Will Lightning headers installed on a stock 2000 Merc. 502 efi cause a lean condition? if so is there any way to correct it short of ecm recalibration? Thanks

If it's efi it should take care of itself. If it's a carb check your plugs and jet as needed.

The EFI won't "automatically" adjust itself because there isn't an oxygen sensor in the system, but it's my understanding that they're set up a bit rich with the stock exhaust to begin with.



Doug

Read the plugs.
If it looks lean, up the fuel pressure...

Yes up the fuel pressure on a non-adjustable system. You have to buy and install an adjustable fuel pressure regulator to do this. CMIs and Eickerts will cause a lean out, Gils and stainless will not, don't know about Lightning.

"The EFI won't "automatically" adjust itself because there isn't an oxygen sensor in the system, but it's my understanding that they're set up a bit rich with the stock exhaust to begin with."

Uh, yeah, Thats what I meant.

I have 2 more questions for that engine. Which exhaust will be louder cast headers or CMI's. I like it loud, I love dry exhaust but that is too much for every day. And is it true that there will not be any performance gain with the EFI engine? If not why not?

Thanks
Russ

HP Manifolds Will gain you about 200rpm and Headers about 300rpm...
Even on my little 310HP/7.4MPI, I saw a gain of 200rpm with Stainless Marine over the stock cast iron exhaust. 4400rpm to 4600rpm max. with the same prop...
A friend of mine also saw a gain from 4800 to 5000rpm with Stainless Marine on his 502MagMPI...

let us know what you see for a rpm gain,when i put my lightning headers on my 2000 502efi w/procharger i gained nothing on top end but did gain noticeable midrange torque,Smitty

Ditto on Smitty' comment. I noticed mid range but no top end. But we're both huffing and puffin'.