don't close and reopen for each cylinder as the accelerator pump squirting fuel each time will wet the cylinders and alter your readings). Then do another test with about 3 squirts of oil down the carb. Crank a few times to circulate throughout cylinders then redo compression test. You readings should be slightly higher because of the better sealing in the cylinders from the oil. If any cylinders don't come up it would indicate valve related issue and the respective cylinder.
Was the plug wet with fuel or oil?

[yaapeet30]

I think Harv and Craig are leading you in the right direction. Checking valve clearance and presence of a burnt valve would be an option. However dont discount electrical as you have slightly touched upon. Check the distributor cap for a crack. If unsure use another one if you have a spare.

Might be worth a look if you are problem solving the issue.
Cheers

Rod

[EKUTE]

Thankyou for your imput,valve clearances are ok,went over them both cold and hot so thats not the problem.I cooked the motor badly because the temperature sender got cooked which was by the way only a month or 2 old and I didn,t realize it till steam came out from under the bonnet because the warning light didn,t work.It turned out to be a welsh plug behind side cover at the rear.Though I found no visible cracks in the bore I may well have damaged it because it got real hot.The radiator has always lost water and requires topping up from time to time,never found out why though I pressure tested it 3 maybe 4 times over the last few years,up until the over heating problem it didn,t miss so possibly the over heating may well have opened the gap.Looks like its going to be a tear down,bugger it,s my daily so hopefully won,t be down to long,thanks again for your thoughts,I was just hoping it wouldn,t come to the a major surgical proceedure,wishful thinking.........One more note regarding compression,the head I got from the head shed had been milled down to the max,the milling circle max markers barely visible so the compression should be higher than normal for a start.When I first got the motor I ran compression test over cylinders 150 over all 6 cylinders,it was a gem rebuild if I remember rightly.It cooked real good,guess it didn,t like that.............One more thing I bought sender unit from repco,45 bucks if I remember rightly,went back to buy replacement they wanted 75 bucks,found one online for chev,late 50,s for 26,repco ended up giving it to me for same price.General Motors used many parts that it used on holdens,ie 59 chev door handles,switch knobs ej ect ect.

[Blacky]

If it got that hot it might have buggererd the rings ...

[Craig Allardyce]

Robert I'd definitely re do the compression test (dry then wet) to make sure. 115 psi should be ample to allow the cylinder/s to fire.
Its possible your misfire is unrelated. Was the plug wet with fuel or oil?
I'd also start looking at cam lift to see if you may have wiped a cam lobe. Cooked engine (very hot engine oil/loss of pressure) could have done damage elsewhere that you may not have known till now.
For me if the compression is still around 115 psi and the plug isn't wet with oil I'd be looking elsewhere. Ignition is still a possibility too.
You never did mention, is it still using coolant since the new head went on?

[EKUTE]

Thanks again,the head was recoed,that means valves,guides,seals,decked,pressure tested,the valve clearances are ok,I checked them twice cold and hot.I did go to super cheap and put a can of compression in it and it,s improved alot so it,s bottom end related that,s clear.May well have cracked a ring,it,s gonna be a tear down.I guess the reco head being shaved down so far put strain on it and being central in the block heat dissipation or the lack of it might have been a factor in its demise.

[rosco]

EK ute - you've had some really good replies to your issue.
A lot of the time, we can often determine a faulty component by simply changing it with one of the others... as in plug, lead etc.
Nothing comes to mind immediately which points to any one thing that I would suggest.
As Tim has stated, for the bottom end to be the issue - it would really have to be driven until it seized... not just steam coming out from under the bonnet.

Another option, and I don't know why this would happen - is for one of the pushrods to get a bend in it.... easy enough to rule out... just pop both of them out from #4 and roll them along a flat bench top....
But, you state that your valve clearances have been checked... just trying to rule things which don't make sense out.... sometimes, you get a surprise...a bent rod might always "fall" into the longest bent length when static, but in running - it might be keeping one of the valves open whilst it is turning on the head of the cam lobe...... this stab in the dark is a real long shot.

Nothing coolant related I can think of would simply cause a miss - unless you were getting water through the cylinder wall, but it would need to be a considerable leak to cause the plug to short.

When you pull #4 plug out, does it look perfectly clean..? as in no carbon - this is often an indication that there is water getting into the cylinder... water will clean carbon from within the combustion chamber... many period systems actually had water injection to do just this... in the latter days, it was used in the Nissan engine Commodore Turbo engines to prevent detonation.... so, take a good look at your plug when it's been running for a while.

If it's wet with fuel - then I would point towards electrical.

If it's wet with oil - well, could be anywhere - from rings to cracked piston or something in the valve guides/seals etc.

Compression with a decked head should be a little higher than 115, in my opinion.. but this depends on your gauge as well.
It's been mentioned above that the most important thing is to have them all within 15 or 20 of each other...

If you have the engine running with the plug lead just sitting loosely on the plug - and the engine is missing, try pulling the plug lead off and note if there is a distinct difference in the miss - if not, you're looking for electrical.

My suspicion is that you won't know until you pop out that piston..... you will be able to look down the full bore and also look at the piston and rings.

If you need to test a piston for cracking, clean it up as best you can then invert it. Pour some dirty kero into the cup (after blanking up the oil holes in it) and use some compressed air to blast away at the kero into the cup of the piston. If you've got a crack - the dirty kero will show through and can be seen quite easily through the crown and down the sides of the piston from the top to the lower piston ring gap.

I suppose most of us are jumping to conclusions here, but they are all suggestions which are worthy of consideration.

Oh, and I forgot to mention - as for always having needed topping up with water..... unless you are using a coolant recovery system, every radiator will lose around 1 1/2 - 2" of water level when the motor cools right out....
If you fill a radiator then run the engine up to normal temperature, the expansion will cause about that amount to get blown out through the over-flow pipe and down the side of the radiator.... so, filling them right up every time is really just a waste of water (and effort).
As long as you can see water in the neck of the radiator no more than about 1 1/2" down from the filler - it's fine..

If you want to fit a recovery system, you'll need to fit a special recovery cap.. it has an additional seal in it so that vacuum can be formed and draw coolant back in from an overflow tank.

A recovery system will eventually exhume all air and oxygen from the system - which over time will prevent a lot of rust in your cooling system.
It will further give you a very accurate indication of whether you are losing coolant, you simply check the level when cold each time.. you'll soon know if that level is dropping - and you need to track down where it's getting out.

Adding the correct amount of glycol/anti-freeze etc. will assist with keeping the water pump bearings lubricated, the metals in the system protected to some degree and also both lower the freezing point and raise boiling point.
Many do not realise this, but even though the coolant is still "green" - it doesn't mean it's still ok .. I've seen rust in systems which have this coolant .... which have simply been left in there for far too long.
Another benefit of using a coolant additive - the stinking stuff usually is a give away when you get a leak somewhere... you can smell it long before seeing it.... it's a very "sweet" smell.. reeks in fact.
You'd certainly see it on a plug as it would leave traces of the blasted stuff on the electrode and inside the core gap around the plug - I don't believe it's "combustible" ... unlike water, which will turn to superheated steam and disappear with the exhaust gas.

About every two years is what I would suggest.. draining, flushing and re-filling just before summer is the most beneficial time to do a coolant change.... sorry, off topic... again...

frats,
Rosco

[Cal]

130,000 miles is a lot for a grey. Usually lucky to get 100,000.

Tim, surprised at that. I assumes if properly maintained a grey would last much more than that

[WayneXG95]

Can I ask did you retension the haed after you ran the motor in?
If you did, with the new gaskets today your not supposed to because you will crack the gasket.
Just a thought..

[rosco]

Forgot to mention,
if you are leaking coolant through the cylinders or head gasket into the combustion chamber, it sometimes/usually shows up as white "smoke".
Not the usual condensation which occurs as the engine/exhaust system warms up - but beyond that ....

Coolant is raised to super-heated steam temperature on combustion then enters the exhaust system where it cools down again and condensates - and emits as water vapour.

Another indication is "bubbles" in the top of the radiator... especially when you rev the motor. This is compression entering the cooling system - the air passing to the top of the system.

As mentioned, it would be rare for this to cause the engine to mis-fire - more likely to keep the top of the chamber clean.

On the compression note, an engine will fire at much, much lower compressions than that. I can remember having an old Standard 8 which was simply worn out. A compression check had one of them down to 65 psi, but the motor ran without missing.. it oozed oil around the rings and down through the valves which caused the plug to foul - an almost daily clean was required to keep the little motor running.
I believed that the pistons took a detoured route on the way up and down... the engine was really in very bad shape, but for a paddock car - it was a very good grounding (excuse pun) and my "quantum leap" up from motorcycles.

Another alternative to try would be to slightly advance your ignition - as a test. What this would effect is to "build" some false compression in #4.... if the miss were to disappear due to this, I would expect that you have a compression leak... but continue to struggle to understand why it would miss with the 115 you believe you have in that cylinder.

Watching this thread with interest.

frats,
Rosco

[yaapeet30]

Another thing I forgot to mention. I had a miss a couple of years ago and it turned out to be quite simple. I lifted the bonnet at night and could see an arc from one of the plugs. Whats the condition of the distributor?

I would start simple and slowly eliminate each before you got to the tear the motor down.

Cheers

Rod

[EKUTE]

Thanks again fellow members for your imput,I,ve ruled out electrical because I,ve changed everything,when the head was off I noticed this cylinder had far less carbon than the others indicating water somehow to be a factor in solving the mystery.I,ll let you know once it,s been torn down so stay posted.ie might be awhile before the riddle is solved,I,m working on a suzuki 73 waterbottle right now getting closer to launch day.

[Craig Allardyce]

120,000 miles.............that's 192,000 km. That's pretty good for an engine with a pretty average oil filter system (bypass or nothing) and high rev operation due to low gearing. 100kph on standard running gear is approx. 3600rpm. Not many cars these days put up with all that and last much longer. Wear rate on an engine equates with how much distance the piston and crank has covered over time (and all other components), how much fuel is burnt relative to loading hence why so many cars these days employ overdrives or multispeed gearboxes.
A full flow filter conversion, EFI, synthetic oils, 6 or 7 speed auto/manual, lock up clutch, cruising rpm of 1500-2000 rpm and your old grey would do a whole lot better. Its all relative.