Non Mopar carburetor opinion

2 Darts said

RRR,

Not bad call on the CR. Nominally, Ford called it an 8.0:1 CR.

The 351C-2V and the 351M used very similar small passage heads. The situation on this motor sounds a lot like the 318. It is easy to over-cam and over-carb. Since the M motors are so similar to each other and to the Cleveland engine, suggest considering a 351C-4V heads for the 400 in order to avoid the same situation on your build up.

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I had thought of that.......and might. The 4V heads though will require intake spacers since they came on the Cleveland only. Since there was no 4V 351M or 400, there was no 4V intake for them. They are similar to the 440 in that the 351M and 400 are tall deck engines and the Cleveland was a short deck, so to use the 4V heads on the 400, the spacers are required.

That said, I would never in a million years use the upper RPM HP those heads are capable of. Plus, the 70-74 Cleveland 2V heads have much greater velocity in the lower RPM range as the 4V. Also, the 351M and 400 heads have a terrible bump in the roof of the exhaust port. The heads are drilled all the way the entire length with a thermactor passage, so the bumps were required. I had planned on the early 2V heads for the 400. I think they will actually be better suited for the low RPM torque I am looking for with the truck. They do not have the thermactor bump and flow very good.