[chiphead]

So I did the cam break-in today on the 400, with my nervous but very accommodating wife spotting for me. I had to shut down the break-in twice for fuel leaks, but I got the whole 20+ minute break-in done without too much drama. Keep in mind this is a seasoned high mile engine with just a cam swap. Has some sort of stall converter and TH400 tranny.

Oil pressure was good, temp was good, RPMs stayed between 2K-3K the whole time. Engine revvs quickly and sounds good. Ready to let it eat, I think...

Then I start it back up and let RPM drop to a curb idle of about 800 RPM. Something starts making the most horrible knocking, rattling and banging noise I've ever heard. So I stop it and look it over, nothing obvious. My neighbor comes over and says, man, is it knocking? So I crank it back up and it sounds like it's eating rocks at idle. Rev it up and it goes away. Let it come back to an idle and it eats rocks again. It's super loud under the car, like its going to fly apart any minute. But I just spent 20 minutes watching and listing to everything and revving it and it sounds great???? Above 1000 RPM it quiets down, but let RPM drop below 1000 and it's see rock city.

I took this video and then went for a rip around the block. It ran great, but at idle or coasting it sounds like a tin can full of rocks. If you ignore the fan noise you'll hear a harshness under all the normal engine noises.

https://youtu.be/Nl_VgiGfVas

[Schurkey]

Fuel pump lever/cam eccentric assembled properly?

I can't make out anything on that video. And I don't know if that's due to old ears or a crappy cell-phone microphone.

[mrmark1957]

Start pulling plug wires off one at a time with the engine knocking. If there is a problem with any cylinder's piston,pin or rod bearing the noise will change as the wire goes on and off.

[turbo69bird]

I had some loos torque converter bolts once that made a hell of a racket. Just loosened up on me enough to make me think the engine was coming apart ina. New build so maybe check that.

And there’s been LOTS of cam to lifter issues lately and you said it’s a new cam so that would be a likely place to look see if the push rods are spinning. I’m doing a. New build and think I’m gonna use one of the older unused cams I have on the shelf because there’s been so many issues lately. If it was a rod you’d hear it get louder on the tip in of the throttle right as it changed RPMS. I can’t hear it that well on my I phone to know if it’s doing that .

[dataway]

I'd say only considering things that you touched when swapping the cam.

Sounds to me like rubbing grinding ... something amiss with the cam chain.

I'd start with removing the distributor to look at the gear for problems, spin it by hand outside the engine to see how it feels.

Next pull the timing cover ... kinda sounds like slack in the cam chain rubbing on something ... you didn't have any left over bolts did you?

[PunchT37]

I would check easy stuff first. Like converter bolts, flexplate bolts, dust cover, etc.

[25stevem]

Mostly likely it’s something related to the cam change.
The potential good news is that if it was a rod bearing or wrist pin issue it would get louder under load and yes even when reving it up out of gear.

DO NOT RUN the motor any more and try removing the plug wires as suggested!

I would start by taking everything apart that you had a part to stuff the cam in to look for problems.

I really can fathom why the heck you took a chance and drove the car around with a issue taking place?

[Holeshot71]

Use a long screwdriver or a section of hose and put one end to your ear. With the screwdriver, touch areas around the engine and find where the noise is the loudest. With the hose, listen around the engine. The hose will help isolate the noise. It helps to cup your hand around the end and put you hand to your ear. HTH

[abefromen]

cam/timing chain related. Excessive cam end play a possibility.

[grandam1979]

First thing I would do is remove valve covers and give everything a good look over one miss adjusted rocker could do it.

[400 Lemans]

Yeah like the others have said, torque converter bolts loose. Have had that happen on mine before.

[Half-Inch Stud]

Fan hitting shroud? pull 1 or 2 belts for a quick noise check. Loose crank pulley, fan pulley?
Alternator noisey?
TQ bolts good idea.

Pull valve covers and check each Rocker for tight-sloppy loose. Check for rubbing on ALUMINUM covers.
Last resorts; Fuel eccentric done wrongk. Or water pump plates done wronk.

[mgarblik]

Can't tell a thing from the video. But take a symptomatic approach. Before cam change, no noise, now the noise. So logic dictates cam change is the issue. Things involved with that. The fact that you say it goes away when reved up points to things that change in that situation. Fuel pump, arm, drive cup would be on my list. Remove the fuel pump, look at the arm. Stuff some tape over the hole or a rag tightly in the hole and start the engine. Noise gone? you found the problem. It will run 15-30 seconds without a fuel pump. Same noise still there? Put pump back on and take valve covers off. Start engine and look for loose rocker arms, non-turning push rods. I am assuming this is a flat tappet cam. Just go step by step. While I agree flex plate and bottom end noise is possible, why would these noises happen right after a cam change? How about a loose harmonic balancer? You had that off. Everything involved with the cam change needs to be looked at first. Hope you find it without damage and too much work to fix.

[Murf]

Originally Posted by Half-Inch Stud

Fan hitting shroud? pull 1 or 2 belts for a quick noise check. Loose crank pulley, fan pulley?
Alternator noisey?
TQ bolts good idea.

Pull valve covers and check each Rocker for tight-sloppy loose. Check for rubbing on ALUMINUM covers.
Last resorts; Fuel eccentric done wrongk. Or water pump plates done wronk.

+2, I had my fan hitting & it made a hell of a racket! It’s worth a look.

Good luck
Murf

[66beaumont]

I had a similar noise in mine. Found loose bolts on crank pulley.

[NeighborsComplaint]

Another vote for loose convertor bolts. the sound would be most prominent with the loping of the motor at idle in gear. Would go away when driven.

[chiphead]

Originally Posted by mgarblik

Can't tell a thing from the video. But take a symptomatic approach. Before cam change, no noise, now the noise. So logic dictates cam change is the issue. .

Sorry for video quality, its all I had at the time. I cant say there was no noise before the cam change. I've basically had 10-15 minutes runtime with this engine prior to cam change, and it never idled below 1000 prior to the cam change. I just bought this car and I know nothing about the engine. The PO was evasive when I asked anything about the engine. So there were already red flags that the engine had issues, and I priced that into my offer.

When I had the cam out, I noticed some slight clanking when I turned the engine rapidly back-and-forth with a breaker bar. I looked down at the crank and rods through the valley and didn't see anything wrong. I should have dug further at that time, but I was so invested in the cam change I wanted to get that done first. I admit this is a failure in my diagnostic effort since I heard a noise while turning it over by hand. It sounded like it was coming from the back or behind the engine.

Right now I'm hoping it's a broken flexplate or a trans issue. I'll dig into it and report back. How safe is it to disconnect and push the converter back and run the engine by itself?

[flat-bill]

What is the oil pressure when the noise is present?

[1969GiPper]

Originally Posted by NeighborsComplaint

Another vote for loose convertor bolts. the sound would be most prominent with the loping of the motor at idle in gear. Would go away when driven.

I vote for loose converter bolts too. If one of the bolts came out completely and you have a metal converter inspection cover it could get kicked up by the flex plate and bounce around like the steel ball in a pinball game. With a plastic cover it would be loud. But not as loud.

[77 TRASHCAN]

As others have said!!!

Don't start it again!!!

Get the valve covers off!!!

Go from there!!!