Shaker vs. Shaker
Now, also in 1977 with the addition of the Olds 403 engine, the bases of the shaker scoops also changed to accommodate the differences in the size and offset of the engines. So, the shaker scoops for the years 1978 to 1981 all had the same style when looking at the scoops from the top, but the bases attached to the bottom of the shakers is what changed. There were basically 4 different configurations for the shaker scoop bases from 1978 to 1981. There was the 400 base, the 403 base, the 301 base, and the 305 base. The shaker scoops themselves from 1978 to 1981 were all the same on top.
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| 1977 Shaker ridge line |
1977 Shaker 2 inches tall |
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| 1978 Shaker ridge line is gone |
1978 Shaker 2 1/2 inches tall |
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| 1977 Shaker 2 inches tall |
1978 Shaker 2 1/2 inches tall |
403 vs. 400/305/301 shakers
Now, also in 1977 with the addition of the Olds 403 engine, the bases of the shaker scoops also changed to accommodate the differences in the size and offset of the engines. So, the shaker scoops for the years 1978 to 1981 all had the same style when looking at the scoops from the top, but the bases attached to the bottom of the shakers is what changed. There were basically 4 different configurations for the shaker scoop bases from 1978 to 1981. There was the 400 base, the 403 base, the 301 base, and the 305 base. The shaker scoops themselves from 1978 to 1981 were all the same on top with the exception of the 305 shaker. The shaker for the Trans Ams with the 305 engine had a notch sticking out of the side of the scoop on the passenger side. So you can easily tell a 305 shaker scoop from the rest by looking at the outside.
For the rest of the shakers from 1978 to 1981, the top part of the shaker assemblies were all the same for the 301, the 403, and the 400, but it was the bases that were different. The Pontiac 400 and the 301 shaker bases were all centered in the front middle of the shaker scoop. The difference between these shaker bases were that the 400 (W72 and the L78) the base ring measured 16 1/2 inches and the 301 base rimg measured only 14" wide. So, if you look at these two bases you can see that they are centered in the frontmiddle of the scoop.
Now, if you compare that to the L80 Olds 403 base ring, it is offcenter of the shaker scoop to the front and to the left. As you can see in the photos below how the base ring is offset to the front of the scoop and also off to the passenger side as well. You can also usually see this from top and side angles as well. You can also see from the side shot that the base ring of the L80 Olds 403 set-up that it is quite a bit taller than the 400 or 301 counterparts.
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| 305 Shaker with notch |
Inside 305 Shaker with notch |
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| Pontiac 400 shaker scoop centered |
Olds 403 shaker offset forward and right |
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Olds 403 shaker offset forward and right side view for better understanding and show thicker base. |
