[ta man]

Originally Posted by Steve C.

Regarding the comment above " If the Crane springs then 1.460"

That is the same diameter as the Crane 99893 spring that Dave Bisschop has used many times in the past for his Old Faithful hyd roller cam. Dave has stated he found they were 145-150 set up at 1.800" installed height. And he noted they lose pressure after run in. At that installed height it is a good fit for your valve lift. But that cam is not as aggressive as your Xtreme Marine roller.

As noted Dave is now using the Comp 26925 spring. Rated 141 at 1.810"

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I'm also running a set of Dave's heads with the 26925 springs with .391 and .400 lobe lift with 1.65 HS rockers.

[AG]

I set up my brother's Eddy RP heads with Crane 893 springs at 150# seat pressure for the OF HR cam, no rpm limitation.

[ta man]

Originally Posted by AG

I set up my brother's Eddy RP heads with Crane 893 springs at 150# seat pressure for the OF HR cam, no rpm limitation.

Same springs that Dave used before my heads were reworked and cam swapped. Zero issues.

[Steve C.]

The 26925 spring is listed here on page 301
https://www.compcams.com/valve-spring-chart

It is rated at 1.810" installed height.
Comp suggests it's 145 at 1.800" installed height. With a 1.100" coil bind.

As AG mentions Dave used them set up at 150 lbs. Looking at the Comp chart I would think a .030" shim with his 1.800" installed height would be close.
This said would it be compatible with the specs on his cam. And the distance from coil bind with the shim.

Dave's OF2 hyd roller cam on the intake:
288
236
162
.3900" lobe lift

His Xtreme Marine hyd roller cam on the intake:
318
262
179
.3800" lobe lift


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[ponjohn]

Curious: what is the expected power from this combo?

[Jay S]

If I was serious about turning the engine hard with a lot of street driving using that marine cam with those big valves I would run a compcams 26056 beehive. Their is a nearly identical PAC spring, I don’t recall the number though.

The 26925 like those guys mentioned is a really nice spring too for a dual spring. I’d second that one if the beehive if not your flavor.

If your not as serious about top end power, then that 914 comp spring mentioned earlier or a howards 98441 are basically the same spring and would work with the marine profile yet. The 535 should hold the rpms down compared to a 455, and the marine cam doesn’t require the spring rates that the OF grinds need.

Or you can call up Bulter’s and ask them and they will ship out their beloved eddy springs…

[Steve C.]

"...and the marine cam doesn’t require the spring rates that the OF grinds need."

Jay, would you mind elaborating on this a bit. I presume this because the so called 'intensity' number of the marine roller is larger, despite it having more .200" duration. Also the fact it has less lobe lift.

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[Jay S]

If you compare these marine lobes to a comparible duration profile with similar lift, such as say a comp QXI profile, the marine will have quite a bit less duration at .2”, with more seat timing. Less overall acceleration. The marine profiles were designed to turn more RPM’s and be easier on parts, and require less spring rate, versus what most run for HR cams on the street. Even though it looks a lot bigger, a marine style cam will have quite a bit less acceleration than a more aggressive smaller cam with similar lift. In other words the OF cam at the same rpms with the same lift at the valves requires more acceleration than the bigger marine cam. The smaller cam has time to open the valves.

I run a marine style cam in my T/A with .630 lift and 255@.050”. It only has 354 spring rate with 2.125” valves. 2.25” would need quite a bit more spring than what I have to turn it hard. That is why I suggested the 26056, or the others I mentioned. 26925 is a pretty impressive spring too. The 98441 Howard is marketed more for solids roller in smaller cube stuff, but it is a pretty decent cheap replacement for the cranes springs that use to be commonly used on HR cams set up by SDP.

[Jay S]

That comment from that last post “The smaller cam has less time to open the valves” wasn’t very good wording. Less time to accelerate the valves is a better description. The bigger cam obviously can be capable of turning more rpms . But for the same rpm it needs less spring.

My spring comments are making some assumption about the combo too. Such as I am assuming this cam is a fairly narrow LSA, and not all the 340 cfm is in by that .621” lift. If all the flow is in by .621 and it is running a power adder or has the cam events spread out for some reason then you’d probably want more spring than what I mentioned.

If it is a serious street engine that has high expectations for miles without getting into the engine much, the other thing you can do to meet those goals is to increase the installed height of the spring and run a little bigger diameter spring with bigger wires. It will end up having a little better harmonics and less deflection on the spring for the same valve lift. You can back down on the spring pressure some over the nose of the cam, set it up for a little more distance on the coil bind, and keep the same control of the valve terrain at high RPM’s. End result is longer life out of the springs and a quieter valve terrain.

Most just pick the spring with a factory diameter that best fits the given installed height, and match up the pressures for the rpms for the cam that is used. That is honestly fine most of the time when we don’t put the many miles our street cars anyway. Most everyone already has a installed height in mind at the point they are asking what springs to use, but when initially setting up the heads there are usually some spring options that can improve the life of the valve terrain over stock terrain parameters utilizing conical type springs and other changes like I mentioned..FWIW

[chuckies76ta]

Originally Posted by ta man

I'm also running a set of Dave's heads with the 26925 springs with .391 and .400 lobe lift with 1.65 HS rockers.

What RPM are you spinning too at the track?

Also, are you doing the solid roller lifters on Hydraulic cam?


Thanks.

[Steve C.]

Jay,
As always very good information posted, thanks.

Internet searching for information regarding the Comp marine lobes used in Pontiac specific applications can be a bit futile. But searching a Chevy source one such discussion was an application for a "marine hydraulic roller cam" for a street only driven 454 Big Block Chevy with a lower RPM, and to help help keep valve spring pressures low in order to extend the life of the valvetrain. Maximum horsepower wasn't the priority, but valvetrain longevity was. The general consensus was a spring in the 150/400 area. That fell in line with some suggestions here. Also keeping in mind this was for a BBC valvetrain mass involved which would typically be 'more' than our Pontiac applications.


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[ta man]

Originally Posted by chuckies76ta

What RPM are you spinning too at the track?

Also, are you doing the solid roller lifters on Hydraulic cam?


Thanks.

Currently 6000 shift, I'm still working on shift points most likely wind up to 6200/6300rpm eventually. Hydraulic rollers. Dave said this setup is good for 6500 rpm with zero issues.

[65madgoat]

Thanks for all the replies everyone. Here are the springs I plan to run:

https://www.racingsprings.com/index....ring-3981.html

PAC-1219X RPM Series HP Ovate Wire Beehive

OD Large End 1.307
ID Large End 0.885
ID Small End 0.650
Install Height 1.800
Load at Installed Height 145
Spring Open Height 1.175
Spring Open Load 358
Recommended Valve Lift 0.625
Spring Rate (lbs/in) 340.000

[Jay S]

You might need to put a little shim under those springs. .020-.030”. Beehives work better set up so they run close to coil bind, they require it more than a normal spring. Usually check it after it is together, the bottom three or four springs are suppose to be bound up at max lift. Max coil bind is 1.1 on those springs, theoretically your set up will be .079” away from the max coil bind, and will be more than that operating. I would set it up for .050”-.060”away. Pretty good size valves for those springs. Should work fine though with your cam, even better if you take time and set the spring up proper.