Danspeed1

iTrader: (1)

I am swapping the cam out on my 2005 LS2 Corvette. I ordered the cam from a well known performance shop, so I would assume the parts are correct, however I am getting conflicting opinions on the following questions. Hopefully someone with the right information can help.

I am no cam expert, and this is my first cam install.

The specs of the cam are 223/235@.050, with an advertised duration of 274/285, and a .625/.625 lift. I am using the stock rocker arms, as well as the stock lifters.

This brings me to my first question. I understand the safer than sorry mentality and I am usually an advocate of it. However, I was told by the cam builder there is really no need to change out the lifters for the cam I am installing. Reading online I have found quite a few posts where aftermarket cams have caused stock lifter failure, although no one ever seems to list the specs on the cam they had installed at the time of failure. Am I pretty safe using the stock lifters with this cam or am I required to change them? I am looking to get a long life out of this engine. Currently has 40K miles.

The second question I have is on push rod length. The heads have never been off the vehicle. Cam is already installed, how do I calculate to find the correct push rod length? Some people are telling me I need a 7.400 others are saying I need 7.450"

Thanks,

DG

Mez

iTrader: (1)

I have ~25,000 miles on a cam with more lift than yours and the stock lifters have been fine. I don't think you need to change the lifters.

The stock pushrods are 7.40 inches. More than likely, the stock pushrod length is correct. The pushrod length is what sets the lifter preload of between .25 to 1 turn of the rocker arm hold down bolt. To check, after you install the cam, make sure the valve is closed and install one pushrod . Tighten down the rocker arm bolt until you reach zero lash on the pushrod. Then torque the bolt to 25 ft lbs. If the bolt turns .25 to 1 full turn from zero lash, the lifter pre-load and the pushrod length is correct.

However, with your cam you need to strongly consider upgrading the pushrods. The stock pushrods are kind of weak so tend to flex especially with higher lift cam.

Danspeed1

iTrader: (1)

Thanks Mez,

Doing more than just changing the cam. If you want to take a look.....

http://forums.corvetteforum.com/c6-t...charger-5.html

I am being told on the corvette site, I should be getting 1 1/2 to 1 3/4 turn. Seems like alot. From zero lash to pre-load (the recommended 22 ft/lbs) I am getting 3/4 of a turn. If YOUR calculations are correct i am within spec.

DG

Mez

iTrader: (1)

Since the pushrods are cut in increments of .050", the better way is to simply set the pushrod checker to zero lash then add .050" to that for the proper length.

So, for example, if at zero lash the pushrod checker is at 7.350", then 7.40" is right. If you are at 3/4 of a turn now, that is just about perfect.

I rounded to 25 ft lbs but 22 ft lbs is the spec. not sure if 3 ft lbs makes any difference but you don't ever want to break a rocker arm bolt.

A couple of things to look out for is the rocker arm hitting the valve cover. An easy way to check is to put a finger on the rocker arm while the engine is idling. If you feel a nice, sharp "rap", then a rocker arm is hitting the valve cover inside baffle. Pull the rocker arm cover and check it carefully for shiny areas on either the rocker arm or valve cover. That's where it will be rubbing. Many times it the rivets or the round bumps. Use a Dremel to cut away the offending area but never grind the rocker arms.

Don't over tighten the valve cover bolts. Too tight and it pulls the valve covers down too close to the rockers. I just turn the bolts down until firm. It seals up fine and doesn't leak.

redtan

iTrader: (5)

Is this a supercharged car?

Danspeed1

iTrader: (1)

Yes it is

chrisfrost

iTrader: (8)

I think He meant to put a finger on a valve cover to feel if a rocker arm or arms are hitting the valve cover .

Danspeed1

iTrader: (1)

There has been a few updates on this project.... Primarily:







So now I need the lifters. I have been reading on this site for the past 2 days and these appear to be my options: Lunati/Morel Linked Bar Street Lifters, the higher priced Morel high RPM Lifters, and the really really high priced Comp Cams Linked Bar Lifters. The comps are out of the question. What it comes down to is do I really need to spend $700 on lifters or can I get away with the reasonable priced lifters. I would like to think for $300 the Lunati/Morel Street lifters are BETTER than my stock LS2 lifters OR LS7 Lifters would be. Am I correct in thinking this?

I listed my cam specs in the first post. Since I took the heads off, my local machine shop is opening up the exhaust valves to 1.60, and cleaning the bowls up. This should make my 243's flow a little better. I am topping the engine with a Magnuson MP112 supercharger with an Innovators West Overdrive Crank Pulley and a 3.0 Maggie Pulley which should yield 10lbs of boost (I think). LS9 ZR1 Head Gaskets, Nick Williams 102mm Throttle body........................... I think the real question here is how high or low (I am thinking low) of an RPM will I need to spin this thing to make power. I know most of you guys are spinning your heads/cam cars to 7500RPM but this is a blower car. If I make all my power by 6500 the street lifters will be fine. If not I might have to bite the bullet. In any event I need to make a decision quick as this is holding the whole project up,

DG

Mez

iTrader: (1)

Whoops! That's what i meant!

Don't try to put your finger on the rocker arm while the engine is running. That could really hurt!

Mez

iTrader: (1)

With that cam, springs, and RPM range, stock lifters are fine. You will not see any reliability or performance improvement with aftermarket lifters.

I have a higher lift cam and after 26,000 miles, the stock lifters have been fine up to 6600 rpm. With a blower, you probably should stay around 6000 rpm. Aftermarket is not always better performing than GM.