Hey guys I plan on buying a GM847 Cam for my 87 Iroc with a LT1 swap. I was wondering what springs to go with. The ones in it are good for about a .550 lift, and the GM847 with my 1.6RRs is .575/.595,

Mods are in my sig. I would perfer them to be available at summit since I am gonna get the cam from there and ship to a ups store in MI.....I live across the river from there and dont feel like making two trips.


Thanks Jay

 

comp 924's should work... advertised for 700 lift and add .050 for safety you get .650 lift. 112 lbs on seat, 355 open, about right for hydraulic rollers

else abit bigger is the 930 but is good for 600 lift with that .050 safety margin..so its still good. 153 on the seat, 383 open... maybe abit much on the spring side but better safe than sorry. heat cycling is said to reduce those rates alot tho


then again comp recommends the 986 spring which has a max lift of .600 without any margin of safety for their biggest XFI cam which has .584 on the intake. but then again, alot of LT1 guys are runnign the 918 beehive spring which is rated to .600" lift with big 468 XFI cam on 1.6 rockers, so it could work too

EDIT crane makes the GM847 cam and recommends their 99846 springs... if you dont want beehives at that price of 189 bucks, then go either those 846 springs from crane or perhaps the 924's/986's from comp

 

Do not go with anything less than 130 lb on the seat with the 847 cam if you want to utilize its rpm potential. If mine, I'd shoot for 130 lb on the seat with Beehive springs or 150 lb with conventional springs.
I have to ask if you realize how much rpm you'll need to spin a 355 with the 847? If you're trying to improve that 12.9 ET, this cam should not be on your list at this point.
1. 3000 stall is not near enough converter for it
2. I hope you're not planning to use a stock GM LT1 computer to run this thing; it won't work beyond 7000 rpm, which will be below your optimum shift points to get some ET out of the car.

To give you an idea how well small cams work with the short runner LT1 manifold, I've gone 12.36 @107+ with the stock LT1 B-cam in my 1996 ImpalaSS. I had it down to 3800 lbs for those runs in cold air, but it routinely goes 12.8 -12.9 @ 102-103 at full weight in the summer heat.
Believe me, that LT4 Hotcam, while not ideal for a dragstrip car, has far more potential than 12.9's in your car. If you made no changes other than going from the Hotcam to the GM847, your car will defintely slow in the 1/4 mile.
The Hotcam really benefits by advancing it to a 107 ICL, rather than the "straight-up" 109 ICL intended for its original roadracing application

If I've missed your objective here, and you simply want to go with the 847 cam for a mean sound, then have at it.