ok. so I've been doing research for days about a good/easy rebuild. I have an 89 camaro with a stock 305 tbi. first let me say im keeping the 305 and not investing in a 350. I have the 305 pulled out already and have a friend doing the rebuild. I just want a little more power but keep the build relatively easy. so just looking for suggestions on heads and a cam that work well together. I've read the 305 tbi heads are a waste but it sounds like if I use anything else like vortec heads their is more work to be done. is it an option to port the 305 tbi heads, put a decent cam in it, bigger injectors and of course headers and full exhaust. what kind of power will I be looking at? I've also read a lot about the l98 aluminum vette heads. any input is much appreciated. I think I've been overwhelmed with all the info I've found and maybe just need some direct opinions and advice.

 

You'll get a lot of differing opinions on this. As I have similar plans in the long run, and have tried to read all I can find on the subject, I'll share what I think I've learned!

Going racing? Need max power from your 305? Or more than 250 - 300 horse? You need different heads. Can they be ported? Yes. Will it help, yes. Will it give you the same ultimate bang for the buck in total CFM flow as a non-swirl port head? No.

Cam...any of the SBC factory hydraulic roller cams will be a nice upgrade....L98, LT1, LT4...there are differences, so read up. They call the later LB9/L03 cam a "peanut cam" for a reason.

Vortec heads. L31 (5.7L) heads will flow better, no doubt. The best factory iron head. But they are for an engine with a bigger bore, so you will lose some C/R. There was also a Vortec 5.0L (L30), which offered the same power gains over it's TBI predecessor as the 5.7L did (even a few more ponies, actually). A little harder to find, and they won't draw the same community love from those who worship at the L31 alter, but they won't cost you C/R either (at least not via an oversized chamber). Will need a different intake I believe, due to bolt hole angles.

113 casting Corvette L98 heads. A decent head. A part of many GM crate engines. Saves weight, breathes better than what you have. A well used set will need to be reworked. A turn key set will cost you some bucks. The Vette L98 used a remote EGR (NOT mounted on the intake), so you would have to replicate that functionality in some way, or delete EGR.

Bigger injectors, yes. Fuel pump too, with an adjustable regulator, and a gauge would be nice.

Better exhaust from the ports in the heads to the exhaust tips...very much yes. Pretty universal agreement that it's the weakest part of the L03. Improvements can be had all around.

Power level? Good question. You are starting at 170hp. LB9s and L69s were 190hp for many years, and you'll find a lot of folks who will turn their nose up at an L03 that like their LB9/L69 cars. I ran a stock LB9/Auto car. Even giving away rear axle ratio, he was NOT head and shoulders faster. But was slightly faster (and just where you'd expect it...just as my swirl ports ran out of breath are 4k, he'd pull ahead just a foot or two. Shift, and run right with him until 4k, lose a few more feet, shift....you get the picture). If you can add 50 horsepower, and be at 220...hotter than the hottest LB9 or L69, and on par with early 5.7s (but not on torque...sorry)...add a better rear gear...would that be enough? Only you can decide that. But it's something to think about.

 

thanks for the response. if I want to keep the heads and just have them worked on, add a cam, headers, exhaust and gears will i need to get bigger injectors for the tbi and upgrade the fuel pump? also how much power do you think a setup like that will put down. I'd be happy at the 250 range

 

I've heard of some pretty absurd gains on L03's just from headers, a good cat-back exhaust system, and a tune. The stock exhaust is horribly restrictive, and is probably a good place to start before worrying about head and cam swaps (DynoDave listed pretty much all the good, budget-friendly options). TPI 305 heads (can't remember the casting number atm) might be another decent, and dirt cheap option for more flow.

IIRC, the stock TBI setup on the L03 won't handle more than about 210-220 HP without upgrading the fuel injectors. I think the 350 injectors will support up to 250-260 HP without needing to upgrade the fuel pump. A TPI fuel pump and EBL Flash is probably want you want if you're after more than 250 HP.

Don't forget about rear gear ratios too. Lots of L03's came with "economy" gears (3.08 with the T5, and I think 2.73 w/autos). A switch to 3.42 or 3.73 will probably wake the car up by quite a bit.