Building a 5.4 Lightning, few questions..
 

I just got some manley forged pistons, the sheet recommends .0035" (0.0899mm) piston to wall clearance, for experience, that's a big gap, and im sure that would make the piston knock when cold, how tight can i go?.. Also, what ring gap should i have? i'm using speed pro rings...

That sounds right, thats 35 ten thousandths.

run what it says to run. They may rattle a bit on startup and that's life. Warm it up a few minutes and go. Ring gap is going to be different from motor to motor depending on the boost/n20 levels. With added heat from boost and gas comes the need for a little more gap to leave room for expansion. I'd call up Speed Pro or consult a manual for the ring gap. I don't even recall what my ring gap was set at. You could call up MMR or any of the other builders and ask their polite and helpful techs.

looks like the lightning swap is gaining momentum. i know people have done it but it seems like its getting more popular. good luck with your project. wish i had an option for a positive displacement blower for my b headed 5.4.

Sorry, I didnt see the ring gap question. Speed Pro should be able to tell you what ring gap to run, and I would run what they tell you. Good Luck

wish it was for my 00 gt... it's for my friend, but im keeping the crank, and forged rods, because he wanted new ones.. :D, a friend is going to give me a 5.4 block..

about your b headed 5.4, what intake are you using?? what's your combo? maybe i should use my next 5.4 in my 96 cobra, haven't decided yet..

Thanks guys, tought 0.0035" was too much, the machine shop said the same, but they haven't worked on a modular before, I already asked mmr for my final decision, the lightning ran 18psi and broke a valve because of nitrous, so the engine will still have 18psi, but without nitrous...

Whats this here swap your talking about:p