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Hi guys,
I have problem with my 1977 C3 - all original L48. There is rattle sound from valve cover on driver´s side on idle. On opposite side is running of valvetrain smooth.
It is thin mechanical rattling, and when I touch valve cover, I feel rattling too. There aren´t misfires, no valve knocking, engine is strong. I opened valve covers before month, when I adjusted valve latch, and there are not any visual problems. I had suspicion on broken valve spring, but they seems to be fine, but I dont see under seals(cups)on top of the springs, if there is something broken. I taked a few photos, which I attach here.
It is strange that on first cylinder intake valve ( second from left) , that cup on valve has clean circle on top, on cyl.5 (third from right) is clean circle too. Is it normal, or it is indication of broken top of valve spring as spring rotates with cup? Have anyone similar experience?
Thanks Jakub
It might just be me but in your last pic it looks like there are mismatched valve spring retainers. In your pic, number 1 and 3 cylinders seem to have different retainers on the exhaust valves. Check the bevels. Number 1 intake retainer looks like it is badly worn compared to the other two but it might just be the pic. That intake spring should be covered by the retainer and not moving around side to side.
I can't tell because of the glare in the picture. When an engine has exhaust valve rotators only the exhaust valve rotates so the spring remains stationary. Its very common for rocker arms to make contact with the oil baffles that are spot welded to the underside of the valve covers so look those baffles over closely for signs of "polishing" from the rocker arm rubbing against them. If you see any signs of contact you can peck it with a ball peen hammer or grinder to make some clearance.
Cut yourself an oil splashgaurd using a piece of cardboard. Fit it along the bottom edge of the springs, and long enough to curl around the end of the springs. Make it about 6-8" tall. Now find yourself an automotive steathescope and start your engine up to pinpoint where your problem is.
The valve guides on those two valves could be very worn, or it could be a pushrod end wearing out....I've seen both of those before. It could also be a mis adjusted valve as well.
Cut yourself an oil splashgaurd using a piece of cardboard. Fit it along the bottom edge of the springs, and long enough to curl around the end of the springs. Make it about 6-8" tall. Now find yourself an automotive steathescope and start your engine up to pinpoint where your problem is.
The valve guides on those two valves could be very worn, or it could be a pushrod end wearing out....I've seen both of those before. It could also be a mis adjusted valve as well.
I cut out a stamped steel valve cover to use as a splashguard back in the days when I adjusted stamped steel rockers while running. Also, a long screwdriver makes an excellent stethoscope. Try it!
I solved it yesterday. I made compression test before week, compression was good. Yesterday I inspected rattling again, and found source of rattling in two minutes! It is caused by PCV valve in valve cover. I replaced old valve in summer by new one Fram brand, I think that there is big steel ball inside, and when engine idling, it is possible to hear how ball jumping inside the valve!! :-))
Rattling valves
