Your donations help keep this valuable resource free and growing. Thank you.
|
Valve springs |
Post Reply |
Author | |
xfactor
AMC Nut Joined: Sep/09/2012 Location: Port McNeill BC Status: Offline Points: 478 |
Post Options
Thanks(0)
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
|
|
401MATCOUPE
AMC Addicted Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5370 |
Post Options
Thanks(0)
|
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.
|
|
Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
|
69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
Post Options
Thanks(0)
|
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
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
|
tsanchez
AMC Addicted Joined: Jul/09/2007 Location: Arizona Status: Offline Points: 4302 |
Post Options
Thanks(0)
|
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.
|
|
dbomb
AMC Addicted Joined: Jul/22/2012 Location: new jersey Status: Offline Points: 705 |
Post Options
Thanks(0)
|
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
|
|
xfactor
AMC Nut Joined: Sep/09/2012 Location: Port McNeill BC Status: Offline Points: 478 |
Post Options
Thanks(0)
|
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
|
|
69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
Post Options
Thanks(0)
|
Good call!!
|
|
Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
|
Post Reply | |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |