decompression? - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

falcon_boy · 07-14-2004, 01:01

hey all, i just bought my i6 block and head. im ready to rebuild for turbo application. i wondered if i can get shorter pistons instead of running decompression plate with 2 head gaskets. or would is it possible to de-stroke it via rods? is there any aftermaket stuff or just get custom stuff? any ideas

svo347 · 07-14-2004, 01:19

Why not go for deep dish pistons or get them machined a tad?

ebxr8240 · 07-14-2004, 01:47

Talk to ACL they have a race series set..Have you thought of using XR6t pistons and rods ???They use longer rod which is better..
You can;t destroke with just rod, the counterweights will hit piston skirt at b d c ....

falcon_boy · 07-14-2004, 02:28

yes i have considered ba xr6t pistons and rods, then i have longer stroke and need to decompress more right?

ebxr8240 · 07-14-2004, 03:13

What do you have ???
The latter rods are longer and he pin height is higher in piston to make this up..Btw this was done from AU's on...Not sure of the twin cams but I'm sure the stroke was the same from 4.1 right through....The bore changed alittle..Also the old 3.3 had a longer rod.. The trick was with 4 Ltr and X flo motors is to use 3.3 rods and custom pistons..

falcon_boy · 07-14-2004, 03:52

sorry, i thought u said baxr6t rods were longer and better? i didnt know how longer would help. i just want to avoid using decompression plate but still lower compression.
acl have standard or higher compression pistons not lower compression. my engine is just a stoko 3.9litre atm.

shano6 · 07-14-2004, 06:27

The other way of decompressing is to open up the combustion chambers in the head. Depending on the head, and how low you want to go, this is sometimes an option. Try talking to a performance head place

ebxr8240 · 07-14-2004, 07:07

Throw a EB /ED head on there.. Comp will be nice and low...
As the EA's had bigger dish piston, while the 4 Lt's had less piston chamber and bigger head or combustion chambers...
Actually thats whats done to 4 Ltrs ...They fit .030 [or so ]oversize EA pistons...But it's not .030 over on 4 ltr block as there bore is bigger...

Gunns · 07-14-2004, 15:31

I am running a set of Federal Mogul HP series 30thou over pistons in my build, but I only plan to run 14psi. These are a deep dish piston, and should drop your comp a reasonable amount depending on the head work you plan to do.