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the best choice to replace "S" cams

Hello

any advice to replace early "S" cams on my 2.7RS stock engine ?
best regards
Philippe
Old 01-05-2005, 03:28 AM
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Street? Track? Race?
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'69 911E

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Old 01-05-2005, 04:35 AM
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I like the "S" cams in my 2.7. You can get abit more low end without sacraficing top power by going to Elgin "Mod S" cams. Camgrinder should be able to give you good guidance for a cam. Keep in mind that if you stray from the "S" cams you'll need to upgrade your valve springs for the incrased valve accelerations the newer cams use. This increases the expense of this upgrade quite abit.

-Andy
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Old 01-05-2005, 11:14 AM
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do you still use the MFI with it?
if so , then whatever cam you put in , will require the cam drive
that's usually extra cost
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Old 01-06-2005, 07:10 AM
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yes i'll still run MFI

aftermarket cams are supposed to go "in place" don't they ?
Philippe
Old 01-06-2005, 07:18 AM
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yes and no , the cams themself will fit , no problem

but you will need to make sure that whatever cam you put in
also has the mfi drive
( most cams don't have em by default, since they are not required for Carburettor , electronic injection or CIS injection )

without the mfi drive, your mfi pump cannot be timed, driven and will not run

another thing , mfi pumps are matched to the cams , so the cams you put in , will have to be somewhat similar

eg , a T or E cam with an S pump will not work

maybe others can comment with more experience on this
but to my understanding, whatever cam you put in , will have to be so similar to the existing cam , that it's probably not worth the effort for the marginal difference in results
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Old 01-06-2005, 07:27 AM
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The mod-s cam (my dc-40) is a good upgrade for the original MFI S engine. There is no down side. Like eagledriver stated, the low speed is greatly improved with no loss of top end power.
The Mfi drive adapter adds some cost to the new cams, but the adapter is available.
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Old 01-06-2005, 08:48 AM
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My assumption here is that the engine is going to be used for street and light track work (ie: occasional DE's, but not necessarily redesigned for maximum track performance).

Some cams of roughly the same "hotness" as the early S cam and some really rough estimates of the impact on the engine. Listed from mildest to wildest. In order to keep the valves close to the cam, you might need to investigate either lighter weight retainers or stiffer springs for some of these cams. If Camgrinder weighs in, his comments will trump mine .

* GE40 - Better low and mid-range then the S cam, but similar high RPM performance.
* Crane P296 or GE60 - Similar low to mid-RPM performance to an S, but better high RPM performance

Camgrinder has a few other grinds in that range you might want to consider.
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Last edited by jluetjen; 01-06-2005 at 11:11 AM..
Old 01-06-2005, 08:56 AM
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If you can keep the rpm below 7000, my DC40 (GE40, Mod-S) cam will work with properly set up factory springs. If you intend on 7500 rpm shifts, I would recommend an upgraded valve spring.
Like John says, springs and retainers are required for most aftermarket cams hotter than the DC40 etc.

You should list any other mods done to the car/engine and how you intend to drive it.
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Old 01-06-2005, 09:22 AM
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it's going to be used both street and track, not an ultimate car

i have stock 019 pump

what would be the extra cost to run MFI ?

best regards
Philippe
Old 01-06-2005, 12:15 PM
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Hi camgrinder

"My assumption here is that the engine is going to be used for street and light track work (ie: occasional DE's, but not necessarily redesigned for maximum track performance)."

YES


what sould be the extra cost ? what should be the modification ?
may you tell me if you do it, sell it , price ?

PM if you want
best regards
Philippe
Old 01-07-2005, 01:40 AM
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for further information : engine is on rebuilt, it'll be stock except muffler (home made) and cams
Old 01-07-2005, 01:49 AM
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Hello Philippe,
I sent you a Pm with the specifics.
I do make the DC40 cams with the mfi drive for the early 911.
It is basically a drop-in. The only thing I recommend changing are the valve springs.
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Last edited by camgrinder; 01-07-2005 at 08:06 AM..
Old 01-07-2005, 07:59 AM
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