Topic: piston swap F to K

[borjawil]

I have been digging around and can't find much. Most of the information I have found is regarding the head swap between the K and F model. Seems you can't swap the K head on to F or piston meets valve. F head on to K and the compression drops.

So, can I swap the pistons from an F over to a K? center of pin to top of piston for the F is 24.5, where as the K is 25.5.  Which doesn't make sense to me since the compression would drop in my K engine with F pistons? Unless the F stroke is different. Any who, just want to know what will happen if I use the pistons - will they work, compression up or down?

[flybox1]

392 pistons are flat.  They came in the Ks and early F's.  These engines came with the corresponding 392 head.
The will fit in 392 heads, and  the later 410 heads (with some compression loss unless decked).

410 pistons are domed.  They came with the latter F's (77/78) 410 heads.
The will only fit under the 410 heads or contact with valves.

Someone correct me if i'm wrong 

...so i guess it depends on which F pistons you have 
They are stamped on the side near the wrist pin cutout

[borjawil]

Contacted dynoman. You are correct. Unless you swap the cylinders and head. Question - you say later K's has the 410 pistons/head? or was it just the F? are a 1978K and 1978F the same thing? whats different?

[flybox1]

Sorry, I think the 410's were just on the F's as they introduced the hotter cam.

[Don R]

 I believe 77/78K's got the #392 engine.

[enwri]

I believe 77/78K's got the #392 engine.

I'll add my bit, My 77k has little domed pistons as well, under a 392 head.

[flybox1]

I believe 77/78K's got the #392 engine.

I'll add my bit, My 77k has little domed pistons as well, under a 392 head.

Those are not 410's.  They would have bent all the valves in your head    The 392 stamp should be near the wrist pin hole on the OD.
This is what a domed 410 looks like.

[enwri]

standard pistons under a 392 head

[flybox1]

standard pistons under a 392 head

Correct, and they should be stamped 392 
They will work under a 410 head.  The 410s I pictured above will not work under a 392.

[enwri]

Found an old post that mentions another variation of the 392, k,s and f's

http://forums.sohc4.net/index.php?topic=107768.0

Are there flat top ones as well? for earlier K's?

Sorry, I'm not helping the original poster, is this why noone likes the 77/78's ?

[flybox1]

Are there flat top ones as well? for earlier K's?

300s

The 392's have different shapes as well.


This 'dome' is why 410s can only go in 410 heads.

[madmtnmotors]

Is this why no one likes the 77/78's ?

I like mine!

[flybox1]

^^^ Nice Wilbur! 

I like mine, too 

[enwri]

Is this why no one likes the 77/78's ?

I like mine!

^^^ Nice Wilbur! 

I like mine, too 

I like mine as well., I've even got a 630 O-ring chain, because the non O-ring didn't look big enough.

One last question, in someone elses thread, could I use either of those 392 piston types in my k7?
Oversize K7 ones seem to be a bit like rockinghorse s*%t as far as my searching goes, I can get aftermarket ones to fit 76 F"s, which should be the higher edged/flatter 392"s with the bigger cutouts to suit.
Does that sound right? Rather not go straight to the big bore kit.