New Head Gasket - Misfiring

[Purbeckfossil]

I am scratching my head here. I have replaced (copper) head gasket due to a blow between 2 & 3 cylinders. Torqued it down to 44 ftlb, set tappets to 12 & 15 thou inlet & exhaust - ran it up to operating temperature, re-torqued head. Running OK. Left it overnight and then reset tappets cold. It now starts but is misfiring and won't tick over. The only thing I could think of is that I got 2 & 3 plug leads on the wrong way so changed them over but that made it worse. Fuel delivery seems OK. What has happened overnight? - I am at a loss.

Any suggestions will be gratefully tried out.

[bmcecosse]

Double check the valve gaps - and maybe try a new set of plugs in case one has been fouled? It's to be hoped the gasket hasn't blown again - did you check block and head for flatness after the last gasket failed? Was the engine run for any time with the blown gasket?

[mike.perry]

Check firing order 1342 anti clockwise. Check equal compressions with starting handle

[Purbeckfossil]

Hi again, I have re-checked the tappets - minor adjustment only. New set of plugs and checked contact gaps also. Misfiring as before. I didn't check the head for flatness as the AA guy said they were bullet-proof. The engine was hesitating on journey home for about 6 miles. If I take the head off and there is no obvious blow, do I need to replace the gasket regardless? Is a metal rule the best way to check flatness or are there any other wheezes you guys use? Cheers

[bmcecosse]

Steel rule will be fine - and yes I would re-use the gasket in that case - no doubt others will reel back in horror.... But - I would be checking EVERYTHING else before lifting the head again. You say the car was 'hesitating' - when the head gasket blows - -it's a LOT more than hesitating!!! Are you sure the gasket was blown - maybe the problem lies elsewhere?? If it was blowing - 6 miles is a long time to drive with a blown gasket, blasting very hot gases back and forth through the gap. there may well be scouring/erosion of block and/or head if driven for 6 miles. The head may be 'bullet' proof - but it's certainly not blown-gasket proof!

[MarkyB]

I'm with Roy and the AA guy, it sounds more like an air leak than a head gasket.
See what colour the plugs are before you pull it all apart again.

[Purbeckfossil]

Appreciate all your feedback. The initial diagnosis was by the AA guy who had a natty small light that illuminated the bore and showed water on pistons 2 & 3 and pressure build-up in the overflow bottle I have recently fitted.

So, having taken the head off and seen the evidence of the blow on the gasket, a new gasket was the obvious job to undertake. What puzzles me is: 1. the engine was running better with the blow. 2. It was running fine on initial start-up to operating temp.

It was only after re-torque-ing the head when cold and re-starting that the running was this bad. I am reluctant to whip the head off just now until I can rule out anything else that might be co-incidental. Oh, I remember I did spill a little 20/50 on the alternator casing when topping up!

If there is an air leak, where might I start looking? Could I have a faulty condenser or anything else electrical? Could the vacuum tube etc. to the carb have anything to do with it?

40 mph on the south coast so I will have some time this week to scrape my head on the bonnet again!

[sudburypaul]

Hi Mr Fossil

I'm no expert on this, so sure those with the knowledge will help out. But when I replaced the head gasket on my engine (due to a broken valve spring) I carefully cleaned up the head and block faces with a stanley knife blade to remove as much tiny bits of crud as possible and then gave a last rub over with fine wet and dry to the head. I see when you re-torqued you left the engine until cold. When I refitted the head and torqued it up I then started the engine until it was warm and then re-torqued while still warm, on the basis that the copper would be more malleable than if left to cool. I've had no problems with it since. I wonder if re-torquing when it was cold was your problem here. I'm interest for my own benefit on this, as wondering when I did it I just got lucky or whether I actually got it right!

Good luck with the refit

Paul

[bmcecosse]

Strange to find water in the bores - from a blow between cylinders 2 and 3 - and the more usual 'blow' is between 1 and 2 or between 3 and 4. They are closer together while 2 and 3 are further apart . Do you have a picture of the 'blown' gasket?? An A series with blown gasket will scarcely run at all - very very rough and can only just move the car (with excruciating vibration) on a flat road....... Ask me how I know!! But as you say - this only happened after the first heat cycle - how odd! Can you pin the problem down to any one (or two) cylinders - buy taking the HT lead off individual plugs while the engine is 'idling' - and see which one(s) make it worse - and which ones don't? If nothing obvious - then yes - off with it's head - it's only a 30 minute job anyway......

[Bazzalucas]

When retorquing the head bolts after the heat-and-cool cycle, is it necessary to loosen them first, or merely confirm that each is still at the proper torque? Also, I notice that many modern head gaskets advertise themselves as making the re-torque unnecessary. What is the conventional wisdom? Thanks.

[bmcecosse]

Just retorque - I have never failed to pull each nut round at least half a turn...

[Purbeckfossil]

Hi Guysngirls, Just to close out this thread I have now determined the problem. It would appear that it is coincidendal that I got an electrical problem occuring at the same time. Got a bit p****d off after all my efforts with the head gasket. So, Changed the rotor arm, then distributor cap, then points and condenser at the same time and HEY PRESTO it runs beautifully. So, it was either the points or condenser but both are are in the bin now. very glad that I took some time to check all this out before whipping the head off again

Thanks for all your comments/help

Purbeckfossil

[mikeysmorris]

Which just leaves the question how did the water get in the bores

[bmcecosse]

I doubt the gasket was ever blown.......but as long as it's working now! It's an easy get-out for the AA man, blown head gasket - can't be fixed by him - tow it away. I would defeat that by producing my spare gasket and asking him long it will take him!!!

[Purbeckfossil]

Definitely had water on 2 & 3, pressure build-up on overflow bottle, and the AA guy had that magic light to illuminate the bores. On the few occasions I have called these guys out, as long as they are AA and not appointed garages, they have gone the extra mile so they get my vote.