Lost a valve on the #8 cylinder....bad day Buick fans!

Look into the spring bind potential problem but miles do eventially come into play in a HP situation. A good reason to have correctly installed dual springs if the cam warrents it. What cam was in it and was it damaged or worn at all? I can't say I have Bruno's eye but I would definitely check how much preload when rebuilding. Maybe get adjustable lifters or correct length ones especially with block/head milling.

A bent exhaust pushrod or broken rocker or even broken shaft at the end between the intake and exhaust can cause havoc with the matching intake valve spring/retainer/rocker/pushrod because when the exhaust valve stops opening the intake valvetrain is under extreme pressure to open up because the exhaust pressure is not being released.

 

Engine is back from the machine shop. Time to assemble. Should be ready for a spring cruise.

 

More progress. Just need to clean the oil pan and timing cover and I'm ready to paint.

 

Good luck with the build, install, and start up.

 

Did the break in yesterday. It went well. Hoping to be back on the road for the 1 year anniversary. Still a few things to button up.

 

Looking great!!

 

DISCLAIMER: I am an internet mechanic. After about 400 miles on the rebuilt engine, I attempted a burnout on Easter Sunday (4/4/2021) and heard something pop. Damn! Shut it off and towed it home. I discovered the #3 spark plug gap had been closed by something. Turns out it was a chunk of aluminum from that piston! Oops! Took it apart, cleaned up the block/valves/intake, replaced lifters/pushrods/pistons/rings/gaskets. I believe this was an issue with detonation, so I focused on the distributor and intake gasket. I also noticed all four intake manifold bolts were slightly more than finger tight (when I disassembled the engine), even though I torqued them to 55 FT LBS during the installation of the metal valley pan gasket. Replaced the bushing to limit mechanical advance with a bronze bushing from a Mr. Gasket kit. I swapped out the Mallory points conversion for a Pertronix III with a rev limiter (don't have a dash tach).

Mechanical advance is now known at 21 degrees. Vacuum advance has been blocked for now, but I do have that limited to 10 degrees with an add-on stop. During previous attempts to document the advance on the distributor, I stopped at about 4,000 RPM. I have since found that the springs were very stiff and I was still getting some additional advance all the way up to 5,400 RPM. Today I'll play with the springs in the Mr. Gasket kit to see if I can get the full mechanical advance "all in" by the 2,000 - 2,500 range.

These were cast (10-1) pistons from TA with the no-file rings.

Anything else I should be checking this time around?

 

I’m not understanding what yer saying, a chunk of the new piston?
A chunk of the old piston?

 

Certainly you replaced all eight pistons when you did the refresh?? The broken piston in your picture looks like it has 100,000 miles on it(?!) something doesn’t add up here...,.,...

Steve weim55 Colorado

 

Yes. A chunk of the new piston(s) I installed in January / February of 2021 cracked after 400 miles. Started over in May of 2021 with 8 new (again) cast pistons. If there is a silver lining, I know way more about the inside of the BBB than I used to.

 

Yes. A chunk of the new piston(s) I installed in January / February of 2021 cracked after 400 miles. Started over in May of 2021 with 8 new (again) cast pistons. I'm hoping what doesn't add up was my attention to the distributor advance after the the Jan/Feb 2021 rebuild.

 

Hope it goes better for you on this round

 

If it wasn't for bad luck you wouldn't have any luck, hopefully it gets better down the road!

Bob H.

 

If your going to persist with that cast piston, then you must accurately calculate your static and dynamic compression ratios, to insure that your within the window for pump gas. Timing is a factor of course, but as bad as that looks, that was not just a couple of detonation hits during a burnout. While the burnout was the straw that broke the camels back, they usually had to sustain detonation over a period of time to break like that.. all pistons will break under detonation.. Forged pistons last alot longer, and let you get away with tuning errors.

Cast pistons are not resistant to detonation, and your piston there is a classic example of how they break the lands off. The other way that happens is if the rings butt together.. this will also pop off the top of a cast piston. Ring end gap on the top ring should have been .019-.022.

Was it?

JW

 

Have you checked you balancer to make sure it has not spun on the hub? I would make sure to check to see the timing mark is in the correct place. It could cause you to be setting the timing wrong.

 

Help me out with "all four" intake bolts. There are more than 4, correct? So, 4 were found to be loose on disassembly?

Did you lube them? If so, with what? Did you torque them in a sequence similar to what is shown below? Did you torque them in increments like snug, 20 ft/lbs, 40 ft/lbs and then final? Did you do a final "circle" torque @ 55 after torqueing in a pattern?

 

7 of the 8 cylinders had an 0.020" ring gap and one was 0.021". I went about 1" down into the bore to check. I was using a formula based on gap inches * bore diameter, but 0.020" was where these checked out.

 

Bolts at 1, 2, 3, 4 positions were "loose" upon disassembly. I used new ARP bolts with their lubricant. Bolts at 5-12 positions were still "tight" upon disassembly. On my second time around (May, 2021), I did torque all the bolts according to the pattern shown in your picture and in increments (not the ones you listed, but similar). I definitely noticed that it took several tries to hold a 55 ft/lbs setting.

 

I started with a "new" balancer from Damper Dudes. I don't have a dial indicator to know with 100% accuracy, but the #1 piston was at TDC when the damper mark was at "0" on the timing cover. I also replaced the timing chain during the January, 2021 rebuild.

 

After putting around 700 miles with short trips on this engine after my 2nd set of pistons, I drove 500 miles straight from Michigan to middle Tennessee (new work location). I brought every tool I had in a "support vehicle" driven by my daughter. Other than having to stop for an initial fill up and four more stops for gas, I had no problems on the trip! (12.5 MPG with a BBB bored 0.040" over and a 3.42 rear gear) Other than my father driving this car from Year One in Georgia to Michigan in 1986 and from Michigan to Bowling Green in 1987, this is the farthest this car has gone.