[oldman]

Originally Posted by 6spdhyperblue

Yeah and as u likely know but I’ll lay it out here, it’s not only a function of lift in a given duration. How it gets to the lift makes a huge difference as well.

yep

Originally Posted by 6spdhyperblue

I’d like to know how much heavier these lt1 valves are over ls1 and ls6 valves

Looks like the LS6 intake is hollow cause it is heck of light:

https://ls1tech.com/forums/generatio...e-results.html


Let me do a memory dump on valve springs I would assume the LT1 spring similar to yellow or blue gm springs ( 90 seat, 295 open at .550). Cam Motion has a upto to .625 lift 1.8 install has a pretty mild beehive that should work. PAC spring would be good, lastly BTR has several kits out now including a conical kit:

https://www.briantooleyracing.com/va...4-engines.html
also BTR beehive:
https://www.briantooleyracing.com/bt...pring-kit.html
If it were me and an AFM cam, I'd probably go with the above and shim to 1.850 install so about 117 lbs seat and dunno too lazy to get a calculator but say 330 lbs open on the AFM cam's .576 lift (Lingenfelter GT30). For the smallest cam motion .596" (DOD delete) I'd probably do the recommended install height.
The only caution I can think of is it looks like the kits come with a .070 seat, You may have to keep the factory thin seat and shim (or not) from there.

I went with a TSP .660 dual spring that has a special seat / valve seal, as it was the spec for my original cam. I'm completely sold on the conical, but it was just coming out when I did my first cam years ago now. Even though my cam is way smaller in lift now with a gentle ramp, the Manley valve is soild (slight undercut head for flow). So that is a lot heavier valve to close. I almost went with LT4 titanium intake... cool and light and solid.

Cam Motion beehive:
http://www.cammotion.com/valve-train...ve-spring-set/

Sorry, I have forgotten the LT1 stock install height vs the Texas Speed with their spring seat, you all have to do your own search.

The tricky part to my mind is that even dual springs have oscillation that there is near zero spring pressure and you want to run the least spring that will not allow valve float / bounce, and least can mean upto 40K miles when you change them out. Hence personally am sold on conical, I just don't know the seat and spring rate on the BTR conical.

Superchevy did their install with a much stiffer (assumed) concial vs the BTR on a AFM cam:
http://www.superchevy.com/how-to/eng...-lt1-cam-swap/
I don't know the longevity on this even with really mild ramps. The dyno is gone but I believe the cam pulled to 7200 RPM.Here I found the quote " The springs we’ll be using (PN 7228-16) have a spring rate of 438 lb/inch, a seat load of 136 pounds at 1.800 inches, and an open load of 412 at 1.170 inches. Comp’s own testing of these springs has shown better valve control for more power over the traditional beehive and cylindrical springs."

Hence my thinking of say 117 seat and 295 open for a mild cam. As a complete and total guess (already noted at the begging), I'd say the stock spring is 98 seat and at .551 dunno 300 lbs open. But I don't know, and it could be the AFM requires an even weaker open spring and that is why the LT4 intake is titanium (weight) and LT1 intake is hollow (weight). I would not be surprised at a sub 300 open spec at a low .551 lift.

Put it in perspective superchevy did a 136 seat puls .572 (comp cam) x 438 = 386 lbs open on the conical. Yes I know that these stiff springs will have much less open pressure due to the relatively low lift. I just wonder on the ability of the AFM lifter to open this.

Just to finish this up Comp Cams Card calls for their 26918 beehive whith 125 seat and 372 ft-in would yield 329 pounds open at .572. Humm not too bad, so it would lend some credence to some people saying that the comp cams, especially the smaller AFM can run factory stock springs, slightly more lift would bring slightly more open pressure with the factory spring. I don't have a spring scale handy or I'd give you all the specs. The beehive are cheap, I'd run a better Pac spring, I'm just giving you all what the mfgs are saying. PAC weakest spring may actually work (need to wait for infor on the stock LT1 spring)

As a last reference point the LS7 lifter is designed to work with a 101 seat spring 310 lbs open, just remember the OEM cams have a very gradual acceleration and deceleration ramp and in this case it would be the gradual deceleration ramp that allows a relatively weak spring. 310 folks!!!!

Anybody know what spring is on the hotcam (DOD delete). I found this:
https://sdparts.com/i-24080674-chevr...1-hot-cam.html so it says the stock 12678635 springs works with .570 lift cams this again lends credence to Comp Cam smaller AFM cams and lower RPM redlines can use the stock spring. I think the hot cam rec speed is 6800 RPM. I have to think yep, but the DOD delete Hotcam has really gentle ramps so they can get away with it. Note GM even says don't change the pushrod or the spring ain't gonna work (assume due to additional weight) so that is how close they are cutting it. i.e. stock spring is good at .570 lift and 6800 RPM with NO additional weight... Maybe just musing, the future holds lightweight 5/16 .075 thinwall molly pushrods and tool steel valve spring retainers, titanium intake valves and stock springs as the way to run AFM cams. i.e. can't increase spring pressure so one needs to cut down on weight.


I'm sorry probably should have broken this down to low lift AFM cams vs low lift DOD delete cams... my bad