do 4v cobra block parts interchange with our 3vs?

[bmaxwell]

The pistons will be fine. I am running 4v pistons in mine. I am still running stock cams tho but there is no problem with valve clearance.

As far a motor mounts go MMR makes an adapter plate.

Are the 3v rods the same length as the 4v 4.6?

 

[Speed+Clinic]

I really dont see what's the issue with the motor mounts because he is just taking the internals... I would use EVERYTHING including the pistons and just buy a new flywheel and call it a day...

 

[007SHELBYGT]

i built two 3v set ups .....1st one was 3v wit a spun bearing and an 03-04 cobra sb with 3000 miles on it with arp 2000 hard ware ....you can take the cobra rotatin assembly and have it re ring and bearing ballanced and installed in 3valuminm block ..you have to fly cut the pistons /reliefs for valves ..or just buy new pistons ..also have the rods checked to make sure there sound ....cost was 200 for blown 3v ....sb from cobra 600....machine work 600...depending which heads your using 2v 3v 4v ..the piston cc makes a difference on compression ....for example when i built my forged shortblock for my shelby gt i built it all new cobra crank arp 2000 hardware and head studs ..manley rods ..aka cobra ...and 6.5 cc dish for use with 3v =9.8.1 comp for use with my centri blower ...
Compression Ratio Chart
PI 2V cylinder head on 4.6 :
Flatop= 12.9 to 1 -11cc=11 to 1 -18cc=9.5 to 1 -23cc=8.9 to 1
PI 2V cylinder head on 5.4 :
Flatop= 11.0 to 1 -11cc=9.6 to 1 -18cc=8.9 to 1 -23cc=8.4 to 1
ALL 4V cylinder heads on 4.6
Flatop= 10.5 to 1 -11cc=9.1 to 1 -18cc=8.5 to 1 -23cc=8.0 to 1
ALL 4V cylinder heads on 5.4
Flatop= 9.5 to 1 -11cc=8.5 to 1 -18cc=8.0 to 1
All 3 Valve Cylinder heads 4.6
Flatop= 10.5 to 1 -6.5cc=9.8 to 1 -11cc=9.1 to 1 -14cc=8.75 to 1 -18cc=8.5 to 1 -23cc=8.0 to 1
ALL 3 Valve Cylinder heads on 5.4
Flatop= 9.5 to 1 -6.5cc=9.0 to 1 -11cc=8.5 to 1 -14cc=8.25 to 1 -18cc=8.0 to 1

 

[bmaxwell]

yea I knew there was something you had to do to the pistons or just get new ones. I was starting to wonder what the truth was lol

 

[jtscuba02]

The camshaft used will be the deciding factor. If you don't go over .500 lift, you can use the cobra pistons, and no valve relief is required. The rods are the same length. The bolt pattern on the crankshaft is different and will require a new flywheel.

 

[Nickoli]

yea I knew there was something you had to do to the pistons or just get new ones. I was starting to wonder what the truth was lol

Here is a pic of MY short block that has stock 3v heads and cams installed on top of them.