Some of you guys have seen my threads and see i think out of the box.
I had a new idea when comparing pistons for my 390.
I dont know i it could work but i have an old 400 and a stock 390 that craped the bed.
Was wondering about taking the 390 pistons and put them in the 400.
From info i found they have the same diameter wrist pin. The 390 piston has a compression hieght that is 0.030 inch taller than stock. and that sould shoot the compression up HIGH. The bore is 0.050 inches bigger and have only heard of 400 going 0.040 over. I would mabey take a little metal out of the chamber of the head if compresion was to high.
All the parts i have are used and no cost to me so i am going to try it.
What do you guys think of this.
Am i over-looking a major reason i cannot find anyone with 390 pistons in a 400.
Feel free to lecture me on the stats of the 400 and 390 if you want.

 

You are looking at CH of 1.66 for your 390 piston vs. 1.63 for the 400, right?

That should give you the top of the piston at 10.2415" in the 10.297" block.

The only trouble I can figure, and based pics I saw, this is probably it: The FE has it's valves in-line, the 400s are canted. Thus, the valve reliefs in the 390 pistons are wrong for the 400, and you'll clink the valves perhaps.

Stick with proven stuff. You can always find someone to buy those low-compression 390 slugs.

 

yes the valve reliefs are different, the fe use floating pins, the 400 is pressed, so you would need small end rod work. Mill the block and use 400 pistons.

 

Whats the problem with a floating wrist pin piston on pressed conrods?
and for the canted problem i can remove the material with a lathe or dremel. I am pretty sure i can make them all the same.
The main reason i am doing this is i haven't heard of it done before. And i have a fond liking of the 400 and 390. more the 390 for the power and 400 for torque. but i want a quick and cheep powerhouse. and i can do this prodject for under 200 bucks so why not.
In horsepower mag they used chevy rods and 340 mopar pistons for a center of main bearing to top of piston was 8.14 inches.
by my mesurements my getup wil be 8.24.
They got 10 to one or something like that. I would mabey be at 13 to 1!!
I have access to aviation fuel so i am not realy worried about detonation.
This will be a drag engine if my idea works.
And if it doesnt then at least I tried.

 

on a 400 cant you just use 351C pistions.... I think the 351C and the 400 share the same compression height, but I am not sure about the wrist pin diameter....

 

If the compression height is the same why not leave in the stock slugs. the compresion ratio would still be a lame 8.5 to 1.
And last night i had a overpowering thought. I plan on taking the 390 pistons and with a lathe i will mill them down to 4.03 inch bore and then bore the block over 0.03, and then use a lathe to remove material for the exhast valve. i think the intake valve will not need a relief. but im not sure.

 

I believe you are on your way to a real POS self-destructing pile of smoking debris.

Turn down pistons to fit the bore.... If they were the last %^&*ing pistons on earth, that might make sense.

If you want to build a "Powerful" 400, this isn't the answer.

 

Why go to so muhc toruble, when lots of high compresion pistons are available for the 400_? forged, hypers, yo can even get 12:1 with open heads using som TIms flat top 0 decked forged pistons...

 

Only the top of a piston is round. You can't alter the diameter of a piston on a lathe.

 

Im am going to have to say that it is posible but i heard your comments and made a few rounds around the junkyard. and what i stumble across might be a even better idea. I found a ford Galaxy 500. not sure of the year but it looks to be a 352. Im not sure if you guys are familure with it but its the 390's little cousin. Did some searching on the web and found its got a 4 inch bore, 0.975 inch wrist pin. only thing i have to do is mill in a valve relief. which should be easy. Only thing is it has a comp height of 1.816 inches. which sounds like its "Over The Top"
Fire your replies back at me and tell me what you think.

 

I think you should buy some pistons made for a 400 and stop wasting your time trying to modify old worn out parts and creating more problems.

Like I said, if you want a "powerful" engine, there is already a path to it in the 400 flavor and it does not include modified FE parts.

 

Who sells 400 pistons? I have searched summit and local performance shops but cannot find and "400" pistons.
Fould 351c pistons but they dont have the comp height i am looking for.
Ideally i want a flat top with comp height of 1.69 inches with a 4.03 or 4.04 inch bore and a 0.975 inch wrist pin. I have also looked at custom pistons from Ross Racing for $776. and im not even sure if they have international shipping.
So if you know of a company with pistons for the 400 that i can get in Canada for less than $400 please let me know.

 

This is the guy with the info/parts on a 400. Unfortunately, his site is not working correctly.

Page 18 in his on-line catalog, maybe it's here:

TMeyer Ford Catalog

TMI/KB2347 is the number shown for 9.5 with stock heads. Probably have to bush the pin, but you'll get that info when you determine if these are right for you.

Regarding the previous idea about the FE pistons....you might be able to turn them down, but what about the ring lands? Cut those deeper and you'll have a "popped top" piston methinks.....

Good luck.

Oh, shipping to Canada, not sure on that angle, I know that's an issue. Find the parts first, then figure out the transport I guess.

 

I have been thinking the same thing... using a 390 piston H395P.

OK Follow me here.
400
Stroke 4"
Rod 6.580
Deck 10.297

1/2 stroke 2" + rod 6.580 = 8.580
Deck 10.297- 8.580 = 1.717 Compression height piston needed for 0 deck

390 piston has a 1.759
1.759 - 1.717 needed for 0 deck = .042 milled off the 390 piston

just remember a stock 400 piston has a CH of 1.63 to 1.47 that puts the piston .087 to .070 down the hole!!!

I Checked with Federal Mogal and the 390 piston is only .125 longer so it might need some trimming and it might not.

I did some figuring and I came up with 11 to 1 compression

I going to buy 1 H395P and start working on it, I'll be sure to let you know how it works. As far as the .050 over bore I really don't think that's a huge problem they sell .060 piston for it. Just make sure you index the boring bar from the very top of the cylinder or the very bottom, don't index it from a worn part of the cylinder.

I can buy those pistons to my shop for 115.00, that's cheep compression in my book if it works.

 

I almost forgot I built a 400 last year and bought a set from Tim, the pin bore is the same cost $262.50 it's a KB2347 piston can't find it anywhere except for on Tims site.
Link to his site TMeyer, Inc. Precision Automotive Machining

Here is a link to another forum I posted the build on, Hope I'm not stepping on any toes posting this link.
http://www.fordtruckfanatics.com/for...ad.php?t=14019