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i just bought a 400 fmx block and would like to know if someone could help me with some info about what type of pistons to use when trying to get 10-1 Cr. I will be using my 1971 4v heads on it and i will be installing in my early bronco. I want to use everything off my 351 4v engine that i can and also is the a good intake i can use?

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Welcome aboard Sonny

I built a performance 400 decades ago. I used custom ordered pistons:

(1) forged aluminum
(2) 351C 4V style flat top (notched for 4V valves)
(3) 400 size wrist pin
(4) for use with pressed wrist pins
(5) 1.685" wrist pin height
(6) standard ring package

Today I would order the pistons from Ross, specifying their round skirt endurance racing style piston (for cylinder wall durability), and a modern thinner ring package.

The engine was based on a low mileage block, I didn't have any machine work done. Therefore the 1.685 compression height of the custom pistons was specified to achieve 10:1 with a block that had not been milled or bored. The new pistons were nominally 0.030" down in the hole. You may want to adjust the piston's compression height for the following reasons:

(1) Desired static compression ratio other than 10.0:1
(2) Engine has been bored, displacement greater than 400 cubic inches
(3) Actual deck height of the block (block has been milled)
(4) Head gasket thickness other than 0.040" compressed
(5) Cylinder head combustion chamber volume other than 75cc nominal

To achieve 10:1 static compression those pistons were used in conjunction with D1ZE open chamber Cobra Jet heads having nominal 75.8cc chamber volume. A closed chamber head would have raised the compression too much. I used the Blue Thunder dual plane manifold along with spacer plates, and a 780 Holley carb. Spacer plates raise the intake manifold, thus a Ford distributor couldn't be used (the distributor hit the manifold). An aftermarket distributor that sits higher was necessary.

There are other ways to go about doing this, but this is what I did in the 1980s, and I still believe this is the best way to go.

I'll tell you what, that engine was a torque monster! 428 Cobra Jet type torque. It went into an F150.


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