Chevy Nova Forum banner

1 - 20 of 44 Posts

·
Premium Member
Joined
·
2,333 Posts
Discussion Starter #1
I finally went to the local exhaust shop and got my mufflers installed and some pipe bent up. Turned out great. On the way home I noticed that the engine was ticking pretty loudly, something I never could hear before when driving with open headers. The ticking got louder with higher rpm and I figured it must be a lifter or rocker arm. I pulled the valve covers and discovered this:



I only put a 1/4 turn pre-load on them and I guess these were too loose and jumped off the pushrod. The center rollers still rotate and aren't damaged, it's just the self guided plates that are buggered up. I could file away the rough metal and put them back in but I'm worried maybe they could crack or something later. What do you guys think?

After engine break in, I only drove the car about 10 miles before this and never more than about 4000 rpm. I noticed at about 3500 to 4000 it kinda missed or ran funny so perhaps it was because the valvetrain was hopping around.

Now where can I get some single crane gold rockers? I can't find them anywhere online and crane's website is useless since they were bought out by that cycle company.

Sure sucks that I can't even enjoy my new exhaust....:mad::mad::mad:
 

·
Registered
Joined
·
1,908 Posts
I would replace them. Also inspect the pushrod cup and the pushrods themselves.

Summit sells some singles. The link is 1.5 and 3/8 stud. Search around you may find an exact match. If not, a different rocker shouldn't hurt.

http://www.summitracing.com/parts/CRN-11750-1/
 

·
Premium Member
Joined
·
2,333 Posts
Discussion Starter #3
Ah thanks, I didn't see those singles since I was looking for self aligning rockers. I'll call Summit Monday and see if they can hook me up.
 

·
Registered
Joined
·
1,989 Posts
Just clean them debur them and reuse them, but keep your eye on them, mine came lose one time because the nuts backed out so i had to get some locking nuts, had no damage but your damage looks minimal.
 

·
Premium Member
Joined
·
2,354 Posts
As what Ventura says. Are you running guide plates AND self aligning rockers. Alignment must be perfect if you are doing so. Looks like the rocker jumped off the tip. Either run guide plates or the self aligning rockers. Not both. My .02. Dave
 

·
Premium Member
Joined
·
2,333 Posts
Discussion Starter #7
No I'm just using the self aligning rockers on vortec heads. I think they just simply weren't preloaded enough.
 

·
Registered
Joined
·
375 Posts
One quarter turn preload should be fine. Did you lock the polylocks correctly? Is the top of the rocker stud machined flat for the setscrew? Tighten the setscrew and then tighten the whole polylock (nut and setscrew together) some more to preload the assembly. Are your valvesprings strong enough? Definitely change those damaged rockers. Also check the valve tips for damage.
 

·
Registered
Joined
·
4,612 Posts
eh

i've used roller rockers with more damage than that with roller springs. I'd take a dremel tool and very lightly clean them up. It looks worse than it is prolly.

Never used a self aligning roller rocker , always had guide plates here.

I'd say readjust your valves , then set the polylocks and recheck them after a few miles. A bunch of preload is bad IMO.

If those weren't self aligning , a lash cap might have prevented that.
 

·
Premium Member
Joined
·
2,333 Posts
Discussion Starter #10
Maybe the method of tightening the rockers until the pushrod stops spinning is a somewhat inaccurate way of adjusting them? I was pretty sensitive when adjusting them and stopped as soon as I felt a little resistance on the pushrod. Maybe I just don't have the experienced feel yet.

Also, what's wrong with more preload? The lifter has a range of adjustment that just fills up with oil right? More preload shouldn't mean that there's actually more pressure on the cam or anything, the lifter plunger would just sit lower in the bore.
 

·
Registered
Joined
·
1,244 Posts
Maybe the method of tightening the rockers until the pushrod stops spinning is a somewhat inaccurate way of adjusting them? I was pretty sensitive when adjusting them and stopped as soon as I felt a little resistance on the pushrod. Maybe I just don't have the experienced feel yet.

Also, what's wrong with more preload? The lifter has a range of adjustment that just fills up with oil right? More preload shouldn't mean that there's actually more pressure on the cam or anything, the lifter plunger would just sit lower in the bore.
It takes a little practice but its the only accurate way to do it. You might be trying a little to hard and being to sensitive. Use your fingers to tighten the nut and put your other hand on the pushrod. You will feel resistance on both once you hit .00 pre-load. Then you can tighten a half turn, tighten down the lock with a allen key, then tighten the entire thing down a little more until it is snug.

Yes you can run more pre-load. Most cam manufactures recommend 1/2 turn of pre-load. Some people use less or more. To little pre-load and you could end up damaging the lifter, camshaft, pushrod, or rocker (like in this case). To much preload and the lifter may pump up and keep the valve open a little causing it to backfire out of the intake or eventually burn the exhaust valve.

-Dan
 

·
Premium Member
Joined
·
2,333 Posts
Discussion Starter #12
That sounds like some good advice Dan, I'll be sure to tighten them down properly this time.

I called Summit and they don't sell them singularly anymore since Crane Cams was bought out and basically is not producing parts right now. He said a lot of Crane parts were bought up by people that were afraid of no availability later. Luckily Google Shopping search found a place called partsshowroom.com that is selling them individually for $20.78 so I ordered three. Hopefully they are indeed in stock and they ship them quickly.

-Aaron
 

·
Registered
Joined
·
4,612 Posts
ahh

Maybe the method of tightening the rockers until the pushrod stops spinning is a somewhat inaccurate way of adjusting them? I was pretty sensitive when adjusting them and stopped as soon as I felt a little resistance on the pushrod. Maybe I just don't have the experienced feel yet.

Also, what's wrong with more preload? The lifter has a range of adjustment that just fills up with oil right? More preload shouldn't mean that there's actually more pressure on the cam or anything, the lifter plunger would just sit lower in the bore.
thats it though ,, its like you have 16 hydraulic cylinders pushing on the cam with too much preload instead of just the ones that are off of the base circle.

Hmm ,, this problem might go back to not priming the lifters , that would have maybe gave you a more accurate feel when roughing the adjustment in.

I guess its woulda coulda shoulda time though. I like to go back and check them after an initial start, but i like them set as much on the edge as possible. I've even done them with the engine running , yes it makes a mess , but it gets them very close.
 

·
Premium Member
Joined
·
2,333 Posts
Discussion Starter #14
Alright, after re-ordering lifters because the first place back ordered them indefinitely, I ended up getting some from carshopinc.com. I re-adjusted all the valves and put a half turn preload on them. I set the set screw tight and then snugged the whole nut down just a hair like Dan mentioned.

I started it up and it runs a lot different. It has around 10 inches vacuum at idle now instead of 15 like before and idles a lot more choppy. I played with the timing some and it runs pretty good now. Still overall though it seems to run rougher at idle and just off idle. It sounds great at 2500+ rpm though. I'm wondering if maybe since the rockers were loose the valves weren't reaching full lift before? Could it be that with the proper preload it idles rougher just because my cam is a bit more radical than I thought? Remember this is a fresh build so I don't know what exactly to expect from the cam.
 

·
Registered
Joined
·
4,612 Posts
could be

that the valves are too tight ,, if it lossed 5 in. of vacume , they have to be too tight. It sounds different prolly cause the lifters are placing a load on the engine.

I'd check them with it running and up to running temp, loosen one up until it starts clacking , slowly turn it until it gets quiet , i'd put a 1/4 turn on it and lock it down.
 

·
Registered
Joined
·
1,244 Posts
Either the rockers were way loose with no preload causing the cam to act like it was much smaller or the rockers are too tight now. You should go back to a 1/4 turn and see if your vacuum goes back up. Just make sure the poly-locks are tight so nothing comes loose and you wont hurt anything.

Oh, what are the camshaft specs?

-Dan
 

·
Premium Member
Joined
·
2,333 Posts
Discussion Starter #18
here's the cam specs

Cammotion custom grind
236/246 @ .050", .495"/.512", 108 LSA, 104 ICL
 

·
Registered
Joined
·
1,244 Posts
here's the cam specs

Cammotion custom grind
236/246 @ .050", .495"/.512", 108 LSA, 104 ICL
With that much duration and such a close LSA, 10 Hg isnt to far off from what I would expect. My theory now is the rocker became loose or wasnt tight enough causing there to be less duration at the valve so there was less overlap of the intake and exhaust. Your reading were higher and it idled smoother. But that is probably also what caused the damage to the rockers, no pre-load on the lifters and the rocker bouncing around on top of the valve stems.

Again, you can try only 1/4 of a turn to see if it makes any difference in you vacuum reading. However, I dont think you will see much of a change.

-Dan
 

·
Registered
Joined
·
675 Posts
I had a buddy break a pushrod and bend another, and it fouled up two of his crane golds. He found a guy on craigslist in Florida (on the the big drag racing cities) that had gobbled up a ton of Crane stuff before they went out.

I'm sorry I can't give any detailed information like name, number, or exact city,I just know that the guy has enough to where he is selling them by the singles, apparently at the price Summit used to sell them for. My buddy bought his a month or so ago, so if you're interested in putting the time in, he may still have some left.
 
1 - 20 of 44 Posts
Top