Cam Lift and roller rockers
- Thread starter Fast231
- Start date
- Joined
- May 26, 2001
I think you have something confused here.
If the lobe lift is .519" the valve lift would be .856". Doubt if you could fit this large a cam into a 3.8 block?
These numbers probably came from a cam card and actually is the valve lift. You need to know lobe lift to calculate valve lift for various rockers. The card should show at what ratio rocker they calculated the valve lift, then you can find lobe lift.
At .519 valve lift on a stock GN head, you will not have coil bind if that answers the question and cuts through my confusing reply..
If the lobe lift is .519" the valve lift would be .856". Doubt if you could fit this large a cam into a 3.8 block?
These numbers probably came from a cam card and actually is the valve lift. You need to know lobe lift to calculate valve lift for various rockers. The card should show at what ratio rocker they calculated the valve lift, then you can find lobe lift.
At .519 valve lift on a stock GN head, you will not have coil bind if that answers the question and cuts through my confusing reply..
Russ Merritt
New Member
- Joined
- Aug 11, 2002
Doesn't that depend on what valve springs are being used Nick? I thought and have been told that running anything over .500 lift without roller springs (K-750s or Comp 941s) wouldn't work. Or were you saying retainer to guide clearance on stock heads was OK for .511-.519? Something else I thought was too much also.
Russ Merritt
New Member
- Joined
- Aug 11, 2002
Fast231, if the lift of .511-.519 is based on a 1.55 rocker that would put the lobe lift at .330 and .335 making the lift with 1.65 rockers .544-.552. If the lift was based on a 1.50 rocker that would put the lobe lift at .341-.346 making the lift with 1.65 rockers .562-.570. Double checked my math as I have no calculator.
Dam you mean all these other numbers mean something
Nick, yes that is from a cam card, the Lobe lift is .3300 intake and .3350 exhaust, If Russ is correct then it is based on 1.55 ratio (card doesnt say). The heads are GN1's (aluminum), so with that bieng said am I right in saying that at a lift of Russ's calculations (the lift of .511-.519 is based on a 1.55 rocker that would put the lobe lift at .330 and .335 making the lift with 1.65 rockers .544-.552.) I'm going to run into either coil binding issues or clearance issues? (CC Billet roller with CC supplied springs, 109 block))
Seems to me i read that at a lift of over .530 there would be clearance issues??
Thanks for your help,
Nick, yes that is from a cam card, the Lobe lift is .3300 intake and .3350 exhaust, If Russ is correct then it is based on 1.55 ratio (card doesnt say). The heads are GN1's (aluminum), so with that bieng said am I right in saying that at a lift of Russ's calculations (the lift of .511-.519 is based on a 1.55 rocker that would put the lobe lift at .330 and .335 making the lift with 1.65 rockers .544-.552.) I'm going to run into either coil binding issues or clearance issues? (CC Billet roller with CC supplied springs, 109 block))
Seems to me i read that at a lift of over .530 there would be clearance issues??
Thanks for your help,
Russ Merritt
New Member
- Joined
- Aug 11, 2002
Tom Allen at Champion says with K-750s or Comp 941s .600 is max lift with GN1s or his iron heads. I just asked him this question the other day as I built an engine with a 210/210 507/507 with 1.60 rockers and I wanted to know how much lift I could run on Champ irons with K-750 valve springs. He said .600
