Broken valves and damaged piston #4 only

[malcvr4]

2 valves were bent and 2 were broken on the #4 cylinder only. As you can see the piston was completely destroyed. 1,2 and 3 looked fine. Anyone have any ideas what could of caused this?

 

[Marc91GSX]

It looks like some one used that piston as a tool and beat the crap out of it with a hammer. Sucks that it happened though. I do not know how you can cause so much damage to the #4 piston and not hurt #1 as well. When you pulled the head what kind of damage did you see there. Were any of the srpings broken or stressed in anyway? The only cause I can think of would be something in the valve train and the since one was not touched I would look at the springs first.

 

[GTM]

2 valves were bent and 2 were broken on the #4 cylinder only. As you can see the piston was completely destroyed. 1,2 and 3 looked fine. Anyone have any ideas what could of caused this?

It's always difficult to isolate what sequence took place, it's entirely possible it jumped time first one way and then when catostropic event hit it jumped back.

What was the RPM? For that much damage it would almost have to have been driven some distance after the event. Overheat, valve float, valve collisions, or it injested something. Valve seats fall out, springs break, keepers hop out.

With that much damage most likely the head is trash, crank is suspect, rod bent, and the cylinder also destroyed. The question is it worth repairing, probably not. He probably should start looking for a replacement engine.

Cheers,
GTM

 

[malcvr4]

I'm in the process of building another engine. I"m goin with the 2.4 engine. I forgot to mention when I removed the valve cover I saw a rocker had fallen off. How could of this have happened? Cam caps were still torqued, keepers still in place, and spring still seated (Crower S+R). Thanks for all the input...

 

[Marc91GSX]

I'm in the process of building another engine. I"m goin with the 2.4 engine. I forgot to mention when I removed the valve cover I saw a rocker had fallen off. How could of this have happened? Cam caps were still torqued, keepers still in place, and spring still seated (Crower S+R). Thanks for all the input...

The rocker being off is pretty much a good sign that you broke a retainer allowing the valve to drop into the engine. But the retainer could have broken because of the engine jumping time. Either way I am curious to the actual cause here and I want to know what you find out. Inspect every piece of the valvetrain to try and determine what all failed if you don't mind. I agree with GTM your block and just about everything in are trash.

BTW keep the piston as a paper weight, great conversation piece.

 

[98evoIIIpwr]

And I thought I was the only one in the world that that had happened to. My father is a mechanic of over 30 years and he couldnt figure out what caused the same thing to happen to my car. First my water pump failed, replaced it. While replacing it when he turned the motor over he heard a clankin, with this being the result. Ended up replacing the head and buying new stock pistons. Took it to a maching shop and they said the rods were bad. Bought new rods and put everything back together. Wow guess what, car still knocked. Ended up taking it all back apart to find out that the car hand crankwalked or at least the crank was damaged and the block was also no good. To say the least this was a headache and a half. Good thing your going with a new motor because as GTM said your crank is most definetly suspect amoung other things.

 

[malcvr4]

Last summer I spun a rod on #4. Its always had a little knock to it. At the time I knew I'd be building another bottom end so I just let it ride. I never thought the piston could come in contact with the valves.

 

[GTM]

The rocker being off is pretty much a good sign that you broke a retainer allowing the valve to drop into the engine. But the retainer could have broken because of the engine jumping time. Either way I am curious to the actual cause here and I want to know what you find out. Inspect every piece of the valvetrain to try and determine what all failed if you don't mind. I agree with GTM your block and just about everything in are trash.

BTW keep the piston as a paper weight, great conversation piece.

Not meaning to be insulting or contentious, it is a very very rare event to break a keeper (retainer), I _may_ have seen 1 in my life time. There are a good half dozen reasons for cam followers to be found having fallen from their assigned position. Loss of oil pressure allows the hydraulic lash adjusters (tappets) to collapse at the pivot which is an unstable attachment and it just fall over. The cam lobe now rotates to the ramp which now has changed the lift ratio which causes the valve head to strike the piston and it's history. Now with the valve head bent the distance between the cam follower is such that it will fall completely out. Meanwhile when the valve collides with piston or another valve this resistance causes the timing belt to load up and jump time so it suddenly becomes a house of cards.

98evoIIIpwr, my first week as a "mechanic" circa 1963-4 I was given a Lotus twin cam engine overhaul. I moved from that shop to Bugatti restoration shop and then to Jag / RR then to Porsche/Ferrari. Spent a month in Italy partly at the Lancia factory, and working the race circuits so I've been around single, dual and quad overhead cam engines all my life and there is nothing I've not seen or worked on.

This overhead cam design came from circa 1955(?) SOHC Mercedes 190 series who then sold some of the patent rights to Nissan circa 1972(?) who improved it with better materials but keeping the chain drive until the '80s.

Cheers,
GTM

 

[dsm-onster]

This overhead cam design came from circa 1955(?) SOHC Mercedes 190 series who then sold some of the patent rights to Nissan circa 1972(?) who improved it with better materials but keeping the chain drive until the '80s.

Cheers,
GTM

Sorry to post whore but I can't help myself . What a bit of trivia? Are you referring the the L-series engines? Are you saying that there's Datsun roots in the 4G63? Tha Fairlady Z had an L24 and of course the introduction of the 240Z carried the L24 as well. This blue print was reportedly purchased form Mercedes. Although, it is entirely likely that Datsun bought more than one engine model designs from Mercedes. I love working on those old L-seies longblocks!

 

[GTM]

Sorry to post whore but I can't help myself . What a bit of trivia? Are you referring the the L-series engines? Are you saying that there's Datsun roots in the 4G63? Tha Fairlady Z had an L24 and of course the introduction of the 240Z carried the L24 as well. This blue print was reportedly purchased form Mercedes. Although, it is entirely likely that Datsun bought more than one engine model designs from Mercedes. I love working on those old L-seies longblocks!

You are mixing apples and oranges, the Fairlady as brought to the US was a pushrod engine (1600 cc?) not to be confused with the 1600 SOHC roadster that started Datsun's race history here and was driven by Frank Monise #44. (my Lotus twin cam earlier employer) Datsun (Nissan Japan) purchased the rights AND molds for the 1600/2000 SOHC that Mercedes was glad to be rid of this "white elephant" for they had nothing but grief. If you looked at the block you could see where they changed the sand cast molds and filled them in rather than the sheet metal side plates MB had used. To my knowledge the L24 was a stretched 2000 that went from 4 to 6 cylr and was of Nissan design. They literally cut the molds, inserted 2 cylrs for the 2.4. X years later the Japanese Fairlady was reborn and was an impressive piece of equipment but never imported to US because of smog/crash tests. At some point either MB or Nissan sold or patents expired and other makers adapted this cam, cam follower design. Some of this I've not thought about for decades so if memory isn't 100% take pity on an old fart. I should also note that when Lancia gave up racing they gave the molds of their impressive V6 to none other than Ferrari who just added another 6 cylrs, had Del-Orto cast OHC heads.

I have no intention of hijacking the thread and this post can be moved or deleted. Where else can you find this on the internet except DSMtuners.

Cheers,
GTM

 

[98evoIIIpwr]

Not meaning to be insulting or contentious, it is a very very rare event to break a keeper (retainer), I _may_ have seen 1 in my life time. There are a good half dozen reasons for cam followers to be found having fallen from their assigned position. Loss of oil pressure allows the hydraulic lash adjusters (tappets) to collapse at the pivot which is an unstable attachment and it just fall over. The cam lobe now rotates to the ramp which now has changed the lift ratio which causes the valve head to strike the piston and it's history. Now with the valve head bent the distance between the cam follower is such that it will fall completely out. Meanwhile when the valve collides with piston or another valve this resistance causes the timing belt to load up and jump time so it suddenly becomes a house of cards.

98evoIIIpwr, my first week as a "mechanic" circa 1963-4 I was given a Lotus twin cam engine overhaul. I moved from that shop to Bugatti restoration shop and then to Jag / RR then to Porsche/Ferrari. Spent a month in Italy partly at the Lancia factory, and working the race circuits so I've been around single, dual and quad overhead cam engines all my life and there is nothing I've not seen or worked on.

This overhead cam design came from circa 1955(?) SOHC Mercedes 190 series who then sold some of the patent rights to Nissan circa 1972(?) who improved it with better materials but keeping the chain drive until the '80s.

Cheers,
GTM

Hence the fact that we come to you for answers... Thanks for helping me when I have had problems. Good to have someone with major experience. My father was however an ISUZU truck tech so as far as problems with cars he has not been exposed to much, however he knows his stuff. If it wasnt for him I would be knowledgeless (if thats a word) and would have spent at least another 10k in labor on things I have done to my car.

 

[malcvr4]

Ok fellas....I'm cleaning my adjustable cam gears because I'm selling them. I noticed one of them is 6* off. I'm pretty sure this is what caused the damage.

 

[bryanwheat]

Ok fellas....I'm cleaning my adjustable cam gears because I'm selling them. I noticed one of them is 6* off. I'm pretty sure this is what caused the damage.

Dang malcom, i would say that if you use a set of those cam gears again, you should drill an extra hole in them, and put a poprivet in there to make sure that they will stay in place, either that or weld those bitches, either way, sorry to hear about your motor. Where are you getting yor machine work in town, i need to find a different place.

 

[malcvr4]

Dang malcom, i would say that if you use a set of those cam gears again, you should drill an extra hole in them, and put a poprivet in there to make sure that they will stay in place, either that or weld those bitches, either way, sorry to hear about your motor. Where are you getting yor machine work in town, i need to find a different place.

I'm selling the cam gears. I have no use for them anymore. I'm getting the 2.4 together so I'll be using the 2.4 cam gears with that. For machine work I've always goin to JD engine and machine. I havent had any issues with him.

 

[malcvr4]

Ok fellas...The bolts on the cam gears were still tight. I'm thinking when the valves hit the piston the cam gear was knocked outta time. As I said the bolts were still tight and washers left grooves on the gears. Thanks for the input...

 

[Initial DSM]

this happend to me last year and i had a fully built motor wiesco .20 over 9.1 eagle rods mls head gasket ported and polished head 1mm over sized S.I valves web cam dual springs and titamuim retainers 272 hks cams 3 gen lifters and a brand new scm61 turbo..all junk after droppin a valve....car had a good tune... 11.0 a/f ..0 knock.. i kinda put the blame on the SI valves ..i think those did it for me ..talk about shit luck ..when this all happend pieces of the valve went into my brand new 1000$ turbo ..ok so i rip the whole motor apart and keeped aside what i can reuse...i kept the block but from droppin the valve it nicked the cyl walls so i had to do a another .20 over ..so now its a total of .40 over ..i had to get new pistons..but i reused my old eagle rods ....so i reused my block rods but got new pistons and i reused the old crank...it seemed fine ..threw it all back together myself ...(i been building motors for 10 years now i know what i'm doing ) new ported head the whole 9 yards ...500 miles down the road ..the motor spuns a main and connecting rod bearing...i'm the luckest guy alive right ..wonder what part went wrong the sec time i put it togehter ..i think the rod and crank..the block looked fine

car was a 1992 eclipse gsx

 

[GTM]

Ok fellas...The bolts on the cam gears were still tight. I'm thinking when the valves hit the piston the cam gear was knocked outta time. As I said the bolts were still tight and washers left grooves on the gears. Thanks for the input...

Absolutely, once a valve fouled it set of a chain of events which resulted in catastropic failure. The only thing that can happen is the belt will jump time and loose the critical synchronization. Just as a valve can set it off a loose worn whipping belt can set the reaction off. The third cause is loosing oil pressure and the hydraulic adjusters collapse, this allows the cam followers to turn on their side and jam the valve open until the piston or another opposed valve hits it with the same result.

Cheers,
GTM