4.6 cobra conversion

[badman602]

i am thinking about converting over to a 4.6 or 5.4 cobra motor with a t56. what i need to know is what is the diff. from the gt4.6 nonPI block to the 4.6 cobra block. do the cobra heads blot up and the trans. also do they use the same chain covers?

 

[Mike97gt]

the heads will not make a difference from when it comes to bolting to the trans..

Yes the 4v heads can be installed onto the 2v block.. but you would be better served getting a motor out of a lincoln mark 8

 

[Outlaw97GT]

You have to change the pistons also, or your compression will be all jacked up.
It would be easier to find the whole Cobra motor or Mark motor like SVTtec76 said.

 

[RochesterGT]

You have to change the pistons also, or your compression will be all jacked up.
It would be easier to find the whole Cobra motor or Mark motor like SVTtec76 said.

Actually I think the compression would be "jacked down" since Cobras use flat topped pistons, the GT's dished pistons would create more CC's in the combustion chamber, lowering compression.

 

[tomustang]

Actually I think the compression would be "jacked down" since Cobras use flat topped pistons, the GT's dished pistons would create more CC's in the combustion chamber, lowering compression.

Cobra's didn't use flat tops, their all dished, don't know about the 03+ cobras or 99+ Lightnings

 

[Torinalth]

the GT block can be used, but you will need to alter the oil runners i believe. and a 5.4... well... completely different animal. any 5.4 or 4.6 can and will bolt to a T56 (assuming you have the ford bell housing from tremec [also assuming you are using tremec]).

if going with a markVIII block make sure you ditch the heads (worst of the 4v) and intake and just use the block and nothing else. honestly if you plan to make some solid power i think you would be cheaper in the longrun to go ahead and get a built longblock and call it a day. pricing it out of doing it yourself with buying individual components saves a lot less then i thought when i priced everything out.

aside from te engine, you will need the cobra harness and intake and exhaust track.

Torinalth

 

[RochesterGT]

Cobra's didn't use flat tops, their all dished, don't know about the 03+ cobras or 99+ Lightnings

Actually, that was my bad. Starting in '96, all 4.6 and 5.4 DOHC's run DOMED forged pistons, not flat topped. But yea, they're not dished, they're nothing like SOHC pistons. The domed area is what helps bump the DOHC's compression up to 9.9:1 then down to 8.5:1 in 2003.

 

[Outlaw97GT]

Let me tell you a true story. I'll make it short and sweet.

I have a freind here in town, he has a 98 Cobra with a S/C. It started running rough so he put it in the shop ( a well reconised shop)
Well they gave him reason after reason on why they needed to keep the car longer. Well after about 6 months my freind goes and gets the Cobra towed back to his house to fix it himself.
He messed with it, with my help for about a month. He could never get it running right, it would crank but stall under a load. Well he pulls the engine and finds out it was a cast block, not the alumium block it should be.

Come to find out the shop dropped the engine and broke it. So the dumba**'s buy a 02 GT 4.6 shortblock and they couldnt figure out why it wouldnt run right. They didnt tell him and when he called to bitch them out they told him they didnt know it would make a difference.

Now he has the right block and it runs like a bat out of hell once again.

 

[Roger_4.6_96]

Engine
Transmission
Tune
Coolant Hoses
Throttle Cable
Extend some Wires