440 Pistons In A 400

[JG71B]

I know whats coming and I'm already aware of most of it but, I'm doing this on the cheap as much as possible....I want to use what is titled. All I need to figure out is what compression height should I be looking for with the 400 rod and stock 452 heads to get between 9 and 9.5:1 max compression. Blocked will be squared, everything balanced in the end. Trying to stay .020 overbore for stock 440 size pistons. Engine actually runs great, just getting tired and a lot of blow-by. Appreciate it

 

[qkcuda]

I used .060 over 440 pistons in my first 400 build. They were MP 9:1 cast pistons which ended up at zero deck. Two problems, firstly the pistons are too heavy and required extra cost to balance. Second there are no valve reliefs. I am building another stock stroke 400 and this time I'm using KB240's.

 

[Lefty71]

.020 overbore in a 400 is not a standard 440 piston. The 400 is THE big bore engine.

 

[JG71B]

I used .060 over 440 pistons in my first 400 build. They were MP 9:1 cast pistons which ended up at zero deck. Two problems, firstly the pistons are too heavy and required extra cost to balance. Second there are no valve reliefs. I am building another stock stroke 400 and this time I'm using KB240'

What compression are you looking to get with what heads and the 1.908 compression height??

 

[oldkimmer]

I used 67 and 68 factory flat tops .020 oversized in a stock bore 400. Big improvement. I don’t remember the cd. Kim

 

[JG71B]

.020 overbore in a 400 is not a standard 440 piston. The 400 is THE big bore engine.

I worded that way wrong, fixed it

 

[Diodedog]

The 72 and later 440 piston will give you the same deck height as a 68-69 383. I have a nice set of 72 style .040" over Speed Pro flat tops that will go in a 400 if I get a block, it'll be just to sell.

 

[Lefty71]

1.812" Compression distance in a 400 piston, 1.912" for the 72 and later 440. The early style and any racing pistons are going to be even taller. Maybe you'd need the .060" head gasket that is a spacer style to make that work...cuz thats a mile otherwise??? I'm grabbing the bucket of popcorn tho, I'd like to hear the manufacturers names and part numbers of pistons anyone has actually used to pull this off.



Here's my real two cents on the whole subject..... If it were my money, and I know the OP said "on a budget", if I had to buy any pistons, I'd go find an old RB crank, recondition it to like new with 400 mains, and buy myself a nice set of pistons that fit it up perfectly to make a low budget 451.

 

[Hemirunner]

I’m working on a 400 using 6.76 rods and ICON 440 stroker pistons.

 

[JG71B]

1.812" Compression distance in a 400 piston, 1.912" for the 72 and later 440. The early style and any racing pistons are going to be even taller. Maybe you'd need the .060" head gasket that is a spacer style to make that work...cuz thats a mile otherwise??? I'm grabbing the bucket of popcorn tho, I'd like to hear the manufacturers names and part numbers of pistons anyone has actually used to pull this off.



Here's my real two cents on the whole subject..... If it were my money, and I know the OP said "on a budget", if I had to buy any pistons, I'd go find an old RB crank, recondition it to like new with 400 mains, and buy myself a nice set of pistons that fit it up perfectly to make a low budget 451.

Im trying to NOT do that but, getting easier to want to stroke it. Last 400 I checked, ( a stock 71 383 also), was about .120" or more in the hole. Seems that extra .100" may be useful. My other reasons for doing so are to see what this 400 can do with decent compression. I figure if I can get between 9 and 9.5:1 on compression and decent cam this thing should run as good or better than a late 60's 383HP. Ive read IQ52"s 400 threads but, that seems a little different of a route than Im trying to do

 

[BSB67]

You'll need the low compression 440 piston with a compression distance of about 1.91. Speed Pro used to make one, maybe still do. The original 440 piston is 850-870 grams. What is a 400 piston weigh? You might need to balance. If you need to do that, may just as well buy KB 400 piston. If you have the parts laying around, that is one thing, but buying the wrong parts never seems cheaper in the end.

 

[qkcuda]

Stock 400 pistons are 100 grams lighter than that.

 

[BSB67]

Stock 400 pistons are 100 grams lighter than that.

Thought so. 383 pistons are 770.

 

[PRHeads]

Stock 400 pistons are 100 grams lighter than that.

And they’re already externally balanced, which means to use an oe replacement 440 piston the crank would need heavy metal.
That throws the “budget” aspect of it right out the window.
KB400’s FTW.

 

[Diodedog]

And they’re already externally balanced, which means to use an oe replacement 440 piston the crank would need heavy metal.
That throws the “budget” aspect of it right out the window.
KB400’s FTW.

You cut the pin down, the cast 440 piston is about 30 grams heavier than the cast 383 piston, not sure on the 400 cast, I'll weigh one later if I get time.