I`ve made up my mind.I`m going to get a HSR after I do a gear swap, rebuild my trans and up my stall.While my intake is off i want to get some mild porting like radius and bowl blending.Was thinking about going with larger valves since I`m going to a higher rpm intake.With some of the times I`ve seen on here,with basicaly stock L98,I`ve decided to keep the cam I`m running.Would 2" intake valves and 1.6"exhaust be a good idea or might I give up to much low or mid range power.My heads are new,less than 10,000 miles on them.I would like to keep good low and midrange power cause it`s mostly a street driven car.I do go to the track,though and would like to get into the 12`s with the HSR upgrade.

 

Doubt the valves would give up low end. Probably would help, actually. More valve curtain practically always helps. What ET's did stock LT4's get? I think you're only approaching that stock. The gears... ouch.
Just a WAG, but I'd only guess about .5 second improvement. Please prove me wrong though.

 

Found an old car and driver article on it,13.25@107 with 2.0 and 1.55 valves.It made 330 hp at 5800 rpm.I`m assumeing thats measured at the flywheel.Are you saying a.5 second improvement from the hsr or the gears?That would get me damn close to 12`s I think,even closer with gears,sticky tires,and a good tune.

 

TTT.Anybody else have any suggestions on what I should do to my heads while I have them off.

 

When i was big in 3rd gens(90's) i had the Vette heads done like this,2.00 1.56,7/16 studs,isky plates,comp 986 springs,nicely ported mainly in the bowl area,3-angle valve job,1.6 roller rockers,SLP 495/510 cam,24lb inj.,58mm,superrram,perf.resource chip,2600 stall,3.42s 12.70s on radials with a 1.7 60'.....minor suspension mods.....

 

the valves could help some...but the porting will be the best bang for the buck investment. a good bowl blend and clean up the runners, clean up the exhaust ports and give them abit of a polish, you'll see another 20cfm of flow and really start making some power.

But if you want to, 2.00 valves or even 2.02 valves with combustion chamber work to unshroud them will definately pick up alot more flow...perhaps another 10cfm or so. 20-30cfm flow improvement in the heads will be 25 more hp to the ground if tuned right.

I went 12.9's with stock L98 with stock L98 Iron heads and hsr. mind you it was in great air, at near sealevel density altitude.

You'll need something like 2800 stall and 3.42 gears. low end power is still great, over 315wtq at 3000-3200 rpms and just about over 300wtq to 3800-4000rpms. thats a broad power band.

with your LT4 cam and HSR, and 10 to 1 compression, you'll EASILY be 12's in good air with sticky tires, 2800-3000 stall and 3.42 gears. 3.73's and 2800 stall would be a perfect match for that setup.

 

Here's a really good article on porting the 083's

https://www.thirdgen.org/forums/tpi/...d-project.html

There's also a good book that covers porting that I used called "Max performance small block chevy" by David Vizzard. I picked it up at Books-a-million but I've seen it at Autozone too.

I used a 3/8 and 1/2 oval burr and cartridge rolls to port my 083's and am quite satisfied with how my basically stock L98 runs. I used 1.98/1.5 undercut valves with Comp cams springs and retainers. See my sig for more info.

Last run was 8.77 1/8 mi with terrible launches due to a clutch going out and that should put me in the mid 13's with 12's possible as I'm getting things tuned in.