Awwwww, Kraaaaaap. I feel your pain.
Awwwww, Kraaaaaap. I feel your pain.
I spent some time avoiding the ferrari...I figured I should let it sit a bit and think about the way its been behaving so I helped my son with the oil change on his bike and hopefully we got a small oil leak sorted. Then more picking up and finding places for stuff that has really not had a home since I finished the basement and drug it all to the shop.....Whoa! I have a full new box of plug wires!
The project has been going on so long that I no longer have any idea why I have the wires but the wires have been on/off so many times they are starting to fail and thinking I was out and they are NLA I'm pretty sure so yay!
With that score in hand I got after getting it ready to plug and made decent progress...should be out tomorrow.
Its out, now it see what's wrong
In reply to mke :
The amount of automotive carnage in this thread is surpassed only by the absolutely stunning way that every setback is met with a can do attitude and overcome.
I probably would have lit the car on fire and sacrificed it to the gods of speed after the 2nd co-spatial event.
About 5 years ago I was sorting out the last valve failure (tight guide) but I was also recutting the valve pockets because I could see evidence of contact, just barely. I inspected the valves and they were all within .004 TIR but 1 needed a light smack and I had a buddy regrind them.....what do you want to bet I just found the one I smacked? But I can't be sure so now I need to think about replacing them all I guess.
>Log onto GRM after a hiatus with my Bonneville LSR salt missile project having spun a rod bearing at 9k rpm
>Huh, wonder what that weird V12 308 project is up to
>Oh look it's got recent posts, sweet let's see what he did to it now
>First picture I see is a dropped valve
Press F to pay respects
jdogg said:>Log onto GRM after a hiatus with my Bonneville LSR salt missile project having spun a rod bearing at 9k rpm
I'm sad for your spun bearing and very much hoping I don't have 1 or my own. Over the next couple days the plan is get the piston out and see what the rod and bearing look like then I can start making a repair plan.
No work yesterday (no need to poke the bear) and a late start tonight but I did have time to pull the other head and for the most part all is well. Oil
So while I epoxied the huge port leaks there are clearly still leaks in most of the ports waiting for me to weld shut.
Ok. If you look, like actually look at the head off pics you can see the intakes were hitting the pistons. Here's a close up from the worst one in bank 2
So I went rolling back through pic and here is a gasket change in 2022.....if you zoom in its got the same marks
So there is an assignable cause......which leaves me very confused how the clay test looked like this before those run tests.
Once I get the a little further along I'll repeat the clay test and see what it says, I must have screwed it up somehow, I just don't know how.
Engine off the trans
and...no spun bearing!
Its looks a little sad but its pretty cheap.
How high were you revving it?
I don't know about most common engines, or even most uncommon ones, but a certain engine developer who played with B series Hondas for a while found that at 9000ish, the .010-.020 quench volume turned to zero and revving higher would cause pistons to hit the cylinder head. This with quality aftermarket rods and pistons.
This wasn't like a plateau or cliff, just a general extension of the rod and piston and probably crank throw with the G forces involved at ever higher engine speeds.
In reply to Pete. (l33t FS) :
I never thought of the rod stretch. I few thou of rod stretch and a few thou of valve over-travel and what was once clearance is now negative clearance.
What an oof moment. Hope it gets on the mend soon!
I don't think rod stretch is in play here rpms are too low. Also unless cam timing changed, looks like the valve pockets were plenty deep. I have seen valves stretch, which effects spring pressures. That would cause loss of control at high revs, but imo its in the same realm as rod stretch, unlikely.
Right now I'm just assuming I screwed up the cam timing when I did the clay test because it is hard to do on this engine. New thought is I'll pull the lift numbers from Dynomation in 5 degree steps 20BTDC to 20ATDC, set the crank and measure the clearance. If that doesn't find the problem I can mount the timing cover and cams and check the same range with a feeler gage. If niether method finds the issue I''ll start thinking about heat and stretch and all the fancy stuff.....but the simplest answer is usually right and that is I just screwed up measuring.
Damaged piston out, popped out the real springs on #1 put in my testing springs, head on the block.....no they most certainly do not hit so......but clearly they do hit so WFT?
I'm leaning toward saying I do not understand, but another 40thou should fix it. I need to drink on it a bit....
What are your valve guide clearances?
I recall a situation where this happened, and the engine builder set up the clearances tight for bronze guides, but a couple valves needed replacement guides and he used iron ones, which needed 3x more clearance to work, but he didn't know that yet. The valves that had iron guides stuck while running the engine in and hit the pistons.
Learning experiences are fun.
Something is moving around in that engine, did you change bearings between now and when it was built the first time? Headgasket?
In reply to Pete. (l33t FS) :
Intakes are 0.0015-0.0020
Exhaust 0.0020-0.0025
And these are tiny 5mm stems in bronze guides. The go pin drops through with light oil, the no-go pin can be pushed through about 1/2...so nothing on the tight side for sure.
jdogg said:Something is moving around in that engine, did you change bearings between now and when it was built the first time? Headgasket?
Some, not all bearings have been changed and I'm seriously thinking all new so I know all good after thais failure. But they are tight....about 2 thou clearance.
Head gasket have changed many times in the battle to seal but all gaskets I've ever used are 0.050" compress thickness
My focus at the moment is on timing chain stretch/slop during accel/decel or kick-back while cranking. Its a LONG chain and the cam loads very high so it stretches, slop could easily change the timing by 5 degrees and that would be 20-30thou reduction in clearance. Make it 6 or 7 degrees and hot valves and they would hit with the clearance I have I think.
That long timing chain clearly is begging for a conversion to gear drive vs chain. It's just engineering, right?!
Jokes aside, how is chain tension maintained on that motor? Apologies if that info is posted previously in this thread and I haven't dug back into it.
In reply to 4cylndrfury :
Funny, I've been sent a couple copies of this in the last hour or so:
mke said:In reply to 4cylndrfury :
Funny, I've been sent a couple copies of this in the last hour or so:
Looks super easy. I'm shocked you haven't done it already lol
The dull work of tearing down the heads, 1 done.
The thing with gear drives, besides being really loud, is they add a lot of harmonics to the valvetrain that valvesprings hate, at least in the pushrod V8 world.
Me, I like a belt...
This thing soild or hydraulic lifter? One time I had an issue w hydros collapsing when checking on an overly aggressive cam. Since then I don't clay, I just use check springs and measure the clearance from -10 to +10 crank and also check w cam adjustments if equipped.
You'll need to log in to post.
