Dumb question?

[Jesus5150]

So I'm prepared for the flames, but I was thinking... If a 402BBC uses 4.125" pistons, can you put them in a 400sbc? Or is the pin height wrong?

[Keith Seymore]

Answer #1 - yep; dumb question.

Answer #2 - OK, not really because the reality is with enough time, talent and resources a person can do anything (like use Chevy pistons in a Pontiac, or installing pistons backwards to change the rod angle).

The real answer is is depends on all the other criteria that go into designing a piston: pin height, pin diameter, ring land, ring thickness, number of rings, floating pin vs press fit pin, dome vs no dome, valve relief size and location, static compression, stroke, how far down in the hole, etc. All that is in addition to just bore size.

https://diamondracing.net/if-9-custo...rder-form.html

So - if you can answer all those, then you have your answer.

K

[Jesus5150]

I never ever considered ring count and dimensions. That's a big variable. I assumed if it fit in the hole, it would just be a matter of finding the correct length/diameter rods. I'm certainly not an engineer, but I assumed it wasn't possible due to not finding ANY reference to it on the entire internet. I just wanted to know why. Thanks for explaining it.

[Tom]

Valve reliefs in the pistons would be in the wrong spot/size.

[Willshook]

No such thing as a dumb question.

There are a LOT of things to consider for pistons - pin height, compression height, crank counterweight clearance, etc.

In the end...mixing and matching parts takes a lot of thinking It can sure pay off...like the brilliant guy that looked at a 400 crank and a 350 block and came up with the 383.

The JE Pistons custom order form helps think through this if you think you might have come up with a workable combination.

https://www.jepistons.com/custom-pis...ns-order-form/

[Ziegelsteinfaust]

Not with out massive work, and even then it is likely not be possible.

Piston pin locations or height are to different as is the valve lay out.

It could work if you have a tall deck block where you could mix and match to find a combo. With SB2 style heads which are about as close to porcupine bbc heads as I am aware.

Even with the short rods the 400 cam with. Much less 5.7's the pin is nearly in the oil control ring. Which with 6's i think it behind them.

DSS pistons makes custom pistons at a reasonable price.