440 pistons in a 400 ????

[dirty dan]

440 pistons in a 400 with the use of 400 rods.
Is this a workable combo?
If so what would be the resulting deck height with the factory flat top from a74 and 440 up piston.
Befor every one tells me how heavy the 440 piston is .
I already know about.
Also what is the average factory compression ratio of a 74 and up flat top piston 400 engine?
Thanks

[mr_340]

You could run the late model 440 pistons in a 400 and it should give around a 10:1+ compression ratio. The pistons may stick out the bore a bit, so you may have to run the open chambered heads like a 906. A +.030" 440 piston (Ø4.350") will only be +.008" in the 400

[Clair]

Might want to check the 440 piston skirt clearance on the 400 crank counterweights, too. With the taller deck and longer rods, the 440 pistons probably didn't have to worry about getting as close to the crank as the 400 pistons did.

Clair

[Glen440]

If the pistons are not cheap you are wasting your money. KB240's are spec at .019 down and I got them for $500cnd, they have deep valve notches. You get a 8-1 comp 440 piston to put in the 400 and it needs notches cut in them. It won't be cheap. I looked at going that route. The KB's are alot lighter too.

[rellik eeb]

It wont work, or should I say the engine wont last long. The compression height of the pistons are very different. Im not sure of the deck height of a B engine or I could make some calculations. The bob weight will be way off needing a balance job, even if it did work and phyically bolt in a block even though the 440 has a .020 smaller bore a piston of .020 larger 440 would be needed for a swap. Seems to save a few bucks now will cost you more in the long run. You will be better off using stock pistons and shaving the heads, running a thin head gasket.

[duetz]

I just built a 77 400 with 440 pistons .The only ones that will work is the sealpower 424p.030 cast pistons.It leaves you with.020 piston to block depth.Theres no machining required other than honing .008 out of the bore to fit the pistons.I work in an engineshop and have for 20 years.I havent put this engine in my car yet but it sure sounds sweet running on the enginestand with openheaders.I used the orignal 440 magnum camshaft.The way my calculations come out it should be9.01 comp .I hope this helps you.Any questions feel free to email me.

[DartGT66]

I hvae done htat in the past too, when had to do things dirt cheap and there was no aftermarket pistons available for 400's. Actually the first one was a 383 that was bored to .070" and used stock 440 "smog" pistons. The factory piston weight differences between the B and RB engines are not that big, and you can lighten the RB piston to the same weight if you want to avoid the rebalance. The other was a 400 that I used .030" TRW 2266F pistons in. They had a positive deck height, so I recontoured the piston tops to fit in to the chamber, and cut deep valve reliefs to clear the 306R cam that was used. This reciprocating assy was balanced with a 0 balance flex plate where a weight was welded in. It used stock B-rods and a stock 400 cast crank, the CR ended up at about 10:1 (pump gas) with composite gaskets and the engine runs really great. The car hasn't been scienced out yet and it could 60 ft better, but still has run a 10.6/127 mph in the 1/4 in a 2900 lbs valiant.
However, now that there is relatively inexpensive good pistons available (KB), I don't see there is much sence going this route.