Re: Turbo cam in NA I5

[DeWitt Harrison <de@aztek-eng.com>]

On Wed, 03 Dec 1997 14:16:58 -0500, Huw Powell wrote:

>>  # I have heard from a VERY informed source that this is the best cheap
way to
>>  # get power out of a N/A motor.  Short of a Schrick 276 it is the best
thing you
>>  # can do to it.
>>  #
>>  # Anyone care to share their real world experience with using a turbo cam in
>>  # a NA I5? ('86 4kcsq in my case)
>>  #
>> ... If one looks in the Bentley for the 5k (84-88) at the engine specs, the
>> cam timing specs for the NA I-5 (code NF?) look pretty doggone similar to
>> those for the MC (turbo).
>
>So the bottom line is, no one here has done this.  Mike T mentioned in
>reply to one of my previous inquiries on this subject that the lobes on
>the turbo cam lift the valves further, allowing a bigger charge.
>
>I had hit on the idea of transferring the whole head, which would get me
>slightly bigger valves as well and let me do head work (replace valve
>stem seals etc) with my car running.  Trouble would be dealing with the
>many likely broken studs, etc.  If I don't do that I will probably try
>this camshaft swap in a few months.  I will do some measuring while
>they're out if I can.
>
>I want to replace my valve seals anyway, hey the camshaft has to come
>out to do that, I have a 5kt parts car, seems like the thing to do.  Too
>bad nobody actually knows the pros and cons already.

Someone else just pointed out that the low overlap of a turbo
cam is not a good solution for a NA head. Even if it's true that
the turbo cam has more lift than the _stock_ NA cam, you
will still have a more poorly breathing engine. Low overlap is
necessary due to the high exhaust manifold back pressure but
is overwise not a desireable feature. Get a 272 NA cam or
similar. There may be alternatives to the $chrick. Call Sport
Wheels.

DeWitt Harrison     de@aztek-eng.com
Boulder, CO
88 5kcstq