68 series 1.5. I have the ugly intake crossover tract on the dual strombergs. I want to remove it & replace the rear exhaust manifold with an earlier one and cap off the opening on the intake... Has anyone done this? How did it affect drivability/mileage?

 

I removed the crossover duct from my 1968 1.5, but went to tri-carb manifold. If you keep your same manifold and use a cover from Series 2 to close manifold opening, you will be fine; just will need partial coke until engine is fully warm. The crossover is for idle only and makes the most of a very lean idle mixture by heating it off the exhaust. If you blank off manifold so there is no airflow at idle, then you will need to disconnect secondary throttles and wire them full open all the time. Once again manage partial coke until engine is fully warm.

 

I just did this recently with my 68 Series 1.5. I removed the ugly crossover and then put the block off plate on the intake manifold from a series 2 and I removed the secondary throttle plates and disconnected the secondary liinkage. I don't have much to compare to because I did this before I really ran the car. it does seem to take a little bit longer to warm up but it's worth it because you don't want a heated up mixture. Regarding the exhaust manifold, the best thing is to replace the rear manifold but instead of that I was thinking of just putting a plate over the remaining part of the crossover system just to give it a more finished look

 

If your front exhaust manifold is not in good condition, you may want the non-ceramic coated version for rear, and just paint both with High temp Black paint.