Re: Crossfire Injection Question

["nacelp" <nacelp@bright.net>]

> This is a question/comment w/ regard to the Crossfire.  I
> got my manifolds out of storage yesterday and looked at them
> again, the first in a long time.  First, as I mentioned
> before

? when was this?.

one has holes (14057017) between the runners and one
> doesn't (14031372); these being the casting no's for what I
> beleive are 82/83 Camaro/Firebird 305 manifolds.

They perform very differently!!.

  Now my two
> questions:  Should I be concerned about how small the
> manifold ports are compared to even my stock 92 swirl-port
> head ports; That is, there is about a 3/8 to 1/2 inched
> difference in port height.  I'm under the impression that
> the cross sectional area should get smaller to increase
> velocity into the port, not only is this the other way but
> the transition is abrupt (i.e. mismatched).

If you look closely at the manifold, there is a ridge that prevents getting
much taper.  One of those cases of just take you loses, and move on.  If ya
dig in the archives, I gone thru what you need to do to get a XFire to
support 325 honest HP.  Lots of the work is the throttle bodies, ya need 2"
butterflies.
Grumpy

 2nd, does
> anyone know what the lobe seperation angle is for most gm
> TBI's apps?  I know the L-98 and LT-4 are 114, which is what
> I'm running (LT4), obviously this works for port injection
> but is it to wide for TBI?  I'm told that's wide for carb,
> and since TBI is wet manifold I wondered if there was any
> correlation.

My Comp Cams 270H that I ran on a 355 SBC XFire was 110d
>
> -Brent
>
> Okay someone will ask, so: 4400 lbs, 5.7L, 670cfm Holley,
> Stock TBI manifold opened to 2" bore, trickflow heads, LT4
> cam, 55lb injectors, 700r4 (95 Impala SS convertor), TPI
> exh. manifolds w/ 87 monte ss head pipe in single 3" cat and
> exhaust, 3:42 posi
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