Re: 1.6 rockers intake side

[Tom Watters <tomwatters@xxxxxxxxxxx>]

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My Racer Brown cam came with a card that showed lift and duration at 1.5
and 1.6.  The 1.6 gives you a higher lift and could cause valve
clearance problems on a decked block with shaved heads.  But I didnt
think the cam had to be designed for it, you just run it through a
calculation and you can determine what the new lift is.  Using a basic
ratio calculation assuming you know the lift for the cam at 1.5, isn't
New Lift = (Current Lift * 1.6) / 1.5

On an engine being build for Torque and Power, Assuming no clearance
problems, wouldnt a 1.6 ration rocker with a higher lift allow for more
CFM to flow into the chamber?

Am I all wrong here?  Sensible?

--TOM

On Wed, 13 Jul 2005 08:39:59 -0400, "Don Dulmage" <big-d@xxxxxxxxxxxx>
said:
> 
> Yes I know that trick it is often done on chevy SBs. 
> We will give it  a whirl as well but my current belief is that the cam
> was designed to take max advantage of the port design of the mopar head
> and large lifters and it was designed for 1.5 rockers . 
> When we put 1.6s on we go a outside the cams carefully designed features
> and it screws up the valve action and we lose power. I think that  to use
> 1.6 rockers  the cam needs to be designed for them. I dont know if I said
> it here before but we made a set of 1/7 s once from a set of crane iron
> 1/5 adjustables (moved the adjusters inward about 30 years ago )  and the
> results were not unlike the last test.(There was certainly no gain)
> At the levels of cam we are running  which are relatively mild compard to
> a pro stock cam etc  it would be no problem for the cam manufacture to
> make a cam with the same figures and area under the curve with 1/5s that
> would be the same as 1/6s are running on the 1/5 cams we are using
> currently. It is I think though true that cam timing is a very critical
> thing and bolting on a set of 1.6s often hurts more than it helps. We
> will keep flogging this though to find out for sure. I know for instance
> putting 1/6s on a cam like the ST-H-42 Racer brown which is a FULL ON cam
> with absolutley no compromises would almost certainly ruin its
> performance as it is already maxed out. and you cant go beyond that with
> out messing things up.
> 1/6 while they do not change the duration from actual opening and closing
> do change the "effective duration" at 050 and at .200 lift. because the
> valve is open more earlier and flow events are changed.  Serious cam
> manufacturuer give the duration at 200 " and at 050  for this reason. 
> Because the valve would be at the 050 or .200 lift point earlier  the
> duration at these points would be greater than it would with 1/5 rockers.
> It takes very  few degrees to make or ruin cams performance 
> . Anyway we will try several more combos and see if we ever get an
> increase. (i AM BETTING NO)  
> I have yet to see anyone running through the pits saying i put on 1/6s
> and dropped 2 tenths. Usually they are very quiet  because they just
> spent 3 or 4 hundred bucks and got nothing or an even worse result and
> think they did something wrong. We often hear" it feels better" or "seem
> a lot better" but if it aint on the time slip, baby , then it aint there. 
> However i reserve the right to say "I was wrong" should I get positive
> results. This is just my current thinking today.
> Don 
> Author of
> Return to Deutschland (True Adventure)
> Old Reliable (Mopar)
> http://stores.ebay.ca/Don-Dulmage-Enterprises
> [Non-text portions of this message have been removed]
> 
Tom
65 Dart GT 'vert
68 Plymouth 'vert
Las Vegas, NV

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