If I remember correctly,I believe Harold mentioned stock springs where good to .515 lift...need to confirm please.

If you have the LS-6 type double spring yes. If you have the early single with a dampner change them they break just for something to do with very disasterous results.

Aren't the stock, lo-po, BB P/U motor single springs made to run with the .398"/.430" lift cam??

AND only up to like the .461"/.480"lift cam and that was stretching it's use range...

pdq67

..guess I'll wait for Harold..I've run the 'ole Crane 272H with no problems before in a 1974 454

motor in question is a 73 454 w/049 heads

EDIT: GM part # 3859911 is the valve spring used with the L35 396 up to the LS5/L34 grind..maximum lift is .490

We must be lucky as well running the same 454 setup and cam for the last 5 years with no problems. Shifting at 5K gave the best times so high rpm wasn't a factor. Of course a little insurance is always wise.

I don't springs are the issue. Stock oval port heads will have guide/seal - retainer clearance issues. I have used cams up to about .530 lift with no problem, but have seen the seal get pounded down from the retainers with lift above that.

I use the GM 454-502 dual spring. It looks the same as the LS-6 dual spring I replaced. Competition Products (PN #502) lists it with coil bind at 1.27" and specs the open pressure at 1.32" (345lb). That's .050 difference which would be about the right min open coil clearance. At an installed closed height of 1.88", which is usually the stock BB spec, it would be good to .560 lift (1.88-1.32).

i have been using the "427 hi performance" stock springs for many years. they are a single spring with damper and the local machine shop says he uses them for almost everything.i was using them before i met him a few years back. they are cheap springs and seem to do very well. never broken any of them even when i was running a solid 561/600 cam to 7200 rpms. they are even on my car now (not the same spring but same kind) and i run .551 lift with them to 6500 rpms. also have another set on another pair of 049 heads under the bench.

i know i was using these springs too when i was running the 272 cam with 515 lift with no mods to guides. now with my 600 cam i was mashing the seals.....and tearing the keepers....but since i know better nowadays i check clearence for everything and give myself room to grow for bigger lift.

i do know i have been called a liar from time to time with some of my buddys because they didnt think i could run 7200 rpms with a single stock style spring but i think it has to do with some of the old cam grinds i run that are slow and tolerate less spring pressure. but after popping a valve cover a few times to show i was telling the truth they didnt seem to q. my parts i use.

thats why i think i have been so lucky never to have a flatten cam. seems like i go way under what it recommended for spring pressure and of course running older style cams that are slow and easier on parts.

i just use the cheapest parts i can find the cheaper it is the better. but it has worked for me. others swear by name brands and have to be dead on with spring pressures.

now given the newer cams with really fast ramps i might be asking for problems and would go into valve float. but i guess i wont spend big money to find out i like the 50 dollar cams (regrind to about any spec from delta cams) to pick from.....lol

Dennis,

What's the part # of the hi-po, 427 single with damper spring you are talking about??

And who sells them??

Thanks in advance..

pdq67

i have been using the "427 hi performance" stock springs for many years. they are a single spring with damper Do you recall the specs? Competition Products used to sell these generic "427 hi-perf" single springs. I used them in a 396 w/ a .476"/.501" cam (back when I knew a whole lot less, and just bought 'em on a recommendation), but I cannot remember or find the specs for the springs. They are still working OK in the car though... no flat lobes, and no float.

If you are using the factory single springs on anything wilder than the old 350HP cam you are very lucky or about to be very unhappy. The aftermarket springs don't seem to have the problems of the factory ones but the LS-6 type dual is so cheap it's really not worth taking a chance.

C-P sells three of them if not mistaken:

Howards PN 98431/Manton(?) PN 2525 at 1.437 diameter, 1.880 - 145 lbs., 1.500-275 lbs., 1.250 - 370 lbs., Coilbind - 1.180;

Manton PN 2427 at 1.535 diameter, 1.875 - 125 lbs., 1.375 - 350 lbs., Coilbind - 1.200; and,

Manton PN 2454/98611 at 1.550 diameter, 1.880 - 135 lbs., 1.250 - 350 lbs., Coilbind - 1.150.

This last one is called a "single race" spring. Is this the one?? I have them on my Merlin oval that I put on my 496 with a CC 282S solid cam.

And looking back on everything, I probably shoulda went the GM take-out dual springs..

pdq67

I run Crane single springs that are good to .580 lift,stock diameter..99308-1 was the p/n I think