roger3

I have a stock 71 LS5 with 64,000 original miles. When I bought the car it had 53,000 miles.

I drove the car to dinner the other night (40 miles round trip) no issues. Next morning cranked it and heard valve train noise. Pulled both valve covers and found the rocker arm for exhaust valve of number 2 cylinder loose. Made 1/8 to 1/4 turn on rocker arm nut and it quieted down. Let it run in driveway for a few minutes, sounded fine. Drove it into my shop maybe 200ft away. Next time I cranked it noise was back.

Pulled intake last night and found that cam lobe for #2 exhaust has a small flat spot on the ramp and the bottom of the lifter is rough feeling, slightly jagged. The lifter won't come up out of the hole due to the rough jagged edge.

I have read the posts about whether today's oil is/is not the cause. I run 93 octane unleaded fuel all the time, usually Chevron. I keep the oil changed regularly. I've had the car about 5 years and change the oil and filter often. I use Pennzoil 10W30.

Not trying to start a war but would like to hear what could have caused it. Anything I can check.

I'm going to pull the motor and have it rebuilt. Not sure what cam I will put back in it. Thinking of going hydraulic roller just so I don't have to worry about it.

I'll post some photo's this weekend, although its tough to see the flat spot I caught it early. It's easy to feel but not as easy to see.

Roger

63mako

Low ZDDP in modern SM/SN rated oil or weak springs due to sitting compressed. Hydraulic roller is a great choice. Might not need a complete rebuild. Do compression check. If it is all good with good oil pressure new cam, springs, pushrods, timing set, button it up.

hugie82

A basic overhaul and a roller cam will make a nice runner with no headaches!

roger3

Weak springs makes sense and sitting compressed for long periods of time makes sense. I haven't driven the car much in last couple of years. I can imagine cranking the engine only occasionally since oil has mostly drained into oil pan would also play a part. Along with low ZDDP.

I'm going to keep engine stock. Any cam recommendation for equal or slightly better performance?

Thanks

Roger

TWINRAY

In my non expert opinion, modern 10-30 has a max of 1000 ppm zinc. These old flat tappets need probably 1400 ppm. In my '67 327/350 I run Delo 400 15w-40 and 4 oz.@Red Line EOS in each oil change. On my '69 350/300, lifters were shot at 90K miles. Most of it lubed with Penzoil 10-40.

BKbroiler

Why would weak springs flatten a cam lobe? It was the lack of zinc in the oil.

zwede

This one is pretty close to stock duration, but with more lift. You'll see more torque and power with no loss of driveability:

https://www.lunatipower.com/Product....d=4536&gid=289

This next one is slightly hotter than stock but will still work with stock compression & heads:

https://www.lunatipower.com/Product....d=4538&gid=289

Be sure to use matching valve springs. Stock springs will not work. You'll also need shorter push rods.

63mako

OP asked for reasons it might have happened. One or two weak springs will take out your cam lobes. A 43 year old car with 64000 original miles spent a lot of time sitting with a few springs fully compressed. Once the spring is weakened it has a different resonance that will further fatigue it causing worsening harmonics until it starts bouncing in the spring pocket transferring the surge through the valvetrain to the lobe/lifter taking it out, breaking the spring or damaging other valvetrain components. Less ZDDP in the oil will accelerate the odds of damage. Springs might be fine and just the oil but it is one lobe only.

63mako

Didn't Chris Straub get your cam for your other car? You have 8.5 to 1 compression. TH400 Auto W/ 2000 stall, 3.36. http://www.summitracing.com/parts/HRS-123515-10/

garygnu

can the OP pull the lifters from the bottom if the cam is removed ?

roger3

I was thinking if the springs are weak they will not keep the lifters pressed against the cam like they should and the lifter would then be hitting or tapping the cam instead of staying in contact with it and sliding. Not sure if that's really how it works that's what I picture in my mind. Seems plausible.

I've ran the same oil for 10,000 miles. Would it have taken that long to cause the failure? Not sure what brand oil the previous owner used.

Roger

63mako

Need certain spring pressure to maintain contact between the lifter and lobe.

roger3

Yes I bought a cam, lifters, and pushrods for my other car from Chris. I may need to give him a call down the road. I'm gonna pull the engine apart and see what shape its in. If I bore it and replace Pistons I will bump up the comp ratio near 10:1. I do plan on keeping the stock exhaust manifolds, heads, intake, and quadrajet. Not looking to make it a race car just maximize its mostly stock potential. Before this problem it ran very well. It would smoke tires and pulled strong up to 5000 RPM's.

Roger

roger3

Thanks for advice. I'll definitely get matching springs and new pushrods.

What about rocker arms? I have the stock short valve covers. Do they make roller rockers that will fit under them?

Roger

roger3

Here's a couple Picts.





Lifter to left







You can see jagged edge of lifter. Makes me think lifter was loosing contact with flat surface of the cam and when they made contact the edge of the lifter was hitting the cam lobe.

Roger

Les

Great photos. Yea, that's pretty torn up. All that metal had to get circulated in the oil to some degree. Good luck with the rebuild.

Roller rockers will fit under the short valve covers if you get the kind that eliminate the drippers- or you could probably remove the drippers from your current valve covers with a little work. Then just get a set of FelPro double thick valve cover gaskets and you'll have plenty of clearance. I've been running mine that way for many years now.

Little Mouse

Was told by mike jones cam builder that a pro 55 cam core ( higher grade iron cam core ) they can use up to 420 lb springs with regular type lifters. Past that spring pressure to as much as 550 lbs they use steel tool lifters on the pro 55 cam core's. Now these are high lift well past .600 high duration cams. He said Richard Petty driving school cam to him with short cam life problems. He designed a cam for them and now they remove the cams at 36,000 miles just as a precaution and there still ok. Again this is radical stuff with high spring pressures lift and duration compared to what you are doing.
But my question would be as cheap as the extra costs to have a pro55 cam core used for a cam why would a person not simply do this on even a very mild cam with as much as it costs to even rebuild an engine much less a performance engine with really high cost in it. Seems like the cheapest insurance policy a person can buy on the planet if your going to do a flat tappet camshaft.

63mako

Great. Repost when you come to a decision as the cams recommended would be for your 8.5 to 1 engine. A compression upgrade, roller cam and a little higher stall convertor would make a huge difference and could still sound and drive like stock. No one would know. Looking at that lifter I would rebuild it. A lot of metal circulating. You can reach in with a file and file the burred edges of the lifters off and pull it right out.

gerry72

The damage looks like fretting or maybe even false brinelling. Goes without saying that you're in for a new cam and lifters for sure, but look at the other components for anything causing a vibration or resonance in the valve train including the valves.

grumman41

I had the same thing happen to my 71 LS5, about the same amount of miles. I had mine pulled and overhauled, I went with a roller cam and kept everything else stock. It dynoed at 392hp and 475flbs torque with stock carb, intake, exhaust and distributor. I did have forged pistons put in and brought the compression up to 9.5 to 1. Probably should have went another point on the compression and a custom ground cam.

Kevin