I want to put new heads on my car along with a cam. I was thinkin about some gt 40 heads and i was wondering what kind of cam i could go with and still be able to pass emissions. Please tell me if possible and what kind it is.
1990 5.0 lx automatic
Valve overlap is a big part of the equation. A cam with about 110 degrees of overlap is about certain to fail, 112 is questionable, 114 and up should not have a problem. The reason is more valve overlap will increase horsepower but will put out more hydrocarbons (unburned fuel) in the proccess. Also, don't go too wild with the lift.......
I got your number -- my iron GT40 head motor passes California smog with flying colors with an E303. I do also have a BBK high flow 2.5" catalytic converter H-pipe, Mac shorties and an MSD6A which contribute to the result. But this combo actually blows cleaner numbers out the pipes than my nearly identical but completely stock and original 5.0 car (same year and everything). I do agree with Notchbck93 that fresh/big cats are a part of the equation. The cats in the stock car are old and tired stockers, while the BBK's have less than 50k miles on them. I'm not so sure about 87'GTstang's comments on overlap, since the E303 is the main smog legal cam and is spec'd at 110 degrees. As to 88stangmangt's comment about custom cams being better, I think that may be debatable when it comes to smog numbers, but the main point here is that the off-the-shelf E303 (identical to the Crane 2040) is actually certified in California for smog, with an Executive Order certification number. Thus, while some custom cam grinder may promise (or even be actually able to deliver) better dyno numbers, you probably won't find one in the entire USofA willing to step up and certify their cam for smog. I understand it costs upwards of $50,000 to jump through all of the hoops to certification, which is why Ford/Crane are among the few (if not only) ones to do it. They would have to sell a lot of cams to get that money back. If it got down to it, I think the difference would be that the smog referees would be required to call your car legal with a certified cam, and give you whatever exemption you were entitled to if it could not pass. With an uncertified cam, they could just black flag you right off the road, no questions asked. I still have my receipts if they ever want to see them. By the way, the E303 makes loads of power and if i'm not mistaken, has gotten more than a few people into the 12 second range. And with shorties, pipes and Flowmasters, it sounds great.