[hgiv]

I'm going way in here.. and a bit over a guys head.. but... I think the plugs are the most telling. Can't get around that despite all the tranny and timing belt stuff. In order to smash the plugs something had to be in there. The pistons didn't reach them on there own. That would have made quite a bit of noise lol. Also because you had 3 and not one smashed plug we can assume whatever got in there it happened in the intake and was distributed over multiple cylinders. So think stuff rather than "it"? When you dropped rpms vacuum increased. More pull for junk? So next question... if you suddenly smashed 3 plugs what would happen? Might just stop pretty quick. But seize? Not sure about that. Maybe chain reaction into some other part.

Somewhere along the line somebody left some stuff in the intake, carb or heads and it got processed. That made things very unhappy. Thats my guess. Why didn't it happen immediately. Who knows?

I would pull it. Take it all apart and see whats up. At this point what have you got to lose.

[Formulajones]

Sorry to hear about the mishap.

Spark plugs closed says something was floating around.

I'm assuming this thing has flat top pistons in it. The only time I've ever had a piston close a plug gap was with a dome piston.
The last 454 I spun a couple rod bearings in was so bad the piston was smacking the bottom of the cylinder head, and actually marked up the top of the piston. Never touched the spark plugs though, because it had flat tops in it. You would need to have a plug that actually stuck down below the entire combustion chamber for a flat top to touch it, and I've just never seen that.

Most Pontiac builds seem to have either flat tops or dished pistons so my feeling is the plugs weren't closed by the piston itself, but likely some foreign object that got in the combustion chamber. I would expect to see a mark (or 2) on the ground strap from contacting something as well.

[PunchT37]

Originally Posted by Formulajones

Sorry to hear about the mishap.

Spark plugs closed says something was floating around.

I'm assuming this thing has flat top pistons in it. The only time I've ever had a piston close a plug gap was with a dome piston.
The last 454 I spun a couple rod bearings in was so bad the piston was smacking the bottom of the cylinder head, and actually marked up the top of the piston. Never touched the spark plugs though, because it had flat tops in it. You would need to have a plug that actually stuck down below the entire combustion chamber for a flat top to touch it, and I've just never seen that.

Most Pontiac builds seem to have either flat tops or dished pistons so my feeling is the plugs weren't closed by the piston itself, but likely some foreign object that got in the combustion chamber. I would expect to see a mark (or 2) on the ground strap from contacting something as well.

My thoughts too. I would think a piston would hit the head 1`st, and the plug would be further up in the chamber.