[oldman]

Originally Posted by Baddawg53

F It's a track only car, looking to keep near the 550-560 whp I have now with E85. Reliability is the main goal.

I think your HP goals can be reached by a sub .600 lift gentle lift cam by Cam Motion. I don't know if Cam Motion has a spintron, what I do know is I was in the LS1 valvetrain wars and silly me, I went ahead and did it again with a .660 lift cam (you will be alright with LS7 lifters) only to fail the lifter / cam. My advice is the LEAST lift availably for your HP goals.

I think I understand valve motion enough to understand that small changes in temp, RPM, valve guide wear, and valve spring wear... will change your are golden to stuff breaks. That said I do like the conical springs and their ability to absorbed spring harmonics. A gentler cam does several things:

1) there is or can be a cracking issue of the head ported with high valve spring pressure (not a big deal if it is just at the bottom of the rocker stud). The lower lift and gentle ramp cams require far less spring pressure for example the hot cam uses stock LT1 springs and it is a pretty big cam in terms of duration (not sure of overlap as I've seen two different specs). So there are a bunch of off the shelf single beehive springs that will work and I can't find one, but I would hope there is at least one conical that would work (all are too stiff IMO), say the most mild conical not shimmed 1.8" install height. I have been running the TSP dual valve springs titanium retainer (due to be changed out as I'm nearing 20K on them). Long story short a milder lift / ramp cam probably can get away with a single beehive and definitely can get away with a non-shimmed conical. I'd still change them every year / 20K.

2) I never believed there was a seat issue with the stock head, or at least the issue was related to using stock parts with racing application cams (lift and profile). Same goes with any sort of valve failure, the stock stuff was never meant for stress and heat and I've gone to Manley valves with undercut heads, which I've run forever and I've never had one fail. Once again, problem solved NA at least if you stay with a gentler cam.

3) it is really a pain to adjust preload and I may one day just install adjustable rockers. This way the is a stud into the head so I'm not always working the same stock head threads and I can easily dial-in and check preload and yes after 20K they do change a few thousands.... maybe my cam is set in and I'll be dead before preload changes again dunno. It would be interesting to track preload changes on a race engine. You may even go with the SR short travel Johnson lifter which is more finicky but supposedly more stable under race conditions.

IMO you WHP SAE goals are reachable by a build that should last a long time with cheaper parts both on top and bottom end, but once again IMO shy away from an aggressive ramp / lift cam don't care if god or a spintron designed it. This may have changed as I had my heads ported by Pray in 2017 and back then, the LT1 heads stock or ported seem to flat spot or even lose flow over .550 to .600 lift. Maybe that has been all sorted out, maybe not. Note that there are FBO engines into the 9s where full built engines cars still can't do and at that performance range stock cam / AFM is junk a huge liability. Long story short the low hanging fruit is a 220 to 230 cam with a 112 or so LSA and .598 lift with some mild valve springs IMO of course. Will a .660 lift spintron cam make 20 HP more with the same duration? maybe so. Since this is a race car I'd add a 23x / 241 cam on 108 lobes installed straight up and get the 20 HP back plus a huge chunk of midrange torque at no reduction in reliability (idle will be choppy).

GM itself went with a mild lift, ramp profile and spring on the LS7 and spent a whole lot of time on a light valvetrain titanium intake. They had to warranty the stuff so I think replicating that maybe the way to go (new bronze guide and titanium intake) on a race car. Back to the same theory that the least lift, gentle ramp and least spring for application = reliability. It is pretty easy to check for guide wear (a big problem on the LS7). GM says it was an improper machined guide and went ahead and used titanium on the LT4 intake which seem to holding up just fine (way way milder cam). dunno but I am a bit jealous of the titanium valve folks... but if I was looking at a NA track car this would be something to think about.