396 Broken Valve Spring

[MACO]

My 69 C20 396 started to run poorly, it turns out the #3 exhaust valve spring is broken. I understand that Chey's will break valve springs from time to time. The same #3 valve spring was replaced in 2013 before I owned the truck. Does it seem odd the #3 exhaust spring would break 2 times? The previous owner has the engine professionally rebuilt since the first time the spring broke. (not sure if valve springs were replaced) It has a mild crane 901 cam, Edlebrock performer manifold and carb. Replace the one spring or a whole new set?

[70K10Hunter]

I would say pure coincidence, too much time between breaks. just change the one spring, confirm correct valve adjustment tho. How many miles between breaks? If infact it is the same valve spring I would be curious if you might have a sticky valve, there is a possibility that the said valve is of a different composition (sodium filled etc.)and has a different thermal rating.

[Captainfab]

Assuming that the springs are the correct springs for the cam being used, you can change just the broken spring. But at the same time, you have to wonder why that spring broke. Is it a quality spring or is is a Chinese spring?

[homemade87]

Change them all but get a good know quality set of springs . Does not cost that much compared to touching a valve to a piston . I did not look at your specs of the cam but when you go over stock lift , springs are a wear item . I change mine out after several thousand miles . When they sit compressed does not do them any good either . I had one break on one of my engines and was lucky it did not take out the engine before I could get them changed ( it was time for them to be changed ). Lower lifts is not as critical and dont need to be changed as often but when you have one fail it is a alarm to change them all .

[geezer#99]

I'm with captainfab.
You need to find out why it broke.
That's a low lift cam. 4.84 on the intake and 5.15 exhaust.
Normally coil bind breaks them like that. Perhaps somehow a shorter stemmed valve is on there.

[68gmsee]

Been driving Chevies all my life and never had a broken valve spring. Only one I ever had break was on a Dodge van. As mentioned above, check your engine specs if possible and when replacing make sure it's best quality American made.

[homemade87]

Be interested to know if the valve spring replaced was a new one or one pulled from a used pile . Could be the reason the second one broke .

But as mentioned , take a good look at things when it comes off .

[MACO]

I never have much luck with trying to save a buck so I am going to replace all the valve springs with new top quality ones as the previous owner had the engine rebuilt and I don't know what the springs are. Could be some cheap ones or the original 48 year old springs. I have the receipt from the previous owner for the #3 valve spring replacement and there is no valve spring part charged, may have been one from the used pile. I Will take a good look for problems when replacing the springs.

[MACO]

I got the new valve springs in and the engine is running great with 18 inches of vacuum at idle. I ended up replacing the valve seals also as 2 were cracked and one was missing. Also put in new 3/8 push rods and push rod guides. Topped it off with a new set of GM performance valve covers. Now on to repairing the A/C.

[nikwho]

I just had the heads rebuilt on my 427. It had a mild aftermarket cam, forget the specs. I have the spring specs written down somewhere. They only have about 500 miles on them. Had some leak down in one cylinder, which snowballed into a huge full rebuild, with a roller cam. If the springs suit your needs, I will ship them to you and you can have them! I do know that they are stiffer than stock and a quality aftermarket spring. I'll look for the info and send it your way, if you're interested?
Nik



HAHA- I apparently read all of your posts but the last two! Disregard! Should have read more thoroughly.....

[68gmsee]

Originally Posted by MACO

I got the new valve springs in and the engine is running great with 18 inches of vacuum at idle. I ended up replacing the valve seals also as 2 were cracked and one was missing. Also put in new 3/8 push rods and push rod guides. Topped it off with a new set of GM performance valve covers. Now on to repairing the A/C.