valve springs

[Anonymous]

in yhe past 2 weeks since ive gotten motor to run since rebuild ive broken 2 valve springs. the cam is stock and i dont think the machine shop installed new springs. what could cause the springs to break? is this just a weak link since everything else is new and should i replace all the springs with new and should i go back stock or install a heavier spring. thanx cocacolaman

 

[JackFish]

Was is just a head rebuild? Did you install a new cam?

 

[Anonymous]

no a complete re build with new stock cam, but the machine shop was supposed to check the springs. im almost positive they used old springs because they did not charge for any new ones.

 

[JackFish]

Under what conditions did they break? Which valves?
What does it sound like when they break?
I don't know if I can help, I'm just vicariously curious.

 

[Anonymous]

had 1 exhaust on no. 4and 1 intake on no. 5. and when they broke the motor started skipping real bad. the breaks are about 200 miles apart. did not break at the same time.

 

[powerband]

What vintage engine/head are you working on. Is the rebuilt head the original from the engine and did you rebuild the rest of engine?.

The valve springs breaking is usually related to spring bind where the amount of valve lift is excessive or the springs are shimmed and running out of height. A safe limit would be @ .060 spring coil clearance at maximum lift according to the rocker arm specialists at RAS. Can you see if the springs have been shimmed or if they are binding at full lift?. If the head was milled it could cause the pushrods to effectively be longer than they were.

Related to this of course is the rocker arms themselves, pushrods, lifters and hydraulic lash adjustment. Are you using adjustable or non-adjustable rockers?.

Definitely better take a close look because it sounds like something is wrong. Old springs should not break if they aren't binding.

Powerband


8)

 

[Anonymous]

the motor is a 1979 200 with non adjusting rocker arms. there are shims under the springs. i am in the process of replacing all of the springs as we speak should i remove the shims or leave them with new springs? the machine shop said he only trued up the head surface. i know something is not right just dont know what. when i ask machine shop guy he starts talking over my head and gets me all confused. hope this helps. thanx cocacolaman

 

[CZLN6]

Howdy Colaman:

What's happening?

What did you replace the original springs with? How is it working? Did you check for bind once replaced?

Give us an update and some feedback.

Adios, David

 

[wsa111]

Like David says you need to check for coil bind, just can't seem it is possible with a stock cam??

These engines run for over a 100,000 miles with no spring breakage??

Something is just not right, with a stock cam I can't see where you are getting coil bind, unless you have non adjustable rocker arms & have milled the head, again????William

 

[addo]

Corroded springs, acid bath, then hydrogen embrittlement?

Seems about the only plausible route.

 

[Anonymous]

i think the springs already had a hairline crack when springs were installed on head from the machine shop. i took one of the broke springs to a mechanic and thats what he said it looked like to him. if you looked at the spring where the break was it was two different color one was a dark color and one was a silver color like a fresh break. since i found that ive replaced all the springs. hope that solves the problem thanx for all the input cocacolaman