Top end "clack"...adjusting rockers with "purple cam"...clearances/endplay?

[MykeNytemare]

Have a 383 in my Coronet, appears to be completely stock, except it has aftermarket intake/carb. I was told that it had a purple cam, and judging by the idle, that is likely. However, I have no idea which purple cam....

...anyway, the other day I started hearing a clacking from the top end. I plan to pull the valve covers and take a look over the weekend to see if anything obvious is wrong. The car seems to be running ok so I don't believe there will be any damaged components and hopefully its something simple. I do believe I will have to adjust the clearances for the rockers/lifters and I have no idea what a safe spec would be. Can anyone give me an idea what would be middle-ground or "safe" if I have one of the very mild purple cams? I understand it wont be exact, but I definitely can't live with the clacking so I want to take care of it.

Any advice or outside reference pages would be appreciated.

 

[62MAX]

Need a better defination of clacking.Unless someone replaced the original rockers with adjustables,you won't be adjusting anything,more than likely a lifter.

 

[dryheat]

"If" they are adjustable rockers I would start at .008 Intake & .010 Exhaust. Hopefully you did not lose a cam lobe.

 

[Meep-Meep]

Hydraulic or solid cam? If a solid purple shaft then .028" IN .032" EX (cold). If hydraulic, and you have adjustable rockers, one turn in from zero lash. Use the mechanical adjustment procedure to set the valves. If hydraulic and no adjustable rockers then something is wearing out or push rod length wasn't correct to begin with.

 

[MykeNytemare]

Let me check when I get the covers off tomorrow. I'm expecting to see adjustable rockers and believe there will be hyd lifters. But with this car, who knows. Maybe it'll be solid and just need adjustment.

I'm only able to get to the car here and there as its garaged 30 min away and I got a 2 year old at home. Thanks for the input and I'll report back Saturday evening what I find and go from there.

 

[Garys1969RR]

Yes as has been said, they are probably non adjustable. Most every one I have seen is stock non adjustable. If thats the case, then you could either have a bad lifter, (most likely cause), bent pushrod from over revving the engine, a little carbon stuck under the valve, which would hold it open slightly and cause too much clearance, (not likely at all), or loose rocker shaft hold down bolt. You can use a length of hose and put one end to your ear, and the other end move along the rocker arms (with engine running) till it gets the loudest. That is the rocker arm/lifter position you should look at. You may be able to isolate it to 1 or 2 arms. Easiest to hear with the valve cover off of course, but be prepared for alot of oil leaking out and flying around. He He

 

[Dennis H]

Mine had two mildly bent rods and a clack after a self induced oil pressure loss episode. Had to spin them in a drill to see it - detect it. Replaced them and it got quiet. Got lucky. Good luck.

 

[MykeNytemare]

I'll get the rags and blankets ready while I listen. Hopefully not an overrev/pushrod issue as the car was fine before getting the tranny/driveshaft redone. Hopefully it's a hold-down or at worse a lifter... Then I'll just have to source a replacement Thanks for all the great input.

 

[Garys1969RR]

I'll get the rags and blankets ready while I listen. Hopefully not an overrev/pushrod issue as the car was fine before getting the tranny/driveshaft redone. Hopefully it's a hold-down or at worse a lifter... Then I'll just have to source a replacement Thanks for all the great input.

Did you state that the engine only started the noise after you got it back from the driveshaft/tranny shop? So it was quiet when you took it in, noisy when you picked it up?

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What type of work did they do to the drive shaft or what did they work on?

 

[The Horvaths]

Perhaps they took a test drive something like a scene from the film Ferris Beuhler's Day Off.

 

[Garys1969RR]

I don't like taking my RR to any type of shop. Only the most highly trusted ones will ever see it. Had to get the front end alignment done at Goodyear, that worked out fine. You never know when some youngster or over enthusiastic mechanic will take it for a test drive, and "LETS SEE WHAT THIS THING WILL DO" ! Lol. Its happened before and will happen again. If anyone is gonna flog this beast, it's gonna be me. Ha ha. Just a word of caution when taking your prized possession to a shop for repairs.

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I do almost all my work myself

 

[MykeNytemare]

Well the shop is very reputable and has done work for my family for years and they get some real performance cars in there so I really hope that isn't what happened. It's possible I didn't notice the noise before but now I keep second guessing.

Anyway it seemed like the drivers side head. Pulled the cover to find they are stock 452 heads. Except for the cylinder under pressure, they all have very little play. It's raining here and I don't have a covered spot to work so I covered the exposed head and will try to mess with it later.

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Did find our the manifolds are Hp with a 900 on one side and a 865 on the other... Weird.

 

[Garys1969RR]

Good to see you got to this point. Next step, isolate it to the noisy rocker (s). You may want to pull the rocker shaft off, and lay each pushrod on a hard flat smooth surface, such as the dining room table. Lol. Roll them along to see if any are bent.

 

[67 coronet]

if all the rods are strait,you may have a collapsed lifter.

 

[MykeNytemare]

I'm gonna try to get something done tomorrow as the weather is predicted to be nice. Let's see if I can isolate the noise and I'll pull the rods. Thanks again everyone.