Anyone know what lift and duration the stock 496HO cams have?
Adding headers and also have a 1.8 set of roller rockers with guide plates, pushrod, correct studs..., the hole setup off another motor. shoud not gain too much in lift, gussing aroud .025" but should add some horsepower and reduce wear.
Though I saw someone post some cam numbers but no result when I do a search.
Thanks

Be careful changing the rocker ratio on a stock 496HO with a stock HO Cam the valve relief in the stock piston is tiny and .510 to .520" is all the intake can take before it will start dancing with the top of the piston, especially with those low poundage stock valve springs. Add the headers and leave the ratio at 1.7 and be safe. The tiny bit of extra power you might get is definitly not worth grenading a stock hypereutectic piston in your 496! When you need more power than headers can add, you'll have to change the cam, heads or seriously rework the heads and then the intake manifold will limit your increases, because it will hit the wall on how much air it can flow. "There is no cheap power fix for a 496, only the right fix!"

Regards,
Ray @ Raylar

Ray,
Thanks for the info. I know from reading on here you are the man on the 496's and it is great to have resoures like you out there. The 1.8's were on a 496ho motor I bought from a guy I know and the price was right so I was thinking while I was putting the headers on it would be a good time for the rockers. Guess I'll scrap that idea.
How about a fuel pressure regulator with the headers, think I need that too? Don't want to lean it out.
Also have had the ECM re-programed by Whipple (stage 2)along with the low temp thremostat a couple of years ago.
Thanks again for your input.

You should not have to up your fuel pressure on a stock 496HO early model 2001-thru 2005 with headers, especially with the whipple stage 2 program. On the late model 496HO's Mercury leaned out the fuel programming quite a bit to clear some of the sooting issue and when headers are added on the late models, they tend to get a bit lean at 4,000rpms to 5200rpms.
Good roller rockers will help the motor but it gets expensive and trouble some to do them on stock 496 iron heads.
Start where your at, don't get to many parts and mods going to many directions at the same time, you won't be able to track whats working and whats not. Crawl before you walk!

Best Regards,
Ray @ Raylar