ED69ray

Hope you guys don't mind me posting this here as this forum is one of the most tech savy I have had the privledge of joining.

I just picked up a retro hyd roller setup for the 355 in my '73 Camaro. Cam is a Lunati - # 60110. Specs are:

Advertised Duration (Int/Exh): 262/270
Duration @ .050 (Int/Exh): 211/219
Gross Valve Lift (Int/Exh): .507/.515
LSA/ICL: 112/106

It came with a set of Morel tie bar rollers lifters - cam and lifters are both new in the box.

I had originally planned to run a flat tappet and have a set of reworked #186 heads with Z-28 valve springs - they are single 1.25 springs and rated to .550 lift. Now that plans have changed - is this enough spring for this roller setup?

My engine guy is telling me to run a dual spring rated at .600 lift - the 186's would have to be modified ($300) and I don't really consider it cost effective to do so.

Whats the verdict?

Thanks, Ed

TimAT

For the best reliability and performance you should see what pressures that Lunati recommends for that cam. Guessing here can cost you big.

I'm a fan of using the manufacturer's recommended springs. Doing that, you get the correct open and seat pressures from the get go, along with a spring that will take the punishment the cam gives it.

Grumpy 427

Your going to have a bunch of broken parts if you stay with that spring. The valve spring keeps the lifter planted on the cam, too little spring will cause valve float and have the lifter bouncing on the cam lobe.

baxsom

300 bucks now or a engine rebuild later

ED69ray

here is the cam spec card

http://www.lunatipower.com/Product.aspx?id=1987&gid=289

Lunati recommends spring #73943 which is:

Spring Type: Single w/damper
Outside Diameter: 1.266 in.
Inside Diameter: 0.883 in.
Seat Load: 108 lbs @ 1.750 in.
Open Load: 339 lbs @ 1.250 in.
Coil Bind: 1.060 in.
Spring Rate: 462 lbs/in.



The Z-28 springs are supposed to be app. 115/330 lbs on the seat - the Lunati # 73943 springs don't seem to be much of an upgrade over the Z springs.

What do you guys recommend?

Thanks, Ed

TimAT

The spring rate is where the most likely difference is.

I have a set of the Z-28 3927142 springs. Work great with the 3827140 cam.

I still say go get the springs recommended by the manufacturer. Look at it this way- if you run a different spring, one breaks and the keepers come off the valve, where does a valve with no spring go?

MotorHead

I always would advise to go with the spring the manufacturer recommends for the cam, that said, I never do because I usually run 1.6 rockers so it takes a bit of time to select the proper spring. There are many things to consider when selecting a spring.

There should be no guessing, you always want to be sure you have the correct springs for the cam, you need to consult someone who has expertise in this area.