351M/400 pistons in 300?

[86ford]

i am thinking a bout parts to rebuild my 300 with, i have a piston out of an engine i saved from the scraper not shur witch 351M or 400 i have to measer the rod and crank.
acording to the book i have they use the same pin as a 300 .9752 at least in 76 but shouldn't be that mutch of a chore to rebush to fit, i am going to check them boath with my caliper, but at first glance the 351/400 piston might increase CR becouse of a smaller dish, so that with a little off the head should get me that 9.5 CR i would like or more i dont mind if i have to look for 91 or 92 gass.

anny thought would be gratly aprescheated

[shmoozo]

There are several other things you need to check.

1. compression height
2. diameter

[86ford]

i allready know the 300/302/351W,C,M/400 all have the same 4.00" bore, currenly i still have to find out the distance from the top of the piston to the top of the pin, if it should be the same all is good if not i will have to cakulate how mutch to take off to get it flat and below the head gasket, i am going right now to get my caliper to checkit.

[86ford]

piston to deck TDC on my 300-6 .090

300
pin .976
top of pin to top of piston 1.230
bottom of pin to top of piston 2.213

351/400
pin .973
top of pin to top of piston 1.173
bottom of pin to top of piston2.143

by these numbers the 351/400 piston would seem to have less compresion

[crash-harris]

Check these out.

http://store.summitracing.com/partdetai ... toview=sku

The search parameters are set for 4.030" bore (it was easier for me to narrow the search that way). I think I'm going this way with my buildup.

[American Thunder]

The 351M/400 has canted valves, therefore the piston valve reliefs will be canted to match. This may cause issues in a 300 with the wedge setup.

351M, compression distance from center of pin to top of piston: 1.947"
400, compression distance from center of pin to top of piston: 1.647"

300 I6, compression distance from center of pin to top of piston: 1.757"

Of the 4" bore engines produced by Ford, the 351W piston looks like the closest match to a 300 piston, with a 1.769" compression height. That means the 351W pistons would be getting close to zero deck in a 300. (maybe .020" below?) How does the piston pin diameter match up between these 2 engines? My book doesnt show it.
A Boss 302 piston has a compression height of only 1.530",(the shortest one in any 4" bore Ford motor) so with longer 240 rods, you'd have to shave about .325" from the top to make it zero deck in a 300. Not sure that would be safe to do on any piston. Maybe you could get away with doing that to a Forged piece? I don't know.

It's a shame the sinister 427FE has that enormous 4.23" bore, because the compression height of those pistons is 1.752", an almost exact match to the 300.. hmm!

[Lazy JW]

Some have used pistons for the 352 FE engine in the 300 with good success.
Joe

[shmoozo]

Some have used pistons for the 352 FE engine in the 300 with good success.
Joe

I'm having vague memories about that ... something about flat top pistons, milling a little off the tops, high compression ratios and propane fuel?

Let me check ...

Ah, yes ... Take a look at these, for example:

Silvolite Pistons, Ford, V 8 352 / 5.8L, 1958-66

The compression height for the pistons for the 352 FE is 1.816, which is 0.059 more than the 300's 1.757, and from the picture you can see that they are flat top pistons with valve reliefs.

Even milling off, say, 0.060 [60 thousandths] you'll still end up with flat top pistons rather than dished ones and that is going to give you a compression ratio that might be wonderful for propane or racing fuel, but for pump gas? Not so much, I should think.

[Lazy JW]

piston to deck TDC on my 300-6 .090.....

He has .090" deck clearance now. I'm not going to bother doing the math but that's a LOT of room; some flat top pistons "may" be helpful.
Joe

[86ford]

thank you for the info guys allways more to think about.

[American Thunder]

If the 351W has the same pin diameter as the 300, it should be a direct bolt in. They're heavily supported by the aftermarket so they're pretty cheap and available in any design and material.
Ideally, you want flat tops for best efficiency, because both dishes and domes interfere(slightly) with flame front travel across the piston surface.

[shmoozo]

piston to deck TDC on my 300-6 .090.....

He has .090" deck clearance now. I'm not going to bother doing the math but that's a LOT of room; some flat top pistons "may" be helpful.
Joe

Ah, yes, well, you may have a point there. Then again it would probably be a really good idea to do the math before buying a set of pistons made for the old 352 cubic inch FE series V8 engines.



One other possibility seems to be some of the 351 Windsor V8 pistons. They seem to have a smaller pin diameter, but as I recall there are ways of dealing with that. Here is one example of such a piston.

Silvolite Pistons, Ford, V 8 351W / 5.8L, 1994-97

It has a slightly dished top and the compression height is almost exactly the same as it is on the 300 inline six's pistons. My guess is that if a fella can come up with a way to deal with the different pin diameters he might find these would work just fine.

I would note here that the 351 Windsor V8s were built for quite a long time and they appear to have had a variety of different piston designs over the years so it would be wise to check the specifics of a set of pistons before buying.