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I need help diagnosing a rattle issue and the steps to take to troubleshoot it. Quick rundown of the car. I picked up a 72 Chevelle project car that had a 2010 camaro ss ls3 swapped into it with a LSA blower. The builder put a btr stage 3 cam, id1050 injectors, circle d converter and put the supercharger on and never started it after it was put in the chevelle. I bought it, wired up the car, put a pat g tune on it and started it up to find a horrible rattle sound that I am currently troubleshooting. The car has about 70 PSI of oil pressure. I have taken the belts off of the supercharger and accessory drives to rule these our, and the rattle still continues to happen. I have made sure there is nothing physically hitting the motor or headers to cause the rattle noise, it sounds internal. Fluid levels are all good. I have checked the Flywheel bolts and torque converter which looks good.What would be the next best list of steps to take to troubleshoot this? I am going to take the valve covers off and check the rockers. Then pull the push rods out to check for bent rods? Could it be a stuck lifter? Any help or advice would be appreciated. I have 3 videos I made of the car starting and running. The 52 second video is the best to hear the rattle. The YouTube links will be attached below. Thanks!
I agree with you to pull the valve covers 1st and see if anything is amiss. While you are at it pull the filter, cut it open and look for metal in the pleats.
If it were me I wouldn't keep starting it until you figure out the noise.
From what I can hear the noise seems to be delayed for a few seconds once started?
That is one hell of a rattle!
Nice sounding exhaust btw.
Thats a crank-speed rattle, not valvetrain speed. I don't want to jump to the hardest thing, so maybe look at the flywheel or flexplate to see if it's hitting the starter or the bellhousing? If you can put it in gear, even at idle, and it goes away or gets worse that may be an indicator because it puts a thrust on the flexplate.
I have pulled the inspection covers off the bellowing and checked for loose bolts, shiny metal spots or shavings, anything hitting and I don't see anything. This was my original suspicion area as it sounds like a Dingggg bell when it first cranked, like something was hitting then sliding in and out intermittently hitting again.
I may be wrong but a sound that sharp doesn't sound like its coming from inside of the engine.
Its not that uncommon for the flexplate can strike the very front of the starter gear.
This is going to be dumb but you should check that you didn't install the flex plate backwards. Sometimes they are really close to being symmetrical.
Also if its in there with no transmission or torque converter attached then it will hit a resonance and try to turn pringle shaped, hitting the starter, block or the bellhousing.
Yeah I would agree that it sounds like it's outside of the motor. The Flywheel, torque converter and transmission were already installed when I took over the project. I will check to see if the Flywheel is in correctly but it looked like everything was lined up right for the starter to engage and then pull back without interference.
Flexplate bolts are right and is facung the correct way. I disconnected the torque converter, it spins freely and has .125" gap between flexplate when pushed all the way into the transmission. I started the car with the torque converter bolted up and it is still making this clattering noise. I took the belt off the supercharger and serpentine belt off accessories to rule out all of those components and the ticking kept happening with the belts off. I bolted the TC back up and took a video from under the car. I don't see any shiny metal spots of where it is rubbing and I blued the flexplate gear to see if the starter face was making contact, it is not. Here is the video from under the car after the TC is bolted back up. Any advice is appreciated. Header is not resting on the control arm mount although it looks like it in the video. It has 1/2" gap.
That video shows a discoloration on the flywheel. As it’s spinning you can see it. I bet you have interference on something back there. Like people have already said.
That video shows a discoloration on the flywheel. As it’s spinning you can see it. I bet you have interference on something back there. Like people have already said.
The discoloration is from the sharpie i used to "blue" the flexplate to see if there were any rub marks. I didnt see any fresh marks.
Get an engine stethoscope and start probing around until you localize the sound. Anything that loud will be readily apparent when you touch the right spot.
Did you get a stethascope on it….did it happen after you put the LSA blower on?? I put a brand new LSA blower on my nova and it was making the same noise within 100 mi of install , it turned out it was the coupling in the supercharger…i had to pull the snout and put in a solid isolator coupling…..i went with a 2.45” pulley while i was in there!!!
Did you get a stethascope on it….did it happen after you put the LSA blower on?? I put a brand new LSA blower on my nova and it was making the same noise within 100 mi of install , it turned out it was the coupling in the supercharger.
Originally Posted by Fastpass69
I took the belt off the supercharger and serpentine belt off accessories to rule out all of those components and the ticking kept happening with the belts off.
It looks like something it rubbing the inside edge of the flex plate. You can see light rub marks on it. Yeah it’s not shiny, but something is rubbing on it try starting it with your phone recording the flywheel to see if it shows any wear marks.
I’d still pull the snout off the blower to look at the “puck” or tensioner. Just to see what’s in there. Replace it if it’s stock
when u removed the belts and ran it, did you remove the SC belt too? What FEAD setup are you running?
06-07-2023, 02:19 PM
HELP diagnosing 1st startup rattle. LSA Chevelle 
