I wish to use a Isky 264/270-10 Mega Cam with my Vortec heads. Isky recommends the use of their 205-D springs rated at 310 lbs/in., 115 lbs. seat pressure and 268 lbs. open pressure. I bought a Crane spring/retainer set rated at 409lbs/in., 115 lbs. seat pressure and 350 lbs. open pressure. Did I make a mistake gettin these Crane spring with these pressures. :)

Isky would say you did.

But a 310 lb. spring rate is about the same as stock, just more seat pressure. In fact, the 205 is listed as a factory replacement spring.

Most performance-oriented 1.25" (stock) diameter single coil springs will have a spring rate in the high 300s/low 400s.

Examples I have used personally from "mildest" to "wildest":

Comp 981 springs are 370 lb/in spring rate with a 105lb seat pressure (1.70" installed height)
Crane 99848 springs are 432 lb/in spring rate with a 114lb seat pressure (1.70" installed height)
Crane 99846 springs are 425 lb/in spring rate with a 125lb seat pressure (1.80" installed height)

But, hey, maybe Isky knows something the other guys don't. For sure, street performance flat tappet cams are sensitive to seat pressure mostly, so maybe the mild spring rate doesn't matter on that cam.

I can't find your spring specs exactly in the Crane listings. But given the 409 lb/in spring rate I'm going to guess those are the 99845s??

Isky would say you did.

But a 310 lb. spring rate is about the same as stock, just more seat pressure. In fact, the 205 is listed as a factory replacement spring.

Most performance-oriented 1.25" (stock) diameter single coil springs will have a spring rate in the high 300s/low 400s.

Examples I have used personally from "mildest" to "wildest":

Comp 981 springs are 370 lb/in spring rate with a 105lb seat pressure (1.70" installed height)
Crane 99848 springs are 432 lb/in spring rate with a 114lb seat pressure (1.70" installed height)
Crane 99846 springs are 425 lb/in spring rate with a 125lb seat pressure (1.80" installed height)

But, hey, maybe Isky knows something the other guys don't. For sure, street performance flat tappet cams are sensitive to seat pressure mostly, so maybe the mild spring rate doesn't matter on that cam.

I can't find your spring specs exactly in the Crane listings. But given the 409 lb/in spring rate I'm going to guess those are the 99845s??
The spring/retainer sets model no. is Crane 10309-1. Additional info. is 1.255 inside dia., 0.870 outside dia., .550 max lift at 1.750" installed height. Also, the 409 lb/in is what Summit Racing list in their website. I think I saw something in the 420's from Crane on their application sheet I have, and their site, but needs verified. :)

I wouldn't use springs that are way stiffer than necessary. More wear and less horsepower.

I'm running a slightly higher spring pressure than Lunati recommends about the same as your situation. No issues in the past 3 years. I don't think you're going kill the cam with those springs... Just do a proper break in.

You will have reduced cam and lifter life with that much spring pressure. I do my best to keep open pressures below 300# for a street engine for improved life and a hope in hell for successful break in. You will have a difficult time breaking in a cam with those springs without heroic measures. Return those springs and get the proper ones.

I jsut checked- That package includes the Crane 99846 springs I listed on the "wild" end of my spring selections, above. They're very good springs for stock-diameter applications but OVERKILL for what you're looking to do. When I was building a high-revving solid-lifter Vortec V6 for my brother a couple of years ago those are the springs I used, but we we had plans to spin the thing out past 7000 RPMs. You'll note that Crane recommends opening up the installed height to 1.80" for any flat tappet cam application for that reason. And it's not always easy to get an installed height that tall with stock length valves on a stock head.

Here are the true specs on that spring, which I verified are pretty accurate, in my ancient spring tester prior to installing them a few years back:

http://cranecams.com/?show=browseParts&lvl=3&prt=122&action=partSpec&partNumber=99846-16

If you're concerned about wear on a flat tappet cam with today's lousy street-approved oils you might want to consider stepping down to either the recommended Isky 205 springs (which still seem a bit weak to me) or the Comp 981 springs.

I jsut checked- That package includes the Crane 99846 springs I listed on the "wild" end of my spring selections, above. They're very good springs for stock-diameter applications but OVERKILL for what you're looking to do. When I was building a high-revving solid-lifter Vortec V6 for my brother a couple of years ago those are the springs I used, but we we had plans to spin the thing out past 7000 RPMs. You'll note that Crane recommends opening up the installed height to 1.80" for any flat tappet cam application for that reason. And it's not always easy to get an installed height that tall with stock length valves on a stock head.

Here are the true specs on that spring, which I verified are pretty accurate, in my ancient spring tester prior to installing them a few years back:

http://cranecams.com/?show=browseParts&lvl=3&prt=122&action=partSpec&partNumber=99846-16

If you're concerned about wear on a flat tappet cam with today's lousy street-approved oils you might want to consider stepping down to either the recommended Isky 205 springs (which still seem a bit weak to me) or the Comp 981 springs. Damon, I saw the same info. from Crane as you found. The valves I will be using are Manley Budget Performance, stainless steel, which only come in one length (standard) I believe. It seems Summit made a mistake listing the specs. I'll keep that in mind in the future on dealing with them. I'll always verify with the mfr. for now on. Most times I do anyway , but I got "burnt' this time.:screwup: I'll get rid of these and follow with what I heard so far. Anybody else can "chime in" if they wish and give me your 2 cents, but I'll most likely be returning them. :)