Stock heads CC?
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Instructor
Joined: Jun 2002
Posts: 218
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From: Winnetka CA
Stock heads CC?
Does anyone know the cubic centimeters (or inches) of the stock heads on an 87 L98? I am still researching making a 383 and I dont want my compression ratio to end up to high.
Also how do 1.6 ratio affect the lift when considering a new cam?
Also how do 1.6 ratio affect the lift when considering a new cam?
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: Stock heads CC? (amswak)
Chamber volume is 58cc.
Valve lift is cam lift times rocker arm ratio. So the increase in lift from stock 1.5:1 rockers to 1.6:1 rockers is:
1.6/1.5=1.067
For example stock intake valve lift was .410" and with my 1.6:1 RRs it now is
.410 x 1.067 = .437".
Also the 1.6:1 rockers broaden the valve open duration by about 2deg at .050" lift. This is because at each point along the camprofile valve lift is increased by the same ratio, i.e. 1.067. So 1.6:1 rockers open the valve that much more for the entire time the lifter is off the base circle; this has the effect of installing a slightly more radical cam.
Valve lift is cam lift times rocker arm ratio. So the increase in lift from stock 1.5:1 rockers to 1.6:1 rockers is:
1.6/1.5=1.067
For example stock intake valve lift was .410" and with my 1.6:1 RRs it now is
.410 x 1.067 = .437".
Also the 1.6:1 rockers broaden the valve open duration by about 2deg at .050" lift. This is because at each point along the camprofile valve lift is increased by the same ratio, i.e. 1.067. So 1.6:1 rockers open the valve that much more for the entire time the lifter is off the base circle; this has the effect of installing a slightly more radical cam.
