Chevy Nova Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
710 Posts
Discussion Starter #1
I'll do my best to keep this concise but give all the details... I finally got my car on the road this weekend and besides running a little lean and a small lifter tick it was running pretty well. The motor is a mildly-built 383 with cast iron GM double-hump 1.94 heads. I took the car out for pretty hard run and hammered it through the gears fairly hard then put it away. When I started the car again a few hours later the small lifter noise became a loud lifter noise. I pulled the valve covers, adjusted all the rockers, and while doing so I discovered a broken pushrod. Nothing catastrophic, the tip broke off and was still inside the rocker arm. These were old, stock pushrods so I wasn't too surprised. I put in a new set of Comp Cams 1-piece pushrods, readjusted everything and the noise went away. Problem solved... so I thought. Everything was fine until another hard run through the gears and a slight lifter tick returned. I just blamed this on my inexperience adjusting the lifters, and tried again. Once again, the noise disappeard after being adjusted so I took the car on a long drive. I drove it about 30 miles and got on it fairly hard a few times without a problem. Then I decided to really hammer on it and burned the tires through 1st and 2nd gear and guess what...the noise is back. How can it get out of adjustment just by running the RPMs up high one time? I called the guy who built the motor for me years ago and he wondered if maybe I had a rocker stud that's pulling out of the head. This is the only logical thing I can think of. If it was a broken rocker arm or bad lifter the noise wouldn't go away just by re-adjusting everything, right? Any other suggestions of what's going on?

Thanks in advance for your input!
 

·
Registered
Joined
·
673 Posts
a rocker stud pulling is possible. also, how did you breakthe cam in on the motor, and is it a new motor? has it sat for a long time?
it could be that your cam is going flat.
 

·
Premium Member
Joined
·
13,245 Posts
My first guess is gonna be a bad cam lobe. Is the noise coming from the SAME lifter/rocker arm every time? If you are running hydraulic lifters, they are VERY forgiving as far as setting the pre-load is concerned. It COULD be rocker stud pulling out like njciscool said.

Either way, I would turn the engine over by hand and measure the amount of lift on that valve compared to another valve rated with the same lift. These symptoms you are describing are EXACTLY what I experienced with my XE274 cam when it wiped an exhaust lobe last year :rolleyes:



Never pay again for live sex! | Hot girls doing naughty stuff for free! | Chat for free!
 

·
Premium Member
Joined
·
11,072 Posts
Is it a Comp cam? <vendor bashing edit> I know several people that have had trouble and Comp won't do anything about it. An experienced race engine builder I know wiped out 13 lobes within a couple minutes of starting his new engine;and that was using the little tiny break-in springs!! Comp told him he must have other problems. Another friend lost 2 cams in a row doing a story for a magazine; same response from Comp. I have always been a fan of their stuff, but I would never use a flat tappet cam from them.
Another issue could be the lifters you used--were they new? Who made them? Did you break-in the cam properly? Are they stock lifters with a big cam? How's your oil pressure? Maybe they are collapsing?
 

·
Premium Member
Joined
·
10,210 Posts
If its the same lifter you have to keep adjusting I would suspect as others have said that either a lobe/lifter is going south or if you have press in studs that one is slowly coming out of the head..just my 2 cents:)
 

·
Premium Member
Joined
·
8,405 Posts
I agree with the symptoms point to a quickly wearing cam lobe or a rocker stud pulling out. You'd better investigate quickly before you ruin your engine.

BTW, worn lobes on performance flat tappets are not unusual or unique to one manufacturer. Engines that are stored or driven infrequently often suffer more wear during start up due to insufficient lubrication. Cam break in is critical especially for high lift rate cams. You should verify lifter spin during break in. I'll bet in every one of those cases the engine builder will say "Huh? how do you do that?".

You put a paint pen dot on the pushrod. Lift the manifold side of the valve cover and look. The pushrods should be twirling around. If it's not then you need to stop and replace the lifter in the position.

Another mistake is installing the distributor at TDC instead of base timing degrees. The engine needs to fire right away and run at high idle. A lot of builders seem in a hurry and don't have the cooling system and carb ready to go when test firing the engine. Extended startup sessions cause the protective breakin lube to wear off and increase the odds of cam lobe failure.

Bowtie0069: I edited your post. Site rules don't allow vendor bashing so be careful what you post and stick to the facts. Your post implied that all Comp cams are bad citing anecdotal evidence. I'd like to see more hard information on what specific grinds are going flat or if it's random.
 

·
Registered
Joined
·
161 Posts
Lifter noise

The Comp Cams EX (extreme) have steep ramps,and will clatter. Also difficult to break in. I have used them twice.Still have one in my 55 Belair.Clatters worse than a solid cam. Its the nature of the beast. I use only Lunati solid now in my race car. Just a preference. When I can afford it,gonna go to a roller.
 

·
Registered
Joined
·
710 Posts
Discussion Starter #8
Sorry I didn't provide more details about the motor. It's not a new motor, in fact it was last built about 14 years ago but has seen very little use since then since the car was stored for about the past 13 years. I don't believe there could have been break-in issues since it ran fine before being stored. The cam is a Manley brand cam with hydraulic lifters (don't recall brand of lifters). If a lobe has gone flat, wouldn't the problem be there all the time? Would simply re-adjusting the lifters solve the problem temporarily, and why would running up the RPMs hard one time cause the tick to return because of a bad cam lobe? I'm sure it's possible, I just don't understand it. I assume it's the same rocker each time, but I haven't yet pin-pointed which one it is. With the valve covers on I can't determine which one is noisy and when I pull the valve covers none of them have seemed noticeably loose. I bought an old valve cover so I can cut a strip out of the top and adjust the rockers while the engine is running, then I can determine which one is making the noise. Once I know which one is the problem I will inspect it close to try to see if the rocker stud is pulling out. Does this sound like possibly a bad lifter?
 

·
Premium Member
Joined
·
8,405 Posts
Paul Wright said:
Engines that are stored or driven infrequently often suffer more wear during start up due to insufficient lubrication.
This line was buried in my post and may apply to your situation.
Your lobe may not be completely "flat" (no lift left) OR you may be pulling out a press in rocker stud.

Every time you beat on the engine you just make it worse. You can't fix it with the throttle pedal tool!

Pull the valve covers and check the height of the rocker studs. If they are all the same then you need to start the engine and see if the pushrods are rotating. You may have to pull the manifold and pull the lifters. Inspect the bottoms for abnormal wear. It should be obvious. A good, rotating lifter has a circular wear pattern. A non rotating lifter has a linear wear pattern or becomes dished.
 

·
Premium Member
Joined
·
10,210 Posts
JTW said:
Sorry I didn't provide more details about the motor. It's not a new motor, in fact it was last built about 14 years ago but has seen very little use since then since the car was stored for about the past 13 years. I don't believe there could have been break-in issues since it ran fine before being stored. The cam is a Manley brand cam with hydraulic lifters (don't recall brand of lifters). If a lobe has gone flat, wouldn't the problem be there all the time? Would simply re-adjusting the lifters solve the problem temporarily, and why would running up the RPMs hard one time cause the tick to return because of a bad cam lobe? I'm sure it's possible, I just don't understand it. I assume it's the same rocker each time, but I haven't yet pin-pointed which one it is. With the valve covers on I can't determine which one is noisy and when I pull the valve covers none of them have seemed noticeably loose. I bought an old valve cover so I can cut a strip out of the top and adjust the rockers while the engine is running, then I can determine which one is making the noise. Once I know which one is the problem I will inspect it close to try to see if the rocker stud is pulling out. Does this sound like possibly a bad lifter?
Did you prelube this motor before you put it back into service? after sitting for that long the cam and lifter bottoms would be completely dry of any lube and unless the motor fired right up and the oil pressure instantly returned you could have very easily damaged a lifter/lobe just cranking that motor to get it fired up. the lobe may not be completely flat, yet, but is slowly wearing down and each time you give it you are accelerating the lobe/lifter wear which is why the ticking reappears after each hard run.
 

·
Registered
Joined
·
710 Posts
Discussion Starter #11 (Edited)
69NovaSS said:
Did you prelube this motor before you put it back into service? after sitting for that long the cam and lifter bottoms would be completely dry of any lube and unless the motor fired right up and the oil pressure instantly returned you could have very easily damaged a lifter/lobe just cranking that motor to get it fired up. the lobe may not be completely flat, yet, but is slowly wearing down and each time you give it you are accelerating the lobe/lifter wear which is why the ticking reappears after each hard run.
No, it wasn't pre-lubed before being started. Unfortunately I wasn't there when it was first started. It was stored in my brother's basement about 1000 miles from where I live, and was trailered to me. It had been started about once each year while stored, and they said it cranked over and started almost instantly. This problem just appeared this past weekend, even though I've been running the engine and taking short drives for almost a month now. I certainly won't beat on the car now (probably won't leave the garage until this is fixed), but I honestly thought the problem was fixed with the new pushrods and a proper adjustment of the rockers. It ran smooth, accelerated well, and seemed completely fine until one hard thrashing for about 6 seconds and the noise was back. If a rocker stud is slowly pulling out of the head will I have to pull the head off to fix that?
 

·
Registered
Joined
·
508 Posts
I maybe glossing over a point and not catching it, what secures your rocker arms? You have a good idea in getting an old valve cover cut right across the top so you can adjust them running. If you are using stock nuts, you think one might be backing off? I had a Ferd many years ago that would do that when ran pretty hard and I had to install poly-locks with allen set-screw and they would not back off.
 

·
Premium Member
Joined
·
11,072 Posts
Your post implied that all Comp cams are bad citing anecdotal evidence. I'd like to see more hard information on what specific grinds are going flat or if it's random
I don't believe I implied that at all; I said they have a problem they won't admit. You may recall a shortage of flat tappet lifters a few years ago--about that time quite a few people were having cams go flat immediately after starting due to incompatability between the lobe and the lifter. When I spoke to Comp reps at the time, they thought it was related to the lifter issue. When I mentioned it again to Comp at SEMA in Las Vegas, they told me they were unaware of any unusual wear issues.
I work with several staff members of various Primedia publications who do a lot of work with Comp parts--one of the projects involved a friends Chevelle that was rebuilt using a Comp solid lifter cam; it was properly broken-in and failed very quickly. Comp claimed too much spring pressure(springs were supplied by Scoggin Dickey) Another cam was sent, along with the reccomended springs directly from Comp, this one failed the day after it was broken in on the way to dyno test the car. A new Lunati cam was then installed; END OF PROBLEM!
My transmission builder races an NHRA Stock Eliminator car; his brand new race engine is the one that lost 13 lifters in a few moments, sending all the debris thoughout the new, very expensive piece--this using the lightweight break-in springs that the big boys use on race engines. Comp told him it must be an oiling problem. The solution was to install a new Lunati cam, after tearing the engine down to change rings and bearings damaged from the cam debris.
I've spoken with others having the same problems, but they are not the kind of builders I would take my engine to for repair.
The first instances were about 2 years ago, but I still hear an occasional horror story, so maybe they have fixed the problem, maybe not.
Like I said, I have always been a fan of Comp stuff, I've had 3 of their cams in my car and would use them again--just not a flat tappet grind.
 

·
Registered
Joined
·
710 Posts
Discussion Starter #14 (Edited)
Brett said:
I maybe glossing over a point and not catching it, what secures your rocker arms? You have a good idea in getting an old valve cover cut right across the top so you can adjust them running. If you are using stock nuts, you think one might be backing off? I had a Ferd many years ago that would do that when ran pretty hard and I had to install poly-locks with allen set-screw and they would not back off.
Gosh Brett, I sure hope it is something as simple as a rocker nut backing off. My engine builder friend asked me the same question. Once I narrow down which rocker is coming loose I can more closely examine the nut, or I may just replace all the nuts with poly-locks and see if that solves the problem. When I pull the valve covers none of the rockers seem unusually loose, but it's difficult to tell for sure since some of valves are open and some are not. I guess I could I turn the engine over by hand and check each of the rockers on each individual cylinder while both valves are closed to try to determine which is causing the clatter. Maybe I'll try this before cutting up that old valve cover. Thanks for everyone's help, I'll post again when I track down the problem.
 

·
Premium Member
Joined
·
10,210 Posts
JTW said:
Once I narrow down which rocker is coming loose I can more closely examine the nut, or I may just replace all the nuts with poly-locks and see if that solves the problem.
My experence with poly-locks is that not every rocker stud will work. If the top of the stud has not been machined smooth and the end it not level poly-locks will NOT work....they will just keep backing off cause when you go to lock them in place (with the set screw) if the top of the stud is not flat the lock only catches on one side of the stud and sorta gets cocked...it then takes no time at all for them to work loose...been there done that...and switched back to regular nuts.:)
 

·
Registered
Joined
·
710 Posts
Discussion Starter #18
69NovaSS said:
My experence with poly-locks is that not every rocker stud will work. If the top of the stud has not been machined smooth and the end it not level poly-locks will NOT work....they will just keep backing off cause when you go to lock them in place (with the set screw) if the top of the stud is not flat the lock only catches on one side of the stud and sorta gets cocked...it then takes no time at all for them to work loose...been there done that...and switched back to regular nuts.:)
I hadn't heard this before. Good to know, thanks.
 

·
Premium Member
Joined
·
8,405 Posts
bowtie0069 said:
I don't believe I implied that at all; I said they have a problem they won't admit. You may recall a shortage of flat tappet lifters a few years ago--about that time quite a few people were having cams go flat immediately after starting due to incompatability between the lobe and the lifter. When I spoke to Comp reps at the time, they thought it was related to the lifter issue. When I mentioned it again to Comp at SEMA in Las Vegas, they told me they were unaware of any unusual wear issues.
I work with several staff members of various Primedia publications who do a lot of work with Comp parts--one of the projects involved a friends Chevelle that was rebuilt using a Comp solid lifter cam; it was properly broken-in and failed very quickly. Comp claimed too much spring pressure(springs were supplied by Scoggin Dickey) Another cam was sent, along with the reccomended springs directly from Comp, this one failed the day after it was broken in on the way to dyno test the car. A new Lunati cam was then installed; END OF PROBLEM!
My transmission builder races an NHRA Stock Eliminator car; his brand new race engine is the one that lost 13 lifters in a few moments, sending all the debris thoughout the new, very expensive piece--this using the lightweight break-in springs that the big boys use on race engines. Comp told him it must be an oiling problem. The solution was to install a new Lunati cam, after tearing the engine down to change rings and bearings damaged from the cam debris.
I've spoken with others having the same problems, but they are not the kind of builders I would take my engine to for repair.
The first instances were about 2 years ago, but I still hear an occasional horror story, so maybe they have fixed the problem, maybe not.
Like I said, I have always been a fan of Comp stuff, I've had 3 of their cams in my car and would use them again--just not a flat tappet grind.
Sorry, but you can't make a slanderous statement like "they have a problem with their cams" without proof. You need statistical evidence not anectdotal evidence to prove they have a problem. Every failure has a root cause even if it's not obvious to a magazine writer.

It's quite possible that the problems stem from the lifter(s) and not the cam. If that was the case then saying the cam has a problem is not a true statement.

The internet has the uncanny ability to spread misleading or outright false information at lightning speed and turn rumor into fact.

You can't tell us what the specific problem was in your examples so it's just hearsay and allegations. Everyone is entitled to their opinion and free speech however you can't make an accusation that Comp cams have a problem without documented proof Comp cams are defective.

If there was a problem with a batch of lifters (I don't believe Comp makes their own lifters)
and that caused the failures cited, then you are jumping to conclusions and making misleading statements by saying outright or even implying Comp Cams are more inherently defective than any other. If some of the failures were caused by installation problems and some caused by bad lifter(s) it still does not show us how the cam itself is defective.
Where the failures all the same grind? Was the problem caused by inproper hardness? Was the cam sent for metalurgical analysis?

Maybe some cam failures are caused by improperly machined lifters but that should have been caught during break-in by observing if the pushrod spins or not. If any don't spin then that lifter should be replaced. It is the engine builders responsibility that all the parts function properly. I have never had a cam go flat. And at work I've only once seen a comp cams flat tappet cam failure and that was due to incorrect break-in with race springs to meet a magazine deadline. It's rare but not out of the question to see lifters that don't spin, but these get caught before they do any damage.

Bottom line though is the site rules prohibit vendor bashing. I have to remove words, sentences or complete posts that might be deemed slanderous.
 

·
Registered
Joined
·
710 Posts
Discussion Starter #20 (Edited)
Update

Since many of you offered your help and advice I thought I'd post an update to my problem. I cut the top center off an old valve cover hoping to find which rocker was making all the noise, but even with the rockers exposed I could not tell which was the culprit. I tried adjusting each of them while the motor idled, but couldn't seem to make the noise go away. I was hoping I could tighten down the loose rocker and the noise would stop, but that was more difficult than I remembered. Next, I removed all 16 rocker arms and inspected them closely and found no signs of severe wear or damage. The ball pivots also looked fine. I layed a steel straight-edge across the top of the rocker studs and found that none of them seemed to have been pulling out of the head. The dowel pins that are pressed into the heads to hold the studs are all still in place. Several of the locknuts were not exactly in great shape and removing them took a small toll on about 3 of the rocker studs, but I was able to clean up the threads on those rocker studs. I bought 16 new locknuts today, reinstalled all the rockers, and adjusted them again. Like before, the motor was instantly quiet again with the rockers re-adjusted. I marked each locknut at the 12 o'clock position with a paint marker so if the noise reappears I will know if one of the nuts has backed off. I plan to drive the car over the weekend and hopefully find out if maybe one or more of the old locknuts were backing off under hard acceleration. Wish me luck, I'll keep you posted.
 
1 - 20 of 23 Posts
Top