400/406 Builds

[Captainfab]

That's a pretty sizeable cam, but I imagine it runs pretty hard in the mid range and top end

[Markuli]

Originally Posted by Captainfab

That's a pretty sizeable cam, but I imagine it runs pretty hard in the mid range and top end

You're absolutely right. It was purpose built to be a 1/4 mile engine but it behaves decently on the street so long as I cruise around /above~2200rpm.

[Wellmerling]

I found this post on a Honda forum but he refers to the sbc 400. Are these safe assumptions when making cam decisions?

https://www.d-series.org/threads/cam...7/post-2178630

"There are quite a few variables which make the same cam have different power bands in different engines.

Most of my experience with the same cam in different engines is with Small Block Chevies.

On a 400 SBC I would expect.

For an idle of 600 rpm and maximum torque at about 2500 rpm and maximum power by 4500 rpm and nosed over by 5000 rpm you would need about 225 deg duration at 0.050 lift.

For an idle of 700 rpm and maximum torque at about 3000 rpm and maximum power by 5000 rpm and nosed over by 5500 rpm you would need about 235 deg duration at 0.050 lift.

For an idle of 750 rpm and maximum torque at about 3500 rpm and maximum power by 5500 rpm and nosed over by 6000 rpm you would need about 245 deg duration at 0.050 lift.

If you want it to rev to 8000 rpm you need about 285 deg.



For an idle of 700 rpm,

The trends are:-

The longer the rods, the higher the power band.

The longer the stroke the lower the power band.

The smaller the ports the lower the power band.

With the same heads and cam, a 400CI SBC will develop it's power about 700 to 800 rpm lower than a 350. If you use a long rod 400, it changes the peak power to 500 rpm less.

A 350 is 4" bore, 3.48" stroke with a 5.7" rod.

A std 400 is 4.125" bore, 3.75 stroke and 5.565" rods

Long rods are 6" long

If you use after market high port heads on a long rod 400 you can bring the rpm for maximum power back to the same as the 350 with the same cam.

Alternatively with the long rod 400 and the original heads, you need about an extra 25 or 30 deg of duration for 400 to make maximum power at the same speed as an otherwise identical 350."

[Already Gone]

Been well over a year since the last post in this thread so time for a bump and update on my 400 now 406.. The engine parts list that was used is in Post # 137 and engine is now together and been run on an engine stand to break in cam. It will be installed over the coming Winter. I have videos of it running but cant post on here.. 3 year build from when I bought the block till the engine fired up. Biggest delay was the engine machining took 7 months to get done and little snags on the assembly. " Be patient Grasshopper "