Hi, Im kinda new to this forum, but it looks nice, so I will post my question and see what kinda response I get. I am rebuilding my 400 out of my 77 'Chero this summer and a local engine builder brought something to my attention. I am going to be putting Badger Flat Top Pistons in, and depending on decking, it will give me a compression ratio of somewhere between 9 and 9.5. This engine builder told me that the 91 octane "premium" gas wouldnt run with this unless i wanted to expect a lot of pinging. I am running an Elgin 280/290 split duration cam with a .505 lift. Also I will have an Aluminum raditor and intake for better cooling. Does anyone know what Octane gas i will have to use in order to not be pinging?

Thanks in Advance,

Justin Witt

 

I'm afraid with flat tops at 9.5:1 your pistons will wind up about 3/8" down in the hole at T.D.C.. Combined with the open chamber head design you will probably be prone to predetonation and need 93 octane fuel. That was the story with my last engine. However with my present engine I used J.E. forged/dished piston and am probably close to 10:1 and doing OK on 91 octane (at 5,500 above sea level). static compression is about 170 (Total seal rings also). The flat area around the outside edge of the piston fills up the bore area that causes detonation etc.
Food for thought.

 

i have emailed "Keith Black Pistons" about making pistons with their 351c "D-Cup" reverse dome, with the 1.717 compression height needed to get zero deck on a 400.

the "reverse dome" (d-cup) gives you the quench (with quench heads) of flat-tops, but with the lower compression of a dished piston. it looks to me like a 24cc relief would give about 9.8:1, and a 12cc would be about 11:1

they already make pistons for about a dozen 302 and 351 strokers and/or "long rod" combos using stock ford parts, plus pistons for windsors with cleveland heads, and the d-cup looks like a good deal because you get the squish area with quench heads so you can run higher compression, but you don't have to go up to the 12.6:1 or whatever it would be with flat-tops.

i mentioned to them that with the aussie heads becoming cheaper and more common, they might see more demand for a 9.5 or 10:1 quench piston for a 400 - plus the people who want to run 4v heads on a 400 at higher rpm's could use the same piston, except with a shallower d-cup for about 11:1...

if anyone else here is interested is seeing some good pistons for a 400 with 4v or aussie heads, PLEASE email the people at KB - maybe we can get them interested in these old smog motors!

:-X11 here's an address:

tech@kb-silvolite.com

 

[updated:LAST EDITED ON 17-Aug-02 AT 00:20 AM (EST)]>going to be putting Badger Flat Top Pistons in, and
>depending on decking, it will give me a compression ratio of
>somewhere between 9 and 9.5. This engine builder told me
>that the 91 octane "premium" gas wouldnt run with this
>unless i wanted to expect a lot of pinging. I am running an
>Elgin 280/290 split duration cam with a .505 lift. Also I
>

Justin, i got a catalog in from badger yesterday, and found something interesting. in the front of the catalog, there is a "pro-series pistons" section. after 20 or 30 chevy pistons, they had 4 ford pistons. one of them, #40010F, SEEMS to be for the 400. it SAYS they are, but the pic (drawing) shows windsor type valve reliefs. also, it says 6.2" rod...

FORD
CID - 400
cyl - V8
std. bore - 4.000
stroke - 4.000
rod length - 6.200
skirt clearance - .0025 - .0050
Compression Height - 1.640
pin diam - .975 press
head vol - (-)4.0cc
deck clearance - .028 (i got .077)
avail oversizes - STD, .030, .040, .060 (what! no 20?)
rings - (2) 5/64", (1) 3/16"
head type - flat, 2 valve relief
60.4cc -> 11.9:1
76.2cc -> 10.0:1
78.4cc -> 9.8:1

i think it would take a bit of milling to get the compression that high - maybe they got the deck height wrong too - i came up with low 9's, a little higher with decking... basically the same as what your builder told you

PRICE - $15.40 ea. ($123.20/set) (jobber)

okay, so the catalog people don't know jack about 400 rods, deck height, or valve orientation! still, it looks like a decent price, you don't have to bush the rods, and they will give higher compression than some of the others i've seen. just have to talk to somebody to make sure they have the valve reliefs in the right place!

ok - here's the interesting part - the regular 8.4:1 badger dished piston is $17.79 ea. ($142.32/set), and the regular 8.0:1 badger dished piston is $10.44 ea. ($83.52/set) i think those are the prices the machine shop pays. anyway, it seems weird that the "performance" ones were cheaper than the "stock" 8.4 ones, which are identical to the really cheap 8.0 ones, except the 8.0 ones have a deeper dish.

also - i heard back from KB - they don't do custom pistons.

summit sells the KB-108's (heat-treated hyperU, 1.670 compression height, flat top) for $187 a set. they should give about 9.6 to 10:1, depending...

how much compression will open-chamber heads tolerate on 93 octane?
what about on 91?

 

That piston might be for a 400ci stroker kit for a 351W; most of them use a 6.2" rod.

 

>That piston might be for a 400ci stroker kit for a 351W;
>most of them use a 6.2" rod.


that would put the pistons about 3/8" above deck.

one thing i thought of was that they could be for a windsor head swap, but who the hell would put windsor heads on a cleveland?!

most likely they just got a document layout person to put together the catalog, and then whoever was supposed to check it before printing didn't know jack about ford 400's... :+

 

KB108 is for the 351C
http://www.kb-silvolite.com/page53.htm