Engine failure questions (pics)

[Lloyd]

Right, engine in question is 4AGZE bottom end, 8.9:1 compression pistons and a Silvertop head. Bottom end standard and the Silvertop head is standard, 4AGZE head gasket. Engine was running fine for a few hundred kms in an AE92. It was then removed and installed by a professional workshop into an AE111 with a Link. Was running fine for a week or more and then got progressively slower and lower on power. Eventually stopped going and opened up to discover the following. Any ideas on causes? Bits have apparently gone through the turbo which may explain some little bits sitting in number one.

Seems to be a hole in number 4 but not knowing if this was involved in the cause or the result

Cylinder 1
Cylinder 2
Cylinder 3
Cylinder 4
Cylinder 4 Valves
Head
Pistons

[flygt4]

impressive. thats a good effort considering these things are near bulletproof.
I ran mine at 22psi for ~ a month with less than ideal A:F ratios until i put it on a dyno and had the fuelling adjusted and its never had any ill effects.

was the link running a dyno or road tune?

[TRD_ZERO]

Damn that thing is a mess. That kinda thing is gonna give me nightmares

[ke25sr]

I would highly suggest talking to Damian seeing as he is a professional.

He can send away and have parts tested to see why it failed.

Its wasted man.

[Adoom]

Could it have eaten a foreign body that got stuck between a valve and the seat, bending the valve which eventually broke the head off. Then with a valve head rattling around in the cylinder it was all over rover.

My bro had something similar but it turned the whole piston into alloy gravel in the sump. The guy who originally built the engine didn't loctite the rod bolts. So the rod let go of the crank at 6000rpm. It took less than 5seconds to completely obliterate the piston. There was nothing recognisable as piston except some bend bits of piston ring.

[fivebob]

Judging by the marks on all the pistons it looks like the timing may have been out, or slipped at some point. Either that or one hell of an over rev, like shifting 5th->2nd

[matt dunn]

Judging by the marks on all the pistons it looks like the timing may have been out, or slipped at some point. Either that or one hell of an over rev, like shifting 5th->2nd

Yeah the marks by the Exh valve cut's in the pistons look exactly like when my 20V engine with GZE pistons slipped the cam pulley on the crank,

It bent 12 out of the 20 valves, the exhaust ones were the worst, but luckily none snappedb the head off like that has done.

My guess would be cam belt or cam timing failure.

Check the cam sprocket on thye crank still lines up in the correct place when you visually get no1 to TDC.

[Crucible]

My guess would be cam belt or cam timing failure.

That would be my guess also....

. Was running fine for a week or more then got progressively slower and lower on power.

Most Ive seen usually just stop!, but maybe it jumped a tooth or two first before valve timing went way out of whack and it become interferance? The garage that done the swap to the 111,... did they do a cambelt at the same time?

[ke25sr]

Surely if it was the cam timing it would have $&#$% more than just 1 cylinder.

[fivebob]

Surely if it was the cam timing it would have $&#$% more than just 1 cylinder.

Nah, first one to go stops the engine, the rest don't get a chance

[Lloyd]

Well its trying to be pinned on me for selling the guy the engine which was running fine in the AE92. Dude drove it around for a week or so after getting it fitted and then reckons it started to get worse. Also have been told the engine suddenly wouldn't idle one day and was down a bit on power but it kept getting driven. At a guess I'd put this down to the exhaust side jumping a tooth and throwing the ignition timing out also (it got comverted back to distributor, god knows why as I gave him the twin coils for it).

Haven't seen the engine in person, have only been shown those pictures and been told its on me as there was an assembly issue, regardless of the fact I drove around on it for a few hundred kms with no issue and so did the new owner.

[ke25sr]

Take it to damians work ( Graham Page engine recon) He can send parts away and find cause of problem. At least it will get you out of the shit.

[Jdawg]

Was running fine for a week or more and then got progressively slower and lower on power. Eventually stopped going

Would expect more damage if it was the belt. Maybe a seized valve.
Did you do much engine braking? You may have stretched a valve.

[Alex B]

Why would you expect more damage if its jumped a tooth? Its pretty obvious the exhaust cam has come out of sync. The fact it was being driven around in the first place with out issue would kinda show its not an assembly issue so you would think.

[Jdawg]

All 4 cylinders have equal opportunity to get damaged, he's driven it round a bit after first noticing a loss of power that got progressively worse. the noise would be very loud from the moment the belt slipped. If an exhaust valve started sticking you would get a loss of power but no mechanical noise until the valve failed completely. likewise, if he done some heavy engine braking and stretched a valve, it would leak, more abuse and the valve head would break. 2 of the valves look like a clean break, which I have seen twice before. On a big diesel the had stretched the valves and on a 302 windsor during deacceleration. The valve stems stretch then the head snaps off like a carrot.

[matt dunn]

Here is a pic of that marks that can only appear if the cams are in the wrong place at the wrong time.



They look very similar to the marks in your pics.

[edwagon]

The only other time Ive seen valves let go like that was in 265 valiant hemi in a stockcar where it used to come in wickedly hot after races (maxing out a 250F gage!), huge revs and with mega spring seat pressures, the 2 piece valves would litterly become 2 piece and do similar damage.

Point is, that sort thing only happens as the result of major mechanical misadventure, not because you saw it coming and sold it before it let go!

Really, the fault lies directly with whoever kept on driving it when it wasn't right.
Id would tend to agree that the cam timing has shifted and been hammering the valves, the valve(s) on number 4 were the weakest and broke first, and once a valve head starts bouncing around in there, thats the finsh

[matt dunn]

Kind of hard to see in the pic, but are the rest of the exh valves bent?
looks almost as though some are.

[sergei]

looks like cambelt failure, either cambelt has broken a few tooth a time untill valve met the pistons, or it jumped because of loose tension. Or the tensioner bolt gave up or was not tight in first place.
My bet would be on broken tooth on cambelt as it would explain poor performance before failure - it would break 1 tooth, timing would be slighly off but still run, then another, and then another until valves touch pistons...
Or other issue might be in broken crank shaft key, which locates the cambelt sprocket. These fail because of crank shaft pulley was not tight enough.
If it was 1 valve failure you would not see marks on other cylinders.

[Mr.Phreak]

Surely the "professional workshop" would've checked the timing before/during the transplant, especially if they changed the ignition system