valve spring height question

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Darren

Darren

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hey guys my comp #911 valve spings have an installed height of 1.90
i measured all my springs and my shortest measurment is 1.835 to 1.872
i was wondering what the tolerance was on these springs the engine is a mild 383 with a purple 68 RR cam. thanks
 
If I'm reading this correctly Darren, I think you'll be fine. Just slightly more pressure on the seat and at low lift.
 
How are you measuring? Using a spring height micrometer?

Maybe grab some +.050 locks and shims to get your height back.

That decrease in installed height, .060ish, will add about 20# on the seat 122 to ~145.
 
crackedback said:
How are you measuring? Using a spring height micrometer?

Maybe grab some +.050 locks and shims to get your height back.

That decrease in installed height, .060ish, will add about 20# on the seat 122 to ~145.
Click to expand...

digital caliper.
 
I could have sworn you only had 1.835 in the original post? If I'm mistaken, I apologize...

While I still think those springs can work, the 1.83 to 1.87 numbers could really affect the preload if your not running adjustable rockers. That's quite a bit of difference if you're relying on pushrod length alone for your adjustment.
 
No avoiding it, set them closer to 1.900..
 
crackedback said:
How are you measuring? Using a spring height micrometer?

Maybe grab some +.050 locks and shims to get your height back.

That decrease in installed height, .060ish, will add about 20# on the seat 122 to ~145.
Click to expand...

can you explain this alittle more? i am kind of a rookie it this. thanks
 
take the heads & springs to a machine shop. they will show/teach/help you i have never had a bad experience if you come to them and ask them to show you what needs to be done.

many times i've went with stuff like that and they say we'll cut the spring seats for $50 bucks or whatever. and you learn somethin. it's a win - win and you know it's done right too

they love to share knowledge... i've never been to a machine shop where they were mean and nasty, generally a great group of people.
 
can i get thinner retainers or modifyed locks?
thanks
 
Are there any washers under the springs now? If there are you could get thinner ones
 
anyone know what the installed height on the stock valve springs (1968 383 with 906 heads) i have a good set of the red ones.
 
Jo Diesel said:
The specs call for 1.850 installed height
Click to expand...

maybe i should just use my stock springs. when i had my heads rebuilt last month the machine shop sais my stock springs were fine. But i went ahead and got new comp # 911. because i got a new 68 RR cam.
Can i just run my stock springs with that cam? the rest of the engine is rebuilt to stock specs besides the pistons ( KB 400) thanks
 
any one know if comp cams retainers # 744-16 is the same thickness as the stock BB retainers? i am hoping it is thinner so if i get them i can use the 911-16 springs then shim springs to correct height.
 
CPMotorworks said:
X2
Shim the high ones to 1.835" to match the shortest and run them.
Click to expand...
So you think 146 lbs /in on the seat is OK?? I think this is totally the wrong way to go for a street hydraulic cam under .500 lift. I can't understand why anyone would think this is a good idea.
 
Darren said:
any one know if comp cams retainers # 744-16 is the same thickness as the stock BB retainers? i am hoping it is thinner so if i get them i can use the 911-16 springs then shim springs to correct height.
Click to expand...

If this helps......

Just seconds ago I tried a factory retainer and lock and switched to the Comp 741-16 retainer and 627-16 (2-groove/4-groove) lock and gained .032" installed height.

Pause for thought.........is Chrysler a true 7 degree lock? Can you use Chrysler locks on Comp or Crane 7 degree retainers?
 
Bakerlite said:
So you think 146 lbs /in on the seat is OK?? I think this is totally the wrong way to go for a street hydraulic cam under .500 lift. I can't understand why anyone would think this is a good idea.
Click to expand...


Yes, I do.
In fact I just had a customer come in for me to fix a bent valve and replace an exhaust seat from too little seat pressure. Spring surge can't control the valve, piston meet valve. Bent valve now beats the snot out of the valve seat.
Try to explain this to a customer that thinks because he's only revved it to 6000 2x in 15k miles it should be ok. Seat pressure means very little, base circle of the cam doesn't much care.
 
i also have another option. I called compcams tech line i told him my problem and he recomended me using #972 spring instead of the #911 spring.

#972 -16
rate 308lbs
1.060" ID 1.460" OD
seat load 124lbs at 1.800"
open load 293lbs at 1.250"
coil bind height 1.195"
with damper


this would solve installed height i could shim to spec.
any see any problems with using these springs with 906 heads and a 68 335HP 458 lift MP cam? thanks
 
just to compare the #911 spring (i have know)

#911-16
rate 373lbs
1.110" ID 1.524" OD
seat load 122 at 1.900"
open load 309lbs at 1.400
coil bind height 1.200"
with damper

i think the 972 spring will even fit the retainer better.
what do you guys think? thanks
 
I think you are over thinkin it. I would have that beeotch runnin with the 911 sprAngs by now. But that's just me.
 
i am over thinking it. i wipped out a new cam in my last 440. that was possible due to using incorrect spring. i will never forget how i felt when i pulled out that #4 intake lifter. i hope you guys dont think i am being annoying, i really appreciate the help and info.
 
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