Another update…

I removed a couple of valve springs to measure the valve spring seated height.

I measure 1.840
With what looks like a Durabond 6140 shim at 0.060
The springs were installed at 1.780


New toy !


Durabond 6140 at 0.060 ?


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I had to clearance the micrometer for measuring seat height as the valve retainers would not fully seat. Not something I like doing, but I did not see a way around it.

I do trust the measurements.

EDIT: That said, I am a little surprised by how tall these valve stems are. Is that typical for aftermarket performance ?

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Suggestions on shims and springs are absolutely, welcome. I will measure the valve stem height on another cylinder just to be sure.

I imagine, the keepers and retainers will likely need to be swapped out, particularly if I go the beehive route

 

So I am considering, if the measures confirm again...



COMP Cams 26918-16 Beehive Valve Springs

· Type: Beehive, single spring (no damper)

· Installed height: 1.800"

· Seat pressure: 125 lbs @ 1.800"

· Open pressure: 367 lbs @ 1.150"

· Spring rate: 372 lbs/in

· Max lift: 0.625"

· Coil bind: 1.140"

· OD: 1.075" (top) / 1.310" (bottom)

· ID: 0.650" (top) / 0.885" (bottom)

· Set of 16





COMP Cams 4705-16 Valve Spring Locators/Retainer

· Type: Steel locator, inside shoulder

· Thickness: 0.060"

· OD: 1.300"

· ID: 0.570"

· Inner spring ID compatibility: 0.875"

· Set of 16

· Adds ~0.060" shim effect + stabilizes spring on the seat



COMP Cams 614-16 Super Valve Locks

· Stem size: 11/32" (0.342")

· Style: 10°, single groove

· Material: Hardened steel

· Installed height change: +0.050"

· Set of 32 (for 16 valves)



Net Installed Height Impact

· Base spring spec: 1.800"

· Locks: +0.050"

· Locator: –0.060"

· Net: ~1.790" installed height (approx.)





Context:

· Hydraulic roller setup (1969 SBC, RPC aluminum heads)

· Previously measured: ~1.840" installed height without shims

· Current springs (old): ~90 lbs seat, ~~160 lbs open (estimated)

· Target: ~125 lbs seat / 367 lbs

 

I know you are overseas, but is it possible to call comp cams or PAC and to be absolutely sure?
Those hydraulic lifters you have will only tolerate "x" amount of valve open spring pressure.

I had to build a spreadsheet to keep track of all the measurements, and yes every spring needed to be shimmed a little bit differently.
It depended on how deep each spring pocket was cut in the heads.

And beehives like to be run close to coil bind at max lift, there is a spec for that, you need to be close to the spec. That is what dampens the vibrations. IIRC I set each spring to be .060" away from coil bind at max lift.

IIRC those sharpie notations were my installed heights before any shims.
And yes I think modern beehives look positively hysterical on an old school big block, don't you?


There were only a couple of springs that gave me my desired seat pressure, and open pressure.
IIRC I settled on the PAC 1255s. Big Block springs.
I wanted valve control on a BBC, with solid roller lifters, at 6500 rpm.
Springs need to be a little stiffer, for more rpm.
I figured out all of my targets before hand, then compared springs, at my installed heights, not their book spec, which was a different lift.
But I enjoy the math.
I set mine for 190# seat, 400# open, at my .600" lift, on a BB. Your SB settings will need to be lighter.

You could just have Comp or PAC do it for you.
But you will need to give them a lot of info when you call, so have it ready:
Cam, lift, desired rpm, lifter type (HR?), lifter part number, valve lengths, Installed heights, with current spring retainers, spring retainer number or measurements, etc.
Yes some valves are taller, it would be mandatory to figure out your valve height/length, std or taller.
Some hydraulic roller lifters do not handle stiff springs, some do. Many will not support over 5500 or 6000 rpm.
I talked to both and got much better info from PAC.

You "may" have luck by email:
https://www.racingsprings.com
Phone: (866) 799-9417 9-5, M-F, Michigan

Here is a high speed video of valve spring movement in action:

You Tube

Here are Crane Cams valve spring recommendations:

For a SBC, It looks like a good recommended seat spec is 120-145# on seat, and 300-360# open.
IIWY I would stay inside of that range.
Only if you are going to push it over 6000rpm would I go to 350-400# open.
I would imagine that is a 5500rpm cam in a 400.




Here is my valve spring spreadsheet, in case it helps.
Excel 97
Funny things happen to spring pressure once you change to your installed height.

 

IMO your going way overboard on spring pressure. The COMP recommended springs for this cam have 120 lbs @ 1.8" on the seat and 290 lbs @1.25" to control the valves at max RPM.
I think your just going to wear things out at 365lbs open pressure.....there's just no need for these pressures for a street cruiser.

The Comp 972-16 is very close to what the book recommends for a matching spring for the cam...check it out
https://www.compcams.com/single-oute...1-060-i-d.html

 

Those 120/290 springs are also within the recommended range of 120-145# on seat, and 300-360# open. As installed. Not book specs.
All the manufacturers basically use the same suggested range.

It is the cam lift, taller valves, shims, and retainer height that can really mix things up, and change the as-installed values from the books spec rates.
Since this cam is only a .502" lift cam, all those spring numbers will change. Most springs are spec'd at .550 .600 .650 etc.

He will need to run the numbers at his max lift height, .060" away from coil bind, and then see what the numbers are open, and then shim from there.
The shims change both values at once.
Seat pressure is the most important at this stage. He is way too light at present. He could shim his existing springs to get seat psi up, but they would more than likely go into coil bind. But maybe not. Run the numbers.
It can be done in a spreadsheet before you start, to make sure you have the right combo of springs, shims & retainers, and then doublechecked when installed.

I would never suggest to just throw in a set of recommended springs, without measuring them.
There are too many places for it to go wrong. Even on a cruiser.
IE: He is 30# too light on seat pressure now.

Going too light will cause more problems than slightly too heavy. The high end is just "what you get" with spring "X" after getting the seat psi correct. If it is way too high or low then pick another spring. It just needs to be somewhere in the right range.

Non beehive springs are not as fussy about being near coil bind. They have flat dampeners.

 

Hopefully the new springs solve some of the OPs problem.
The current springs are 30-55# less than recommended on seat psi. That is quite a bit low.
This would make the heavy HR lifters bounce off the seat, and then re-open slightly. That would increase both the duration and the overlap.

This could be a source of several of the OPs concerns:
His noisy valvetrain comments, his fluctuating vacuum at idle comments, and the sound comments that it sounds like it has too much duration.

Let's hope so.
And hope that the cam lobes did not get damaged in the meantime.

Even at idle, each exhaust valve is closing 6x every sec. That's a lot of racket if they are bouncing. And in a set of hydraulic lifter, there are always a couple that leak down faster than the rest.

 

Wow- lots of great information here. I always enjoy geeking out on these things.

I am very sure that shimming already more than it is will push me into coil bind.

I will carefully measure one more time then place a summit order.

I have to say I was shocked when I checked the seat pressure to discover how soft it felt.

 

Only a small update.

I measured the valve stem at 1.840 on tow other cylinders. I think we can accept that as final.

I like keeping the valves up with compressed air… but not so easy with a corvette with exhaust manifold. Not even sure it’s possible. I may be busted back to the rope method. Not a terrible fan of that one.

 

Honestly can't understand installing a cam and not using the correct valve springs recommended by CC. You don't even have to buy the springs from CC but they will give you the specs. Just not right in the first place, not even knowing the specs. of the springs, sorry.

 

NFK, the ramps on my XR286R solid roller look almost vertical to base of the cam

 

It’s a secret. Strangely enough involves the cult of Grey Skull

 

PAC springs ordered - should be delivered today.

 

Those old springs, with a FLAT damper inside: seem to be very common "Z28" springs.
And, that configuration (same as OE C3 sbc) is typically referred to as a "single with flat damper" --- Not "double" anything.
The pressures and lengths you measured also indicates those old ones are "Z28" springs.
In one writing, it seems you indicated they were installed at 1.810" but elsewhere seems you measured 1.780" ?
If those are typical Z28 springs, and if they were installed too tall, they'll be too weak; thus may've helped valves to float ?
I should also note --- "Z28" springs are also commonly available with otherwise same specs BUT an extra +0.100" longer.
(e.g. Pioneer Z28 spring P/N RV-943 free length = 2.040" --- while plus +0.100" P/N RV-1943 free length = 2.140")
I've successfully used Z28 springs (with Damper Deleted) in iron GM Vortec heads as one part of "ghetto grind" setup.
I like (name brand) Z28 springs and their longer cousins, but their FLAT dampers have a history of breaking & scattering bits.

When properly installed; NEW PAC beehives will be far better.

Perhaps a larger diameter rope/cord would work more easily ?

 

Only problem with beehive springs, if they break your outta luck, not even a damper spring. In worst-case scenarios, a broken spring allows the valve to drop into the cylinder.

 

GM uses bee hive springs in LS motors. They seem to hold up just fine. My 302 uses them for the past few decades. I just assembled a 355 with PAC bee hives and I sleep just fine.

If you break a Z/28 valve spring, you can't rely on the damper to hold it up. Maybe just over thinking it.

 

We all know the drill


One. I rate aggravation at 7/10

 

I'm happy for you, I don't pull things out my azz, it is a well known fact, sleep well

 

So…exercising a little patience, the compressed air worked for all the cylinders. Did not need to used the rope trick even once.

 

How's it running-sounding now ?