Bottom end checks after massive piston to valve contact.

[AC sports]

Well like it says! In line, 8 valve, 4 cyl. Quite healthy output. Something went wrong up top and the no. 1 exh valve contacted the piston and bent like a banana. Lucky they are 1 piece and didn't drop their head. All other exh valves bent too but not like no.1.
Piston tops show obvious signs of contact but not too bad. I mean they will clean up with needle files. My question is, when this happens what bottom end checks are the norm. I'm guessing I got to take the pistons out and look for cracking in the pin boss area, rods ? The piston decks are all equal. Rod bearings? Would people change these if they looked ok? Engine has only done 1000 miles. Main bearings? Crank? Where do you draw the line?
Anything else?

[mag2555]

And what was your piston to valve clearance at room temp?
Have you checked the springs for pressure that came off that badly bent valve compared to the others that only bent somewhat?

[Carnut1]

Sorry for the bad luck. What I would do is a full disassembly and mag of each part, block, crank, rods, pistons, bores, main webs, cam and lifters. Every moving part that may have been effected by the collision. Crank and rods must be checked for straightess. I would also look deeply into the causes. Possible valve train overrun which caused valve spring overheating and loss of load?

[Amilcar]

Well like it says! In line, 8 valve, 4 cyl. Quite healthy output. Something went wrong up top and the no. 1 exh valve contacted the piston and bent like a banana. Lucky they are 1 piece and didn't drop their head. All other exh valves bent too but not like no.1.
Piston tops show obvious signs of contact but not too bad. I mean they will clean up with needle files. My question is, when this happens what bottom end checks are the norm. I'm guessing I got to take the pistons out and look for cracking in the pin boss area, rods ? The piston decks are all equal. Rod bearings? Would people change these if they looked ok? Engine has only done 1000 miles. Main bearings? Crank? Where do you draw the line?
Anything else?

Looking at that massive lack of clearence only on one valve, sounds like the this valve did sticked to the guide, don`t you think?

[naukkis79]

Plenty of overrevs and exhaust valves always look pretty much like that. This engine probably is HEMI-headed as there seems to be pretty big angle between valve and piston to bend valve that way.

Valve to piston contact usually do nothing for bottom end but overrevs that caused that might - but when I played with high revving 4-bangers usually just fixed top end, and it newer backfired.

[Newold1]

Is this a DOHC engine?

[Mark O'Neal]

Look at the rod bearing in the fork of the rods. If it's squashed, keep checking. If it's not, don't.

[peejay]

Check the piston skirts, I've seen them get bent by P-V contact before. In street applications, it mostly just results in some righteously loud piston slap.

[AC sports]

This was a DOHC engine. Hemi type head hence the angle.
No over rev. Was only doing 5-5500 rpm.
The valve didn't actually drop. It was still quite solidly attached by its collets. I had to cut the retainer to free the springs and valve. Which means it could have seized in the guide but can't be 100% sure cause the valve clearance adjusting shim was also broken in half. It's quite thick at 4.5mm though, so not highly likely but still possible. Valve springs actually all spec out correctly. So have to rule that out .

[englertracing]

Shim over bucket?

[AC sports]

Yes shim over bucket.

20180223_162806.jpg

[Geoff2]

Valve spring probably lost tension, THAT valve floated...& you know the rest...

[integrale Evo]

Sorry for the bad luck.

It isn't bad luck.


Is this the same engine featured here a few weeks ago or a different one?
1. Valve to piston clearance?
2. What is the relevant recent history of it?
3. What valve springs?
4. What cam lift in and ex?
5. Valve lift at TDC in & ex?
6. Had the guides been replaced? If so whose and what were they?

It doesn't look like a massive collision really, i'd check rod bearings at both ends, rods for straight and crank for the same initially moving on to the lesser likely areas.

[Krooser]

I'm still wondering how the OP gets those valves to hang upside down on the shelf!!!

[Truckedup]

I'm still wondering how the OP gets those valves to hang upside down on the shelf!!!

Valve Float....................