Engine sound I don't like

I've had my Unique on the road for about 2 months. I've just got a few hundred miles on it; mostly from sorting out runs. The engine is a SA 351w with a hydraulic lifter cam and roller rockers. I've enjoyed driving it and the engine has been great. But it has started running rough and the engine has developed a fairly loud, rapid, metal-on-metal tapping sound. The timing is where it's supposed to be. Oil pressure is fine. Bill and Lyle have been talking me through valve adjustments; thinking that is the problem. I've been through about a dozen rounds of valve adjustments. I have all the rockers set at zero lash. I have also tried tightening the rockers down varying amounts past zero lash, but the sound is still there. I'm concerned about potential engine damage, so I've decided not to run it any more until I get this figured out. I plan on continuing my discussions with the SA folks next week, but since it's the weekend I was wondering if anyone out there has any thoughts as to what's causing the tapping sound? I'm hoping it's nothing major, but I'm a little worried.

DU

just an idea, check the inside of the valve covers to make sure the rocker arms are not making contact with the valve covers. I had this happen years ago and it drove me nuts!

Try to determine where the noise is coming from. Top end or bottom. A stethoscope really helps here. A long screwdriver with your ear on the handle and the tip on the engine also works well.

Check your rocker shaft pedestals. They may not seem loose with the valves springs tightened down. I broke a rocker shaft in three pieces .

Ralph

make sure you didn't blow out a chunk of your header gasket between head and header. will sound like a loud clacking lifter. jim o

Thanks for the ideas. I talked to Lyle down at SA today. He really feels that the sound I'm getting is one or more rockers hitting the top of the valve covers. Well, this evening I loosened up the covers and ran the engine. I can lift the driver's side cover an inch above its mounting position and I am still getting a loud clacking on that side. It sounds like it's coming from one of the rockers near the front. The passenger side is quiet. I've adjusted all of the rockers many times to zero lash (hydraulic lifter cam). I've checked the head bolts, and the gaskets between the heads and headers are good. What would create loud clacking of a rocker with the lash set where it's supposed to be. Could it be a damaged cam lobe?

Pushrod perhaps..

Ralph

Richard I would pull the valve cover on that side.
Remove all of the spark plugs (on both sides)
Turn the motor by hand on the crank bolt
watch and listen to that side
look for a rocker that is not fluid in movement
look for a cracked or broken spring
if you do not see anything suspect get a dial indicator and check lift at the rocker to see if lobe is down.
if you have a lifter that went down and you set it to zero lash collapsed it could have caused a problem. lobe damaged or bent pushrod
If you have aluminum roller rockers make sure someone did not install one of them with the shaft upside down. They have a flat side and a round side where the adj. nut sits.
Look where the aluminum rocker curves over the top of the edge of the retainer. See if the rocker radius comes in contact with the edge of the retainer.
Make sure the roller tips are ok
Make sure the steel inserts that recieve the pushrod tip are still in the rockers.
Do you have lash caps? Are they all there?
Check the inner valve springs to make sure none are catching.


I guess the point is STOP RUNNING THE MOTOR until you have exhausted all of the easy to get to and fix items.

No reason to let a small cheap item ruin a motor.

Good luck,

Thanks Brent for the detailed guidance. Yes, after seeing that the rockers are not hitting the under side of the valve cover(s), I've stopped running the motor until I figure out what's going on. The loud clacking sound is still there. I've got fluid movement of the rockers and they appear to be installed right side up. I've had a couple of phone conversations with the SA folks. Yesterday I got some great news from Bill. Next week he's bringing a Unique up to Chicago that he's done some motor modifications on. He's decided to come to my house in Naperville to "get my car running right". I'm amazed that he's willing to do this, but then I've heard from others that Bill goes over the top to satisfy his customers. With what I've learned in recent months I'm expecting my problem to be a lifter issue, a bent pushrod or lobe damage. We'll see. I'm just greatfull that Bill will be figuring it out and not me. I feel like I'm being rescued. Hopefully the fiix won't be too involved and I'll be back on the road soon. Thanks again!

Dick

Be sure to follow up and let us know what the gremlin is-was.Somebody had a distinct knock in what sounded like the engine back at homecoming, new car-engine--I would swear the noise to be something in the valve train or rod cap loose---heck turned out to be loose nut-bolt in flywheel-torque converter where torq. conv. bolts to flywheel---heck--can,t remem. what you call it---senior moment, flexplate. Had a automatic trans. in it.Retightened it and good to go. But, Brent is right, shut her off till you gently find whatever ,no need to ruin engine.But, let us know. Will-alabama

Well??? What was it??? Hope you got it squared away...

From what I hear from Susan at SA it turned out to be a blown header gasket, I will let Dick fill everyone in. It amazes me how far Bill wil go to help a customer.

Alan

This past Monday, Lyle (from Southern Automotive) delivered another car in the Chicago area they did some work on. I've been talking to Bill and Susan the last few weeks about my loud clacking noise. They had Lyle come to my house yesterday after he delivered the other car. Lyle came prepared to take apart my engine in my garage. He came with replacement parts (extra camshaft, etc.) in case they might be needed. Lyle was great. It turns out my novice status when it comes to engines really came out, because the problem was just a blown header gasket. I had tightened the bolts, but the damage must have occurred before I tightened them. I'm still amazed at how bad the engine sounded with just a blown gasket. After the quick fix, Lyle showed me how he adjusts valves and readjusted mine. He was very patient with me and answered every question I threw at him. I learned a lot during Lyle's visit. The engine now runs fantastic!
All I can say is wow! I never expected SA would come to my house to solve my engine issues. These folks really stand behind their engines, and they really care about their customers. It's great to see a company that really cares about what their doing. I'm very grateful. If I ever do engine upgrades, or another engine, I know who I'll be dealing with.

DU

I had a similar experience with a 351-C I shoehorned into a 71 Mercury Comet. I had a local shadetree mechanic replace the header gaskets. The headers necessary to get that Cleveland to fit into the Comet engine bay were composed of 12 pieces--8 individual pipe (two of which crossed over and connected to the collector on the other side), two collectors and two cones, and that Comet ate header gaskets at an unbelievable rate. When I got it back it had a very similar sounding knock. I didn't give the header gaskets a thought b/c they were suppose to be new. I decided that it must have been a wrist pin, so I had him take out the motor/transmission and I tore the motor down. Nothing wrong. Later I found out his motto was "Drive it like you stole it" whenever he had his hands on a fast car. You'd think a header gasket would last longer than a test drive, but I learned the hard way that those didn't.

So glad to hear your efforts were more successful.

Doug