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I red something about to use only stock springs to brake-in a new cam.
I don't know if I need to change the springs in my heads ( AFR 195cc street heads) for cam break-in. Since I don't know much about valve spring pressure, I copy this from AFR's site, to give you some idea about what i have; "1.450" OD Hydraulic dual valve spring w/ dampener, 120lbs on seat, .550" maximum lift"
Is realy necessary to change my springs for stock ones?
I would like to know what you all think about?
With springs this mild I would not worry about it.Just follow the cam manufactures directions when you break the cam in.Quote:
Originally posted by Alan76
I red something about to use only stock springs to brake-in a new cam.
I don't know if I need to change the springs in my heads ( AFR 195cc street heads) for cam break-in. Since I don't know much about valve spring pressure, I copy this from AFR's site, to give you some idea about what i have; "1.450" OD Hydraulic dual valve spring w/ dampener, 120lbs on seat, .550" maximum lift"
Is realy necessary to change my springs for stock ones?
I would like to know what you all think about?
no need to change the springs, do valve adjustment before start up, once started run at about 2500rpm for 30 min.
Here's info from Crane. Be sure to read the note at the bottom. My feeling on this is that if you are not willing to do everything you can to prevent wiping a cam lobe, then you shouldn't be changing the cam in the first place.
C) Spring pressure
Normal recommended spring seat pressure for most mild street-type flat tappet cams is between 85 to 105 lbs. More radical street and race applications may use valve spring seat pressure between 105 to 130 lbs. For street hydraulic roller cams, seat pressure should range from 105 to 140 lb. Spring seat pressure for mechanical street roller cams should not exceed 150 lb. Race roller cams with high lift and spring pressure are not recommended for street use, because of a lack of oil splash onto the cam at low speed running to help cool the cam and lubricate the lifters. This high spring pressure causes the heat created at the cam to be transferred to the roller wheel, resulting in its early failure. Any springs that may be used must be assembled to the manufacturer’s recommended height. Never install springs without verifying the correct assembled height and pressures.
NOTE: Increased spring pressure from a spring change and/or increased valve lift can hinder lifter rotation during cam break-in. We have found that decreasing spring pressure during the break-in period will be a great help. This can be accomplished by using a shorter ratio rocker arm to lower the valve lift; and/ or removing the inner spring, during the cam break-in time, if dual springs are being used.
Cam break-in is very important with a flat-tappet lifter. The easier alternative to spring swaps is the installation of low ratio rockers. I use a set of Comp 1.3 for most all of the XE series break-ins. They are set up for 7/16 studs. Just in case some don't know, the screw in studs in heads have the same size hole where they screw into the head whether the studs are 3/8 or 7/16. The break-in rockers from comp are part no.1012-16. If you have 3/8 studs, you can use a set of cheaper (than ARP) 7/16 studs and just swap them for break-in with the short ratio rockers. If you opt to "take your chances", at the very least, don't run a 1.6 during break-in as this opens the valve a good bit higher, thus using more spring pressure.
Great point about the reduced ratio rockers Ray, thanks.