I have a 350 std bore, stock bottom end. Lunati Voodoo .510/.525 lift cam, casting 605 305 heads, with .550 max lift springs mildly ported, 3 angle valve job with stock 1.84/1.5 valves, 55cc chambers. Comp cams 1.5 roller rockers, Edelbrock performer intake and a 1406 edelbrock carb. Wondering if someone has a ballpark estimate on what compression ill be running, and also how much horsepower ill be pushing. Any help is welcome.

 

300-350ish

 

How much roughly would I gain if I get the heads to 2.02/1.6 valves

 

350 from what? With 55 cc heads compression could be unworkable. Does this engine run? If it does, do a compression test and your compression ratio can be calculated with reasonable accuracy as long as you have specific cam specs.
As for a HP gain with "2.02/1.60" heads, it depends on whose heads. Could easily be a 50 hp swing between the best and the worst.

 

325ish if tuned right 250 if not. You would need to tell me what pistons are installed to figure out compression.

 

He would need to know more than the piston type to calculate SCR. The piston to deck and head gasket values would also need to be known.
On the other hand, a compression test with the known intake valve closing event (provided the cam is installed straight up) will provide a very good indication of the static compression ratio. Dynamic compression ratio too.

 

Many, many, many years ago when my car had an old school 383 in it with large chamber smog heads, 700R4 and slightly above stock stall converter, it ran 14.0 in the 1/4 mile. Engine had a really good camshaft but it wasn't matched to the rest of the engine. The engine came with the car so I just left it as it was and went racing. I gutted it the first day I owned it and have never street driven it.

Over the winter, I changed the heads to some highly ported camel heads with 2.02/1.60 valves. I also swapped out the transmission for a TH350 and a 3800 stall converter. First pass of the new season and the car ran 12.0. Everyone was asking me where I hid the NOS bottle.

At the end of the year on my last pass of the season, the 383 with stock 400 rods, rod bolts and stock cast 350 pistons didn't like spinning to 7000 rpm and the engine blew up. I yanked the intake and heads off it and threw the rest out. It even broke the camshaft. I still have the heads sitting in the garage with a bunch of bent valves in them.

As for your heads, it's not just about chamber size. Small chambers allow higher compression to make more torque but the smaller chamber also shrouds the valves which adds restrictive flow of the incoming air/fuel mixture. There's also the fact of how large the runner size is. Smaller chamber heads designed for smaller displacement engines may not flow enough air for a larger displacement engine.

Many times it's better to just buy an aftermarket set of heads. They'll usually be better right out of the box than worked over OEM heads. The cost of aluminum heads isn't what it was 30+ years ago and they're now more affordable to the average person. Many people have had good luck just using a Vortec head.

 

This. Unless you have some personal reason to keep the stock heads, I would just get some vortecs or aluminums. Hard to guess a number as there are so many variables.