Big Block Weak Valve Springs? How To Tell...

[savatreatabvr]

1st question, I'm guessing there's a spring compression gauge tool thing to check valves springs but are weak springs that critical to the performance on a BB? 2nd question, how can I check to see if my camshaft has worn/flat lobes while still in the engine?

[INSIDIOUS '86]

You have to take the spring out and put it in a testing tool to test open and close pressures.

As for telling if you cam is flat run the engine if the valve covers are off and look at the rockers. If a lobeis wiped it will not move or hardly move the rocker. This will be easy to tell and will usually feel like a cylinder is dead
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[raceman6135]

Moroso makes an on-head valve spring tester. Note that it can only test the seat pressure of a spring, and not the open pressure.



http://www.moroso.com/catalog/catego...?catcode=27105

[SSC's76]

what symptoms do you have? older bbc engines like to eat timing chains and cam lobes assuming both parts are stock I haven't seen one with worn springs not to say its not possible. is there any ticking? if you pull the valve covers off are any of the rocker arm nuts screwed down further then the other ones? if you have a friend crank over the engine pull dizzy power wire see if the rocker arms have the same amount of movement up and down. other then that may want to have a shop check and or rebuild the heads.


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[savatreatabvr]

There's no ticking but when I first bought the truck the previous owner had several rocker arm nuts way to tight and one kept loosening up! I did a running valve adjustment and adjusted them all back to normal and it ran fine, I just don't remember if the push rods were spinning or not! The one that loosens up will tighten but I have to crank it down a little bit more than the others to get it to stay, and that's with Loctite! I've watched the rocker arms go up and down and they seemed to all move the same but that was running, not cranking!

Originally Posted by SSC's76

what symptoms do you have? older bbc engines like to eat timing chains and cam lobes assuming both parts are stock I haven't seen one with worn springs not to say its not possible. is there any ticking? if you pull the valve covers off are any of the rocker arm nuts screwed down further then the other ones? if you have a friend crank over the engine pull dizzy power wire see if the rocker arms have the same amount of movement up and down. other then that may want to have a shop check and or rebuild the heads.


Posted from 67-72chevytrucks.com App for Android

[Desert1957]

Originally Posted by savatreatabvr

There's no ticking but when I first bought the truck the previous owner had several rocker arm nuts way to tight and one kept loosening up! I did a running valve adjustment and adjusted them all back to normal and it ran fine, I just don't remember if the push rods were spinning or not! The one that loosens up will tighten but I have to crank it down a little bit more than the others to get it to stay, and that's with Loctite! I've watched the rocker arms go up and down and they seemed to all move the same but that was running, not cranking!

Doesn't sound like weak springs, but maybe the nuts are just worn (Happens on older engines) another problem on small and big block engines is the stud itself can start to pull out of the head. Unless they are screw in studs its hard to check while the heads are assembled.

Desert

[raceman6135]

Originally Posted by Desert1957

another problem on small and big block engines is the stud itself can start to pull out of the head.
Desert

Big block Chevrolets have screw-in rocker arm studs from the factory.

OP, purchase some new adjusting nuts from the dealer or aftermarket and try those. Or, pinch your existing ones as that is how the factory keeps them from backing off.

[billnorman]

One must run special oil, and not the newer oils in a flat tappet cam engine nowadays. The only one I know of is Shell Rotella, it's inexpensive and easily available, still has the necessary zinc additives.

[Desert1957]

Originally Posted by raceman6135

Big block Chevrolets have screw-in rocker arm studs from the factory.

OP, purchase some new adjusting nuts from the dealer or aftermarket and try those. Or, pinch your existing ones as that is how the factory keeps them from backing off.

Not ALL big blocks had screw in studs , the early 60's engines didn't, OP did not say what heads were on his current combo. He has posted many threads on high mileage engine problems before.

Desert