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Valve springs

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xfactor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote xfactor Quote  Post ReplyReply Direct Link To This Post Topic: Valve springs
    Posted: Nov/27/2014 at 11:14pm
How do you tell if your valve springs are weak? 401 solid roller cam, roller rockers, dual valve springs. Motor was built some time in the late 80's.( not by me ) Lash was very loose, adjusted it to where the cam card says, intake 22 exhaust 24 hot. Just doesn't seem to have snap it should have feels like a lost a bit with the adjustment. Did it twice just to make sure
Ray Harper 69 AMX 401
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2014 at 6:34am
If the engine seems lazy, compared to past perfromance...especially in a high lift cam application, it could certainly be springs.  The ultimate test would be to remove one a have it checked on a Rimac Spring Tester.  Check with your local shops....maybe check the local general machine shops....that is where I bought the one I have.  I would check an Intake first since typically that would have the high lift, and in my Brand X (Ford) experience....they seemed to show fatigue first.  A late 80's build is still 25 years old.  My brothers son has a SBF Stroker with Blower in 65 Fastback, had 30 passes and some street duty, initial build it was running mid 10's...at best, then falling slowly.  It was pulled to freshen and then reinstalled to dyno and would not rev above 5K under load (14 pounds boost) 256 RWHP.  The dyno guy tweeked some stuff and the electronics were all double checked, first thing he said was valve springs.....he was dead on.  Only valve spring change yeilded 6800 RPM, first run dyno 455 RWHP.  You could hear the difference even at very lower (under 2000 RPM), the entire curves on HP and TQ curves changed dramitically.  No expert, just telling you what we saw.  The dyno operator said it was commonto see.  Hope this helps.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2014 at 8:25am
Yep, even at lower rpm's the old springs are lot following the lobe profiles.  I see this all the time on engines that have sat or that have a very pronounced resting position when not running.  Some springs are always sitting at near full open and they get very weak and collapse.  ALWAYS back off the valves when storing an engine for any legnth of time.  It also keeps the critters and other bad stuff out.
Steve Brown

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2014 at 8:34am
First you need to know the installed height and installed spring pressure and rate, then you can either check them while installed using a on head tester(sometimes not accurate) or remove and test each. If you know the lift duration and rpm use then I could probably tell you close what pressure you need. Although different ramps need different rates and pressures.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dbomb Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2014 at 1:44pm
there are spring pressure testers that work with valves installed just look around the web or check fleabay. better to replace before the snap . Or like my pal Brox did on his old satellite he threw a couple pushrods through the hood just like a BULLET
rebuiling 73 amx need parts
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Post Options Post Options   Thanks (0) Thanks(0)   Quote xfactor Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2014 at 10:54pm
I think with their age ,I will call Schneider cams for a new set and replace them. Its just money well spent I think .Thanks Guys
Ray Harper 69 AMX 401
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/29/2014 at 1:40am
Good call!! 
Steve Brown

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