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Lyn Smith · 09-09-2020, 01:49 PM

When NHRA put the older cars back in the guide a few years back they raised the 1955 4bl HP from 180 to 200. It has been lowered some to 197. Needs to go further down, as the 55 265 has to use flat top pistons which means you have to use a cam with 230 degrees duration or less, or you will have valve to piston clearance problems. Mid way thru 1956 GM started building 265s with valve notches. They discontinued the over counter sales of the flat top piston about that time also. In the Jr Stocker days you could use the notched 265 pistons, but not now. Go figure.

09-09-2020, 01:49 PM	#37
Lyn Smith VIP Member Join Date: Dec 2001 Location: Pontiac,il. Posts: 1,121 Likes: 217 Liked 841 Times in 156 Posts	Re: 1955 Chevrolet Q/SA Build When NHRA put the older cars back in the guide a few years back they raised the 1955 4bl HP from 180 to 200. It has been lowered some to 197. Needs to go further down, as the 55 265 has to use flat top pistons which means you have to use a cam with 230 degrees duration or less, or you will have valve to piston clearance problems. Mid way thru 1956 GM started building 265s with valve notches. They discontinued the over counter sales of the flat top piston about that time also. In the Jr Stocker days you could use the notched 265 pistons, but not now. Go figure.