lt1camaroman93

well i found out today that i didn't lose the bottoem end. When we started the eingine for the fist time in the begining of the week we heard a slight chatter.. thought it to be a little loose rocker or something.. I have open long tubes also so you can't hear much of anything.. Well when i pulled the heads off today, every single cylinder had a butt load of metal chunks in them. I found an exausht valve on teh number 3 cylinder broken of and it looked like it was in there bouncing around for a good amount of time, long enought to almost wear a whole through the piston, and make enought metal shavings to get into every last cylinder. They were in the intake also.. So my guess is the valve broke and with how loud the car is we didnt really hear it that well.. Then on the one rev the piston smashed teh valve into the head and couldn't finish the rest of the movement hense the reason i couldn't turn it over. with the heads off the engine spins quite nicley. a few of the cylindes were filled with oil also. So i am just buying a stock long block and going from there. I wish i knew what caused the valve to break.

Derrick Redd

Stock LT1 shortblock. I've put mine through some serious abuse and it still pulls the wheels. Try not to rev so high in neutral next time.

lt1camaroman93

As i stated in the last reply.. It wasn't the rotating assembly that gave up.. it was a stock exausht vavle that broke and just bounced around in the cylinder.

Derrick Redd

I read your post. I know your stock shortblock is fine. That was my point. A stock LT1 shortblock is pretty damn strong. Mine is pulling near 126 mph traps and is still in one piece.

Momar

Unfortunately I have heard that is a comon problem with the pontiac motors. I heard this from my friends dad when he cam out to check out my brothers car in which he has spun some sort of bearing. It is a 79 Trans AM SE with the pontiac 400.

Ben

KyleMailman

Dark Gray green metallic.... one of 4,350... nice! I have one the same color!

Dr.Mudge

All I know, is with a TH400 and who knows what rear gear (2.73?) 130 MPH to work every day was pushing my luck, and my luck ran out after awhile. It was 3am so I saw no more than 3-4 cars on the way there, for those who would like to chap my hide.

If your valve springs are weaker than they should be (incorrect spring height, or old) then they will not be able to close fast enough, this is the valve float you experienced.

For valve springs that are marginal for the cam/rocker ratio they are setup with, you unfortunately have to be carefull with RPM and they should be repalced more often than if you had a bit more headroom with the springs. If you have .595 lift on the exaust and .600 lift springs, thats not alot of safety margin.

Momar

Thats about how fast my brother was going. I believe his has 2.56 gears or something crappy like that, but at least the motor had torque. Unfortunately his didnt last long after he got it. Hopefully he will be able to afford to get it rebuilt soon. I was told that these motors didnt do well with sustained rpms because of their oiling systems.

Ben

phoenix64

Would it be the vibration that causes damage when you rev in neutral? Strange side note. I have a 90 jeep 4.0L that gets rough if you go above 3000rpm in any gear if you're at part throtle. But it is smoth all the way to 5500 if the pedal is to the floor, and the engine is under a heavy load. Maybe it just the 150,000 miles.

Dr.Mudge

My gut feeling says the crank is going to look ugly when not under a load and revving high, I think maybe a form of crank float along the bearings and oscillation from front/rear, but who knows. If thats true though that would account for an effect like rod stretch, which could also punch a piston.

If valve springs are 150k miles old, they will not take high RPM safely, and these things can happen, and do. This happened to one of my dads cars about 10 years ago, that at the time was about 15 years old. One valve hit a piston and punched a whole in the piston and broke the valve.

lt1camaroman93

I hope my vlave springs aren't to weak.. They are the crane cams dual spring.. i can't remeber the part number but there supposed to be good up to .600 lift and i only have maybe at tops 7-800 miles on them.

lt1camaroman93

Here are a few pics of some stuff that went wrong. Just click the link that says broken parts. http://www.angelfire.com/freak2/crawlinz/index.html

Joe Brodman

I've spun my stock shortblock to 7200 a couple times under load.

Not under load....dunno, 6500 I guess. With a stick car, when running N/A when you don't have enough gearing (car is set up to run best on the spray, not N/A), you gotta rev her pretty high when you drop the clutch to get out of the hole well. When I was internally stock, I'd do 6000RPM WOT clutch dumps off of the MSD rev limiter; THAT was fun.