Engine failure after 20000 km.

[Vicus]

At the beginning of June I was on my way home from the FoMoCo Nationals in northern Germany. Almost 1000 km in one weekend is something out of the ordinary, even for my Mustang. The oil pressure was high, the temperature gauge was in the relaxed range and I drove between 120 and 140 km/h at 3000 to 3600 rpm in the places where it was possible. Suddenly, shortly after Frankfurt and still 160 km from home, I heard a rattling, rev-dependent noise coming from the engine compartment. Oil pressure and AFR still top. Fortunately, there was a freeway service station a few hundred meters away. I got out immediately and switched off the engine. I didn't have enough tools with me and had the ADAC, the German equivalent of the AAA, take me home. My investigations revealed that the push rod of exhaust valve #2 was massively bent and had broken off immediately on removal from the engine. So it was clear that the engine had to be removed, because I had to check whether parts of the push rod or the abrasion had caused further damage. I later discovered that the push rod of exhaust valve #5 is no longer straight either. Also, some exhaust valves have clearly worked their way into the casting of the cylinder head. I have work to do!


On the way home with a little help.


Bend pushrod


Broken pushrod


Start removing transmission and exhaust


Cleveland on a hook


Bend pushrod of exhaust valve #5


View on the valves.

Cheers Frank

 

[Stanglover]

That SUCKS Frank.
I can't make any recommendations as for what to do, but maybe time for beefier parts in that motor.
This is one of my big fears, blowing the motor.
Good luck moving forward.

 

[Sheriff41]

Smart move to have brought home on a flatbed. I wonder if you might have floated the valves when you were drag racing a while back. This is not uncommon on Cleveland engines. High rpms, float valves, tap the piston, and bend the pushrod. Are there any signs on the tops of the pistons that a valve may have contacted?

 

[giantpune]

That seems like there's only so many things that could happen to bend pushrods, but the engine still runs. Its not like you broke a timing chain, cause then it would have stopped.

Were these stock parts or some aftermarket stuff?

 

[Spike Morelli]

The one view of a pushrod looks like it was chafing against something. Now, did the chafing cause the pushrod to fail and bend, and subsequently break..... or did the pushrod loose it's rigidity, bend, and then rub on the head casting? If you've changed the cam and/or springs, you may consider another set of pushrods, moly tubing, or case hardened, or both, to keep this from reoccurring, clear of there being an interference issue with the valvetrain. On another note, the wear pattern appears to be radially, not just up-and-down, suggesting that the pushrod has indeed been spinning, as it should. Very nice car though.

 

[Don C]

It's good you shut down when you did, you likely saved the block.

Exhaust valve recession is a real problem for engines that were not designed for no lead fuel. Even though some supposedly received induction hardening on the valve seats my experience has shown that the only solution is installing hardened seats.

I wonder if the valves became stuck in the recessed area, causing the bent push rods. I haven't had that happen, but have had the valves recess so far they could no longer seat, causing power loss and rough idling.

 

[giantpune]

The one view of a pushrod looks like it was chafing against something. Now, did the chafing cause the pushrod to fail and bend, and subsequently break..... or did the pushrod loose it's rigidity, bend, and then rub on the head casting? If you've changed the cam and/or springs, you may consider another set of pushrods, moly tubing, or case hardened, or both, to keep this from reoccurring, clear of there being an interference issue with the valvetrain. Very nice car though.

I was thinking it was the pushrod bent badly, then chafed up the side. Cause the other pushrod bent and isn't chafed. My vote is the same thing caused them both to bend.

 

[Cleveland Crush]

Sorry to hear of your dilemma. I would recommend a pressure test and installed height check on your valve springs to ensure there're to specs.
Also "Cruzing" at 3600 rpm's for any distance will certainly stress/overheat street level valve springs along with your oil temperatures!!

 

[Vicus]

Smart move to have brought home on a flatbed. I wonder if you might have floated the valves when you were drag racing a while back. This is not uncommon on Cleveland engines. High rpms, float valves, tap the piston, and bend the pushrod. Are there any signs on the tops of the pistons that a valve may have contacted?

I can't imagine that the four runs at the drag days provoked this damage, because it was nothing more than not taking your foot off the gas pedal after a start at a traffic light, only without fear of a speeding ticket. I didn't find any marks on the valves or pistons to suggest that the pistons and valves had touched. The pushrods and rocker arms are original. The valves are one-groove stainless steel aftermarket parts. I am currently unsure of the origin of the valve springs. My guess is that the sunken valves have something to do with it. Perhaps the geometry of the valve train has changed and caused the pushrods to bend. Both then grinded against the openings in the head. I can also see the grinding marks on the push rod of exhaust valve #5. Exhaust valves #2 and #5 are also the ones that have worked their way deepest into the cylinder heads.

 

[Vicus]

It's good you shut down when you did, you likely saved the block.

Exhaust valve recession is a real problem for engines that were not designed for no lead fuel. Even though some supposedly received induction hardening on the valve seats my experience has shown that the only solution is installing hardened seats.

I wonder if the valves became stuck in the recessed area, causing the bent push rods. I haven't had that happen, but have had the valves recess so far they could no longer seat, causing power loss and rough idling.

These are the original cylinder heads and I had already asked several engine builders in the past about fitting hardened seat rings. Unfortunately, no one here in Germany wants to do the work. They argue that the valve seats of the two valves are too close together due to the angled design and that a permanently tight fit of the hardened seat ring can therefore not be guaranteed.

 

[Vicus]

I was thinking it was the pushrod bent badly, then chafed up the side. Cause the other pushrod bent and isn't chafed. My vote is the same thing caused them both to bend.

On closer inspection, I can see that the push rod of exhaust valve #5 also shows signs of grinding. I can only assume that the pushrod of exhaust valve #2 had been scraping along the edge of the cylinder heads for some time and now the time had come for a burr to form there, which triggered the final deformation of the pushrod. As I said above: I can't see any signs that the piston and valve have touched.

 

[Vicus]

That seems like there's only so many things that could happen to bend pushrods, but the engine still runs. Its not like you broke a timing chain, cause then it would have stopped.

Were these stock parts or some aftermarket stuff?

When I need spare parts for my Mustang, I try to use either original parts or, if this is not possible, quality spare parts. In the engine, for example, I have the original crankshaft with original connecting rods and pistons. The standard oil pump, not a high volume or high pressure, is from Milodon and the timing chain is a True-Roller from Cloyes. For the valves, I changed from the original Ford 3-grooves to 1-groove stainless steel valves from an aftermarket supplier. I still have to check the valve springs.
Maybe now is the time to start thinking about aluminum heads, even though my goal is more torque than horsepower. CHI has some really nice products in its range. It remains exciting.

 

[Vicus]

That SUCKS Frank.
I can't make any recommendations as for what to do, but maybe time for beefier parts in that motor.
This is one of my big fears, blowing the motor.
Good luck moving forward.

That's right, Geoff.
But I can repair an engine myself. Bent body panels would be a bigger disaster for me. Fortunately, this season has already lasted a bit and I've already been able to put over 2000 km on the clock. So it doesn't hurt too much when I'm back in the workshop instead of sitting behind the wheel with a smile on my face.

 

[Vicus]

Sorry to hear of your dilemma. I would recommend a pressure test and installed height check on your valve springs to ensure there're to specs.
Also "Cruzing" at 3600 rpm's for any distance will certainly stress/overheat street level valve springs along with your oil temperatures!!

I usually drive my Mustang on the back roads. Here, that means a speed of around 80 km/h or 50 mph. On long journeys, I can't avoid the highways. Then I go around 120 km/h, plus 20 or 30 when I overtake someone.
If I were to drive slower, I would be a traffic obstruction for everyone else. Nobody in Germany expects a vehicle that clearly doesn't look like a truck to be driving at 100 km/h or less on the highway.
Another idea to reduce the revs is to reinstall the original rear axle reduction. I currently drive a 3.25:1 gear ratio, the original would be 2.75:1.

 

[Vicus]

Perhaps one more note: since I rebuilt the engine in 2019, a lack of oil pressure or high water temperatures have never been a problem.
I had the engine completely disassembled and cleaned. All water channels were flushed several times and all oil channels were also meticulously cleaned. The original radiator was also given a deep clean.
Even when driving on the highway or stop-and-go in city traffic at 40°C in summer, neither the cooling water temperature nor the oil pressure were a problem.

 

[Cleveland Crush]

I usually drive my Mustang on the back roads. Here, that means a speed of around 80 km/h or 50 mph. On long journeys, I can't avoid the highways. Then I go around 120 km/h, plus 20 or 30 when I overtake someone.
If I were to drive slower, I would be a traffic obstruction for everyone else. Nobody in Germany expects a vehicle that clearly doesn't look like a truck to be driving at 100 km/h or less on the highway.
Another idea to reduce the revs is to reinstall the original rear axle reduction. I currently drive a 3.25:1 gear ratio, the original would be 2.75:1.

Maybe time to consider installing an overdrive transmission Frank...

 

[Roland]

Bad! I assume this grinding cannot be happen in the short time of engine failure, see pic.

 

[Vicus]

Maybe time to consider installing an overdrive transmission Frank...

I've also thought about a transmission with overdrive. In most cases, however, my Mustang would then lose its registration as a classic car. I think that installing the original 2.75:1 differential on the rear axle will help considerably.

 

[Vicus]

Bad! I assume this grinding cannot be happen in the short time of engine failure, see pic.

Roland, that certainly didn't happen overnight. It was a gradual process since the valve started to sink. At some point, the wall of the push rod simply wore through. A ridge then forms there, which suddenly inhibits the movement of the push rod. I will definitely have to check whether this impact has damaged the camshaft as well as the push rod and the hydraulic tappet.

 

[c9zx]

Frank, As bad as it is, it could have been MUCH worse. At least you don't have a window in the block. Oliver P. may know someone willing to replace the seats. Also Abudi in Wien may know someone. The CHI heads are indeed great. However they seem to be overkill for how you use the car. If you want to use original heads, 2V or 4V, I can find a set and have them rebuilt to suit the cam you want to use. New thick wall pushrods, in custom lengths, are available from Trend, Manton, and Smith Brothers. I've used all of them with no problems but Smith Brothers ar easier to deal with in my experience.
I would disassemble the short block to clean and check for collateral damage. Hopefully you won't find any. Let me know if I can help. Chuck