Hi guys,

I have a 68 400 motor that is brand new. Roller cam, rockers, forged pistons .030 over etc. It is now knocking when it is revved up. Sounds to me like a rod. What do you think? you can hear it kick in at :12

Thanks,

Craig

https://www.youtube.com/watch?v=koD8...ature=youtu.be

 

Could be top end. Check all of your rockers.

You say "brand new" - why not bring it back whence it came?

- Eric

 

Sounds "rocker armish". That's where I'd start investigating.

 

The engine builder is out of town. Just wanted to get everyones opinion. I adjusted the valves prior to this. They are all about a half turn tighter than first set. Maybe I'll pull the covers off and try again. I'm hoping that is all it is! Thanks all.

Craig

 

How are you adjusting lifter preload? The "knock" sounds low, I' would already have the oil filter cut open..

 

First attempt was to find zero lash and add a 1/2 turn. I think I am going to try to adjust them running. This is how I've always done it in the past. (non Olds)

The engine builder is highly reputable so I doubt it is anything coming apart.

Craig

 

Reputable chevy ford or reputable olds builder. Very different worlds. Im hearing both valve train and lower end noise. Never heard loose rockers knock that loud and I have had 2 rockers fall off because they where so loose that during break in the fell off and made no noise !

 

Is the knocking at rev when its cold only? Mine has forged pistons and it is not good to rev the motor till warmed up because you can scratch the cylinders. The forged pistons expand as they warm up to fit properly and do knock some until then. Either way it is best to park it till he can check it out. I would not even start it again (tow it if you have to) to his shop. Its on him and its in your best interest to take every precaution to protect your investment. Good luck with it.

 

He has built big engines since the 60's and is good friends with Joe Mondello's son. I'm hoping he knows what he's doing. I was hoping it was just my crappy valve adjustment but you guys are scaring me now!


I drove it around the block a few times, it idled fine it just makes noise when I put my foot into it. I'm now thinking I'm going to wait for him!

Thanks for the advise!

Craig

 

When I bought my car the motor had 8000 miles on it. No knock, just a rear seal leak. Turned out the thrust was not set proper and ruined the crank. Sorry to scare you but a knock is not a symptom of a rebuilt motor. He should know if it is the sound of forged pistons or something more. I just think in this case less use is better. I would rather spend towing cost than drive a car with possible issues. Regardless of the cause you have the upper hand now because it was just rebuilt by him.

 

The correct way to adjust lifter pre load on any engine is EO-IC...exhaust opening-intake closing, there are at least a few thousand hits on Google...it's the best way to set lifter preload.

 

Thank Gary, He is a great guy and should fix it for me. Better safe than sorry!

 

Yeah, It is just a real PIA to do it with the engine in the car! Hard to turn the motor by hand! What do you think about adjusting them running?

Thanks!

Craig

 

Sounds like bottom end to me.

 

Great, you are not helping!

Craig

 

Since he built it he may want to do the adjusting on the lifters. JMO. I did not have to do anything on mine, just drop it in.

 

That sounds like lower end knock to me. What is your oil pressure? What rockers are you using?

 

It's hard to tell just from the vid,if it was valve train it wouldn't come and go it would be a constant noise,i think?

 

I run forged speed pro's and never heard them knock when its cold.

 

Copper cutlass; now I'm scared.

 

As was mentioned look at your oil psi or hook up a mech. Gauge. I once thought I had a rod knock but it turned out it was a really loose motor mount and the header on the dr. Side was hitting the frame when the engine was idling. If you aren't comfortable with the situation just wait until you and your engine builder can truly begin to dig into the issue.

 

Thanks all, looks like I'm right back to where I started! I am using the stock oil presure dash gauge and it is indicating halfway (normal)

Stay tuned! I'll post something when he returns!

Craig

 

Ouch! Wrist pin?
My ears say rod related,
with some top end ticking as well.

 

That rebuild is a fail, sorry to say.


Good luck.

 

My 2 cents, is the car an automatic trans? I have heard cracked flexplates sound like that...

 

I must agree. Take it back.

 

It is an automatic. The sound seems to be coming from the passenger side

 

X2. Check the flex plate.
After having my 350 rebuild, I put it back in the car, took it for a spin after breaking in the cam and similar knock occurred. I thought bottom end for sure, turns out cracked flex plate.
It's hard to tell from the video, but I would look into that.
Also What rockers are you running?
I also had a problem with Compcam Magnum Rocker kit that developed a knock after about 300 miles. It turn out to be the heat treated steel pushrods supplied in the kit were getting chewed up and mushroomed by the rockers. I replaced them with Trickflow Chrome moly and now it runs fine.

 

I'll check the flex plate! I believe they are Compcam roller rockers.

Thanks for the info!

Craig

 

https://classicoldsmobile.com/forums...-begins-6.html

Here is the thread with some images of the roller rockers

 

Check the pushrods. Few other CO members had the same or similar problem with them.

 

IMO Sounds like a rod. Did you look at the oil and inside the oil filter. My bet is it looks like sliver paint.

 

I did pull the dip stick a few times and wipe it on a white cloth. Looked ok.

 

Pull the filter, cut it open.
This will give you a tell.

If you find a lot of metal shavings.....
You can tell him to bring his wrecker too.

 

The video doesn't sound good to me either. I'll offer up one more suggestion, I don't think was mentioned. Check to make sure the dampner bolt is good and snug. AKA balancer is tight or not? Good luck.

 

I would not start it even one more time until you cut the filter open.

 

The dips stick will not tell you what you need to know. To properly assess whats going on you need to drain the oil completely in a clean container to see whats in it as well as cutting the filter open to see whats being caught up in the pleats. This is rebuilt engine trouble shooting 101.
Careful cutting the filter open. You cut around the top seam. Dont confuse the metal from cutting with whats deposited inside. Oil filter cutters are available. But careful... Hack sawing or cut off wheelin will do the trick.
And yes do not run this engine until you do this. Ill bet one of the crank journals looks like a beaver was gnawing on it but I hope not.

 

Talked to the engine builder. I am going to check the oil filter. Stay tuned (and cross your fingers!

Craig

 

Fingers and toes bud!

 

Thanks!