I will be running a GM847 cam and 1.6 RR therefore near .600 lift. Seat size is not an issue (already enlarged). I know from searches, some people run the 985 springs but no one seems to be running the 978. This spring is between the 985 and the 977 load wise with the same install height as the 985. I plan on reving this motor to 6700+ and I dont want valve float. Also I will be running the Comp. R lifters. Thanks for the imput. Ken

 

this is not a advanced thread but look into the kmotion 800s

 

Moderators can move it if necessary. Thanks for the input.

 

Someone has to be using these springs. Thanks, Ken

 

I have 985s on my car, tons of seat pressure, they hold my cam with .577 lift to almost 7000 without breaking a sweat, setup with a .030 spring seat on each valve and a .015 shim on each each exhaust valve. They should suit an 847 fine I would think.

 

Thanks Spinner. Anyone else.

 

What spring does teh GMPP catolog say to run? That tells you the specs, then find the quality spring that matchces it. The manufacturers put allot of R&D into there valvetrain, I recommend following there advice.

 

I dont know about GM but the Crane recommended spring for their equivalent cam is a single and I am not sure I want that.

 

If this link works, here is there spec requirements. I am sure you already looked at it. http://www.cranecams.com/index.php?s...&lvl=3&prt=122
But if not comfortable, cal Crane and ask them what they recommend. With the Singles, maybe they will recommend a rev kit, or just recommend some duals. Allot of valvetrain companies are going singles nowadays. CompCams just put out a newer beehive that they used ona big Block, and they have had no problems. I am using beehives, but my cam is only 555 max lift , but it is a XE cam which is a little more aggressive on valvetrain due to its design.
But, I do recommend calling crane, they know valvetrains better than us.