Loud noise after head/cam swap

[dcvickers]

So I finished up my head/cam swap tonight and fired the car up for the first time. Sounded weird the first time and then I remembered that I had forgotten to reconnect the O2 sensors on the driver's side (driver's side exhaust was the last thing I installed so I was getting anxious at that point). So I hooked up the sensors, cleared the codes, and fired her up again.

However, there was this thumping noise (it seemed really loud too me but I may be overreacting) that would happen every so often. It happened often at first (not constant, but it was consistent), but kind of went away. Mind you that I had installed one of Todd's tunes beforehand so maybe there was some relearning going on. As the car warmed up the noise pretty much went away. I didn't want to bring the RPMs up in the garage so I decided to pull it outside and rev it up a little bit. No thumping noise whatsoever under load (I brought it up all the way to 4K RPMs).

I came back inside to do a little research for about an hour and then went back outside and started it up again. I only heard the noise once over the course of 15 minutes. It almost sounded below the car, but I couldn't pinpoint it as it never happened when I was out of the car. I did install a ton of other things at the same time (slow bleed lifters, hardened push rods, plugs, plug wires, poly engine and trans mounts, MGW shifter) so I don't really know what it could be.

Does anyone know what this could be or what I should start checking first? Should I be worried since the noise has almost completely disappeared (I'm going to test it out again tomorrow morning)? FWIW, I went with NGK BKR6E plugs based on Todd's recommendation. I also noticed that the oil pressure dropped to 23-24 PSI at idle after the car warmed up but I think that's normal (it was 55-60 PSI at 3k RPM). Can anyone ease my anxiety about this and chalk it up to everything settling in after the install?

 

[dcvickers]

Any thoughts on this? I can't quit thinking about it. The noise was the worst when I started the car up the first time without the O2 sensors connected. The second time I started it up the noise started going away and the third time I only heard it once. Maybe it was just a backfire? There is some popping as the RPMs drop, but this noise was almost under or right in front my my feet.

 

[dcvickers]

Forgot to mention that the noise was only apparent at idle. I think it only happened once a bit above idle and never above 1500 RPM.

 

[V3NOMOUS]

It could be fuel igniting in your exhaust. Does it have cats?

 

[jasond29]

since you put new engine mounts in maybe the exhaust is hitting the body or frame. When you first start it up it will run a little ruff until it warms up then it will smooth out so maybe the excessive vibration during warmup is causing the exhaust to hit the frame/body.

 

[martyb]

Something hitting somewhere?? At idles everything shakes a bit more, more so if you put in a bigger cam. Get a piece of hose, put one end to your ear and fish the other end around where you think the noise is coming from, should be easier to hear with the hose.

Also, I think my oil pressure is higher than 24 pounds at idle, may want to verify what it should be before firing up again.

 

[dcvickers]

It could be fuel igniting in your exhaust. Does it have cats?

No cats. That's kind of what I was thinking, though, but it felt like it was up more towards the headers.

since you put new engine mounts in maybe the exhaust is hitting the body or frame. When you first start it up it will run a little ruff until it warms up then it will smooth out so maybe the excessive vibration during warmup is causing the exhaust to hit the frame/body.

Quite possible. From inside the car it sounded almost like something was hitting the frame. I'll check that out.

Something hitting somewhere?? At idles everything shakes a bit more, more so if you put in a bigger cam. Get a piece of hose, put one end to your ear and fish the other end around where you think the noise is coming from, should be easier to hear with the hose.

Also, I think my oil pressure is higher than 24 pounds at idle, may want to verify what it should be before firing up again.

I'm going to look and see if something is hitting the body/frame. I'm thinking that is probably what was happening because the idle was really rough upon first startup. After a while it seemed like the car learned how to deal with the new setup and everything calmed down. What is the RPM at idle for a stock car? I think my car was idling at ~750 RPMs last night. I did a search and others have said the 05 and 06 cars have 25-30 PSI at idle so I'm not that worried about it especially since it increased appropriately under load.

 

[Camfab]

First off, stop Reving the engine. If it's making bad sounds that usually doesn't help things out. Vipers have a lifter issue that pops up when you install a cam. You may be experiencing that, or you might have a multitude of other issues. I really don't know how you built your engine top end, so It's all a guess. Did you degree the cam, did you check the piston to valve clearance, did you order the proper pushrods length after measuring for your set up. Do you have aftermarket rockers, are they making contact with your retainers. Spark plug wires loose or crossed. Did you have to force anything during your installation?

If it were me, the first thing I would do is not fire up the engine. Put the car up on a lift and check out everything you've done under the car. Pull the oil filter and cut it open, check for obvious signs of metal. Pull both valve covers and inspect the rockers and the lash settings. Pull all the spark plugs and check them for any signs of contact or damage. Use a borescope to check the cylinders as well as the chamber surface of each cylinder. That should keep you busy, and don't rush through it. Sounds like excitement over your project may have caused you to miss some details. Good luck...

 

[dcvickers]

First off, stop Reving the engine. If it's making bad sounds that usually doesn't help things out. Vipers have a lifter issue that pops up when you install a cam. You may be experiencing that, or you might have a multitude of other issues. I really don't know how you built your engine top end, so It's all a guess. Did you degree the cam, did you check the piston to valve clearance, did you order the proper pushrods length after measuring for your set up. Do you have aftermarket rockers, are they making contact with your retainers. Spark plug wires loose or crossed. Did you have to force anything during your installation?

If it were me, the first thing I would do is not fire up the engine. Put the car up on a lift and check out everything you've done under the car. Pull the oil filter and cut it open, check for obvious signs of metal. Pull both valve covers and inspect the rockers and the lash settings. Pull all the spark plugs and check them for any signs of contact or damage. Use a borescope to check the cylinders as well as the chamber surface of each cylinder. That should keep you busy, and don't rush through it. Sounds like excitement over your project may have caused you to miss some details. Good luck...

The noise wasn't in the engine, though. Lifters are all new and pushrods were measured for my setup by Todd when he had my heads, intake manifold, and cam. Rockers are stock. double-checked the plug wires when I put everything back together and then again last night after I started the car. Nothing was forced during install. Like I said, the only thing I forgot was to connect the driver's side O2 sensors. And I didn't rev the engine when the noise was present.

I started the car up without the sensors connected and it was making the noise so I turned the car off. I then hooked up the sensors, cleared the codes, and started the car up again. From that point on the noise only happened 3-4 times over the course of 30 minutes - 1-2 times at idle and twice when the RPMs dropped below 1k. It's almost like it was misfiring and causing the engine to shake and something was hitting the frame/body. I'm going to pull the spark plugs anyway and recheck the wires as well as look for any signs of contact on the frame. When I pull the spark plugs I'm going to turn the engine over by hand to see if I can hear any contact, but I did this during the install and everything was fine.

 

[martyb]

I am guessing its exhaust hitting the frame. Pull the sills, put it up in the air and take a look. New mounts can raise the exhaust up a bit, you may be hitting where the exhaust passed through the frame.

 

[dcvickers]

Found my problem. Pulled the plugs and they looked fine so I decided to pull the valve covers and take a look. Passenger side was fine, but when I pulled the driver's side I was missing a push rod for the exhaust valve on #1. And my missing I mean it had broken in half . Half was in the head so I'm going to pull the oil pan and filter to try and find the rest. This explains why the noise went away. Anything else you guys think I should do? I have no idea why it would have broken. Just wondering if I should pull the head as well and put in a new head gasket. Any other things to look for would be appreciated.

 

[NI-KA]

Be very careful to get all of the metal out. If you do not, you risk damaging the oil pump (timing?) cover. The oil pump gears are pretty sturdy but the cover is made of aluminum and expensive as hell. If your oil pump doesn't work right bigger problems could result.

What kind of rockers do you have? Is the geometry correct if non stock? Do you think you improperly set or sized the push rods?
There are a lot of variables when setting this stuff up. It might be best to take your time and find a professional to assist and guide you.
Perhaps whoever recommended the CAM could help?

 

[dcvickers]

Be very careful to get all of the metal out. If you do not, you risk damaging the oil pump (timing?) cover. The oil pump gears are pretty sturdy but the cover is made of aluminum and expensive as hell. If your oil pump doesn't work right bigger problems could result.

What kind of rockers do you have? Is the geometry correct if non stock? Do you think you improperly set or sized the push rods?
There are a lot of variables when setting this stuff up. It might be best to take your time and find a professional to assist and guide you.
Perhaps whoever recommended the CAM could help?

I've already spoken to Todd about this. He said it should have only broken in half and I should be able to fish the other half out. I put another push rod in place of the one that broke and turned the engine over manually and there was no binding and everything seemed fine. I'll probably pull the oil filter to see if there's anything in there, but everything was running fine after the push rod broke so I'm hoping the damage is contained.

I'm going to take a look at the rest of the push rods and make sure none of them are bent. Other than that I don't know what could have caused this. Todd's going to send me another push rod next week and we'll see how that goes.

 

[dcvickers]

Be very careful to get all of the metal out. If you do not, you risk damaging the oil pump (timing?) cover. The oil pump gears are pretty sturdy but the cover is made of aluminum and expensive as hell. If your oil pump doesn't work right bigger problems could result.

What kind of rockers do you have? Is the geometry correct if non stock? Do you think you improperly set or sized the push rods?
There are a lot of variables when setting this stuff up. It might be best to take your time and find a professional to assist and guide you.
Perhaps whoever recommended the CAM could help?

In response to your questions, though, I have stock rockers and Todd did all of the measuring for my setup when he had all of my parts. I turned everything over by hand during the install and didn't notice anything out of the ordinary. Maybe it was just a weak pushrod? I have no idea. The noise happened right upon startup so it pretty much snapped instantly.

 

[NI-KA]

Could simply be that the lash wasn't set right. It happens. ***** but if that is all that it is then you should be OK.

 

[dcvickers]

Could simply be that the lash wasn't set right. It happens. ***** but if that is all that it is then you should be OK.

At this point that may be the the source of the problem. I checked lash on that valve while Todd was on the phone and we determined that it should have been fine and that the push rod length is appropriate. I've done multiple head/cam swaps before and I've never had an issue like this so it may also just be an anomaly. Who knows.

Now if I can just find the other piece of the broken push rod...

 

[Dan Cragin]

You must have installed the pushrod with the tip not centered in the lifter. Its easy to do. Always look into the hole in head gasket for the pushrod with a flashlight and make sure the pushrod is centered.

 

[dcvickers]

You must have installed the pushrod with the tip not centered in the lifter. Its easy to do. Always look into the hole in head gasket for the pushrod with a flashlight and make sure the pushrod is centered.

I thought I did that twice but maybe I missed one. I fished out the other half in the lifter valley. It was a pretty clean break (it bent quite a bit before it snapped). I installed another one in its place and turned the engine over by hand and everything moved freely and there was no coil binding so your assessment is probably correct. Do you think I could have bent a valve? I'm going to check that today.

You must be registered for see images

 

[Camfab]

Glad you found the result of your issue. As an FYI for anyone else reading this thread, you can only definitively determine pushrod length AFTER you've assembled the engine. If you've snapped a pushrod, you should be checking the rocker as well as the fasteners for an over stressed part. I'd also be concerned about the lifter itself. Dan is probably right on the money with your problem.

 

[dcvickers]

Glad you found the result of your issue. As an FYI for anyone else reading this thread, you can only definitively determine pushrod length AFTER you've assembled the engine. If you've snapped a pushrod, you should be checking the rocker as well as the fasteners for an over stressed part. I'd also be concerned about the lifter itself. Dan is probably right on the money with your problem.

I think so, too. I checked the end of the pushrod after I replied to him and sure enough there was some damage on the end. Also, just to note, I didn't blindly pick some pushrods and install them. Todd had all of my parts and set them up to get the correct pushrod length. I hate to admit it, but this was more than likely user error (though we'll never know for sure ).

 

[dcvickers]

UPDATE: Todd sent me another pushrod and after installing it the car sounds much, much better. Started right up with no weird noises .

 

[ACPERFORMANCE]

Thats what i like to hear

 

[SquadXX]

woohoo. glad to hear no damage.