I'm trying to decide the right cam for me, I do plan on getting heads in the future, and I'm putting in a 30,000mile longblock.

If I do get this cam how much tuning am I going to need, and what Springs, Rockers, etc. will I need. I want this thing to be half *** reliable, I don't want it breaking valve springs.

 

hmmmmm anyone?, so far I found this part

99846

Outer Diameter Top 1.255
Inner Diameter Top .870
Damper YES
Seat Pressure @ Installed Height 115# @ 1.750
Open Pressure and Height 350# @ 1.175
Coil Bind 1.100
Average Spring Rate 409 #/IN



will this sit in our heads?

 

ok, I keep answering my own questions here but maybe some of this **** will help others...



that part is supposed to fit the stock head without machining BUT
which means that if it is using a 1.6 rocker it goes over that limit?

 

The springs that you are looking at won't cut it since GM 847's exhaust lift is .595" (You probably know that already). I think your best bet is to call up one of the supporting vendors and talk to them about which springs to use. As for the rocker arms, can't go wrong with the Comp Pro Mags, do the non-self aligning ones for such a high lift cam to be on the safe side. You will also need hardened pushrods and guideplates with those, but it is better to do it once the right way then to take your chances and risk more damage. Good luck, but once again, don't be afraid to call up experts and talk to them, they won't hurt you.

 

I am about to swap over to the GM847 as well and I have been looking over the same things that you are. Here is what I am considering using.
Comp 987 Dual Springs
Comp 4771-16 Locators- These will have to be ground a little to fit the stock seat
Comp Retainers 740-16
Comp Locks 611-16

I have also been considering using the Crane 99893 Dual Valve Spring and the above Comp components since the Crane's come with crappy shim rather than locators.
Another option would be the K-motion K-800 single valve springs. I think Atljar is running these and I am interested in them, but I don't have the info about what components to match up with them. I sent Atljar a PM to see what he is using so hopefully I can find out more about them later.
As for roller rockers Comp Pro Mags are alway nice, thats what I am using anyway.

Hopefully some of the folks who are running high lift cams like the GM847 will chime in with their setups and we can get some more views on this like the valve spring that they are using and the installed height etc...

 

there is something I don't understand, the installed height. is it like a form of shimming?

and as far as the comp locators, the part itself has to be ground to fit the head?

thanx for the info.

 

The installed height determines how much seat pressure the valve spring has. You can adjust it to a certain extent depending on your needs. It needs to be measured though and as exact as you can get it on each spring. I am sure someone who knows way more about tech than me can chime in with more detailed info about installed height. As for grinding the locators I was told this by Lloyd Elliott and I am sure he has installed a few sets. The way he explained it there isn't much to it, just a small portion needs to be removed. This allows you to run the locator without machining the head. I would probably use the Crane kit if it came with a true locator and not a shim. I am sure someone will correct me if any of this info isn't correct

 

ttt altjar?

 

does anybody know what the life of these springs(in this thread) are for mileage? what are the .200 #'s on the gm 847 cam?

 

Well, I can tell you what atljar uses since he has replied to one of my posts before about the GM847. He uses the K-motion k-800 springs from summitt. Nice springs, no head-machining required and it is good up to .700" lift.
Or this is straight from Crane's website (Crane makes the GM847):
Spring Requirements:
Loads - Closed 115 LBS @ 1.750 or 1 3/4"
Open 336 LBS @ 1.210"

Any spring with specs close to that will be fine for the GM 847. Good luck again.

 

I use the exact setup, however if I were you, I'd go with CC985 springs (atleast), especially if you are going to use 1.6 rockers

 

The cam card recommended springs for this cam are not enough if you are running 1.6 or 1.7 RRs. I have the specs on the beefy Crane springs they recommended for my setup at work and will pm them to you Mon. I think it's 99893-16 springs which will handle over 1.7rrs just fine. I'm using Comp's Hi-Tech 1.7 Stainless RRs with the GM847 and the springs I used were simple plug/play with the provided shim. When you go to heads you may have a machine shop set the spring load etc, but on the stock lt1 heads the single shim is fine.

 

Just saw this thread.

Im using the k-800 springs on the stock heads with a standard .060 shim. I should also mention i am running TI retainers with .050 additional installed height in the locks, so that would be like a .010 shim on a normal install

Im at 10k ish miles since the springs went on, and they still are golden. When i do heads im going to check the spring pressure and see how they are holding up.

 

CRANE CAM: GM847-PN#12370847-234/242 @ 0.050 112-LSA (539/558 w/1.50 rockers)
CRANE SPRING KIT: PN#12370847-Crane Spring 99893-16 (Spring Specs Below)
OD: 1.460
ID-1: 1.075
ID-2: 0.803
DAMPER: No
SEAT PRESSURE: 130lbs@1.850
OPEN PRESSURE: 402@1.150
COIL BIND: 1.080
Mx nt Lft w/0.60 Clear: 0.170
Rt (lbs./in.): 391lbs/in.
FYI - Rocker Arm Ratio: 1.70 = Valve Intake: 0.610 Valve Exhaust: 0.632

home this helps you a little, obviously there are several spring combos that will work, I optioned for Cranes recommendation over what the Cam Card recommended which the spring kit listed is the 99846 spring kit which suffices for 1.50 rockers. Good luck

 

I'm using the K-800s as well, not sure of the shim thickness I used I just det it up to where I had .600 lift with .030 to the coil bind.