99GreenGT

ok I got a 5.4 sohc motor I want to rebuild with forged internals and i was wondering if i can put 99 cobra heads on the 5.4 block?

defconfire

Yeah, you could but you probablly want to put 03-04 cobra heads on it from what i understand they flow better.

Also your compression ratio will change when you change the heads, i think it goes way up.

99GreenGT

how much better are mach 1/03 cobra heads than 99 cobra heads? 03 cobra heads are a lot more money.

defconfire

Off they top of my head I cant say I know you probablly want to look at some flow charts for both.

Also if you want to use a stock intake manifold off of a cobra or mach 1 you are going to need some adapter plates due to to difference in deck height between the 4.6 and the 5.4

boduke0220

a 5.4 SOHC is the same as a 4.6 SOHC isnt it? other than bigger bore & stroke. so I wouldnt think they could fit but idk.

99GreenGT

ok thanks. if anybody has suggestions or facts i should know please post thanks.

Chris98Gt

I do belive swapping 4v heads on a 2v lowers compression rather than upping it. And as defconfire said the 5.4's are wider from head to head, so unless you use adapters, 4.6 intakes won't fit.

Sxynerd

That project is way to big for you... You'll see.

Fobra

The 03/04 heads dont outflow the 99/01 heads by much if at all, they do have a little bit better springs, but they are essentially identical, B heads from my research actually flow the most with imrc deletes and port work, but between all of the above the difference is nominal

99GreenGT

ha i dont think so I've built two 302s and a 351 just never a modular before.