Natester

Liter 6.0
CID 364
Engine Make 2004,Chevrolet
Engine Model LQ4.

Hello,
I want to replace the stock cam with this one
Howards Cams Hydraulic Roller Camshafts 190395-13
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,600-6,600

Duration at 050 inch Lift/Exh: 218 int./224 exh.

Valve Lift with Factory Rocker Arm Ratio: 0.604 int./0.612 exh.

Lobe Separation (degrees): 113


How do I determine the correct valve springs and pushrods to replace the OEM?
OEM spring specs are 76lb@ 1.8in Closed and 220lb@ 1.32in Open. .48in difference.
Intake stock valve lift w/rocker arm ratio is .464in. Lift difference is .096in
Exhaust stock valve lift w/rocker arm ratio is .479in. Lift diff is .081in.

For the pushrods I thought you could measure the difference between stock and aftermarket lobe height and determine the new pushrod height.?
Any help appreciated.
Thanks

madmann26

iTrader: (7)

Get a set of BTR .660 springs. Pushrods you're going to have to measure.


I wouldn't be surprised if you came up with a 7.450 rod.

arthursc2

iTrader: (5)

I have yet to replace pushrods just from doing a cam.

Natester

If the lobe of the cam is increasing overall height by .096" would the pr's go down in size by the difference?

wkdivr

iTrader: (8)

No. That would negate the lift of the cam.

Natester

Gotcha, I was thinking there has gto to be a way to calculate PR length mathematically.

03sierraslt

iTrader: (22)

Did you actually measure to see? Normally you can get away with it with stock lifters as they have a decent about of preload room to play with but its still a shot in the dark if you don't check a couple.

madmann26

iTrader: (7)

So, a couple of years ago I was wondering the same thing. I found a post buried by Frost (I think) and he said that when you go over .600 lift, the base circle of the cam is turned down smaller so that the cam will fit in the engine.

I never officially measured mine but with 7.4's it sounded like a pissed of Volvo and with 7.425's, it sounded less like a pissed of Volvo.

With 7.450's, it was quiet as stock. I put almost 50k on that cam and pushrods and never had a single but of trouble out of it.

Spend the 20 bucks and measure it to be safe. Everyone's opinion is YMMV because of different setups.

arthursc2

iTrader: (5)

I have only used "low lift" cams. A .559, a .550 and a .590. No I didn't measure. Just slapped it all together and let her eat. All 3 of those engines are still running and none are making any valvetrain noise.

Ill be sure to measure on my 408, but a built engine is a bit different than a mid to high mileage 5.3 seeking more power.

Natester

With those low lift cams you didn't have to change springs either? In your opinion did you notice any significant gains in hp or acceleration.?
thanks