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Author
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Topic: Valve springs-how to know when they need replaced?
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Rustang
Gearhead Posts: 805
From: Clarion PA
Registered: Nov 2000
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posted 08-19-2005 01:13 PM
   
Still chasing the gremlins in my car  How do I tell when it's time to replace the valvesprings? Is there a certain percentage the spring rate will fall off before they need replaced? Would this be checked at installed height or at max lift height? Also, is there a good, cheap spring checker that will work with the motor in the car? (302 in a '68 mustang...remember...shock towers!) ------------------
'68 mustang 351 clevor- 10.92@124
'67 Stang, 351W -11.18@118
'69 351C Torino-14.90@100
'78 Pickup 351W-15.56@88
'79 Pickup 460 ET=??
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capri man
Gearhead Posts: 7249
From: doerun, ga.
Registered: Nov 2000
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posted 08-19-2005 01:50 PM
here is one that will check them at installed height. summit #MOR-62390
the best way is to remove them and take them to an automotive machine shop where they have a machine to do it with. good luck------------------
mike r
racing is real
everything else is just a game.
81 capri-302-7.25 @93mph 1/8
1.54 60ft 50 % of the fun dragracing is meeting people who will give you the shirt off their back to wipe the grease off your hands.
M&M member #839 http://perfectrun.com/ipw-web/bulletin/bb/images/smiles/icon_5usaribbon.gif
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steve'66
Gearhead Posts: 9489
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 08-19-2005 01:58 PM
http://www.spiderautomotive.com/valsprinseat.html
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V8 Thumper
Gearhead Posts: 4652
From: Phoenix, Arizona
Registered: Dec 2001
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posted 08-19-2005 02:26 PM
A high-end miss is potentially valvespring related  ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" 12.58/110 on street tires, more to come;) All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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jsracingbbf
Gearhead Posts: 2904
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 08-19-2005 03:54 PM
Best way is to take them off and test them in a press, using a spring tester.
those "on the car" type are unreliable, so I've found. Just my .02.
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Rustang
Gearhead Posts: 805
From: Clarion PA
Registered: Nov 2000
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posted 08-19-2005 04:07 PM
thanks so far.
I think I'll take js's advise and use my "off the car" checker.so....how far off from spec can they be before they need tossed? 
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jsracingbbf
Gearhead Posts: 2904
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 08-19-2005 09:51 PM
that would be your personal preference. heads up 5% Bracket racing 10%? is your top end 1/4 MPH going down?
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kid vishus
Gearhead Posts: 6405
From: middle of NC
Registered: Oct 2000
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posted 08-19-2005 10:53 PM
The shop I used to go to always recommended changing them out at 10%. But that was on a spring with 250# on the seat.
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rustang@home
Gearhead Posts: 134
From: Clarion, PA
Registered: Jan 2004
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posted 08-19-2005 11:38 PM
quote:
Originally posted by jsracingbbf:
that would be your personal preference. heads up 5% Bracket racing 10%? is your top end 1/4 MPH going down?
No, but I've hit a wall with my top end mph. Also, I've got a problem all of a sudden with rocker arms coming loose.
this is a heads up NA class motor so things like p to v are very tight.
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kid vishus
Gearhead Posts: 6405
From: middle of NC
Registered: Oct 2000
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posted 08-20-2005 07:58 AM
How tight is the piston to valve? Just thinking outloud, but maybe the valves are kissing the pistons at the higher rpms? Not enough to bend them, but enough to keep it from making optimum power. I've done that with one of my clevelands. When I took it apart, all of the intake valves had a shiny ring around the edges of them from where they were 'rubbing' on the pistons.
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rustang@home
Gearhead Posts: 134
From: Clarion, PA
Registered: Jan 2004
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posted 08-20-2005 05:35 PM
quote:
Originally posted by kid vishus:
How tight is the piston to valve? Just thinking outloud, but maybe the valves are kissing the pistons at the higher rpms? Not enough to bend them, but enough to keep it from making optimum power. I've done that with one of my clevelands. When I took it apart, all of the intake valves had a shiny ring around the edges of them from where they were 'rubbing' on the pistons.
I'm thinking you're right. I was running 1.7's on the exhaust only and when I tore it down a couple months ago there was signs they were hitting. So I had another .020 taken out of the pistons and hoped it was good. Since that time I've thrown the 1.7's on the intake as well  So today I've stuck the 1.6's the whole way around. Hope it works! By the way, check spring pressure on all the springs. worst one was maybe 6-7% down on seat pressure The majority were right where they were supposed to be ('course, maybe I need more spring ?!?!) I'm going to T&T tuesday night. We'll see what happens
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