Valve spring delima !

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Valve spring delima !

Post  whitefield on October 17th 2017, 10:05 pm

I feel like I have talked with several reputable engine builders about this particular situation that has me confused! scratch

I have a small block stroked to a 408 13.0:1 compression.

8000 RPM

Cam is a solid roller with

Lift
Intake .688 exhausted .672
Duration @.050
Intake 276 exhaust 284
Lobe seperation 107
Installed @103
Some more info :
Lobe lift
Intake .4300 exhaust .4200
Timing events intake op 35 cl 61  exhaust op 73 cl 31

1.6 rocker ratio

Spring psi that cam company wants me to run is
250+ on seat
780 open
Installed @ 1.90

What do you guys suggest ?

Thanks Whitefield


Last edited by whitefield on October 18th 2017, 1:36 pm; edited 2 times in total (Reason for editing : Add more info !)
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Re: Valve spring delima !

Post  Mark Miller on October 17th 2017, 10:53 pm

whitefield wrote:I feel like I have talked with several reputable engine builders about this particular situation that has me confused! scratch

I have a small block stroked to a 408 13.0:1 compression.

8000 RPM

Cam is a solid roller with

Lift
Intake .694 exhausted .698
Duration @.050
Intake 268 exhaust 274
Lobe seperation 107
Installed @103

Spring psi that cam company wants me to run is
250+ on seat
780 open
Installed @ 1.90

What do you guys suggest ?

Thanks Whitefield







I don't know much but that seems way to high on the open pressure to me!!!

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Re: Valve spring delima !

Post  BBFTorino on October 18th 2017, 12:48 am

A lot of it depends on the ramp rates. Some solid rollers will whack a valve open faster than the speed of light!!
Lobes like that need big spring pressures. Other lobes are more forgiving and you can back the pressures off a bit.
Are you experiencing valve float or broken springs??

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Re: Valve spring delima !

Post  dfree383 on October 18th 2017, 7:39 am

you building a race car or a street car?

What's the installed height? Lobe lift? Rocker ratio? Spring rate?

Who's lobes and what numbers?

And just for the record those are not super big springs.



But I do suggest listening to the cam manufacture over soliciting online random suggestions.
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Re: Valve spring delima !

Post  whitefield on October 18th 2017, 9:51 am

dfree383 wrote:you building a race car or a street car?

What's the installed height? Lobe lift? Rocker ratio? Spring rate?

Who's lobes and what numbers?

And just for the record those are not super big springs.



But I do suggest listening to the cam manufacture over soliciting online random suggestions.

It is a race car
Bullet racing cam
Installed 1.900
1.6 shaft mounted rocker arms
3/8 .080 push rods
Spring rate 644lbs./in.

I will get the rest of the info in a few minutes.

I agree with your last statement, but there are a lot of good experienced people on this forum. I am not on any other forums anymore this one is home. Thanks

P.s. The other reason I was confused is I was getting two different answers from two different people from bullet.
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Re: Valve spring delima !

Post  rmcomprandy on October 18th 2017, 10:08 am

Personally ... I would use the PAC-1244 valve springs.

The Lunati #74744 is the same spring.

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Re: Valve spring delima !

Post  whitefield on October 18th 2017, 1:34 pm

I added some more info about cam and changed some things I had wrong in first post.

PAC-1225 was the spring they recommended. Thanks Whitefield
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Re: Valve spring delima !

Post  rmcomprandy on October 18th 2017, 2:35 pm

whitefield wrote:I added some more info about cam and changed some things I had wrong in first post.

PAC-1225 was the spring they recommended. Thanks Whitefield

A PAC-1225 has 314 pounds force at 1.900" installed height.
765 pounds force at 1.200" height.

A PAC-1244 has 227 pounds force at 1.900" installed height
747 pounds force at 1.200" height.


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Re: Valve spring delima !

Post  dfree383 on October 19th 2017, 1:33 pm

whitefield wrote:
dfree383 wrote:you building a race car or a street car?

What's the installed height? Lobe lift? Rocker ratio? Spring rate?

Who's lobes and what numbers?

And just for the record those are not super big springs.



But I do suggest listening to the cam manufacture over soliciting online random suggestions.

It is a race car
Bullet racing cam
Installed 1.900
1.6 shaft mounted rocker arms
3/8 .080 push rods
Spring rate 644lbs./in.

I will get the rest of the info in a few minutes.

I agree with your last statement, but there are a lot of good experienced people on this forum. I am not on any other forums anymore this one is home. Thanks

P.s. The other reason I was confused is I was getting two different answers from two different people from bullet.

Either Spring Randy suggested would work IMO.
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