VS Commodore 202 Drag Car :)

[Holden202T]

I know its not the flexplate as we could see all that and it all looked fine, its steel cam and crank gears, but definitely sounds more of a solid noise than that though. i'm putting my money on a big end or a piston issue, but its runs fine as far as not missing so I don't think its a piston issue so much.

[Holden202T]

oh an the pistons are acl race series

[vs ss]

Flex plate to crank bolts?
Just hard to pick up how deep the noise is in the video.

[vlad01]

sounds like piston skirt failure to me, or something piston related.

bottom end is a much deeper more dull sound and constantly persistent. All of which this isn't

[vlad01]

oh an the pistons are acl race series

those are generally cast.

[v6bucket]

Sounds like you fitted a diesel engine!
How did the car go before the noise appeared?

[Charlescrown]

I keep listening to the noise and it seems like it disappears when the revs are up but at low revs real rattle. I did have a Holden that spun the bearings and the pistons started hitting the head. It still ran OK. Very similar noise. It made it difficult to diagnose because it wasn't the norm. I took out the plugs and turned the engine over just past TDC then with a screwdriver through the plug hole you could lever the piston down a few millimeters. Might be worth a try.

[Holden202T]

yeah they are cast pistons, but they are also not really working that hard, the hq race cars use them all day long, i'd say its either leaned out or knocked enough to hurt a bearing or something, the other thing I noticed, it was nowhere near as bad on the day it happened to when it was cold in that video, which leads me to thinks its something that oil pressure can assist with to lessen the rattle, like a big end etc.

not bothering with much in car diagnosis, just going to rip the motor and stripe it down, my brother is going LS1 in it anyways so we'll just start down that path, this motor was only ever a "for the mean time" to get the car back on the track while he works on the LS1.

it has done a few yrs in the Gemini on the dyno a few times plus copious race meetings, all with constant abuse so im not surprised

as far as how it went before the failure, it did 4 passes that day, 9.2-9.3's over the 1/8th, and the last run I did and it was 9.293 @ 119.28kph and it sounded totally fine, and I didn't notice the knock at all coming back to the pits, it was just when I got back to the pits and put it in park and then there was an occasional noise!

we were probably only going to get one more run that day anyways so we decided to trailer it and go back to the caravan park and have a look over it after it cooled down, plugs looked fine, crank and torque converter bolts all looked fine and when lying under it on the trailer running could hear the noise was rear of the motor and a lot louder under the car than above it.

so we got drunk

[Holden202T]

well motor came out this arvo, sump off, pulled all the rod caps, nothing there, pulled all the mains, nothing there either.

all the flex plate bolts were still tight as, as were the converter bolts and the locating bush looks normal!

so we moved to the top end, all the rocker gear and springs looked fine, nothing visually wrong with the lifters, so we pulled the head, all the valves look alright and all the tops of the pistons look fine, as do the bores.....

so we are left with broken rings or pistons, or maybe the cam gear or something, but I couldn't see anything obvious from the bottom of the motor!

so we'll have to get the balancer off so we can see the front of the motor and rule out cam.... bit of a mystery still.

[delcowizzid]

might of smashed the convertor to bits LOL