20sickss00

iTrader: (19)

A few months ago I did the following mods.

prc stage 2.5 ls6 heads
tsunami cam
ls6 intake
pp throttle body
7.4 tsp pr's
gm mls gaskets
ls6 ported oil pump
powerebond ud pulley
trunion rocker upgrade kit
all new gaskets
ls7 lifters

and any of the smaller things in the mix was replaced.
The car was tuned by jeremy formato and made 430/391. Car runs perfect, very fun to drive, he dd a great job with it.

The setup has maybe 1200 miles on it and made 3 passes down the track.

Driving out the road the other day doing 45-50mph, not beating/no missing gears. just normal cruising down the road, the motor starts knocking/tapping, gets worse so I pull over and have the car towed back to the house. get it home, narrow it to the pass side of the motor. check valvetrain, springs, rockers, prs all look good and straight. I pull the head off and see the 3rd cylinder piston has an imprent of the head/valve on it. very slight, but its there. This is the only piston it is on. the other ones on that side look fine. I have not pulled the drivers side head off yet to see how that looks. The pass head has uneven carbon marks on that same cylinder chamber. Now I assume I most likely have a bent valve there, but my question is what caused this all to happen. incorrect clearance? wrong length pr's? rod bearing left loose? It is only on the one piston. If it was clearnace issues I would more think this would have happend on all of the pistons, on both sides or am I wrong. any ideas/input is appreciated. And what to check for next, or where do I go from here on?

PREDATOR-Z

Did you measure PTVc upon install?

Black 99 Bird

iTrader: (31)

What are the specs on the tsunami cam?

20sickss00

iTrader: (19)

The cam specs are 235/240, .648 .609, the clearance wasnt measured because the heads were not milled at all because of the size of the cam. Texas speed walked me through everything and I was not supposed to have any clearance issues, which is why there was no milling involved. If I did have issues that would have been noticed right away I would think. This only happened on one cylinder and thats why i'm not certain it is a clearance issue. If it was I would assume it would hit on all the cylinders, correct me if I'm wrong. This car ran absolutley perfect after the cam, I am very happy with the setup and the good tune, just do not understand why this just left loose. The car is a weekend driver and only has 70k miles on it. its a 2000 ss. Any more thoughts are greatly appreciated, I want to get this thing running again.

S10xGN

iTrader: (11)

You've already got the heads off. Check the PTV, flycut if needed, and buy some new valves.

Black 99 Bird

iTrader: (31)

What is the LSA on the cam?

PREDATOR-Z

These 2 comments make me suspect a spun rod bearing.

LilJayV10

iTrader: (39)

Predator Z as usual is spot on with his post. With a spun rod bearing the piston will actually come up farther that it's suppose to.

I would drain the oil and cut the filter open to see if there is any metal in it. Depending on how bad the bearing is sometimes you can rotate the crank back and forth a little bit with a long ratchet and see/feel the slack buy watching the piston.

If that's not it I would have that valve spring checked to see if it's weak and maybe wasn't controlling the valve correctly.

RedLed

Sorry not trying to high jack the post but I was grazing though this trying to figure out what exactly a spun bearing is other than "that knocking noise you hear" which is what some mechanic tried telling me.

20sickss00

iTrader: (19)

cam is a 111 lsa. I was just thinking today about weak springs on those valves making them float and tap the piston. And tonight I am going to turn the motor with a ratchet to see if the piston does come up with slack/or a touch about the cylinder. I drained the oil last night and found very very tiny metal shavings on the drain plug, but otherwise the oil looked pretty normal. I will have a friend check the springs, and tonight ill take a look into the piston itself further. thanks for the input, i'll keep updating. dont want to have to tear the other head off if not needed.

s346k

iTrader: (4)

did you cut the oil filter open?

there shouldn't be flakes of anything on the drain plug.

20sickss00

iTrader: (19)

I did not cut the filter open yet, Don't have any time to work on it tonight, some other things came up,I'll try and get to it some tomorrow.

LilJayV10

iTrader: (39)

The bearing is two pieces. One piece fits in the rod and the other in the cap. Each piece has a "tang" its basically just a tab, that locates it in the rod or cap. When the cap is bolted to the rod, because of the location of the "tangs" the bearing is not able to spin or rotate inside the rod journal even though they both are round.

When you "spin a rod bearing" the crankshaft has actually come in contact with the bearing. Normally there is a super thin layer of oil between the crankshaft and the bearing and the two never shall meet.

When they do meet the crankshaft starts to destroy the bearing. Crankshafts are cast or forged steel and the bearings are aluminum/copper/babbit.

Sometimes the crank just hammers the bearing flat. Sometimes the rod bearing actually spins inside the rod journal. Either way the rod bearing gets thinner and the rod is able to travel more because it's not centered on the crankshaft journal.

When this happens the rod/piston goes further up the cylinder than normal which can result in piston to valve contact and/or piston to cylinder head contact depending on what you set your quench at.

If I had a picture it would really help. It's hard to explain things over a computer.

I hope this answers your question and I didn't ramble for five minutes for nothing.

20sickss00

iTrader: (19)

was just told today by another member on here that the bearings that typically go out first, whether it is true or not, are the 6th and 7th cylinders, which mine being the 6th, makes sense with his theory. When we started it here in the garage to narrow it to the right side of the motor, there was a squeeking that came and went which would also lead to a bearing. Is it worth pulling the other head to check the pistons/head? there was no noise coming from there. the noise was 100% on the side I pulled off. And also, thinking ahead, is it just chancing it to repair the bearing and crank(if damaged) or just spend the money for a forged 346 or go the extra bit futhur for the 383. This is trying to be a budget fix but I understand getting low end is not cheap any way you look at it. do i chance another stock bottom end which may only last a year or go for it with the build and have reliablility for years.

LilJayV10

iTrader: (39)

I know number 7 cylinder is more prone to detenation/ring land problems due to the intake design. This is the first I've heard of the rod bearings unless you take in consideration if you have bad detonation you can hammer a rod bearing.

If the bearing is bad the whole engine has to come apart so it doesn't really matter if you take the other head off now or later.

You said squeaking. Have you taken the front belt off during your testing?

20sickss00

iTrader: (19)

I was inside the car while my neighbor( a 20+year mechanic) was listening. The squeek seemed more deep you know, not a belt I have heard that before. I am no mechanic, I'm a painter/custom paint at a body shop. I did the install with assistance from others who know these motors inside and out and with much research and because I wanted to learn more about this. Everyone has different thoughts and ideas on it so I'm just turning around in circles. Don't know what to check first. At the track 2 months ago, the car had a few random backfires. shut it off and trailored it home to where i could look at it. Just a simple plug wire against the emissions plug on the pacesetter header. great placement for that plug by the way.... so replaced the wire and with a better plug boot this time. and ran fine. I got another 3-400 miles on the motor after that happened and it ran perfect in that time then this happens just driving down the road. so not sure if that would have had anything to do with it. The bearing deal all makes sense where it made the piston travel farther up and hit the head, because the markings on the piston almost have the outline of the cc on it, and on the head the cc is not carbon around the outside, where the piston must have been hitting. so this is all starting to make more sense. I guess I'll have the head checked out first to see if any springs are weak, but It looks like the car will wait to be a winter project, if the funds are available and pulling the motor and digging into it. keep the thoughts/advice coming guys. thanks

LilJayV10

iTrader: (39)

Good post man. Sounds like you are going about it the right way. There was a post on here about two months ago where the guy had a squeaking noise. He took it apart and it was a bearing. He had video and everything of it. I have no idea how you would search for it.

Regardless keep us updated on what you find. It will help people out in the future.

black00ssFL

iTrader: (24)

Like predator said its a spun rod bearing. I had the same issue on a "good" shortblock I bought off craigslist.

Number 6 looked like this



Notice the head imprint like you say yours looks like?

Here's what the bearing/journal looked like

20sickss00

iTrader: (19)

ouch, my piston doesnt look nearly that bad, but the car wasnt driven at all as soon as i heard the noise, so it didnt have a chance to hit harder or worse, but that does look like what im dealing with and has the same markings. I would put pics up but I can never get them to load on this site.

black00ssFL

iTrader: (24)

Ya, that engine was obviously run that way for a good amount of time due to the amount of wear on the journal. I bought it this way (stupid me for not at least pushing on the rod caps when buying or getting it home), and had about 15 minutes total of run time trying to figure out where my tapping was coming from.