Valve Spring Question: Coil Bind Versus Spring Quality

[YO7_A66]

I am looking at two valve springs for a possible upcoming cam swap. This will be for a solid flat tappet that will max out around the 6300rpm range with 1.65 rockers.
Note: I have been told in the past that the 1.65 rockers will need a little more spring pressure versus the 1.5 rockers.


The two springs that I am looking at are the Isky 6105 and the 6105SP (SP = Hi-Tensile chrome silicon outer spring, Spintron proven up to 8000rpms).

Question 1: Is the 6105 spring a good spring choice up to 6300rpms?
At my installed height, coil bind clearance for this spring would be about .080” at max lift.
Spring Pressures: apx 155lbs & 331lbs max lift

Question 2: Is it worth it to buy the 6105SP upgraded spring (+ $48 per set) if my same installed height coil bind clearance would now be in the .140” range?
Would the better spring material hold up at the higher coil bind clearance?
Spring Pressures: apx 163lbs & 361lbs max lift
Any issues running the 163/361lbs on a solid flat tappet? I just pulled out a solid flat tappet that I had setup apx. 149/365lbs with EDM lifters and the cam/lifters looked good, but with very low street miles.

I have talked with three cam vendor's and they all suggest something different for their version of a solid flat tappet spring pressure with EDM holes:
a) 135lbs/360lbs
b) 145lbs/365lbs
c) 130lbs/340lbs MAX!


Thank you!

 

[Bewy]

I would use the 6105. Always check coil bind to see it is what the spring maker says it is. My experience is that you can check for max valve lift using a light check-er spring. When you then check again with the actual springs in place, some lift has been lost due to flexing. Going from 1.5 to 1.65 rockers with no other changes is automatically compensating with the v/springs. The higher ratio needs a slightly stiffer spring, & you get a 10% increase going from 1.5 to 1.65. You just need to check coil bind with the extra lift.

 

[YO7_A66]

Thanks for the response Bewy!

I have the checking springs and my new springs will not be ordered until the cam is in, and the actual lifts have been measured. I have never used the 6105’s, so I am unfamiliar with them. I have an estimate on the loss of lift from my previous cam swaps on this motor, and that estimate puts my lift right around the .550” range which is right on the edge of the 6105’s lift range. So, I will wait until the setup is finished before purchasing the springs.

I have also been looking at the Comp 925’s and the 978’s too.


Thanks again!

 

[Bewy]

When I have checked coil bind versus the manufacturer dimension, the actual coil bind is usually a bit less than specified. Don't know if it is poor QC or the manufacturer building a small 'safety' margin.

 

[furrystump]

I’m at .190 coil bind clearance and have been for a very long time. .557 max lift, solid flat tappet shifting at 6400-6500 stripe 6800. PAC hot rod springs 135 lbs at 1.80 and 340 lbs at .557. Just changed the springs to the exact same ones because they were 10 years old. There was no real pocket wear and it pulls 6800ish so I don’t think they are surging, but to you question I would go the better spring as long as the pressures are appropriate. A dropped valve is SO catastrophic.

 

[YO7_A66]

I’m at .190 coil bind clearance and have been for a very long time. .557 max lift, solid flat tappet shifting at 6400-6500 stripe 6800. PAC hot rod springs 135 lbs at 1.80 and 340 lbs at .557. Just changed the springs to the exact same ones because they were 10 years old. There was no real pocket wear and it pulls 6800ish so I don’t think they are surging, but to you question I would go the better spring as long as the pressures are appropriate. A dropped valve is SO catastrophic.

Furrystump,

I was just looking at the PAC catalog yesterday and found a few of those HR springs in the range that you show. Do you mind giving me the PAC number that you used?

My only concern was what you mentioned, about the larger coil bind clearance. I would like to use the ISKY or the PAC’s but they both give me a lot of coil bind clearance (.120”-.180”) at my lifts. There are a few of the Comp springs that would work, but I would rather purchase one of the above brands for this rebuild.



Thanks!

 

[furrystump]

PAC 1903, got them from Summit. $158? I thought about shimming them to close up the coil bind clearance, but the old set worked fine for over 10 years that way, so I didn’t.

 

[YO7_A66]

PAC 1903, got them from Summit. $158? I thought about shimming them to close up the coil bind clearance, but the old set worked fine for over 10 years that way, so I didn’t.

I currently have the 1903's on my heads with only a few miles on them before I had to tear down the block. The only reason that I was looking for another spring was because I have them setup for apx a .590" lift and that comes out to about .150" coil bind clearance. So I thought to start looking for another spring. But if the PAC's can run with this much clearance, then I may be able to reuse them.

Thank you.