With this and another post, I am going to chime in;
Quote:
Originally Posted by Kenth
1968 L74 MT uses the 068 cam, #111149 distributor, #7028267 carb and 3.55:1 std gears.
1968 L74 AT uses the 067 cam, #1111270 distributor, #702268 carb and 3.55:1 std gears.
1968 L67 (RA) MT uses the 744 cam, #111149 distributor, #7028275 carb (early), #7028273 (late) and 4.33:1 std gears.
1968 L67 (RA) AT uses the 068 cam, #1111270 distributor, #7028274 carb (early), #7028270 (late) and 4.33:1 std gears.
1968 L67 (RAII) MT uses the 041 cam, #1111941 distributor, #7028273 carb and 4.33:1 std gears.
1968 L67 (RAII) AT uses the 068 cam, #1111941 distributor, #7028270 carb and 4.33:1 std gears.
|
Now Pontiac did some things around this time that really only served to confuse matters - especially for the general buying public.
Unitl recently I too was confused with how an HO differed from a Ram Air car...
At the time the 'HO' was intended as a nominal increase in power from the std 4bbl engine (which I believe normally carried RPO L78), and acted as a stop gap between the L78 & RA engine;
Prior to 1969 L67 was "the" Ram Air RPO code;
I'm going to try to keep things simple by first looking at the offerings at the beginning of the 1968 model year:
(cams, smaller to larger; 066-067-068-744-041)
L78(mt) = 2-bolt main block, D-port #16 heads, standard exh manifolds, 067 cam, std air cleaner
L74(mt) = 2-bolt main block, D-port #16 heads, standard exh manifolds, 068 cam, std air cleaner
L67(mt) = 4-bolt main block, D-port #31 heads, RA exh manifolds, 744 cam, ram air induction
**Automatic version of the above engines received a one-step-down camshaft**
I need to take pause here, because I want to punctuate the differential gearing which Kenth posted;
The RA cars always came with 4.33:1 on the GTO (and 3.90:1 in the Firebird) - while the HO had more street friendly gearing.
I would think that for day to day driving, this was the biggest differentiator.
So, compared against your car an early 1968 Ram Air GTO would have had:
4-bolt block, a bigger cam, cold air induction, RA exhaust manifolds, and lower gearing.
Not to be contradicting, but I'd wager a guess that if lined up together, there would be a substantial difference in E/T's between your car and a RA car (assuming both cars had the same prep).
Late in the 1968 model year the Ram Air option quietly changed to what we know as the RAII;
In essence it changed the heads, and upped the cam from a 744 to a 041.
It has been written that the RAII was essentially a stop-gap to the forthcoming RAIV;
Starting in 1969 the RPO L67 was for the round port RAIV.
This was around the time that Pontiac muddied the waters;
The "HO" (RPO 'L74') became the Ram Air III, and essentially was a 1968 400-HO with RA exhaust manifolds, and cold air induction.
The 1969-L74 maintained the conventional 'D'-port heads with the smallest combustion chamber size;
Early 1969 RAIII/mt cars came with the (previously RA spec) 744 cam, but later in the model year, the 744 was no longer used, and the 'HO' (068) cam was the standard cam (at this point in time the automatic cars stopped receiving smaller cams).
The 1969 'L74' did not require the low gearing of prior RA cars.
I could be mistaken, but believe some early 1969 literature still referred to the L74 as an "HO".
(Hopefully this post didn't have too many errors in it.)