1975 Corvette Loose Rockers?


#1

Had my local repair shop replace my valve cover and got the following message

" Rodney, many of your rockers are loose. This means one of three things.

  1. They simply need to be adjusted (a lot). This is the best case scenario.
    Cost about 100-150 to fix
  2. The studs have unseated or the tappets have bled down and are bad. This
    is a mid range fix, requires removal of intake and replacement of tappets or
    studs. Cost about 359-450 to fix
  3. The cam is wiped. Meaning the engine has to be rebuilt. Cost, a lot.

We would start with number 1 but don’t know if that will fix it until we try
it."

But the car drives fine???


#2

No noise?


#3

No more then a corvette should make


#4

What he’s saying might be true, but if you’re happy with the 'Vette the way it runs and sounds simply do not do the work.

Perhaps if the valves were opening as designed you’d have more power and the engine would run quieter, but so what? Listen, if the valves aren’t opening fully, if the tappets aren’t riding the cam lobes properly, and this has been going of for thousands of miles, any damage to be done has been done. Just keep driving it. If you ever decide to pursue the question further, get a second opinion. If you begin down the path he’s suggesting, keep your checking account well stocked. Everything in the valvetrain will probably need replacing. And then you’ll also want to look at the condition of your cylinders. Or, if you ever decide the engine is no monger meeting your needs, you could search out a rebuilt long block.


#5

An engine can run apparently fine with loose tappets but determining if the cam lobes are worn should not be a difficult job.

Remove valve cover and any questionable rocker arm. Attach magnetic base dial indicator, measure cam lobe lift, and compare that to the factory spec.

There were a few problems with camshaft lobes going flat on this ear of engine so it is something to consider. If the oil pressure is good and the engine burns no oil then I see no reason to overhaul or replace the engine.
Throw a cam/lifter kit and new timing chain set and be done with it if flat lobes are the case.


#6

Question to OK4450:
would the valves and valvesprings need to be tested and possibly reseated/replaced with the new cam and lifter kit? Would the poorly feeding & evacuating ports have caused carbon buildup, and would the new cam lobes perhaps cause old valvesprings to allow float?

I’m not being difficult, I really want to know. You’re “the man” when it comes to rebuilds.


#7

I’ll start by correcting my typo. ear - era. :slight_smile:

I don’t think there will be a problem with the valve stems and valve springs or any valve float issues unless the engine is way up there in miles and/or has seen some severe overheating in the past.

As a foreign car guy (the word foreign is iffy anymore) I haven’t dwelled too much on the domestics much like a full time Ford or Chevy guy might but I do remember on occasion getting into a couple of flat cam lobe situations with small block Chevys way back when. Replacing the cam and lifters fixed the engines right up but in both of these cases the engines were known to be carrying good oil pressure and good compression.

If flat lobes are the problem and this has gone on for a long time the valve stem face should be carefully examined for mushrooming though. In cases where the stems are mushroomed a little the lifters may be damaged and of course in the case of the stems this would mean a complete valve job and replacement of any damaged stem valves that may exist.

It seems to me the shop the OP mentions is going about some of this backwards. The cam lobes can be easily checked with a valve cover off and the intake manifold does not have to be removed to change the lifters out. There’s a tool that fishes them out through the pushrod hole.
Just my opinion and hope it helps.