Technical 4 days after head rebuild

[chesh]

Hi
I've re-con my head cylinder of my 999cc uno (carb).

Car was fine for 4 days, but drove with unadjustment distributor, so the engine had ringing noise when I press the gas all the way.
After 4 days, I drove at 120KM/H gas all the way, and suddenly big white smoke.

This is what I see after I took off the head again:

What could cause that?
I've closed the head exactly at 20nm, then 30nm, then 2 times 90*.
My friend told me the head may be low height, and that it would happen again if I put a new head gasket.

 

[portland_bill]

Looks like you've been a very lucky bunny!

The ringing noise is likely to be detonation, or 'pinking'. This is where the fuel explodes in the cylinder. Normally the fuel burns very rapidly, it does not explode. When the fuel explodes, like any explosion, there is a lot of force. This will usually pop a hole in the top of the piston. It appears from your pictures that it has just pushed the head gasket aside, into the coolant passages. Putting coolant through the combustion chamber will give white smoke.

If the head and block faces are ok, a new gasket should fix it. Make sure you clean out all the coolant from the tops of the pistons. Change the oil, as some coolant will be in there too. Then set the ignition accurately before you put any load on the engine.

A new set of head bolts is probably a good idea too.

 

[a73uk]

Pinking could have been the distributor timing, but could also be a timing belt 1 tooth out (Uno`s do run with 1 or even 2 teeth out).

Did it overheat when you got the smoke coming out?

Are those grooves on the block under the damaged part of the head gasket? Whats the state of the block?

Assuming the block & head are ok (get the head re-checked for flatness & re-skim if necessary), put it back together with NEW head bolts.

 

[chesh]

yes I didn't adjust the distributor timing after I installed the head.
I thought it would be ok driving without it timed for a few days.

My temp gauge doesn't work, but I checked with a heat gun and fan always kicked in around 82c.

Block looks ok but I don't really know how to check.
I tried to move the pistons and there's not movement.

Compression test was around 150 in all the cylinders.
I tried to pour diesel fuel into the cylinders to check the rings.

After 3 hours, in no. 2 there wasn't any fuel left.
In No. 4 where the headgasket was ****up, there was half.
Is that ok?

 

[a73uk]

It doesnt really make sense that you read an even amount of pressure in the cylinders with the head on, but when checked with diesel, 2 cylinders leak. unless I`m missing something?

If you were doing 120kph when it blew, theres a good chance it overheated to some degree, in which case the head should have been checked for straightness & skimmed if needed, sounds like you havent done that. if the head isnt straight, the clamping force on the gasket wont be even, even if you torque the bolts down correctly, & will fail where there are any imperfections.

When overheated for a long period, or repeatedly, it can cause damage to the alloy block too.

Your block looks machined, but heavily scored.. I`ve not done an early FIRE head gasket for years, but I dont remember the machining being that pronounced.

 

[portland_bill]

Head face can be checked for flatness with a steel rule and feeler gauges.
The face machining marks look OK, unless it is not flat.

The fuel leakage past the rings is probably OK too. I'd only be worried if it drained away in less that 10 minutes, as diesel fuel is quite light and there are gaps in the rings of course, so I'd expect it all to drain away after a few hours.

Block is iron, so less likely to distort. I've had a Mirafiori OHV engine overheat, quite considerably, then had to drive it about 150 miles before repair. No skimming needed. My Argenta, 2000 DOHC also popped its head gasket and got a little hot, didn't need to skim that one either.

I don't subscribe to the theory that an alloy head will need skimming every time it is disturbed. In my years in the workshop, very few ever needed any skimming. Even when it overheats, it is still clamped tightly. As long as it is cold when removed, they mostly seem to be fine. Physical damage to the faces is a bigger issue, as can occur when gaskets leak. If the surfaces are fine, pop it back together. Ensure cam timing is correct, and set the ignition correctly.

 

[chesh]

Hmm I just found this on cylinder no. 1 after cleaning.

How bad could it be to put the head back on that?

 

[portland_bill]

I guess you are referring to the little 'hole' in the top. Difficult to see from th epic, but you need to assess how deep it is. This looks to be the start of a detonation hole, where the fuel has been exploding, and looks just under the spark plug, which is where I'd expect it to start. If you can ensure the timing, both cambelt and ignition is correct, it'll probably be fine. If you get any detonation again, with it already weakened it will pop through more easily. If when driving you hear the little rattly noise, back off!

 

[varesecrazy]

What could cause that?
I've closed the head exactly at 20nm, then 30nm, then 2 times 90*.
My friend told me the head may be low height, and that it would happen again if I put a new head gasket.

I agree , so far it's NOT a mechanical issue.., just the incorrect timing..,

the marked piston crown.. your call.. it could last years..

I've never had to skim a head either..

what I HAVE found is that the low torque , +90' , +90' can give great imbalance to the actually torquing of the head to gasket surface,

I go through all of that.., then use a "deflection type" torque wrench

around all the bolts in the same order/pattern

noting the highest figure the bolts "creep" at..
there is often a difference of @30..

so I then go around it all again to the highest figure..
I don't have HG issues after this

biggest things for me are CLEAN , and DRY for the gasket faces,
and clean and oiled DAMP for the bolts.

Charlie

 

[chesh]

Ok
I got the head re-skimmed for free.

I put a new head gasket, and installed all again.

Car started ok, gas pedal respond was great, fan kicked in at around 82c.

I saw SOME smoke around 1-2 min of start, but not as much that was before.
It got reduced as the car heated up. a few oil drops came from the exhaust on the floor.
I guess it's some left over oil in the exhaust system?

I hope it's gone, I'll start the car again today and check.

After releasing the timing belt bearing again, in order to set up the belt (it wasn't in the center of the grooves).
I can see this:

It wouldn't fit property as I turn the crankshaft bolt. the tensioner is pushed all the way.

 

[portland_bill]

That looks like the wrong belt. Belt teeth should fit snugly into the gear, without any gaps. Do you still have the old belt? Check teeth size, number and spacing. Put both belts alongside each other.

 

[chesh]

This is the old belt.
Ok I got it all tighten up (it had tension on it and I could twist it with resistance) and drove for like 15 min.

When I got home, it lost the tension at the red circulated part, and I could twist it way more.
(Don't mind the teeth at the back, it just the same picture).

 

[portland_bill]

If it has lost tension, either the tensioner has come loose, or the water pump is shot.
Check the tensioner carefully. Sadly, some have managed to damage the mounting bolt in the block, so it won't stay tight.
Water pump is the only other thing on the belt. If it is old, the bearings may be giving up, causing the belt to change tension.

If you are certain the belt is correct for the pulleys, ensure the timing marks are correctly aligned, and retension it. Run it, gently, and recheck.

 

[varesecrazy]

If it has lost tension, either the tensioner has come loose, or the water pump is shot.
Check the tensioner carefully. Sadly, some have managed to damage the mounting bolt in the block, so it won't stay tight.
Water pump is the only other thing on the belt. If it is old, the bearings may be giving up, causing the belt to change tension.

If you are certain the belt is correct for the pulleys, ensure the timing marks are correctly aligned, and retension it. Run it, gently, and recheck.

Or the old belt is failing..and that is the section of belt that is letting go- stretching..

On VEE Belt you wouldnt see this effect..but the teeth can hold thr belt together..as seen on the cam pulley.

 

[Ev0luti0n_FX]

This is one hell of a backyard garage job. Well, at least the guy is trying and this, is not an interference engine... lol i'll bet you guys this car will be scrapped in a matter of days. :|

 

[varesecrazy]

This is one hell of a backyard garage job. Well, at least the guy is trying and this, is not an interference engine... lol i'll bet you guys this car will be scrapped in a matter of days. :|

Why..?
The op didnt retime the engine

New belt.and properly timed itll last years

 

[chesh]

Today I've putted the belt again, this time I stretched it and put the tensioner all the way and bolted it good.

Distributor bolts were about 2-3cm far from where they should be.
No pinking now, and smoke is gone.
Drove for about an hour and everything was fine!! not too fast for 1.0 45 but I'm happy again

 

[portland_bill]

Today I've putted the belt again, this time I stretched it and put the tensioner all the way and bolted it good.

Hopefully not actually stretched.
Too tight will do as much damage as not tight enough. Needs to be right, although it will tolerate some variance.

The teeth do not do the driving, they are there to maintain the timing. The main belt does the driving, by being tensioned correctly.

Too loose relies on the teeth pulling the pulleys, which causes the teeth to pull off the belt.
Too tight, stretches the belt between the pulleys, which then has to compress the teeth together as they arrive at the next pulley. This also pulls the teeth off.

 

[chesh]

Yes, I can twist it 90d by hand.
Looks good now.

 

[g8rpi]

Hi, First time I've looked at this thread. You need to get a new timing belt. Either someone fitted the wrong belt (or a badly made one) or it's stretched. Either way it needs replacing. Get a gates or other known brand. With the belt untensioned the teeth should fit perfectly in the pulley.

Robert G8RPI.