LT1 an "interference" engine?

[Malice]

Are the valves and pistons on an LT1 able to hit eachother if a valve were to float or something? Is there proper clearance in the engine with the stock cam, or would there be damage?

EDIT: the title says "and", when it's supposed to say "an". sorry.

[my95z28]

go to edit, then go advaced and you can edit your title

[Fastbird]

Edited. And yes, if you start floating valves, you run the risk of creating valve reliefs or worse. Not as prone as the big brother, but it can still happen.

[Alex94TAGT]

The LT1 is supposed to be a non-interference engine. That is, if the timing chain were to break and the camshaft/valves froze in position, the pistons should not make contact with the valves. That would naturally be a worse scenario than 'valve float'.

It seems that all the cases of bent valves I've seen on the forums over the years have been on cars with aftermarket camshafts or rotating assemblies. Though, it wouldn't surprise me if someone has managed to bend valves on the stock setup. People manage to do everything...

[Malice]

The reason I asked was due to my own dumb mistake. I was installing 1.6 RR's yesterday, and when I started the car, one of them was making a really loud tick. I tightened the nut a little more. It continued to tick. I tightened the nut more... it continued to tick.

I tightened the nut MORE, and the rocker came dislodged from its position. I shut off the motor and found that I had bent the everloving shit out of that pushrod. It looked like a "S".

I was afraid that the piston had smacked the valve, bent it, and bent the pushrod.

I got new pushrods, installed them, and then installed my RR's. The engine runs just fine, with no audible tick. The valvetrain is a little louder than it was stock, but I attribute that to my new, stiff valvesprings. No single cylinder is making a loud noise.

I'm guessing I got off really lucky, and I won't be modding an unfamiliar engine again without someone assisting me who has some experience.

[Malice]

I spoke too soon. The engine ticks like hell on the passenger side. The engine is down on power. When I goose the throttle at low RPM, it stumbles and then barely accelerates. At high RPM it doesn't seem to stumble, but it doesn't seem to have full power.

[Z28pr0jekt]

I spoke too soon. The engine ticks like hell on the passenger side. The engine is down on power. When I goose the throttle at low RPM, it stumbles and then barely accelerates. At high RPM it doesn't seem to stumble, but it doesn't seem to have full power.

you might have adjusted the valves too tight

[Malice]

If the valves were too tight, would that make it tick loudly? I thought it would just make it backfire and whatnot on acceleration.

[1badz]

They're probably too loose if they are ticking. Re-do the entire valve adjustemnt (takes like 15 min) and make sure you do it right and make sure each required piston is at TDC before tightening down the rockers. Use the rocker adjustment guide in "How to Rebuild Small-Block Chevy Lt1/Lt4 Engine" book. I've always used it with no failure.

[Z28pr0jekt]

They're probably too loose if they are ticking. Re-do the entire valve adjustemnt (takes like 15 min) and make sure you do it right and make sure each required piston is at TDC before tightening down the rockers. Use the rocker adjustment guide in "How to Rebuild Small-Block Chevy Lt1/Lt4 Engine" book. I've always used it with no failure.

yea sorry brain fart, too loose lol

[Alex94TAGT]

Malice,

Herein lies the problem with having two threads regarding the same issue. You tried tightening until the clicking went away, and you wound up with bent pushrods, and now we're going in circles trying to help -- leading you in the wrong direction.

If you aren't sure what you were doing, you should research it fully before ever starting the engine again. I fear you may be causing more serious internal damage to your engine by continuing on this path -- damage to pistons, valves, lifters, or even cam bearings.

Others may have different advice, but if it were my engine, these would be my thoughts:

1) It's still possible that your valvetrain is still maladjusted, as your method of adjustment has been a little haphazard up to this point.

2) The 'ticking' noise you hear could be a collapsed lifter due to the mechanical binding / bending of the pushrods. Further, you may have damaged the lifter roller that rides along the camshaft. If it were me, I'd take off the intake, remove the lifters and inspect them all.

3) Again, you've had mechanical binding either through coil bind of the valvespring or through pistons hitting valves. The factory pistons are hypereutectic aluminum alloy, which is quite brittle. You can either dish out the money for a bore-o-scope, or you can run a compression and/or leak-down test to verify that your pistons and valves are ok.

Not trying to be mean or to scare you, I'm just trying to prevent you from getting into further trouble here. If only you lived closer to Kansas, I'd drive over and try to help...

[Malice]

They're probably too loose if they are ticking. Re-do the entire valve adjustemnt (takes like 15 min) and make sure you do it right and make sure each required piston is at TDC before tightening down the rockers. Use the rocker adjustment guide in "How to Rebuild Small-Block Chevy Lt1/Lt4 Engine" book. I've always used it with no failure.

I'm pretty interested in reading that book. Unfortunatley, I had to fix my valvetrain today, and I would have to order the book and wait for a few days for it to arrive.


Malice,

Herein lies the problem with having two threads regarding the same issue. You tried tightening until the clicking went away, and you wound up with bent pushrods, and now we're going in circles trying to help -- leading you in the wrong direction.

If you aren't sure what you were doing, you should research it fully before ever starting the engine again. I fear you may be causing more serious internal damage to your engine by continuing on this path -- damage to pistons, valves, lifters, or even cam bearings.

Others may have different advice, but if it were my engine, these would be my thoughts:

1) It's still possible that your valvetrain is still maladjusted, as your method of adjustment has been a little haphazard up to this point.

2) The 'ticking' noise you hear could be a collapsed lifter due to the mechanical binding / bending of the pushrods. Further, you may have damaged the lifter roller that rides along the camshaft. If it were me, I'd take off the intake, remove the lifters and inspect them all.

3) Again, you've had mechanical binding either through coil bind of the valvespring or through pistons hitting valves. The factory pistons are hypereutectic aluminum alloy, which is quite brittle. You can either dish out the money for a bore-o-scope, or you can run a compression and/or leak-down test to verify that your pistons and valves are ok.

Not trying to be mean or to scare you, I'm just trying to prevent you from getting into further trouble here. If only you lived closer to Kansas, I'd drive over and try to help...

I understand what you mean. I've kinda been shitting up the tech section with my worries. I know better than to mod my only means of transportation, but I let my powerlust get away from me this time.

I've done this work before, but it's been along time. I thought I remembered more than I did. At any rate, I pulled the covers off yet again and I found one loose rocker. I tightened it up and the car runs great.

My method was half-assed, but the textbook procedures I was trying to adhere to were not working. New rule: never work on an unfamiliar engine alone!

[lethal93ta]

I agree with alex 100% on this I was going to make the same post till I read his. this is what can happen when something in the valvetrain goes bad I had valve float on mine.
http://www.streetlethal.net/boom/1.jpg
http://www.streetlethal.net/boom/2.jpg

[Z28pr0jekt]

I hope you have polylocks on the top of those rockers and not just nuts... did you make sure to lock the polylocks?

[Biggin'89]

i would suggest a leakdown test while your rockers are off. its fairly simple and will tell you quite a bit of information.

and patients is key, take your time and don't get in a rush. thats how things get forgotten or only partially done.

[Malice]

Wow. That bent valve is crazy. How much noise did that make when it happened?

Thanks for all the help everyone, I got my valvetrain all sorted out and the car has alot more power now.

[lethal93ta]

id didnt make any the power just dropped off and I could barly keep it running.

[1994Z28Lt1]

i do believe the stock LT1 is an interference engine, even though the stock pistons have "so called" "valve reliefs" if a valve is wide open when it shouldn't be i would say you'd definitely be looking at a bent valve