Advanced timing ****ed my pistons

[TJ1978]

Labor will kill you, especially tracking down a noise. I’d do all the trouble shooting you can. Idle seems high, drop it lower to like 750 or 650 if you can so, drop the belts.

You can also get stethoscope and listen, or pull valve covers one a time and run it.
I had a horrible engine experience but I wont high jack your thread. Best bet get a chevy manual take video.

 

[Russell]

That engine sound does not sound like it has serious mechanical damage to me. Usually the clacking noise of a failed bearing or broken piston hammering away comes through very clearly on a phone's mic. Your sound is too fast to be bottom end. I'm guessing you either have a solid exhaust leak or a broken / loose valve train component. All of which are easy to troubleshoot and repair. The fact that the noise goes away when the engine warms up points me more towards an exhaust leak. Check your headers / manifolds at the heads and look for black carbon scoring where the exhaust is leaking out. You should be able to hear the noise quite clearly when the engine is cold. It does not cost anything to take a 9/16 wrench to the exhaust bolting into the head and tighten it up when the engine is warmed up and the bolts are expanded due to heating up. It may very well fix your issue outright.

If you cannot find any exhaust leaks, valvetrain would be my next guess. Take a long screwdriver and put the handle to your ear and the driver to your valve covers. See if the noise is coming through clearly to your ear and slowly move up and down the valve cover on each side to see if the noise is louder in one specific spot or not. If it is, then take a 7/16" socket and remove the valve cover above the sound. There will be 8 rocker arms under each side, make sure that none of them are loose, have a cracked valve spring or have a rocker arm stud that is being pulled out of the head (they are just pressed in, not threaded in factory heads).

Cast pistons can rattle when they are cold as they expand at a different rate than the engine block does so clearances can get too big and allow the piston to rattle. This one of the nice things about hypereutectic pistons - They are designed to expand at the same rate as the engine block which prevents the excess clearance and rattling sound. Piston rattle (or piston slap) is usually not an overly big deal for your engine as long as you let it warm up a bit before you start to put any real load on the engine. I've taken plenty of LS engines apart which rattled like crazy when cold started and could find no visible evidence of it after disassembly.

If you are truly unable / unwilling to troubleshoot your engine by yourself - I would find a different shop. North American made engines are not the same as local European stuff. They probably have never seen a small block chevy engine before and are grasping at straws. I'd take it to a couple different places and get them to check it out and diagnose it before you take it anywhere. If they all come up with the same diagnosis then I'd feel better about taking it somewhere but I am going to guess every place gives you a different answer.

Again - We can help you sort this out on your own. I am sure that it's a little more difficult to get parts and tools as you can't just run down to your next door autozone or harbour freight for tools but if you have the will, there is definitely a way.

 

[tRustyK5]

There needs to be a "Double like" button IMO.

 

[gonefishin]

If you ruined a piston from the timing you would have serious blowby. Have you pulled the oil cap while engine is running? I didn’t read everything here.

also a stethoscope would be your best friend. I don’t think you have major engine damage

 

[wasted wages]

As I stated above, the first thing I would do is drop all of the drive belts to rule out something in the accessories... remove the cover on the torque converter. set the emergency brake, block the wheels.

Start the engine and get it off of fast idle.
It's not going to hurt anything to run the engine for a few minutes with the belts off.

Then slowly move around the engine, and slide under the truck with a flashlight and look at the flexplate and torque converter.
See if there is any excessive noise or vibration underneath....

Look and listen for exhaust leaks, etc.
rule out the simple things first. Your truck is talking to you... you should be able to figure out the general area the noise is coming from...

 

[Chevy305]

My money is on a loose rocker arm. Pull the valve covers and adjust the rocker arms. Plenty of YouTube videos with the step by step instructions to walk you through it.

 

[campfire]

I wish I had the tools and a shop to undertake my own rebuild but I do not.
...
You sound super knowledgeable. I would expect this information from an engine shop.
...
I suppose if I was more knowledgeable I could do more investigating. I am at the mercy of the motor shop that will be looking at my knocking motor.
...
I agree it's best to do it yourself, but I am not very knowledgable.

I'm detecting a theme here. But knowledge comes from learning about your truck and your engine. None of us were born with it, it's learned along the way. This adventure is a chance for you to learn, and by doing so you will gain the knowledge you currently wish you had.

 

[TJ1978]

You could at best just have your idle too high.
What is cold idle rpm? What does it kick down when you stomp the gas pedal, it should go down about 200-300 rpm. Idle will depend on cam/engine as well.

Check your oil for gas smell as well.

Get screw driver or stethoscope, unhook belts, fire it up and listen with screw driver or stethoscope.
You will feel and hear where the noise is. I would exhaust all suggestions here before dumping a few grand on and engine.

It takes time, Im learning as well. We all are. These trucks are fun and can be very finicky even in perfect weather.

 

[red EOD]

If you ruined a piston from the timing you would have serious blowby. Have you pulled the oil cap while engine is running? I didn’t read everything here.

This, it's a quick and easy check that doesn't require tools. Pull the oil fill cap like he mentioned with the engine running and record the blowby gasses coming up/out. There will always be some (especially on a cold start before the metal parts have expanded).

 

[TJ1978]

Also its not a deep sound. From the vid it’s consistent and sounds higher up... check ye rockers dear Swede..

Remember if nothing goes wrong, you dont learn anything.

 

[Kyle1983]

Yes it will fit. That said you will need a new flex plate and dampener and intake manifold, possibly have to modify some accessory bracks for the new 350 ho.
The 350 ho has vortec heads and an internal balance crank your motor has gen1 heads and an external balance crank

So it's basically use a 350/290 block? The basic GM 350 block if I want it to match up?

 

[Kyle1983]

This, it's a quick and easy check that doesn't require tools. Pull the oil fill cap like he mentioned with the engine running and record the blowby gasses coming up/out. There will always be some (especially on a cold start before the metal parts have expanded).

I can do this. Seems very easy. What will this tell me or not tell me?

 

[Kyle1983]

Labor will kill you, especially tracking down a noise. I’d do all the trouble shooting you can. Idle seems high, drop it lower to like 750 or 650 if you can so, drop the belts.

You can also get stethoscope and listen, or pull valve covers one a time and run it.
I had a horrible engine experience but I wont high jack your thread. Best bet get a chevy manual take video.

I'm 700 dollars into mostly labor and some spark plugs, and I promise they don't know half of what you guys do.

 

[Kyle1983]

That engine sound does not sound like it has serious mechanical damage to me. Usually the clacking noise of a failed bearing or broken piston hammering away comes through very clearly on a phone's mic. Your sound is too fast to be bottom end. I'm guessing you either have a solid exhaust leak or a broken / loose valve train component. All of which are easy to troubleshoot and repair. The fact that the noise goes away when the engine warms up points me more towards an exhaust leak. Check your headers / manifolds at the heads and look for black carbon scoring where the exhaust is leaking out. You should be able to hear the noise quite clearly when the engine is cold. It does not cost anything to take a 9/16 wrench to the exhaust bolting into the head and tighten it up when the engine is warmed up and the bolts are expanded due to heating up. It may very well fix your issue outright.

If you cannot find any exhaust leaks, valvetrain would be my next guess. Take a long screwdriver and put the handle to your ear and the driver to your valve covers. See if the noise is coming through clearly to your ear and slowly move up and down the valve cover on each side to see if the noise is louder in one specific spot or not. If it is, then take a 7/16" socket and remove the valve cover above the sound. There will be 8 rocker arms under each side, make sure that none of them are loose, have a cracked valve spring or have a rocker arm stud that is being pulled out of the head (they are just pressed in, not threaded in factory heads).

Cast pistons can rattle when they are cold as they expand at a different rate than the engine block does so clearances can get too big and allow the piston to rattle. This one of the nice things about hypereutectic pistons - They are designed to expand at the same rate as the engine block which prevents the excess clearance and rattling sound. Piston rattle (or piston slap) is usually not an overly big deal for your engine as long as you let it warm up a bit before you start to put any real load on the engine. I've taken plenty of LS engines apart which rattled like crazy when cold started and could find no visible evidence of it after disassembly.

If you are truly unable / unwilling to troubleshoot your engine by yourself - I would find a different shop. North American made engines are not the same as local European stuff. They probably have never seen a small block chevy engine before and are grasping at straws. I'd take it to a couple different places and get them to check it out and diagnose it before you take it anywhere. If they all come up with the same diagnosis then I'd feel better about taking it somewhere but I am going to guess every place gives you a different answer.

Again - We can help you sort this out on your own. I am sure that it's a little more difficult to get parts and tools as you can't just run down to your next door autozone or harbour freight for tools but if you have the will, there is definitely a way.

I am not back to the vehicle for about a week. I will absolutely begin troubleshooting. I am not lazy. I have a set of american sockets. I will make a list of everything that you guys have mentioned on here and go down the list. Of course I will start with the simplest stuff first. Its possible with a newly built motor that something has become lose and needs a simple tightening.

 

[Kyle1983]

There needs to be a "Double like" button IMO.

Agreed. Double like all the help from everyone.

If you ruined a piston from the timing you would have serious blowby. Have you pulled the oil cap while engine is running? I didn’t read everything here.

also a stethoscope would be your best friend. I don’t think you have major engine damage

I will pull the oil fill cap and take a look while the engine is running.

As I stated above, the first thing I would do is drop all of the drive belts to rule out something in the accessories... remove the cover on the torque converter. set the emergency brake, block the wheels.

Start the engine and get it off of fast idle.
It's not going to hurt anything to run the engine for a few minutes with the belts off.

Then slowly move around the engine, and slide under the truck with a flashlight and look at the flexplate and torque converter.
See if there is any excessive noise or vibration underneath....

Look and listen for exhaust leaks, etc.
rule out the simple things first. Your truck is talking to you... you should be able to figure out the general area the noise is coming from...

I will do this. Thanks again for the help

My money is on a loose rocker arm. Pull the valve covers and adjust the rocker arms. Plenty of YouTube videos with the step by step instructions to walk you through it.

The shop checked them and said it was ok. I can check myself.

I'm detecting a theme here. But knowledge comes from learning about your truck and your engine. None of us were born with it, it's learned along the way. This adventure is a chance for you to learn, and by doing so you will gain the knowledge you currently wish you had.

I am going to start checking everything. Nothing but time and tools.

You could at best just have your idle too high.
What is cold idle rpm? What does it kick down when you stomp the gas pedal, it should go down about 200-300 rpm. Idle will depend on cam/engine as well.

Check your oil for gas smell as well.

Get screw driver or stethoscope, unhook belts, fire it up and listen with screw driver or stethoscope.
You will feel and hear where the noise is. I would exhaust all suggestions here before dumping a few grand on and engine.

It takes time, Im learning as well. We all are. These trucks are fun and can be very finicky even in perfect weather.

I am actually looking forward to learning alot.

This, it's a quick and easy check that doesn't require tools. Pull the oil fill cap like he mentioned with the engine running and record the blowby gasses coming up/out. There will always be some (especially on a cold start before the metal parts have expanded).

I will check this

Also its not a deep sound. From the vid it’s consistent and sounds higher up... check ye rockers dear Swede..

Remember if nothing goes wrong, you dont learn anything.

I'm an American. They checked rockers but came up with nothing. I guess I will have to check.

 

[Kyle1983]

I will make a list of everything I need to check based off what everyone has told me. I will go 1 by 1 down the list and take pictures and videos until we get this problem narrowed down or fixed. Worse case scenario will be an engine teardown.

 

[campfire]

I will make a list of everything I need to check based off what everyone has told me. I will go 1 by 1 down the list and take pictures and videos until we get this problem narrowed down or fixed. Worse case scenario will be an engine teardown.

Now we're talking!

I'm 700 dollars into mostly labor and some spark plugs, and I promise they don't know half of what you guys do.

Keep that in mind when they quote you 15 gazillion Krona for an engine swap. If it's not something they're used to working on, they're probably not the right guys for the job.

I can do this. Seems very easy. What will this tell me or not tell me?

When combustion gasses blow past the pistion rings (blow-by), they build up in the crankcase. Normally this is vented via a PCV valve, but this has a little bit of resistance. When you open the oil cap the gasses freely flow out the cap, and it gives you a measurement of how much the engine is blowing by. A loose or broken piston (your original assumption) will allow large or even huge amounts of gas to blow by, and that will all come gushing out of the oil cap when you remove it.

It's normal for engines, especially old ones and big ones and cold ones, to blow by somewhat. But take a video and post it up for analysis. Preferably a cold video and a hot video. This test won't by itself prove which piston is leaking, but if you don't find excessive blow-by it can conclusively prove that you don't have a detonated or undersized piston.

 

[Wes Harden]

When @campfire says gas and gushing, he does not mean liquid gas. It will be more like smoke, a little smoke ok, looks like coal burning freight train ... Bad news.

 

[wasted wages]

Good news here is that you have come to the right place !
Most of us here live and breathe these old Chevy trucks and engines...

If you are willing to roll up your sleeves and listen to the feedback you get here, I have no doubt we could even walk you through a complete engine swap yourself...

Most of us learned by jumping right in and figuring things out for ourselves...and asking for help and guidance when needed.

Once you learn how to do various things on your rig it will get easier as success will build confidence..

There are no stupid questions...and tons of help here!

 

[Kyle1983]

Now we're talking!



Keep that in mind when they quote you 15 gazillion Krona for an engine swap. If it's not something they're used to working on, they're probably not the right guys for the job.



When combustion gasses blow past the pistion rings (blow-by), they build up in the crankcase. Normally this is vented via a PCV valve, but this has a little bit of resistance. When you open the oil cap the gasses freely flow out the cap, and it gives you a measurement of how much the engine is blowing by. A loose or broken piston (your original assumption) will allow large or even huge amounts of gas to blow by, and that will all come gushing out of the oil cap when you remove it.

It's normal for engines, especially old ones and big ones and cold ones, to blow by somewhat. But take a video and post it up for analysis. Preferably a cold video and a hot video. This test won't by itself prove which piston is leaking, but if you don't find excessive blow-by it can conclusively prove that you don't have a detonated or undersized piston.

So start the cold engine and wait a minute then remove oil fill cap and record how much blowby. Then wait 30 minutes until engine is warm and do it again. I will do that and upload
Then I can move on to step two.
So if I have alot of blowby I did some damage to the pistons while timing was over advanced?

When @campfire says gas and gushing, he does not mean liquid gas. It will be more like smoke, a little smoke ok, looks like coal burning freight train ... Bad news.

Ok great. Thanks

Good news here is that you have come to the right place !
Most of us here live and breathe these old Chevy trucks and engines...

If you are willing to roll up your sleeves and listen to the feedback you get here, I have no doubt we could even walk you through a complete engine swap yourself...

Most of us learned by jumping right in and figuring things out for ourselves...and asking for help and guidance when needed.

Once you learn how to do various things on your rig it will get easier as success will build confidence..

There are no stupid questions...and tons of help here!

I will definitely get working on the Blazer.
I have to make a list like 1 to 10 steps to narrow down or solve the noise. I refuse to pay another $350 for 4 hours of looking at the motor but finding nothing.