Cam lift question

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gerty

gerty

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I have a 360 with magnum head conversion. I'd like to use a comp xe-268 cam with lift of .477 intake and .480 exhaust with 1.5 ratio rockers. The Magnum has 1.6 ratio rockers. So the question is will there have to be machine work on the heads at the valve stem area to use this cam? Seems I heard the magnum heads would only take around .500 lift without clearance problems. I don't want to disassemble the engine at this point for the cam change, but I really liked the xe- 268 in a 318 I once owned.
Bob
 
you'll gain approximately .030 lift going from a 1.5 to a 1.6
 
Foggy memory says that max lift allowable on a Magnum head is .525; your exhaust lift will come in at .512, which says you just make it.

To be sure a little more research would be advisable.
 
duration is not involved with clearance to valve seal or springs, it does come into valve to piston clearance
 
IMO, you're better off with the XE262 which ould be comparable with 1.6 rockers.
 
I think you will be fine. Keep in mind, you lose about .020" of lift at the valve because of the terrible pushrod angle.
 
I have a set of Bone stock magnum heads here in the shop. I will take a measurement for you and give a real world answer.
 
Ok, checked it with bone stock beehive retainers and after market 1.400 retainers. Both came up with .550", and thats the retainer touching the seal.

Theoretical lift would be .512". Your good there, and there aint no way your going to get .512 at the valve. Slap the right springs on for the cam and go with it.
 
MRL Performance said:
Ok, checked it with bone stock beehive retainers and after market 1.400 retainers. Both came up with .550", and thats the retainer touching the seal.

Theoretical lift would be .512". Your good there, and there aint no way your going to get .512 at the valve. Slap the right springs on for the cam and go with it.
Click to expand...

Hey, you're pretty handy to have around!
 
We always say .525" just to have a bit of extra clearance. Funny how often people on here say you cant go over .475" on factory heads....the truth comes out.

OP, you can always use 1.5 ratio rocker and take advantage of extra duration. Replacing the stamped factory ones is a good idea anyway, the ratio can vary from 1.4-1.6 just from inconsistency in stamping. PRW makes an inexpensive roller tip that will work well with your level of build. 1.5 or 1.6
 
So, seems like some of our "unreal" world answers were right. Imagine that?
 
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