redtan

iTrader: (5)

Been thinking about this and have gotten different opinions on this topic from fellow car buddies.

When you turn off the car, inevitably some springs remain compressed due to the timing of engine. So leaving a car sitting for months on end means some springs are relaxed and uncompressed while others are completely or partially compressed. Does this create any issues long term to the lifespan and ability of the spring to hold the valve during these different conditions? Or am I overthinking it?

KCS

iTrader: (20)

Well, they should all be partially compressed since the installed height is usually shorter than the spring's free length, but I wouldn't think it would wear the springs. I could be wrong but I always thought it's the open and close cycles that wear the springs (under normal operation), not their state of rest.

Taxman20

iTrader: (11)

Actually compressed springs will weaken them when sitting for long periods of time. This is going off the advice or several race engine builders like Reher-Morrison, Sunset ect. On our race engines that have high pressures, we spin them over at least once a week. Your just trying to get the close the valves that are now open and vise versa. I prefer to start the engine and let it run for about 5 minutes.

On our Tops Sportsman cars and ProMod we would loosen every rocker arm once we got them back into the shop.

On stock springs, I wouldn't care about it.

redtan

iTrader: (5)

What is a long period of time? I'm storing the car for about 4 months.

Taxman20

iTrader: (11)

I dont recall a set time frame. Tons or people never worry about them. I myself have let them sit for a couple weeks. Its up to you really. Might be best to contact the manufacture and see what they suggest. My opinion is if your worried about it just loosen all the rockers and then theres no problem.

TurboBuick6

iTrader: (2)

this is the key here. It has more to do with the stress range of the spring itself. LS springs are very low stressed (relatively speaking).

lazermule

A close friend of mine that I attended engineering school with and now works for a mojor aftermarket valvetrain company (for 20 years now) answered this question for me. Like anyone else, back in the day we thought that we needed to back off the rockers when storing an engine or cranck it over 90 degrees a month or so, etc. Turns out, his new advice to me is no you don't. I was like "What? You were always the biggest proponent of this!" He said, "Yeah, I know, it's just not necessary". I geuss case in point, I had a SB Ford Mustang stored at my dad's for the better part of 20 years where it remained unfired. It does have a fairly agressive cam and heavy valve springs. The car was started 3 years ago and driven weekly or so now and shows no signs of weak springs although we took no precautions in preserving them.

Hope this helps....

LM

bowtienut

iTrader: (1)

Your engineer friend is correct. If this WERE an issue, it would happen to the springs sitting in the compressed state immediately after hot shutdown via a process known as secondary creep (permanent relaxation of the material exposed to high temperature yet stressed below its yield strength). Rotating the engine after it's cooled does nothing for the springs.
Creep is not a concern in metal at less than ~40-50% of its melting point. This would be over 1000 degF in tool steel valve springs (2600+ degF melting point). We DO have creep concerns in the turbine engine design business

SuperSport01

I don't believe that springs are measureably damaged by sitting compressed for long periods. However I still will turn the motor 90 degrees every month or so of storage. I think more importantly is how you bring a motor out of storage. Such as letting the motor get to full operating temp before driving it. If it has been sitting for a few years fully priming the oiling system before the first startup isn't a bad idea.