exploding rocker arms.

[Malice]

For the past few days I've been installing new 108lb valvesprings and edelbrock headers. It's been kindof a PITA.

I got the car all buttoned up today, and started it up. It ran great...... and then I heard a loud POP followed by loud clattering from under the valvecover. I revved it a few times, and I'd get considerable backfiring felt through my air filter at 1500rpm or above.

I popped the valve covers off, and one of my pushrods had pushed through the top of the rocker arm like a ninja turtle popping his head out of a sewer.

I replaced the rocker arm, and backed all my remaining intake rockers off by 1/4 turn to eliminate anymore backfiring.

The car runs just fine, but the valvetrain clatters like hell and I'm scared to death that another rocker will fall apart while driving. ugh......


Why o' why did I decide to mod my DD?

Furthermore, my headers changed the geometry of my exhaust ever so slightly, and now it buzzes while under load.

[Fixxer99TA]

The buzz you hear is more than likely a small exhaust leak, look into that...

If the rockers are exploding, my guess would be they were improperly adjusted in the first place...

[z rated]

are they stock rockers? how tight did you make them?

[Malice]

The buzz you hear is more than likely a small exhaust leak, look into that...

If the rockers are exploding, my guess would be they were improperly adjusted in the first place...

I would not argue that point for a second. It was my first time adjusting old school rockers, and I'll bet I overtighted that one.


are they stock rockers? how tight did you make them?

They are stock stamped 1.5 rockers. When both pushrods were all the way down for each cyl, I would tighten the rocker nut untill the pushrod was difficult to spin with greasy fingers, and then tighten the nut 1/4 turn further.

[lt1-xjs]

Do a search on how to adjust rockers on a lt1 or sbc after you've pulled all the rockers and checked for bent push rods, hopefully there is no more damage.

[Tyler Wheat]

Maybe this will help you. That shouldn't just be happening randomly. There must have been something wrong when you set the valves to begin with.

http://shbox.com/1/4th_gen_tech2.html#adjust_valves

Correct me if I'm wrong, but the 1/4 turn technique doesn't necessarily apply to factory rockers. I believe it is required that they go a full turn. I'm not 100% on that, I've only messed with roller rockers. Never did set any stock ones. Try the shbox method by finding TDC. Its pretty easy and it worked well for me.

[Malice]

Maybe this will help you. That shouldn't just be happening randomly. There must have been something wrong when you set the valves to begin with.

http://shbox.com/1/4th_gen_tech2.html#adjust_valves

Correct me if I'm wrong, but the 1/4 turn technique doesn't necessarily apply to factory rockers. I believe it is required that they go a full turn. I'm not 100% on that, I've only messed with roller rockers. Never did set any stock ones. Try the shbox method by finding TDC. Its pretty easy and it worked well for me.

I used the shoebox method, I think I just messed it up along the way. I'm really thinking about just getting some 1.6 rollers, hard pushrods, and doing the whole thing over again. I can get my valvecovers off in like 5 minutes now.

Part of the problem is that I have a B-body cam. It is sooo small that I couldn't really tell if I was at TDC on #1 or #6 because the pushrods barely moved when I spun the crank.

[Malice]

http://store.summitracing.com/partdetail.asp?part=PRO%2D66915&autoview=sku

I just ordered those rockers. THey are compatible with the LT1, right? Can I use stock pushrods, or do I need to get a set of hard pushrods?

[Tyler Wheat]

I think you should be fine with the stock pushrods and those rockers look like they will work. You shouldn't have to modify the valvecovers either. I think the only ones you have to modify the valvecovers with is the Pro-Magnums.

[Alex94TAGT]

Can I use stock pushrods, or do I need to get a set of hard pushrods?

Factory 1994 pushrods should be hardened from the factory. Check for a small 'dot' indention along the shank of the pushrod.

For the pushrod to physically turn the rocker into a shish kabab, it would seem to me that there would have to be some amount of mechanical binding going on somewhere (ie, valve possibly kissed a piston, or coil-bind at max lift -- which is unlikely given the small cam). Nonetheless, you should remove the pushrod from that cylinder and check it on a glass table for straightness.

Valve lash on a hydraulic lifter can be tricky since the lifters will bleed off. If the plunger isn't pumped up, you'll end up with a vastly maladjusted valvetrain. If you adjust it once and later find it loose and readjust again, you'll have overtightened the lash. If it was physically hard to turn the pushrods, I'd say you may have overtightened them as well. I adjust only to the point where there's a very slight drag while rotating the pushrod, and no vertical movement -- then give the 1/4 to 3/4-turn lifter preload.

[Tyler Wheat]

:noob:

HAHAHA I couldn't resist, Alex

[1badz]

Factory 1994 pushrods should be hardened from the factory. Check for a small 'dot' indention along the shank of the pushrod.

For the pushrod to physically turn the rocker into a shish kabab, it would seem to me that there would have to be some amount of mechanical binding going on somewhere (ie, valve possibly kissed a piston, or coil-bind at max lift -- which is unlikely given the small cam). Nonetheless, you should remove the pushrod from that cylinder and check it on a glass table for straightness.

Valve lash on a hydraulic lifter can be tricky since the lifters will bleed off. If the plunger isn't pumped up, you'll end up with a vastly maladjusted valvetrain. If you adjust it once and later find it loose and readjust again, you'll have overtightened the lash. If it was physically hard to turn the pushrods, I'd say you may have overtightened them as well. I adjust only to the point where there's a very slight drag while rotating the pushrod, and no vertical movement -- then give the 1/4 to 3/4-turn lifter preload.


All 93's had hardened pushrods, only a select few 94's and 95's had hardened pushrods.

[1badz]

http://store.summitracing.com/partdetail.asp?part=PRO%2D66915&autoview=sku

I just ordered those rockers. THey are compatible with the LT1, right? Can I use stock pushrods, or do I need to get a set of hard pushrods?

Two of my friends bought those and did a great valve adjustment and they both enialated the rockers. Don't go cheap on valvetrain

[NicksTAgt]

All 93's had hardened pushrods, only a select few 94's and 95's had hardened pushrods.

Wow, never heard of that before, I will probably still replace mine when I do my cam swap but thats good to know.

[Tyler Wheat]

Two of my friends bought those and did a great valve adjustment and they both enialated the rockers. Don't go cheap on valvetrain

I ran those on my old LT1 truck for a couple of years without any problems. I bought them used from a friend and he never had any problems out of them. Just have to set them and check them from time to time to make sure everything is in check and I don't think you'll have any problems.

[Adam]

Lol "one of my pushrods had pushed through the top of the rocker arm like a ninja turtle popping his head out of a sewer."

[Alex94TAGT]

All 93's had hardened pushrods, only a select few 94's and 95's had hardened pushrods.
All of the 1993 and 1994's had hardened pushrods from factory, as well as some of the early 1995 models. GM part number 10046173. They were heat-treated (hardened) because GM originally had them in earlier engines using guideplates, supposedly.

Regardless, you can buy new hardened pushrods from Comp for under $40. No big deal...

[Malice]

Jesus H. Christ I can't believe how much of a pain in the ass this has been. The valvetrain has been clattering loudly all week. I got my roller rockers today, and tried to install them using METHOD 1 on shoebox's website.

The numbers he has listed don't match up at all with my engine. When # 1 is at TDC, only about half of the valves are closed like thier supposed to be. When I turn the crank 360*, only about half the valves move the way they're supposed to.

I started the car with the valvecovers off to make final adjustments. I still had a tick noise on the passenger side. I tried tightening each rocker a little, and I ended up bending the hell out of a pushrod.

A friend of mine is gonna go out and get me a new set of pushrods, but I'm stranded until then.

[1badz]

Jesus H. Christ I can't believe how much of a pain in the ass this has been. The valvetrain has been clattering loudly all week. I got my roller rockers today, and tried to install them using METHOD 1 on shoebox's website.

The numbers he has listed don't match up at all with my engine. When # 1 is at TDC, only about half of the valves are closed like thier supposed to be. When I turn the crank 360*, only about half the valves move the way they're supposed to.

I started the car with the valvecovers off to make final adjustments. I still had a tick noise on the passenger side. I tried tightening each rocker a little, and I ended up bending the hell out of a pushrod.

A friend of mine is gonna go out and get me a new set of pushrods, but I'm stranded until then.

There's a Book along the lines of "rebuilding the LT1/LT4 engine" and it has a real good valve adjustment guide on there. I use that method every time with great results.

[Alex94TAGT]

Jesus H. Christ I can't believe how much of a pain in the ass this has been. The valvetrain has been clattering loudly all week. I got my roller rockers today, and tried to install them using METHOD 1 on shoebox's website.

The numbers he has listed don't match up at all with my engine. When # 1 is at TDC, only about half of the valves are closed like thier supposed to be. When I turn the crank 360*, only about half the valves move the way they're supposed to.

I started the car with the valvecovers off to make final adjustments. I still had a tick noise on the passenger side. I tried tightening each rocker a little, and I ended up bending the hell out of a pushrod.

A friend of mine is gonna go out and get me a new set of pushrods, but I'm stranded until then.

Well, it's clear you are over-tightening the lash if you're bending pushrods as you adjust.

I actually don't recommend using his "Method 1" -- ie, adjusting all valves at two crank positions. Especially with larger cams, that can get you into trouble. Just the same, I practically never adjust with the engine running, but some swear by it.

Try this:

I start by putting the transmission in neutral and removing the #1 cylinder spark plug. Under the car, put your thumb over the #1 spark plug hole in the cylinder head, and turn the engine over with the other hand. When you feel air rushing past your thumb, the piston is on it's upward compression stroke (both valves should be closed - lifters down). When the air just stops rushing past your thumb, you'll feel the piston reach the top of its travel (turning the crankshaft by hand will get to an 'easy spot'). You can then adjust both the #1 intake and exhaust valves.

From that point, you can put a mark at 12:00 on the crank pulley with whiteout. Turn the crank 90-degrees clockwise (to 3:00) and adjust both valves for cylinder #8.

Just keep turning the crank 90-degrees and follow the firing order until you're done. 1-8-4-3-6-5-7-2. It'll take two rotations of the crankshaft to adjust all valves.

And again, don't over-tighten. The instant you feel a slight drag on the pushrod as you spin it between your index finger and thumb, that's zero lash. Give your preload and don't touch it again.

[Malice]

Well, it's clear you are over-tightening the lash if you're bending pushrods as you adjust.

I actually don't recommend using his "Method 1" -- ie, adjusting all valves at two crank positions. Especially with larger cams, that can get you into trouble. Just the same, I practically never adjust with the engine running, but some swear by it.

Try this:

I start by putting the transmission in neutral and removing the #1 cylinder spark plug. Under the car, put your thumb over the #1 spark plug hole in the cylinder head, and turn the engine over with the other hand. When you feel air rushing past your thumb, the piston is on it's upward compression stroke (both valves should be closed - lifters down). When the air just stops rushing past your thumb, you'll feel the piston reach the top of its travel (turning the crankshaft by hand will get to an 'easy spot'). You can then adjust both the #1 intake and exhaust valves.

From that point, you can put a mark at 12:00 on the crank pulley with whiteout. Turn the crank 90-degrees clockwise (to 3:00) and adjust both valves for cylinder #8.

Just keep turning the crank 90-degrees and follow the firing order until you're done. 1-8-4-3-6-5-7-2. It'll take two rotations of the crankshaft to adjust all valves.

And again, don't over-tighten. The instant you feel a slight drag on the pushrod as you spin it between your index finger and thumb, that's zero lash. Give your preload and don't touch it again.

I'd had it with shoebox's "method 1", so I was going to use your method to finish the install today. It was raining though, and I didn't want to crawl under the car every few minutes and get my back wet. I came up with my own "method" and it seemed to work very well.

I removed all the rockers and held a credit card over the intake/ex pushrods of a cylinder. If the credit card was level, then both valves were closed. My logic was that both valves on a single cyl would not be open the exact same height at the exact same time. The pushrods would only be level if the valves were both closed.

I tightened the nut on the rocker until I felt drag on the pushrod, and then I tightened the nut an additional 1/2 turn, then tightened the polylock. When both rockers were done on a cyl, I'd move on to another. When I needed to level a set of pushrods, I would bump the starter for an instant. It was a really fast way to work, and the car runs fine now.

The valvetrain is a little noisier than it was stock, but I'm assuming that is due to the stiffer valvesprings.

[Alex94TAGT]

I'd had it with shoebox's "method 1", so I was going to use your method to finish the install today. It was raining though, and I didn't want to crawl under the car every few minutes and get my back wet. I came up with my own "method" and it seemed to work very well.

I removed all the rockers and held a credit card over the intake/ex pushrods of a cylinder. If the credit card was level, then both valves were closed. My logic was that both valves on a single cyl would not be open the exact same height at the exact same time. The pushrods would only be level if the valves were both closed.

I tightened the nut on the rocker until I felt drag on the pushrod, and then I tightened the nut an additional 1/2 turn, then tightened the polylock. When both rockers were done on a cyl, I'd move on to another. When I needed to level a set of pushrods, I would bump the starter for an instant. It was a really fast way to work, and the car runs fine now.

The valvetrain is a little noisier than it was stock, but I'm assuming that is due to the stiffer valvesprings.

Whatever works -- glad you got 'er running. One other small tip -- sometimes it helps to slightly tighten the poly-lock BEFORE the preload is set. This makes the poly-lock very tight, in hopes that the rockers wont loosen up over time. However, if you have a socket wrench with allen sockets, that'll get the job done too. The little hand-held allen wrenches just don't let you get a lot of torque...

If you installed roller rockers, those are actually the cause of increased valvetrain noise. It was for this reason that the LT4 engine supposedly received a 'de-sensitised' knock module within the PCM (since the LT4 engine came with roller tipped rockers from factory). A lot of guys buy the LT4 knock module in hopes of eliminating false knock, but I didn't notice any difference in knock retard between it and stock LT1.

[Malice]

I always figured the rollers would be quieter since they don't have to slide around on a ball pivot. Good to know.