Sam Mellace

I need some help before I break something. I recently did a full DoD delete and installed an LS7 cam in my G8. I replaced the lifters and the Springs using GM performance parts LS series springs with Max lift of .600. I was told that in order to achieve same lift as an LS7 I would need to change the rocker arms. I ordered the yella Terra 1.85 roller rockers. I believe the stock LS7 has a 1.8 rocker. So my question is will the 1.85 increase my lift over .600 and do I need to change my Springs again? I believe the lift on a LS7 is .591 or thereabout. Pushrods are 7.400.

kinglt-1

iTrader: (26)

Edit*

Better measure for coil bing or move up to a higher lift spring.

Jontall

You should have ordered a cam with the specs you wanted. It's not good to try and add lift by altering the rocker arm ratio. If it was me, I would have ordered the cam that I wanted, added Tooley platinum springs (.660), upgraded push rods, and a Straub Bushing Trunion Kit. It's a rock-solid setup that most here use very successfully.

kinglt-1

iTrader: (26)

The cam he purchased is designed for higher ratio rockers. There is absolutely nothing wrong with higher ratio rocker arms combined with a cam designed for them.

slogo

I guess I am doing the math wrong.
I divided .591 by 1.8 to get cam lift .328
then multiplied .328 by new ratio 1.85 and got .606
will that work with .600 lift springs???
Did I do the math wrong???

Sam Mellace

I think it's right. I came up with .607 which is why I posted this. Dosent seem like much.

mOtOrHeAd MiKe

iTrader: (8)

Do it and report back if the springs could not handle .007" extra lift. I mean it is just .007", right?

But, you probably should have bought the right cam and spring package from the outset.

DavidBoren

Welcome to the forums.

Personally, I would get springs that will not be operating so close to coil bind. You can pick up some PAC-1904 duals from BTR for $150. They are rated for .650" lift and 150#/400#, should be fine for most applications.

And please, measure for pushrods. Changing cams, heads, and/or head gaskets can all change the length of the pushrod required.

The '09 G8 has the LS3, correct? If yes, then the LS7 cam will probably do well. If the '09 still has the LS2, I do not expect the LS7 cam to compliment the cathedral port heads.

Sam Mellace

It has the L76 6.0 with the l92/ ls3 heads. the pushrods are 7.400.

KCS

iTrader: (20)

You need to know your installed height and coilbind clearance. There's usually enough variance in the stock parts to run a little bit over the "max lift" rating of most springs, but it's not very smart to do without knowing how they're setup in the first place.

Also, a 1.8:1 rocker will move the pushrod in closer so you will need to make sure they clear the pushrod holes in cylinder head.

Sam Mellace

The Springs are GM performance parts LS series springs with a .600 Max lift rating.

KCS

iTrader: (20)

Yes I saw that, but that's doesn't help much. You need to measure or just go with different springs.

kinglt-1

iTrader: (26)

Oops my mistake...I thought you meant the total lift with 1.85 rockers is .591 lift. What you posted is with 1.8 rockers. So yes that little extra bit of ratio is going to put you over .600. I would measure for coil bind or just get some .625 - .650 lift springs.

KW Baraka

iTrader: (7)

Get new springs.

Agreed!!!

KW

DavidBoren

The LS7 cam will probably work pretty well with the L92 heads. Not optimal, but better than it would on cathedral port heads, I am sure. Anyways, there is absolutely no need to run the springs that close to max. It is an exercise in recklessness. You could run stock 1.7 ratio rockers with the LS7 cam and use the GMPP springs you have now. Or you can run 1.85 rockers with the LS7 cam and change to properly rated springs. The choice is yours, but I encourage you to use this opportunity to step up to some dual springs. Pushing a single beehive spring to its limits is an excellent way to break a spring, drop a valve, and ruin your ****.