Catastrophic Engine failure. 454 gen 6
 

Before I pull my engine and do the autopsy... Seeing what some theories are on what let go. Engine wouldn't rev past ~2,200 rpms, but seemed to run perfect up to that. 8* timing. Seeing how we launched and I had my wife and son with me I decided to just put up the river and anchor for a while. 8.5 mph up against the current for three miles. No issues. Sat for several hours and then putting back with the current at ~ 11mph and a loud bang from the bilge and silence. Engine died. I didn't even bother trying to turn it over. I knew it was catastrophic. I looked in the bilge and sure enough there was oil.
Up until this point I was running 160*, 50 psi oil pressure and 2,000 rpms. No alarms or any kind of warning before it happened. There's a small crack in my oil pan from what I can only assume is a rod coming through. I just finished rebuilding this motor and finally got everything dialed in. Or so I thought... I did all the work except the machining and have the pics to go back through and see what I did. The only thing I can assume is the rod bolts let go on the third or fourth piston or I dropped a valve and it got wedged. Any other guesses? I'll pull it in a couple of weeks, but for now here are a couple of pics and a vid of it running. Listen to the valve train. I didn't like it from the first start. Too loud for a hydraulic roller motor. It's the factory non-adjustable rockers and lifters. Torque to spec and call it a day. I was planning on putting an adjustable set in over the winter...https://youtu.be/KekmU_mr6PA

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150psi oil pressure at 2000rpm??? 😳

Give us some history on why engine was rebuilt in 1st place and it’s overall condition along with any rigging/exhaust parts replaced too.

What were the rod and main bearing clearances set to ?

Some crazy oil pressure huh? 50 psi... Engine came with the boat. Needed to be rebuilt. Tired and beat. Nothing in particular. Sent it to the machine shop. Cleaned, line bored, honed, new cam bearings. Crank polished. All the tolerances were in spec, but I don't remember off the top of my head. I have inner and outer gauges and measured everything. No plastigauge... I reused the pistons and rods as well as the lifters and pushrods. Cleaned all the parts well before reinstalling them. Topped the short block with L29 heads that I cut for posilocks. This is also an L29 block. 9.3:1 compression. I'm running a new/used mag cam.
It has a new full closed cooling system. Runs at 160-165 which I verified with laser thermometer. The exhaust manifolds, 3" spacers, risers and elbows are all less than 2 years old. Very clean. Now running antifreeze. Rebuilt the OE 9780s Weber carb a few weeks ago because I thought I might have had plugged secondary's. No difference. It has a new intake also.
I'm also wondering about hydro lock as a possibility, but I can't see how. New flappers and it was after driving for two miles while moving.
Last thing. I had two issues that I had to straighten out that might have added to the problem. 1. Less than 10 psi oil pressure on first start. I didn't install three galley plugs under the spider. Figured it out quick and installed them. 70 psi after I installed them. 2. I had a problem with my FWC. I was running at 210 because a hose was running to the top of my exhaust manifold instead of to my spacer. Fixed and 160 after.



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Video is pretty noisy like its starving for oil up top, did you look at the crank and rod bearings after you noticed the lifter valley pugs missing ?

I didn't like the sound of the valve train at all. Sounded like a diesel. I wasn't able to pull the caps to look at the bearings. The motor was still in the boat. I just pulled the intake to reinstall the plugs. I saw the oil pressure was good so I just figured it was a noisy stock valve train. I have the exact same motor in my 69 Camaro, but I used Lunati lifters and adjustable rockers among a few other mods... Very quiet.

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Oh, okay. I read about it in this book. :(
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I missed something I think... I know payup asked about my cam from the notification email. That's Ultraslick cam lube. None of it was dry.
SB, book probably wasn't for me lol, but that about sums me up right now if it was.

The issue of not reving over 2k is strange, what kind of ignition are you running ? is this efi or carb

Very strange. Carb and TB V. I did set it in base timing mode.
edit: maybe flooding the cylinders then hydro locking? On the other hand, it was running too well for that.

Is the TB 5 the one you have to set kind of like EFI ?? what are you seeing total advance,

There's two different ones. One where you unplug and use a jumper and one like mine where you ground a purple w/white wire.

Base timing mode
TB5 - ground purple/white wire
EST - 12V to lead and jumper other 2 wires together on right side connector of distributor

My oldest son and I pulled the engine last night. So far it looks like a #8 piston failure and contact with the intake valve. No obvious signs of other damage so I'm hopeful. All the other cylinders appear perfect using a bore scope.
I'm pulling the head and piston this morning for the autopsy and should know more then.
Now, why....?

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Fargin non-adjustable rockers bit me. Had plenty of PTD clearance, but didn't check valve clearance because it was all stock parts. Live n learn... Never again will I use the non-adjustable set up.

Edit: I checked my notes and I did check PTV clearance. Should have been plenty. wtf?

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Valve seized in head and took piston out. Lack of oil as indicated by the loud lifters. You're clearance was good till it seized. Probably started galling when the plugs were left out.

Plenty of oil. Cam phasing problem. All the intake valves were kissing the pistons. At the machine shop right now.

Phasing? What was it set at? That should have been felt while turning over by hand if it was hitting all the intake valves. Glad you found the problem. Hope you can salvage the rest of the season.

So what did you use for rocker arms on this engine?? Non adjustable shoulder bolts?? Those won't work with anything other than the original stock heads and cam. Probably the cause of the valve train noise and why it wouldn't rev.
Also, look at the other pistons. Looks like a valve hit everyone. Timing chain installed improperly and was advanced or retarded too much and valves hit piston. BTW, been there and done that. I bent 8 intake valves and broke a bunch of rockers.

The heads are stock L29 heads on an L29 block. The only change from stock was the mag cam which wasn't enough of a difference to do much of anything and a Summit timing set. Valves, rockers etc were stock.
The timing set was setup at zero and installed correctly, but I'm wondering if there was a problem with it. I couldn't degree the cam correctly for the life of me. I didn't have a cam card so I just went with it because it was a stock cam. Never had that problem before and I should have stopped right there I'm sure.
The valve train noise was the intake lifters just barely kissing the pistons for sure. I checked my notes and I had plenty of ptv clearance. Intake .102" Exhaust .168".

How did you check ptv? To go from .102 to less than 0 something changed

Light spring, TDC and a dial set up on the retainer. You have a good point and the only thing I can think of are push rods or rocker arms being wrong. God knows it wasn't the . 484 lift cam...

I don't believe using the wrong push rods or rockers are going to change the PTV clearance. They should at the very least be consistent. Compressed lifter while taking the measurement will change it, but 0.102" with a light measuring spring is quite a bit. IMO

What was the lift on the stock cam??

Why would you think pushrods or rockers wouldn't change the PTV clearance? Effectively more lift is going to push the valve down further towards the piston. What if the rockers were 1.8 instead of 1.7 or the pushrods were too long?
The stock cam is .480/.483 and the mag cam is .483/.483.

My thoughts too

How did you measure piston to valve clearance? By the questions you’re asking I’m pretty sure you did it wrong.
I put clay on top of the piston, torque the head down, assemble the valve train for that cylinder, rotate the crank 2 revolutions, pull the head off, measure the compressed thickness of the clay.
so unless you checked it with one set of pushrods and rockers, then ran the engine with different parts you’re piston to valve clearance didn’t change

Even more basic question, was the block milled and/or the heads decked and the actual measurements of clearance not accounted for as the components were "stock"?

Just throwing that out there as the pics are showing more than one piston contact.

Dave, that really sucks. Looks like you're on top of it and should be back together quickly.

That's pretty much a stock engine. When it goes back together, use the factory GM single-chain timing set and measure for proper pushrod length to make up for deck changes (probably fine with factory push rods too). The non-adjustable valvetrain is perfectly fine on that engine, but if you need a conversion set, I've got a Comp set that I bought for mine a while back - basically brand new.

Piston-valve-clearance needs to be measured during timing events. Running up to TDC and checking doesn't give the whole story. Rolling it over on the stand, did it ever feel tight?

I'm guessing something went very wrong with the Summit timing set.

That's one way and common, but not the only way. My way was right for actual PTV clearance, but it doesn't take into account the rockers and pushrods.

I didn't have the block decked or the heads milled. I had a lot of PTD clearance. I should have been able to zero deck it if I wanted to.

Thanks Tom. Yes, non adjustable should have been fine, but... I agree about the timing chain. That's the only real unknown right now. It would explain all the problems I had with degreeing the cam.
Definitely should have checked PTV with timing events, but shouldn't have had to with all stock parts. I made assumptions I shouldn't have with that.

I doubt it was the lifters that were loud. I think it was the valves touching the pistons.
Also, there would have been evidence of oil starvation and there isn't. Guides are perfect and even the broken valve doesn't have any signs of an oil issue. I'm talking about the shaft left in the guide.

Oh….,,,,,okay….,,(bright light over my melon) I remember TomZ asking in a thread about the person sho bought his Bbc mag cam having issues degreeing it, or something like that.

You where the one. Now I get it.

Okay, so refresh us. When you where degreeing in the cam what issues where you having ?

Yessah. That was me. It should have been a very simple and basic degreeing of the cam and the numbers were all over the place. I really think this is looking more and more like a timing set issue.

If i remember the mag cam, it has 115lsa (115.5 ?) and should be installed at like 111icl and 119ecl

the non adjustable valvetrain will only work with the stock cam ,any cam with a different base circle diameter wont work.i suspect this is the cause for the failure.

not accounting for your pushrods, rockers, or cam timing is essentially useless. Had you measured while taking these into account you would’ve caught this failure before it happened. But good luck

Never heard of doing it without mocking it up and using clay. How else can you measure it ?