i recently got a pretty good deal on a weiand 142 blower (extra-long nose) that I'm going to put on my 350 the bottom end is stock it has about 40,000 miles on it. I'm wondering what would be a good cam and a good set of heads to achieve about 450 to 500 horse

 

To supercharge a motor with significant boost on pump gas, the engine needs a Low compression ratio. 8.5:1 or less. less is better (allows more boost and power) 7.5:1 optimum (92 octane). {allows the most reliable (non-intercooled) power and boost with the least ignition retard} For a 350 you want dished pistons and large cc chamber heads.
Intercooling allows for higher compressionand or more boost without detonation. So does water injection.

Supercharger Camshafts: Flat tappet:
Crane cam number 113801 (HMV278) is a very nice street supercharger cam. (hydraulic lifters)

Crane number 113841 (F-278-2) is a great street supercharger cam (mechanical lifters) for more power and rpm.

Heads:
If you're using stock chevy 76cc heads porting and large valves are recommended. (441 487 336 920 best)
large chambered aftermarket heads are even better. like RHS pro action Lightning 200cc 72cc
Any of these heads can be modified to 80cc chambers to get the best cr.

On a supercharged motor with more than say 8psi boost the pistons top ring gaps need to be larger than normal to account for the increased heat load under boost.
What pistons (flat top, dish top) and cylinder heads (casting number) and on your motor now?

 

its a l98 motor i'v been told that the 142 might not hold up to 500 hp what do you think about the 177? i'v been looking at the #113801 crane cam now about the heads should i go with 76cc 78cc or 80cc if so who makes a good 80cc head with about 200cc runners i was looking at the dart heads i don't no what do you think? any info will help... Thanks

Brock

 

The only stock GM head with a 80cc chamber was the 487x head on 71 72 400's
No aftermarket company makes a 80cc cylinderhead. All the large chamber 72,74 ,76cc aftermarket heads can be modified to enlargen the chamber size thou.
You want to lower the cr as much as possible to allow running more boost on pump gas. More boost=more power.
If you're using a stock L98 short block you want to limit the boost to about 10PSI.
The only aftermarket head I would avoid is the Dart Iron Eagle 180. Don't flow worth a S&^%$ out of the box.(needs lots of porting might as well rebuild and port a 76cc GM head)
Dart 200 platinum and Pro1 good. RHS lightning180 or 200 good. Do not use a felpro head gasket as a guide to opening up the chamber walls. Its way too big @ 4.166". You could use a factory type steel shim gasket as a guide with a little common sense. It's 4.10"

The 177 Weiand blower will make more power than the 142.
Looks like a good deal to me.