It has been awhile since I have been here, and I need your help. I got a set of early (2005)CNC ported AFR 225's and paid for the valvetrain "upgrade". It turned out really bad. Long story short: The valvesprings were REV, and I was one of the guys who got a bad set: I broke 2 of them within 300 miles of start-up. This motor was brand new. It was/is a 427 Darton sleeve block. I have had great luck with it, and put on over 30,000 miles since the valvesprings were replaced with 921 Comps (as per Tony M.'s recommendations). As I said, the 921's have about 30 thou on them- time for an R&R. Tony says AFR has a newer designed spring that has shown 10-15 rwhp over the 921's with virtually NO FAILURES!!! But these 921's have treated me as good as it gets. I also have seen in Summits catalog some Crane springs for the LS1's. They are a dual spring also. Has anyone had any experience with any of these alternatives? My cam is a hydraulic and has about .610 lift, I.&E., with about 240 degrees duration@.050 lift. Should I forget the stock diameter spring, and go for a larger one? I know this entails machining the spring seats larger, but if this is what I gotta do, I will. It seems the larger springs are actually cheaper than the stock diameter!! I also need new valveguide seals, as I believe the broken spring(s) "took out" a few of these, also, as I am getting only 700 miles/quart of Mobil 1! Been this way from the time the springs broke. It has Total seal gapless rings, and checked out at only 4% leakdown, so I am sure it's the guide seals. What seals do you guys think would be best? I am pulling the heads to replace the lifters as well, and I am wondering if there is a quality headgasket available now other than Cometics. I have been told the LS7 gaskets are rubber coated MLS, like the Cometics, and would work with the Darton sleeves. Please help. I respect your opinions, or I wouldn't ask!!! I know this post is long-winded. Sorry about that, but I need a lot of parts and there are some new ones out there I may not be as familiar with as some of you are. Thanks, guys.

 

i'm running the 833 version in my 408. spin up to 7200 rpms without harmonics.

http://vincihighperformance.com/NEW%...TS%20PAGE.HTML
about half way down on the right.

 

Crane 833's are a good alternative to the Comp 921's. However, if you have the Comp seats/retainers/locks then just a spring replacement may be cheaper if you get the Comps since you just need a spring set. Make sure you inspect the titanium retainers real well, they can take a beating on the street. I guess if its not broke don't fix it theory applies.

As for the seals, I would find out from Tony what they use. Not sure if the stock seals fit the AFR heads, but I have never had oil control problems with the stock seals. Can't answer your question on the gaskets, Tony probably can. I went with the GM MLS when I did my heads because they seemed more forgiving with regards to leaks. A lot of guys seem to struggle with the Cometics and I didn't want to deal with the issues for a few extra hp.