I just bought some Lloyd Elliot ported Trickflow heads for my 91. I'm planning on doing these heads, a converted LT1 intake, and a cam (227/239, .560/.577, 114 LSA) all at the same time. I already have the converted intake, and now I have the heads. I'm hoping to order the cam, lifters, head gaskets, and other odds and ends later this week. If all goes well, I'll spend Mother's Day weekend under the hood.

Working on pictures now.

http://img255.imageshack.us/my.php?image=drestgii006hb4.jpg

Lloyd Elliot has a great reputation and makes a great product. Can't wait to see your times with these new heads!!

Sounds good - btw, how did you pick your cam? If I ever get around to porting my heads and doing an intake I'd like to know.

Matthew

It's a complicated process, and most people have differing opinions, so you'll get a lot of answers. This is a grossly over simplified way of looking at it:

Lift: How far the valve opens. I like to go with as much as I can before valve spring bind or piston to valve contact. This spec has less to do with idle or power band than other specs. Stock on my car is about .490 of an inch. I'm going to .570+; so another .10 of an inch or so.

Duration: This is how long the valve is open. Typically, the longer the valve is open the higher the RPM where the engine will make horse power. More lift usually means more power, but the extra power can come at the cost of low end performance and drive ability. Stock is pretty low, usually 210-220, sometimes smaller.

LSA: This is the degrees of separation between the intake lobe and exhaust lobe centerlines. This is also the only cam spec that is quoted in cam shaft degrees instead of crank shaft degrees. This spec is ground into the cam and can not be changed by degreeing the cam. Typically, the larger this number the better the car will idle, and the better the part throttle experience is. With a larger lobe separation though, you are taking away from the engines efficiency because both valves are open at the same time for less time, not taking advantage of airs natural tendency to keep moving once it has started in a direction. By lowering this number, the engine will become more efficient, especially at higher RPM, but idle quality and fuel economy will suffer. Older cars that smell like gas at idle, especially when you stand behind them and get a great wiff of the exhaust, smell that way because they have less lobe separation than modern cars. A stock cam will usually have a LSA of 115 or so. I don't know what it is on our C4's, but LS1 cars use 115 stock. The absolute borderline of street (in my opinion) is 110. Some guys, guys who have much more knowledge than I do, can make a 108 or even a 106 LSA cam pretty livable on the street. They are usually pretty special grinds with lots of research done on them. The Gm LT4 hotcam is a 112 LSA, but it idles much better than a typical 112 cam. I would guess that's because GM has done all the research to build a 112 LSA cam and not have the drawbacks that other 112 cams have.

I should also mention that I only have first hand experience with 8 or 10 cams, so my knowledge is pretty limited.

Thanks - pretty interesting stuff. Yet one more realm of the auto world I know nothing about!

Matthew

I like the Trick Flow and Edelbrocks a lot!

Also, if you can spend the extra few bucks i HIGHLY recommend having the intake valves back-cut, I got an extra 22cfm from the back cut valves on the the low lift.

the Edelbrocks are a good value, too.

Josh is going to lay down some mad times with that setup. Can't wait to get down to the track after you get everything installed. Just don't go faster than 11.65 and I won't have to spend a bunch of money. I suspect I need to start saving my pennies!

I like the fact that they fit well with headers and factory component mounting as well