aussie merc
Well-known member
can anyone tell me if there is a differance in the port sizes and hence the flow between a 255 4 bolt flange manifold and a 239 3 bolt flange manifold
255/239 ports
- Thread starter aussie merc
- Start date
Karl Wolf
Well-known member
MY opinion-
The amount that the intake valve will pass is not as large as to make a larger intake manifold runner size an advantage. If you can determine the optimum flow rate for the engine, it may be to ones advantage to set up the carburetor and the upper part of the intake manifold to meet this demand from the engine.
And, as I have seen, the 255 and the 239 blocks are the same.
Karl
The amount that the intake valve will pass is not as large as to make a larger intake manifold runner size an advantage. If you can determine the optimum flow rate for the engine, it may be to ones advantage to set up the carburetor and the upper part of the intake manifold to meet this demand from the engine.
And, as I have seen, the 255 and the 239 blocks are the same.
Karl
rotorwrench
Well-known member
The manifolds were set up for the larger 885 4-bolt carb on Mercs but the rest is likely the same as 8BA. The 1BA blocks had the new rotator valves so all the 8BA family of blocks were used on both Ford and Mercury. Cranks, cams, and pistons were specific per each application. Mercury heads lowered compression to make the compression ratios about the same for both applications so Ford heads on a Mercury is a vast improvement. Valves were same for both applications in there time of issue whether plain or rotator types.