Okay guys, after trashing my engine back in September ( 11th BTW ), I am finally getting around to looking at dropping another in. What I currently have is a 90 GT 5.0 with about 72k on the clock (can still see original cross hatch pattern on cylinder walls). I am looking at using the following parts from my old heads: Roller rockers Screw in stud/guide plate conversion kit The old heads are E6's and one was cracked when the carb screw that fell out met the no.2 piston (repeatedly...) So, I am planning on using the E7's that came with my 5.0. My question is this: I have a FMS Z-303 cam (228 @ .050", .552 lift). I know I need to change the springs (requires 340# open, 120# closed). What I do not know is how well a set of mildly ported E7's will work with this cam. Obviously a set of 351W heads with bigger valves would be better, but, $$$$ is hard to come by. Anyone have any input to offer my way (other than telling me to use lock-tite on carb screws... ) on either heads or otherwise would be appreciated...
head for me Well the E7 heads have some good sides to them. Question is how much money do you want to spend and to what end result? the Z303 is a big cam.
No way, that cam is way too big. I've got ported E7 heads with GT40 valves, they are as good as E7TE heads can get. I ran very fast with my B303 cam. I switched to an X303 and haven't been able to run any better. I am still in the tuning stages, but I don't think I'll get more than a couple tenths from this cam, if that. All I've so far is 11 mpg and a lopey idle. I went faster with my B303 and got 15 mpg and a nice driving car. The Z cam is an all out racing cam.
Okay, maybe it's just my inexperience talking here... My previous cam was an Edelbrock Performer RPM (224\228 @ .050 and .492\.520 lift). This is a flat tappet cam. Now, I've always read that you can use a slightly bigger roller cam with the same basic engine setup. The biggest difference I see here is the lift. I belive the LCA are close also. If I am wrong, then someone please let me know. I realize the E7 heads would require a good bit of work.
balancing act A cam is a delicate balancing act. Between intended usage and any changes you make. The Z303 cam is a 3500-7000 rpm cam. Below the 3500 it's a dog. Stock 302's cam is a 194 degs at .050" with .375" lift. Boss 302 is .477 lift with a 290 dur. (old measurement) They found the heads to be to big for the cubic inch. Until you got above 3000 rpms. Now the Boss 302 cam specs work beautifully in the 351C size engine. The 289HP was .460lift at 298 dur. It's not actually the lift of the roller that makes the difference, it's the cam lobe's profile. They open faster and close faster. In other words they get to max lift sooner and stay there longer. This allows air flow to be more. Hyd/mech lifters can't follow the roller profiles so it's a more gradual opening and closing. The factory roller hyd cams are a compromise. Good performence with a quiet lifter. That way you can hear your stereo. Best bet if you're not sure which cam, call Crower, Crane or Comp Cams tech phone line and tell them what you're looking at. Don't try and BS them or sound like John Force style racing. Remember, they've tested, done, seen and tried more cam things then we'll ever know. And they know what works. Talk to all three and then decide who you like best. I've used Crane & Crower both street and dragracing with good results. Comp Cam is to generic for me.
