I just checked out cracked flexplate sound on youtube and I can say with about 99% certainty that it's not the flexplate. The sound the flexplate makes is not the same as my motor. And when my motor warms up the sound almost vanishes. So I am thinking it might actually be the piston problem.
CK5
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Advanced timing ****ed my pistons
- Thread starter Kyle1983
- Start date
It is hard to tell from a video as the camera tends to change how the noises sound in person...to me,it doesn't sound like bearings,and the good oil pressure kind of confirms that--doesn't really sound like piston slap to me either,it sounds more like valve train ,top end noise,the noise doesn't seem to be made at the same rpm as the crankshaft--the valve train has a gear reduction in the timing chain ,so it turns roughly half as fast as the crank does..
Maybe a valve lifter is loose in its bore in the block--I've seen a few GM engines that had some of the bores oversized .010 and they needed special oversized lifters,they did that to avoid scrapping an otherwise good new block at the factory...if you put a regular sized lifter in it they'll make scary noises and eventually ruin the bore ..
A loose valve guide can make noises until it warms up good too in some cases..
I had a mechanical fuel pump scare me once,thought my '72 K5 had a loose timing chain,but I figured it out by using a long dowel against my ear,when I touched it to the fuel pump you could hear a loud clacking noise--it was the rocker arm on the pump,it was very sloppy on its pivot and the spring on it had fallen out..
I took the timing cover off anyways,only to find a nice new Cloyes double roller timing chain & gears in it that was tight as new!..
...lot of work for nothing..
I have also had a flex plate fail with no warning too,it cracked all the way around the bolts at the crank,it made a few tapping noises,then one big "clunk" when it came apart and stalled the engine!..it appeared to have been cracked 3/4 of the way around quite some time,that part of the crack was rusty..I was taking off from a red light when it failed..
Maybe a valve lifter is loose in its bore in the block--I've seen a few GM engines that had some of the bores oversized .010 and they needed special oversized lifters,they did that to avoid scrapping an otherwise good new block at the factory...if you put a regular sized lifter in it they'll make scary noises and eventually ruin the bore ..
A loose valve guide can make noises until it warms up good too in some cases..
I had a mechanical fuel pump scare me once,thought my '72 K5 had a loose timing chain,but I figured it out by using a long dowel against my ear,when I touched it to the fuel pump you could hear a loud clacking noise--it was the rocker arm on the pump,it was very sloppy on its pivot and the spring on it had fallen out..
I took the timing cover off anyways,only to find a nice new Cloyes double roller timing chain & gears in it that was tight as new!..
...lot of work for nothing..I have also had a flex plate fail with no warning too,it cracked all the way around the bolts at the crank,it made a few tapping noises,then one big "clunk" when it came apart and stalled the engine!..it appeared to have been cracked 3/4 of the way around quite some time,that part of the crack was rusty..I was taking off from a red light when it failed..
It is hard to tell from a video as the camera tends to change how the noises sound in person...to me,it doesn't sound like bearings,and the good oil pressure kind of confirms that--doesn't really sound like piston slap to me either,it sounds more like valve train ,top end noise,the noise doesn't seem to be made at the same rpm as the crankshaft--the valve train has a gear reduction in the timing chain ,so it turns roughly half as fast as the crank does..
Maybe a valve lifter is loose in its bore in the block--I've seen a few GM engines that had some of the bores oversized .010 and they needed special oversized lifters,they did that to avoid scrapping an otherwise good new block at the factory...if you put a regular sized lifter in it they'll make scary noises and eventually ruin the bore ..
A loose valve guide can make noises until it warms up good too in some cases..
I had a mechanical fuel pump scare me once,thought my '72 K5 had a loose timing chain,but I figured it out by using a long dowel against my ear,when I touched it to the fuel pump you could hear a loud clacking noise--it was the rocker arm on the pump,it was very sloppy on its pivot and the spring on it had fallen out..
I took the timing cover off anyways,only to find a nice new Cloyes double roller timing chain & gears in it that was tight as new!..
I have also had a flex plate fail with no warning too,it cracked all the way around the bolts at the crank,it made a few tapping noises,then one big "clunk" when it came apart and stalled the engine!..it appeared to have been cracked 3/4 of the way around quite some time,that part of the crack was rusty..I was taking off from a red light when it failed..
The more we talk about this motor the more I am terrified it will turn out I need to have the block completely taken down and rebuilt. That is going to cost alot paying someone to lift out the motor and tear it apart and replace parts, re assemble and put it back In.
Not sure what to do from here
One thing I am noticing from the video is the engine does not seem to be misfiring. Most of the time, but not all, if the engine has a serious internal problem the engine will misfire.
Do you have other means of transportation?
Can this sit and be gone through slowly? If not, you might be hosed and at a shops mercy.
If you have other transportation, lets go through this a little before you hand it over to a shop.
Can this sit and be gone through slowly? If not, you might be hosed and at a shops mercy.
If you have other transportation, lets go through this a little before you hand it over to a shop.
It's been posted more than once in this thread; that's impossible. Do some research on "boring" and "stroking". Maybe you understand and are just using the wrong term. You can de-stroke a 400 into a 383 (which is not nearly as popular of course), but to get a SBC 350 there requires increasing the stroke. The more you know what's in the engine, the better you can make decisions. Plus you'll get better help from us with better information.
Of course, sellers don't always tell the whole truth on cars. Sometimes they never had the right information or forgot it.
Is dropping the oil pan something you can do?
You mean my 377 isn't a popular screaming machine? 
What he's saying is that you can examine each spark plug to assess how well each cylinder is running. If one is running hot, cold, oily, has a blown head gasket, or has pieces missing from the piston, you often find clues on the plugs.
If your (assumed) hypothesis is correct, and detonation caused piston slap, that piston will be loose in its bore. As such, you should see large amounts of blow-by, and the cylinder in question should fail a compression test. The lack of compression would also likely show up as carbon deposits on the spark plug, as it would not be burning completely on that cylinder. Given enough miles, you should also see fuel/carbon contamination in your oil (detectable in an oil lab, you wouldn't notice it at home unless the problem is very bad, which yours does not appear to be).
Your truck is capable of telling you many things, but it's up to you to piece together the clues it is offering. Mechanics aren't perfect, and some of them are willing to stretch the truth to earn a lucrative engine rebuild job. Even when dealing with honest mechanics, it's always worth double checking their work. Where did they set the timing? Did they set it correctly for a 383 stroker with aftermarket parts? We're still arguing over whether or not this is a stroker engine, so we clearly don't understand the whole picture just yet.
Engine that were run with over advanced timing usually show signs of it on the spark plugs,they will be ghostly white or have burnt electrodes,specks of melted aluminum ,etc..
Look at the chart below at the pictures of plugs that had "pre-ignition" or "detonation" going on due to over advanced timing..
The electrodes will be burnt away ,and the porcelain will show specks of melted aluminum ,if things got hot enough to do real damage to the pistons--and the plug will likely misfire or not fire at all,making the engine skip or have a dead cylinder..if the compression is good in all cylinders,and your plugs do not look like that,chances are the over advanced timing did no real damage ..
You can also get a low cost "camera" that has a flexible probe like a speedometer cable that will allow you to look directly into the cylinders by removing a spark plug and inserting it in the hole too...this will tell a lot,without having to rip it all apart..
Look at the chart below at the pictures of plugs that had "pre-ignition" or "detonation" going on due to over advanced timing..
The electrodes will be burnt away ,and the porcelain will show specks of melted aluminum ,if things got hot enough to do real damage to the pistons--and the plug will likely misfire or not fire at all,making the engine skip or have a dead cylinder..if the compression is good in all cylinders,and your plugs do not look like that,chances are the over advanced timing did no real damage ..
You can also get a low cost "camera" that has a flexible probe like a speedometer cable that will allow you to look directly into the cylinders by removing a spark plug and inserting it in the hole too...this will tell a lot,without having to rip it all apart..
echo
or is the thing at the shop already?
It's sitting. Not going to a shop anytime soon for the money they want.
I will do more research on boring and stroking.
I have the tool set. I can drop an oil pan.
You mean my 377 isn't a popular screaming machine?
It was sold as a 383. I know very little past that.
I can start troubleshooting the motor and uploading pictures and videos but it won't be until next weekend.
They pulled all 8 spark plugs and although I don't have them anymore, I do have 8 new spark plugs that were put in a few weeks ago. Maybe I can check those?
Not sure how to check compression
Not in a shop.
A compression tester is just a simple gauge,with a flexible hose and fitting you thread into the spark plug hole,and you crank the engine over with the throttle wide open,after disabling the ignition coil so it will not start and run on the other cylinders (I remove all 8 plugs so it'll not start,and crank over faster)...if you've lunched a piston,chances are good that cylinder will have lower compression than the others..and its rare and unlikely all 8 cylinders would be affected,as some run hotter than others)..
The camera I mentioned is probably the easiest and best way to inspect for internal damage without taking anything apart..
Compression tester
The camera I mentioned is probably the easiest and best way to inspect for internal damage without taking anything apart..
Compression tester
Crate 383 maybe a better route for the $
You mentioned over timing.
What was the timing set at for initial timing @ idle, total timing (mechanical advanced timing with vacuum advance disconnected) and at what rpm, and what is total timing with vacuum advance hooked up and at what rpm.
And what did they reset those values to?
Can you provide a pic or list of the parts and machine work involved in the buildup of this engine?
While the engine is relatively cool, pull plug wires one at a time to see if the knock goes away. That could tell you if it’s specific to one or more Cylinders. I know diagnostic labor adds up quick, but it would be a good investment to find someone (maybe a local racer or old school mechanic) who could spend some time troubleshooting it. And document whatever gets done, there are a good bunch of engine guys here who can help you.
What was the timing set at for initial timing @ idle, total timing (mechanical advanced timing with vacuum advance disconnected) and at what rpm, and what is total timing with vacuum advance hooked up and at what rpm.
And what did they reset those values to?
Can you provide a pic or list of the parts and machine work involved in the buildup of this engine?
While the engine is relatively cool, pull plug wires one at a time to see if the knock goes away. That could tell you if it’s specific to one or more Cylinders. I know diagnostic labor adds up quick, but it would be a good investment to find someone (maybe a local racer or old school mechanic) who could spend some time troubleshooting it. And document whatever gets done, there are a good bunch of engine guys here who can help you.
I will buy one and give it a try. I already have $700 into fixing timing and searching for the noise.
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
The 350 ho has vortec heads and an internal balance crank your motor has gen1 heads and an external balance crank
