kgkern01

Just wondering, what would be the safest amount of lift to use with a stock motor (heads/pistons) assuming that the valvetrain is beefed up sufficiently to handle it? I think what I am asking is before you have piston/valve clearance issues?

Z95m6

I believe that stock LT1 heads don't really gain any flow after .500 lift so it is pointless to have anymore lift after that unless you have upgraded heads.

kgkern01

I was asking because I plan on running some Scorpion 1.7 RR on my car, then when I upgrade cam, go to either CC306 or GM842 (i think the GM# is off) which would put me over .600 lift on exh with the 306. When I upgrade heads (down the road) I plan on running ported LT4's and don't want to have to buy a cam but once.
I may possibly port my heads when I do the cam the first time, but I was just wanting to know what the max clearance would be to see if I can run the 1.7rr and a cam.

kgkern01

ttt

jonaddis84

The biggest problem you are going to run into with that much lift is the hydraulic roller part. It will be alright but that is killer on the lifters and springs and such. With that much lift most go to a solid roller setup, you dont need much over .600 unless they are crazy heads. You will be collapsing lifters left and right and replacing springs twice a year with that much lift. I would suggeest just some 1.6s and still get the big cam down the road, it will be plenty.

kgkern01

Thats another thing I was wondering about was the lifters. Forgot to ask about those. If under .600 lift is pretty safe, since only the exhaust side would see lift of about .614 w/1.7, what about using 1.6 for the exhaust side, and 1.7 for the intake side? Kind of "customizing" the lift characteristics of the cam. When I do upgrade my valvetrain, I plan on using the best springs and lifters, etc that I can find. Only want to do that once.

Here's a guy with a hotcammed vette in my area that gained 14 hp with just switching from 1.6 to 1.7 RR.
http://www.kyfbodies.org/vb/showthre...light=scorpion

jonaddis84

There is a bigggg difference between a hotcam and a .600" lift cam, hotcams are only in the .5" lift range, maybe lower than .5, dont know offhand. Which would bump it up to around .510 or .520 maybe, which is good for a stock casting lt1 head motor. but when you are wanting to increase lift to .600" or above, you need some awesome heads since LT1 castings, unless ported by somone very good usually flatten on the flow curve at about .550 and just increase slowly after that. if you think about it logically why would you want to lift the valve past the point where the flow slows down, thats like shifting your car at 7000 if the power peaks at 6500, just doesnt make sense, do some more research into this with searches and talk to some shops that know LT1s, there is more to it than just saying more lift or more duration equals more power.

Edit: On a stock setup yes putting 1.7s will help, but there is no need to on a big cam motor, look at any guy on here with a larger cam than the hotcam that are producing the highest HP n/a, even with strokers in the 450rwhp range, see if any of them have 1.7s, there just isnt a need for them on bigger cam motors.

kmook

Going over 600 lift is when you could expect PTV clearance issues. This will be difrent with each setup, and each cam as duration plays a large roll in PTV clearance. The only way to know is to clay it and check.

Next id recomend staying with 1.6 rockers and getting a custom cam (which will cost about $250 from anywhere about the same as a c306 or an off the shelf cam) and have them grind it how you want with what lift you desire. That way your valvetrain geometry is much better instead of putting 1.7 rockers on.

kgkern01

Thanks for the advice, just what I was wanting to know! Since the cam won't be for a while, I believe I'll do the 1.7 RR with the stock cam, then switch to 1.6RR when I upgade to a cam.

94 CAMRO Z28

Just so you know, the hotcam with 1.6RR is .525 of lift.

Aaron

96 WS6

it's .525 on both intake and exhaust.

S.J.S.

I'm just tryin to figure out why you feel you need to go with 1.7 rr's for?

kgkern01

After hearing everyone's advice, I'm only going to do 1.7 with the STOCK cam, to get a little more lift and a little extra HP out of the stock cam, because it will be a while before I do a cam. I am going to upgrade my suspension before I do anything non bolt-on to the car. (I do consider RR somewhat of a bolt on, since the only thing you tear down is the valve covers.)
THEN when the time comes to do the cam, I will most likely switch to 1.6 RR as I don't need any collapsing lifters on my daily driver, if over .600 of lift will cause that.

stew's94z

If you are using stock valve springs you should check for coil bind with the 1.7's. Some people have experienced coil bind using 1.6's on the stock springs. Some haven't.

Dean Stewart

kgkern01

When I do the 1.7 RR (which will be after LT's of course) I plan on upgrading springs, pushrods, valve seals while I'm in there so when I do the cam, won't have to buy all that stuff again.