jeffs82z28

HI, I'm doing my 1st post on my favorite website THIRDGEN.ORG

I have a standard bore 283 and was thinking about stuffing in an edelbrock performer rpm cam, and then putting a set of 58cc 305 heads on after porting and polishing them.

I'm keeping the stock cc carb and intake, I'd like headers but the wife wants to buy a house so they will have to wait.

I figure with the 58 cc chamber it would bump the CR to 9.25:1 maybe a little more.

I would use the 283 heads, but they don't have the bosses for the a/c, p/s, or alternator brackets.

What do you think?:hail:

Thanks in advance>

I haven't figured out the sig yet so i'll just list my car:
1982 Z-28, LG4, 4speed Close ratio Borg-Warner, 3.23:1 Limited slip, and T-Tops.

Eventual mods:
SFC's, STB, High flow cat and exhaust, and 3.42:1 rear end.

five7kid

iTrader: (14)

Welcome aboard.

The sig is under the "user cp" button.

Typical stock 283 heads were 60cc. With the 305 heads, you'll probably get over 9.5:1 if you have flat top pistons and use a steel shim head gasket.

If you can, put 1.94" intake valves into the heads when you do the porting work. The 283 has a larger bore than the 305, so those valves will work even better than on a 305. You can even unshroud them a little while doing the porting (and I assume polishing) as long as you don't take out too much material and increase the chamber volume. The improved flow effect would probably offset the reduced compression, though.

Not sure why you're taking the displacement hit with this swap. But, it will rev nicely, you've got a 4 speed, so that shouldn't be a problem. Exhaust improvements are really needed to get the most out of it, though - even L69 or LB9 manifolds, y-pipe, cat & cat back would be a big improvement, and you can probably pick that up from somebody that's done aftermarket conversion (I have LB9 manifolds, for instance). I assume you're changing the cam as well while you're at it (cheap upgrade, dramtic improvement in performance).

jeffs82z28

Thanks Five7,

I didn't even think about the larger valves.

I want the 283 for the shorter stroke, I figure it will wind up quicker and higher than the 305.

The cam change is on my list. I want a performer rpm or something similar, that way i'll maintain a good vacuum signal to the cc carb, and hopefully won't be throwing codes.

Thanks again, Jeff

five7kid

iTrader: (14)

Is the 283 in bolt-in-able shape? If not, then you really should consider doing that stuff to the 305.

Unloaded, a 283 will rev up quicker than a 305, true. Loaded, though (like pushing your car down the road), a 305 with the same mods as a 283 will rev quicker because it's going to move it down the road quicker.

If you hadn't said you don't have enough money right now to do the exhaust, I'd recommend an alternative - use the 283 crank in a small-journal (pre-67) 327 block with 302 pistons. 4" bore, 3" crank; .030" over it's a 306. Won't quite have the low-RPM torque of the 305, but won't take it long to overcome that. Been there, done that, in a 12.5:1, 2.02/1.60, LT1 (original) solid cam version - wish I still had it.

BTW, buy the house first...