I have a 1984 Z-28 and have changed out the motor to a older model 350ci. It is a 4-bolt with flat tops,vortec heads, Preformer RPM manifold,headers-full length,Accel ignition,Carter comp. carb, 700R4 tranny and 3.73 rear gears. The cam that is in it is a Wolverine 280 grind 214in. 214exh. with a 443 lift. I have ran a 13.93 at 97mph. for my best time and want to go faster. I have been looking at different cams to put in it, I have talked to Comp cams tech. people to find out how big of a cam that I can run and still run my stock converter as well as my power brakes. They told me a 224in. 230exh. with 477-480 lift and 110 lobe centers which sounds pretty good. My big question is what size valve spings and retainers will I need, diameter that is I know that they have to support the lift of the cam. If you have any other suggestions as to a better cam I would appreciate the inputon that as well as the spring size. Thanks NORT

 

The cam you mentioned as a replacement is a Comp XE268H, which would be a good cam. The next one up in the same family, XE274H, is probably even better for the rest of your setup.

The cam that's in there is pitiful. It's a knockoff of the old GM "151" cam. I'll bet the setup you have now doesn't leave hard, never really pulls hard but doesn't seem to "crater" when it reaches any particular RPM, and feels good right when when it shifts but feels like it "hovers" right before it shifts and stumbles right after. I'll also bet you'll pick up ½ second with a XE274H.

You'll have trouble with those heads and any cam much over .450". The retainers may hit the valve guides. Check that carefully, by dummying one cylinder up, rotating the motor with a crank socket, and looking at the clearance. You should get a set of decent rockers while you're at it; if I were picking parts, I'd put the XE274H, 981 springs, the 10° retainers & locks, and Comp's cast steel roller-tip 1.52 rockers on it.

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"So many Mustangs, so little time..."
ICON Motorsports

 

But I'd add a stall when you do this. Going to a cam that starts pulling at a higher RPM,really needs a 2200-2500 stall. IMHO....

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350 4 bolt main, Speed-O-Motive 383 stroker kit, re-sized rods ground for clearance,TRW Forged pistons,10.7:1 compression,HPC Coated RPM intake, Speed Demon 750 cfm carb,World Products Sportsman II heads,2.02/1.60 valves, Comp Cam 1.6 roller rockers, Comp Xtreme 284 cam,240/246@.050 with .540 lift,Crane pushrods,ATI damper,Proform HEI and MSD6A box,HPC coated 1 5/8 headers, 2.5" exhaust with 40 series mufflers,TH350 with B&M 3000 stall, Powertrax NoSlip Locker, 4.11 gears.

 

I noticed you have flat tops. Do you have any problems with pinging from the compression? I have a set of Vortecs that I thought about installing on my 350. It already has flat tops and Torker Plus cam. I don't remember the cam specs, but I think it was around 480/230.