vt408

Hi Guys!

ive got a 408ci l98 which was a brand new crate motor that was pulled down and built up. it runs a 242/251 112l/s and 638" lift cam, stock lifters (not the ones that can drop cylinders) and yella terra ultralite rockers 3/8 shaft mount.

the lifter noise is intense on first start and only marginally quietens down after it gets oil presure (50psi at ide 45psi idle warm (upgraded oil pump)
the engine has donw it since day one and the engine builder could never find the prob. the preloads are set down 3/4 of a turn. i went 1/4 then ran it than another 1/4 ran it then another 1/4 noise never changes.

im suspecting either a couple of dud lifter, definatly more than 2. or the valve spring pressure too much and overcoming the hydraulic lifter plunger. ive noticed that everhy time i take rocker covers off i can push down on the lifter side of the rocker a couple of mm. i thaught they should be still pumped up .. let me no your thaughts. thanks

gectek

iTrader: (2)

PS one full turn from zero lash is roughly .047" preload on the metric rocker arm bolt. That is prob where you are off. For the LS7 lifter, people usually aim for .050 to .080 ish preload.

vt408

so would that mean that one full turn would be pretty close?

Are the ls7 lifters the lifters that dont control the cylinder dropping in l98s?

gectek

iTrader: (2)

The LS7 lifters are the standard lifter, not the active fuel management lifter or the DOD lifter (same thing some people use diff terminology). They are the normal lifter. And 1 turn normally gets you in the target zone. You can do it exactly if you wish though with an angle meter also. Roughly 30* extra will give you your target range of between 55 and 65 if that is what you want to run them at. Some say more, some say less.

Most of the info I am using for the 1 turn theory is based off of a write up that thunder racing posted quite a while back. It gets recycled on here alot, but is very helpful.

vt408

Thank gektec

Ive spend night after night researching the forum ready threads and ive found people with the same issue but has never been fixed properly.

i gues ast question before i rip the heads off is: after i switch the car of, remove the valve covers, i can push down on the pushrod sode of the rocker
is this normal? like they have collapsed

listening to the noise it is mos evidend if you put your ear or stethascope on the inet manifold.

gectek

iTrader: (2)

Are you sure you put the camshaft in correctly? If you are off by one tooth that would accidentally over advance the cam by roughly 8 degrees or more, and can cause your valvetrain noise as well.

vt408

cam is definatly in correctly, tripple checked. ps noise was there before cam repacement, has been in engine since new, engine buiilder couldnt even work it out has done 1500kms now

vt408

Ive got some comp cams hydraulic roller lifters order, might pull her down, replace and work my way up. i dont think i have an oi pressure prob as its got 50psi colt and around 42 hot. noise does get slightly worse hot.

Gray86hatch

iTrader: (83)

Order the Lunati Street lifters. They are made by Morel. I have them in my car and it will idle with 30psi with no noise.

Also no reason not to use stock rockers with a trunion kit.

Tim