How much abuse can a piston top take ?

I broke a retainer on the top end sunday , at least i think that's what broke first , The piston took a few wacks but not that bad. They are Diamond flat tops .060 stock stroke. Cam is a flat solid 637-648 lift , i shift at 6700 and cross at 6900. I didn't really want to pull the motor and tear it down unless something like this is a must. Also i been thinking about trying Ti retainers and if so do i use Ti locks also or just steel ?

The springs are comp 930 with 741 retainers and 611 locks.

Ti retainer with steel locks in mine. You're lucky that valve head didn't break off and trash the thing! I'd fix the head and run that biotech!

Take that piston out of the engine and measure it. Especially the ring lands and skirt dimensions.

If it is OK then continue to use it.

wow, lookx waay better than mine when an intake valve head broke off. #7 hole diamond piston had a nice ventilation hole in it. then the valve head tried to get back into the head - sideways.

At least pull it out and look everything over good, make sure you didn't hammer something else.

I'd also look over all the springs and lock make sure another isn't failing too.

Thanks for the reply's everyone , I always wondered when its time to replace locks and retainers , I read about springs being replaced when worn but i never see any post about time to replace retainers and locks. Yep I'll pull it then and tear it down to check it all , I'm sure some pieces are in the pan , Just sucks , its the first time i entered for points and wanna give it a try for a full season. Machine shop said he'll have it done this week if i get him the pieces , Only thing i'm trying to find is what guide i need , I ordered some before but i cant find the receipt to see what part number they were.

+1 on you being lucky the valve head didn't break off. Never had it happen to my big block but on one of my modular engines that was in my car years ago it did. Here's the carnage from that one.

I don't see any problem on the piston. You can try "rocking" it back and forth to see if the rings are stuck ( I doubt they are). Good to go. I might look at the bearing on that rod though. The witness marks on the pistons are nothing to be concerned with.

nuclearcobra wrote:I broke a retainer on the top end sunday...the piston took a few wacks but not that bad. They are Diamond flat tops .060 stock stroke. Cam is a flat solid 637-648 lift , i shift at 6700 and cross at 6900. I didn't really want to pull the motor and tear it down unless something like this is a must.

If it were my personal engine and looking like that I'd run it; if it were a customer's engine I'd measure for the collapsed skirt.

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dysan wrote:+1 on you being lucky the valve head didn't break off...one of my modular engines that was in my car years ago it did.  Here's the carnage from that one.

This one's too close to call--you might want to take a closer look.

Nuclearcobra....I'd say you got lucky on that one!!
I'd use steel locks with Ti retainers.

I would say pull the piston and check it plus check the rod and bearing to make sure it didn't damage them also. It is better to check now just in case a set of gaskets​ is alot cheaper than a rod or something coming apart on track.

Well i started to take the heads apart to drop them off at the machine shop in the morning and after looking at the rest of the original guides this replacement one has slipped i guess ? I spoke with Charlie yesterday and he mentioned that they sometimes are put in with red lock tight or maybe he said they always are i cant remember, But anyway if this is a slipped guide is that probably why it happened ? The top of the guide hitting the bottom of the retainer or do they sometimes slip like this when stuff breaks ? This is the same guide that was replaced when a rocker came loose a few years ago and bent the valve and guide and beat the wheel and axle outta the rocker and broke the locks in half. The first pic is the replacement guide

Looks to me like that bent valve stem shoved the guide to the north....with a little help from the piston, of course. Yeh, you're one lucky s.o.b.

I just went out and measured them both , the top of the guide was .762 from the seat and the original guide was .615 , Now i gotta figure out if the guide slipped and caused this or a retainer broke first or the locks.

Funny i'm always the one telling my friends how important valve train maintenance is and helping them adjust lash and checking things over and here i am using retainers and locks that are years old with a ton of passes on them Oh by the way does anybody have some or at least one A460 rocker arm they can part with cause this one took a beating.

maverick wrote:Looks to me like that bent valve stem shoved the guide to the north....with a little help from the piston, of course.  Yeh, you're one lucky s.o.b.

I'd agree, it is strange to have problems with this guide "again" them locks are beat to hell.....

Well what a Pisser , I took the head to the machine shop today and he pressed out the guide with ease , the port side was a egg shape .514 Dia. and the spring side was .504 , the Pisser is the guide boss is cracked so I'm mailing it to a shop in PA to get it welded up and repaired. On a good note a buddy called up and said don't worry about the points races you can run my BBF Thunderbird until yours is fixed again and his brother said the big block 69 Dodge Dart is here for another backup if need be

Depending on where and how bad that crack is I'd be slow to weld on it, JMO. I fixed BBC head that got the valve head drove back through the seat and cracked that guide boss off. Guide hole was screwed up kinda like yours but worse. I opened the hole up and used a guide from a trashed hemi head, just turned it down to press fit. It's been running for probably 5 yrs now in a pulling truck.

Does anybody know how much it can be opened up in a SCJ head before you breakthrough ? I guess the main thing is how deep that crack is.

The retainer broke first for sure. If the roller tip still turns , the rocker can still be used. The pressure is up where there is no damage. Unless of course you can find a replacement right away. Check to make sure the axle pin in the tip isn't broken too.

Well i started to pull the engine and was getting a little nervous when some of the missing valve guide pieces fell out of the driver side collector when i took the headers off Well i then pulled that head once it was on the engine stand and #7 cylinder took a beating more than #4 that failed, it sucked all the pieces from #4 i guess, anyway I hope i can smooth out the piston and head if all the valves and seats look OK , Would you guys take this head to the machine shop as well to be checked or just do some clean up ?

I did cut open the oil filter and it was clean as was the oil pan.

Well Sunday didn't go so well with my buddies T bird I went to the Wednesday night TNT a few days before and made 4 passes 10.99's to 11.00's and then Sunday it ran 10.83 and on the 2nd time run it ran 10.79 and It was a repeat of my car #2 cylinder dropped a damn intake valve right after the stripe , I fear its in worse shape than mine seeing how it had water on all 4 plugs, it wasn't pouring out at all but they had water in them. Kills me to think we could've prevented this with changing new locks and retainers instead of running them forever.

nuclearcobra wrote:Well Sunday didn't go so well with my buddies T bird I went to the Wednesday night TNT a few days before and made 4 passes 10.99's to 11.00's and then Sunday it ran 10.83 and on the 2nd time run it ran 10.79 and It was a repeat of my car #2 cylinder dropped a damn intake valve right after the stripe , I fear its in worse shape than mine seeing how it had water on all 4 plugs, it wasn't pouring out at all but they had water in them. Kills me to think we could've prevented this with changing new locks and retainers instead of running them forever.

One of life's lessons learned.