chevy engines

[Clarence L.Snyder]

Greg Hermann wrote:
> 
> >Hi
> >
> >I know this aint strictly efi but you will know the answers, as it
> >concerns an American vehicle and I am from the UK..
> >
> >I have a 1976 Pontiac Firebird with a 350 CI engine, is this engine GM
> >or Chevy?
> >
> >How can  you tell the difference between the two engines, I was told
> >Pontiac used Chevy engines in some Firebirds but when or in what models
> >I dont know.
> >
> >Is there also any obvious differences between the 350, 400 & 450! ?.
> 
> It is either a Poncho (Pontiac) or Chevy or (slight possibility) Olds 350.
> The Poncho and the Olds are both much bulkier engines than the Chevy. The
> exhaust manifold faces on both the Olds and Poncho are nearly at right
> angles to the bolck deck surface, the same face on the Chevy heads is
> angled in toward the outer edge of the valve cover, so that the exhaust
> manifold flange surfaces are nearly vertical when the engine is sitting in
> the car. The surfaces at the front and back of the intake manifold where
> the manifold seals against the block to close in the valley are flat
> (horizontal on the Chevy. One of those sealing surfaces is lopped off at a
> funny angle on the Poncho.
> 
> Hope this helps. Please see my post from a bit earlier today about looking
> for contact info for Zytek (I believe located in Birmingham, UK) ---TIA
> 
> Regards, Greg
The chevy has an integral intake manifold - it does not sit above a
sheet metal cover pan. The runners all join together with the
distributor coming up through the back of the manifold. If I remember
correctly, the Pontiac and Olds both have the distributor NOT coming
through the manifold.
The chevy engine has narrow squarish rocker covers, where the others
are  either round for the poncho, or "sculptured" on the olds, and
wider. (top surface).
On the 'birds, the 350 was "almost" exclusively Poncho. The 301? and 260
was olds derived.

If the engine code is L, it is a chevy,- not offered in '75 - don't
think in 76. E, H, or possibly N is buick, F is olds.M is Pontiac. This
is the 1975 designation, which I believe was carried through to 1976. In
1975, only the M engine was available in the base Firebird (2 barrel
carb) If it had a J code, it would be a 350 Poncho 4bbl.This would be
standard in a "formula" 'bird.
This is the 5th digit in the VIN.