I have 230 miles on my newly rebuilt 327 w. Flowtek heads, Howards hydraulic flat tappet cam/lifters and Comp roller tip rockers.
I thought I had a valve train noise after the initial 20 minute break in run so I ran the valves again.
I later found the cause of the noise, it wasn't the valves.

I took the car to town a few days ago and knew something wasn't right under the valve covers.
I got home and pulled the plugs, they all look great, rolled it over and checked the valves and five were loose.

I've set them again.

Fearing bad lifters or cam lobes I tried checking valve lift, but with the lifters bleeding off I'm not getting consistent readings.
Is there a way to check valve lift with hydraulic lifters?

I dislike these rockers, my socket gets wedged in the narrow end of the rocker when the valves are closed and throws off zero lash.
I have to make a slight adjustment, remove the socket and check the feel.
I was warned off of these a while back but forgot about that when I was shopping for rockers for this build.

I came and searched through my saved threads here and see that if a lobe or lifters go bad it's usually much sooner than 200+ miles after cam break in.

I will probably put it back together and test drive it, any damage that's been done is already done.

 

To check lift. Remove rocker arm and indicate right off the top of the pushrod.
Your nuts could have backed off? Or you could have wiped a few lobes.
It is a worry.

 

if you haven't done any damage,readjust all the valves and use posi-locks.they won't loosen up like the stock nuts.

 

Removing the rockers so the valve springs won't compress the lifters makes sense, thanks.
I've wondered if the nuts are loosening (I wouldn't have thought lock nuts would), I'm going to measure the length of the studs sticking up above the nut, if it happens again I should know what the problem is.

@blue427 It didn't occur to me to install posi-locks, they'd certainly be easier to adjust. Once I'm sure the cam/lifters are good I'll do that.

 

Yes if you reused lock nuts they can come loose. I know of a few guys that have learned this lesson.

 

I had my BB rebuilt during Covid but not back on the street until a couple summers after. I kept getting returning ticks so kept adjusting the valves - sounded great for a while then ticks returned. Turned out the Comp Cam intake pushrods were soft and the tips were wearing down under the rockers. Of the 8 intakes, 6 were deformed — no issues with the exhaust rods.

Just something to look at.

 

Thanks, I'm picking up a set of polylocks today, I'll check the pushrods and measure the cam lobe lift while I have the rockers loose.
I'm using Trick Flow pushrods, I think I selected them on length and availability, I don't know how the quality compares.

 

I would also suggest that you verify that your push rod's are open inside and clear. I rebuilt my 427 and within an hour it started tapping lightly and it was getting progressively louder as I drove it.

After taking it home and found the blocked pushrod had kept my #6 exhaust valve from getting lubricated and the roller rocker arm was destroyed as it was black and overheated. After replacing the push rod and the rocker arm all was well again.

The oil passageway inside the push rod is small so be sure to verify that each one is clear before using them. If the rocker arms are not getting enough oil then they will get noisy and be damaged.

Best Regards,
Chris

 

Vast majority of friction/heat in all rocker arms are in TRUNNION --- NOT in tip! Prima facie evidence: Look at any LS series motors' much improved rocker arms.

Unless your Howards cam has well Over 0.310" LOBE Lift, Suggest revert to plain stamped-steel, OE-replacement-type rocker arms.

 

I completely dislike the Comp Cam Rollertip rockers.
They solve a problem which does not exist, and completely miss the main issue of heat and friction at the trunion or ball socket.
Just use stock rocker arms.
Old rockers are worn together and paired with their pivot ***** and must NOT be mixed up.

OTOH the stock crimp nut arrangement has been one of the SBC weaknesses since the beginning of time.
They do significantly wear out and get loose if adjusted a few times, and then they will back-off while driving.
This was always a significant challenge on solid lifter cars and was the only reason you had to adjust the valves basically every weekend.

There was a torque spec on these things when new. You could put new ones on and they would still loosen because the threads of the stud also wear.
If you tested a bunch for torque, you could eventually get a set that would hold, for a little while.
Almost all of the poly-locks were too tall and would not fit under the factory valve covers. Since they are made for stud girdles. So new valve covers are required.
Aluminum rocker arms were also too fat and would not fit under stock valve covers.
Arrrggghhh!!!
A viscous circle.
I sold all this stuff in the speed shop for 25 years, and none of it helped the power of a street engine.
None of this stuff was really needed on 90% of the guys that bought it all.

Just use GM rocker arms, with SHORT poly-locks made by Crower, that WILL fit under factory valve covers.
Your valve lash will hardly ever change again. I revved my solid lifter LT-1 to 6800 often (racing & autocross) and the lashed stayed the same for many years straight.
I checked it sometimes, but it never changed.
Eventually I just waited for the sewing machine purr to change, and that took years....
And my OEM aluminum valve covers fit and hid it all.

If you have a really aggressive high lift cam, or a BB with same, then stainless rocker arms are might be a worthwhile upgrade, over factory ones. They are smaller in size then the aluminum ones and fit under valve covers better. That is what I run on my .600 lift solid roller cam BBC, with factory valve covers. With the mandantory short Crower Poly-Loks. But the short ones are still tight fit on a BB.

That is all the valve cover clearance I have, about .100" Above the nut, that is the tight spot, even with the short poly-loks.

 

Thanks Leigh. I don't remember why I ended up with these rockers, I assembled the engine two years ago and finally had time to drop it in.
I picked up a set of ARP Poly-Loks, they do fit under the chrome covers that I'm currently using.
I like the idea of checking the clearance, I'll get out the playdough.

The cam is a .485/.498 lift and I've spun the engine to 5500 a few times.
I'd never had problems with the stock Chevy rockers or nuts before, but most of my prior experience was with stock 283's in old pickups, with no tach.

 

And I now find a better selection of stamped steel rockers on the Summit website, all I had to do was leave out the max. valve spring diameter and more parts popped up.
This engine is a (somewhat) disposable place holder while I get my 383 built.

If these current rockers act up I'll trash them and buy a set of stamped steel rockers.

 

Suggest don't limit your choices to summit.
JME: Elgin "Black Ice" (cryogenic-treated) stamped steel RA's. IIRC, all black ice have longer slots.
OE GM RA's are very good as well.

 

I use the Comp roller tip rockers a lot, with Poly Locs......for three reasons.
1) A stamped rocker arm can have anywhere from 1.4 to 1.5 ratio but never 1.52......I have heard of 1.38 on rockers out of the box.
2) The magnum rocker is about four times stronger than the stamped piece of ****. This rocker combined with an ARP stud makes the valvetrain a lot more stable and is worth a few hundred RPM up top before float...it will also make more power because of it.
3) Though the advantage of the roller tip is debatable, it is MUCH easier to see the pattern and the contact of the tip for pushrod length....and with the poly loc it is easy peasy to feel where zero lash is with your fingers spinning the poly loc at threshold of zero lash.....you will feel a slight resistance when it just begins to plunge the lifter....zero.
4) They are half the cost of a full roller......the left over money can buy a lot of parts like an intake.

I am one who thinks full rollers are waste of money most of the time....but if you have the money, buy them!

OP- Crower makes a short 3/8" poly loc........try that first.

Jebby

 

I've driven just over 100 miles since I installed the poly-locks and I have valve train noise again.
All the nuts are tight, there is a little bit of side to side play in several of the rockers.

I was shopping for roller rockers when a friend mentioned he had a set he replaced on his engine, they're 1.5 ratio.
These will give me a chance to try something different and see if the valves stay quiet after adjusting and driving for 100 miles.

 

CT350 (602) Engine Camshaft Specifications
P/N 24502476 camshaft is installed in a CT350 (602) engines. It is a flat tappet camshaft and uses standard hydraulic lifters. See section on valve lash for proper lash procedure. Valve Lift: .435 intake and .460 exhaust. Duration @ .050": 212 degrees intake and 222 degrees exhaust. Cam lobe centerline is: 112.5 degrees. Intake lobe lift .290". Intake base circle radius: .633" Exhaust lobe lift .307" Exhaust base circle radius: .616" Dowel pin hole: Retarded 5 degrees from centerline of # 1 cylinder exhaust lobe, advanced 107.5 degrees from centerline of # 1 cylinder intake lobe. (107.5 +5 = 112.5 degrees lobe separation.) Note: +/- .010" all dimensions and +/- 5 degrees angularity. Shown below is a graph of the cam profile for cam p/n 24502476 as used in CT350 (602) engines. 24502476 camshaft specifications

above is an excerpt for CT350 track tech manual published & distributed by GM
Same cam P/N 24502476 is installed in 350 HO STREET crate motors; probably hundreds of thousands if not more were made in serial production.
as you can clearly see from specs, it has about TEN degrees LESS intake duration. That makes it Very responsive in street and in traffic.
This cam continues in production today. and both the 350HO motors and CT350 motors continue in production.

 

You are replacing the camshaft....the rockers are not going to deform enough to make it noisy again.....
Pop the intake off and pull the lifters....answer the question....don't keep dancing around the sideline.

Jebby

 

Would the cam go bad this slowly? I thought when a lobe went bad it was quickly and usually apparent after break in.

 

Yes it can.....I have seen them fall out at 500 miles...I have a 30-30 cam here with 6000 miles on it and the lobes are all .020-.030 wore and some not at all....
The only other things that could be going on are you are pulling the rocker studs out....or a shoddy intermittant check valve in the lifter....
You need to pull the lifters and check for wear and/or verify the crown....

But changing rockers after you verify the current ones are not damaged is a waste of time....

Jebby

 

Mine ate a cam somewhere around 1500 miles or so last summer. Cut open your oil filter and see what's in it. That would answer some questions for sure and be a good turning point which way to go.

I hope its clean. Mine wasn't!