Putting A Little Pep In My 390's Step

[Nightmist66]

Thank you Bill and Heo for the kind words. Much appreciated.

Jared, Quick Fuel might be hiring. You could be in charge of product development.

Warped main bodies out of the box, there is something right there you could make sure doesn’t happen, ( I know they are Holley parts but Quick Fuels might be prone to it also).

I suppose you made the tuned exhaust collectors also?

Nice work as usual.

Thanks Jim. The headers are Mad Dog 2" and the same collectors as before. The collectors were spec'd by someone much smarter than me for this combo and were made by REF. They have an O2 bung on each side in case I ever want to go efi or to just check AFR and they were made with a v band to connect to the exhaust for street duty.

[Nightmist66]

Well, as they say, nothing lasts forever. The weather was nice on the 4th and I decided to get the car back out. I swapped my home brew carbs on the night before. I got it running and checked a few things over and took it out for a drive. Cruising around felt pretty decent. Made a few scenic trips to put some miles on. Everything seemed okay. I figured it was about time for a performance evaluation. I headed over to a local test spot(in Mexico) and tried to make a hit. I let the clutch fly at about 6200 and ran in through 2nd and 3rd shifting between 78-8000 and ran it halfway through 4th. Seemed very strong. Came up to the stop sign and took a left and jumped on it a little more, when all the sudden......Smoke rolling from the valve covers(hood is still off). Hmmm. Thought maybe a gasket or something started throwing some oil? Then I hear a faint tapping sound.  Nah, can't be. Well, I make it to the next turn and the tap turns into a knock. I look down at the oil press. gauge and it's not happy with me. Sinking like a lead balloon. Uh oh. I'm only 1/2 mi. from home. Tried to go real easy, but the knock was loud and it felt like it was losing power. I shut it off and pulled over. I called a friend from down the street for a tow home. Looked around on the engine and nothing out of place, everything is dry. Get it pushed back in the garage and let it cool off. Pull the valve covers and see this:

A little milky.....


Then I check the radiator and it's down some. Great. Figure I might as well cut the filter. As soon as I pull the filter I'm greeted with this




Cut it open to find plenty more where that came from.




So, I blew it off and worked on something else the next day. Grabbed my borescope and coolant pressure tester from work and checked it out more last Fri. I pulled all the plugs. Nothing too obvious. Started looking in cylinders and got to #7. Huh, looks like a small puddle at the bottom of the cylinder. I pressurize the water and it starts filling up fast!

https://m.youtube.com/shorts/Vk5vpvK7cUc

On the left side of the screen, you can kind of make out the valve reliefs on the piston. And a bunch of water on the right! Half the piston is submerged. I figured it better come apart so things don't get rusted inside. Pulled the engine out yesterday and got started on the autopsy. Once I got the head off, I found the obvious cause:



The knock:



The cylinder has a pretty long crack.


The big end on #7 rod is pretty ugly. Don't think it can be re-sized, so prolly need a new one. Luckily the damage was very isolated. Every other journal looks like it never ran, like I just assembled it. I think the coating on the bearings and a good oil additive helped me out. Looks like the crank can be turned on just the rods. Cam still looks like chrome from polishing. Can barely see where the lifters were riding.



Crank still nice and shiny.


Haven't gotten the oil pump apart yet, but hoping the aluminum bearings did minimal damage. I guess it could have been a lot worse. It was a one hit wonder. Butt dyno said it was making every bit of the 335hp factory rating when it let go.

[WConley]

Oh man!  I'd say you did get away fairly lightly though.  That could have gotten a lot uglier pretty quickly 

Put another quarter in and hit the Start button!  I think most of us have been there in one form or another.  Sorry to see that un-shiny area on that pretty crank!

[Heo]

Oh no, after all the nice work you put in to that engine :'(

[blykins]

Sometimes you do everything as perfectly as you can and things happen that are just out of your control.  Makes you want to puke.

[Barry_R]

Damn shame.
Been "there" and it hurts...
Failure analysis can be very challenging.

Look VERY carefully at the head gasket.  Take a mic to the areas around that cylinder to check for clamp load and look for deformation around the bore compared to the other openings.  Check piston to see if it clamped the second ring tight.  I have had a head gasket do some considerable damage in the past.  If it leaks coolant it can cause the cylinder wall to split since water does not compress.  Starts a daisy chain of failures.

[6667fan]

Man, not happy to see this. What was the sonic beef number on the cracked side of number 7? Or is the thickness moot as the unhappy rod caused the piston to crack the wall?

Was there a typo on 335? There must be at least 535 with the parts you have in that mill.

Sucks

[Nightmist66]

Look VERY carefully at the head gasket.  Take a mic to the areas around that cylinder to check for clamp load and look for deformation around the bore compared to the other openings.  Check piston to see if it clamped the second ring tight.  I have had a head gasket do some considerable damage in the past.  If it leaks coolant it can cause the cylinder wall to split since water does not compress.  Starts a daisy chain of failures.

I did take a good look-see at the head gasket. No visible issue at the fire ring or water ports. Head was welded pretty good with the copper coat. I haven't mic'd the ring yet, but don't suspect a problem there. I will look. Rings were still nice and free. The piston barely dinged the chamber when the bearing gained clearance. Very small mark that will rub right off. No sign of detonation or pre-ignition on the plug or piston. My gut right now is telling me that cylinder just didn't want to play any more.

[Nightmist66]

Man, not happy to see this. What was the sonic beef number on the cracked side of number 7? Or is the thickness moot as the unhappy rod caused the piston to crack the wall?

Was there a typo on 335? There must be at least 535 with the parts you have in that mill.

Sucks

I have to recheck, but 2, 4, 5, and 8 had sleeves already from the first go. I checked the others myself after it was bored .035" over and as I recall, the thinnest point was .135" at the bottom of a cyl. on a non-thrust. Average was .140-.150". The 335hp twas a tid bit of sarcasm. The last time it was together it went 123.5mph @ 3650lbs with a strong head wind. I'd be disappointed if this time it was only making 535. Maybe I'll dyno the next time for a hard number. We'll see.

Everything was fine the weekend prior. Oil was still clean, water was full, etc. Happened all the sudden when it was spun up.

[6667fan]

It’s been awhile but was that an 11.1 pass? If so Wallace calculators formulates 537 flywheel hp. Not an exact science of course and the headwind certainly skews it.

Minimum .130-140 on major thrust sides sounds comfortable

[Rory428]

Just curious, was the "7800-8000 RPM" a misprint? Short of a NHRA Super Stocker, or very high end build, that seems like an awful lot of RPM!  And to think I don`t even like going 6500 RPM.

[Nightmist66]

It’s been awhile but was that an 11.1 pass? 

It was an 11.22. It was the 2nd time to the track with new adjustable rear shocks, less than ideal 50/50's on the front because a new 90/10 failed, and other suspension adjustments to make. So my 60ft was terrible. Ideally, it would have run 10.7 at that mph, but I feel there was more left in it between launch and head wind.

Just curious, was the "7800-8000 RPM" a misprint? Short of a NHRA Super Stocker, or very high end build, that seems like an awful lot of RPM!  And to think I don`t even like going 6500 RPM.

No typo. It has a lot of attention to detail, good clearances, and a healthy stick for a 390 cube engine. Duration is 270+. Of course, the tunnel wedge doesn't mind breathing a little more than a dual plane either. I shifted the last iteration at 7500 comfortably.  Never felt it nose over.

[Nightmist66]

I was able to inspect the deck and head gasket a little more tonight. No sign of compression leaking anywhere on the deck or head. Fire ring on the gasket was checked with a micrometer in at least a dozen or more locations. Variance was only .001" total. Even right across from the water ports. Here's the deck:

[Stangman]

Damb sorry to see this. Going through all the work you put into it it’s hard to swallow. It could have been a lot worse good thing you shut it off.

[Barry_R]

Well - that don't look too bad.  Can probably rule out the gasket.
Wish I had better ideas but starting to look like a sh!t happens" sort of deal...